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Page No 141:

Question 22:

(a) What is the basic difference between asexual reproduction and sexual reproduction?
(b) Which of the following organisms reproduce by sexual method and which by asexual method?
Amoeba, Cats, Humans, Hydra, Birds

Answer:

(a)

Sexual Reproduction Asexual Reproduction
Requires two parents Requires only one parent
Gametes are formed Gamete formation not required

(b) Amoeba and Hydra reproduce asexually.
Cats, humans and birds reproduce sexually.

Page No 141:

Question 23:

(a) What is meant by regeneration? Name two animals which can regenerate fully from their cut body parts.
(b) Explain why, more complex multicellular organisms cannot give rise to new organisms through regeneration.

Answer:

(a) Regeneration is the process in which an organism can produce new organisms from their damaged or lost body parts. Hydra and Planaria can regenerate fully from their lost body parts.

(b) In complex multicellular organisms, specialised cells form tissues, tissues form organs and organs coordinate to form a system. Due to this high degree of specialisation, multicellular organisms cannot reproduce by regeneration of a part of some tissue.

Page No 141:

Question 24:

Explain vegetative propagation with the help of two examples. List two advantages of vegetative propagation.

Answer:

The process in which new plants are grown from the parts of other plants such as roots, shoots and leaves, without involving any reproductive organ, is termed as vegetative propagation. For example, guava trees can be propagated using their roots, and Bryophyllum can be propagated by using its leaves.

The advantages of vegetative propagation are as follows:

  • The plants cultivated are genetically identical to their parents.
  • Plants can be cultivated faster as compared to growing them from their seeds.

Page No 141:

Question 25:

(a) What is meant by the term 'artificial propagation of plants'?
(b) Name three common methods which are used for the artificial propagation of plants.
(c) Name two plants which are usually propagated by artificial propagation methods. Name the method of artificial propagation used in each case.

Answer:

(a) Artificial propagation refers to the man-made methods of obtaining several plants from one plant.

(b) Three common methods of artificial propagation are cutting, layering and grafting.

(c) Rose is grown by the cutting and apple is grown by the grafting.

Page No 141:

Question 1:

Which life process ensures that a plant or animal species will not disappear from this earth?

Answer:

The process of reproduction ensures that a plant or animal species does not disappear from Earth.

Page No 141:

Question 2:

What is the name of the reproductive process :
(a) which involves two parents?
(b) which involves only one parent?

Answer:

(a) Sexual reproduction
(b) Asexual reproduction

Page No 141:

Question 3:

State whether the following statement is true or false :
Spores produced by the bread mould plant are actually its seeds.

Answer:

True. Bread moulds are fungi. Bread moulds reproduce by spores that can be considered as their seeds.

Note: According to Whittaker's system of classification, bread mould is placed in a different kingdom named fungi and not in the kingdom plantae. However, if we compare bread mould with plants then we can compare their spores with seeds of plants.

Page No 141:

Question 4:

Most of the plants reproduce by sexual method. Name two plants which can reproduce asexually.

Answer:

Bryophyllum and potato can reproduce asexually through vegetative reproduction.

Page No 141:

Question 5:

Which type of reproduction :
(a) involves gametes?
(b) does not involve gametes?

Answer:

(a) Sexual reproduction involves gametes.
(b) Asexual reproduction does not involve gametes.

Page No 141:

Question 6:

State whether human beings reproduce by sexual method or asexual method.

Answer:

Human beings reproduce sexually.

Page No 141:

Question 7:

(a) Name two animals which reproduce sexually.
(b) Name two animals which reproduce asexually.

Answer:

(a) Two animals which reproduce sexually are cow and lion.
(b) Two animals which reproduce asexually are Planaria and Hydra.

Page No 141:

Question 8:

Name one organism which reproduces by spore formation.'

Answer:

Fungi reproduce through spore formation; for e.g., bread moulds.

Page No 141:

Question 9:

Name the method by which Paramecium reproduces. Is this method sexual or asexual?

Answer:

Paramecium reproduces by the method of fission. It is a method of asexual reproduction.

Page No 141:

Question 10:

Name two plants :
(a) which can be grown from their broken stems.
(b) which can be grown from their leaves.

Answer:

(a) Grass and money plant can be grown from their broken stems.
(b) Bryophyllum and Begonia can be grown from their leaves.

Page No 141:

Question 11:

Name the asexual method of reproduction in yeast.

Answer:

Yeast reproduces by the method of budding.

Page No 141:

Question 12:

Name the asexual method of reproduction in (a) Hydra, and (b) Plasmodium.

Answer:

(a) Hydra reproduces by regeneration and budding both.
(b) Plasmodium reproduces by multiple fission.

Page No 141:

Question 13:

What is the name of asexual reproduction method in :
(i) Spirogyra, and (ii) Leishmania?

Answer:

(i) Spirogyra reproduces by fragmentation.
(ii) Leishmania reproduces by binary fission.

Page No 141:

Question 14:

Name the artificial propagation mehod used for the propagation of (a) rose plants, and (b) apple trees.

Answer:

(a) Rose plant is artificially propagated through the method of cutting.
(b) Apple tree is artificially propagated through the method of grafting.

Page No 141:

Question 15:

Which artificial propagation method is used for the production of jasmine plants?

Answer:

Layering is the artificial propagation method used for producing jasmine plants.

Page No 141:

Question 16:

Name the natural method by which strawberry plants are propagated.

Answer:

Strawberry plants are propagated by layering.

Page No 141:

Question 17:

Name two plants which are propagated by layering method.

Answer:

Jasmine and strawberry  are propagated by layering.

Page No 141:

Question 18:

Name any two plants which are propagated by cuttings method.

Answer:

Rose and grapes plants are propagated by the cutting method.

Page No 141:

Question 19:

Write down the different methods of asexual reproduction.

Answer:

The different methods of asexual reproduction are:

  • Fission
  • Budding
  • Spore formation
  • Regeneration
  • Fragmentation, and
  • Vegetative reproduction

Page No 141:

Question 20:

Why are budding, fragmentation and regeneration, all considered to be asexual type of reproduction?

Answer:

Budding, fragmentation and regeneration are considered to be the different types of asexual reproduction, as these methods need only one parent and no gamete formation.

Page No 141:

Question 21:

Fill in the following blanks with suitable words :
(a) the process of...........ensures continuity of life on earth.
(b) Plasmodium reproduces by the process of ............ fission whereas Paramecium reproduces by the process of ......... fission.
(c) Rose plants and sugar cane crop are usually grown by the ........... method.
(d) Vegetative reproduction of potato plants is done by using ............
(e) Strawberry plants are propagated by the natural............... method.

Answer:

(a) The process of reproduction ensures continuity of life on Earth.
(b) Plasmodium reproduces by the process of multiple fission, whereas Paramecium reproduces by the process of binary fission.
(c) Rose plants and sugarcane are usually propagated by the cutting method.
(d) Vegetative reproduction of a potato plant is done by using its tuber.
(e) Strawberry plants are propagated by the natural layering method.



Page No 142:

Question 26:

Describe the layering method for the artificial propagation of plants. Illustrate your answer with the help of a labelled diagram. Name any five plants which are propagated by the layering method.

Answer:




In the layering method, one of the branches of a plant is pulled down into the ground and covered with moist soil in such a way that the tip of the branch remains above the surface. After a few days, new roots start growing from the part buried in the soil. This part of the branch is then separated from the parent plant to let it develop into a new plant.

Plants which can be propagated by the layering method are jasmine, lemon, guava, strawberry, raspberry, etc.

Page No 142:

Question 27:

(a) What is meant by the term 'fission' as used in biology?
(b) How does binary fission differ from multiple fission?
(c) Name one organism which reproduces by binary fission and another which reproduces by multiple fission.
(d) State whether the above named organisms are animals or plants.

Answer:

(a) Fission is the process of asexual reproduction in which a unicellular organism divides to form two daughter cells.
(b) In binary fission, the parental cell divides into two daughter cells. In multiple fission, the parent organism keeps on dividing for innumerable times giving rise to many offsprings.
(c) Amoeba reproduces by binary fission and Plasmodium reproduces by multiple fission.
(d) Organisms named above are protozoa; thus, they are animal-like.

Page No 142:

Question 28:

(a) Can you consider cell division as a type of reproduction in unicellular organisms? Give reason.
(b) What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?

Answer:

(a) In unicellular organisms, cell division can be considered as reproduction, as it produces two independent daughter cells identical to their parent. This process is termed as fission.
(b) Genetically identical organisms are called clones. Asexual reproduction involves only one parent, thus genes from only one parent will be transferred to the daughter cells during asexual reproduction; therefore, the resulting offsprings will be genetically identical to each other.

Page No 142:

Question 29:

(a) The yeast cells fail to multiply in water but they multiply rapidly in sugar solution. Give one reason for it.
(b) Why does bread mould grow profusely on a moist slice of bread but not on a dry slice of bread?

Answer:

(a) Since, yeast is a non-green plant, it cannot prepare its own food. In water, there is no source of energy for yeast to reproduce. However, in a sugar solution it grows well, as sugar acts as a good source of energy.

(b) A moist slice of a bread provides all the favourable conditions needed by the spores of the bread mould to germinate. This is the reason why bread mould cannot grow profusely on a dry slice of a bread.

Page No 142:

Question 30:

(a) What is a tuber? Name one stem tuber and one root tuber.
(b) What is name of the organ of propagation present in a tuber?
(c) Name one commonly used vegetable which is propagated by using tubers.

Answer:

(a) The thickened and swollen stem or root of a plant that stores food and grows underground, is called a tuber. For example, potato is a stem tuber and sweet potato is a root tuber.

(b) The bud or eye is the organ of propagation present in a tuber.

(c) Potato is propagated through its tuber.

Page No 142:

Question 31:

(a) What is meant by vegetative propagation?
(b) Vegetative propagation involves the growth and development of 'something' present in the old part of the plant to form a new plant. What is this 'something'?
(c) Why do green grass plants spring up in dry fields on their own after the rains?

Answer:

(a) Vegetative propagation is the process of growing new plants from the parts of an old plant without involvement of any reproductive organ.

(b) This 'something' is any part of plant such as, roots, stems or leaves.

(c) After it rains, the inactive buds in the dried shoots of a grass plant, lying all over the ground, become active and give rise to new plants. This is the reason why green grass plants start growing on dry fields on their own after a spell of shower.

Page No 142:

Question 32:

(a) Explain how, new Bryophyllum plants can be produced from the leaves of the old plant? Illustrate your answer with the help of a labelled diagram.
(b) How can you grow money plant by vegetative propagation?

Answer:

(a) In Bryophyllum, the buds are present on the leaf margins. These buds have the potential of vegetative reproduction. When these buds get detached from the leaves and fall on ground, they grow into new plants. In cases, where the buds don't detach from the leaves, plantlets start growing, over the later.

(b) Money plant can be grown by the vegetative propagation of its stem. Cut a piece from its stem, comprising at least one leaf, and dip it into water. After a few days, roots will grow from the point of attachment of the leaf, and the stem will start developing into a new plant.

Page No 142:

Question 33:

Match the organisms given in column I with the methods of reproduction/propagation given in column II :

Column I   Column II
(i) Plasmodium   (a) Spore formation
(ii) Spirogyra   (b) Leaves
(iii) Jasmine   (c) Regeneration
(iv) Apple tree   (d) Budding
(v) Bryophyllum   (e) Binary fission
(vi) Potatoes   (f) Layering
(vii) Rhizopus   (g) Fragmentation
(viii) Hydra   (h) Tubers
(ix) Planaria   (i) Cuttings
(x) Leishmania   (j) Multiple fission
(xi) Sugar cane   (k) Grafting
(xii) Rose    

Answer:

Column I   Column II
(i) Plasmodium   (j) Multiple fission
(ii) Spirogyra   (g) Fragmentation
(iii) Jasmine   (f) Layering
(iv) Apple tree   (k) Grafting
(v) Bryophyllum   (b) Leaves
(vi) Potatoes   (h) Tubers
(vii) Rhizopus   (a) Spore formation
(viii) Hydra   (d) Budding
(ix) Planaria   (c) Regeneration
(x) Leishmania   (e) Binary fission
(xi) Sugar cane   (i) Cutting
(xii) Rose   (i) Cutting

Page No 142:

Question 34:

(a) What is meant by reproduction?
(b) What are the two general methods of reproduction in organisms?
(c) How does an Amoeba reproduce? Describe the process of reproduction in Amoeba with the help of labelled diagrams of different stages in its reproduction process.
(d) what is the name of the process by which Amoeba reproduces?
(e) Name two organisms which reproduce by the same asexual process as that of Amoeba.

Answer:

(a) Reproduction is the process in which organisms give birth to new organisms (progeny) of the same species.

(b) Two general methods of reproduction are asexual and sexual.

(c) The cell of an Amoeba after attaining its maximum size starts dividing. The nucleus of the cell divides first, followed by the cytoplasm. Thus, a single cell divides into two identical cells.


(d) Amoeba reproduces by binary fission.

(e) Leishmania and Paramecium reproduce by binary fission like Amoeba.

Page No 142:

Question 35:

(a) What is the difference between the two asexual methods of reproduction : fission and fragmentation?
(b) Name one organism which reproduces by fission and another which reproduces by fragmentation.
(c) What is meant by multiple fission? Name one organism which reproduces by the process of multiple fission.
(d) Describe the process of reproduction in Hydra with the help of labelled diagrams. What is the name of this process of reproduction?
(e) Name one unicellular organism which reproduces by the same asexual process as Hydra.

Answer:

(a)

Fission Fragmentation
Fission occurs in unicellular organisms. Fragmentation occurs in multicellular organisms.

(b) Amoeba reproduces by binary fission and Spirogyra reproduces by fragmentation.

(c) In multiple fission, the parent cell repeatedly divides to form innumerable organisms at the same time. Plasmodium reproduces by this method.

(d) Hydra reproduces by the method of budding. A small outgrowth called bud is formed on one side of its body by repetitive mitotic division. This bud gradually grows into a full hydra, developing its mouth and tentacles. The new Hydra detaches itself from its parent and start living as a separate organism.



(e) Yeast reproduces by the same method as Hydra, i.e. budding.



Page No 143:

Question 36:

(a) Name the method by which bread mould (Rhizopus fungus) reproduces. Is this method sexual or asexual?
(b) What is yeast? Describe the process of reproduction in yeast with the help of labelled diagrams.
(c) Name a tiny fresh-water animal which reproduces by the same method as that of yeast? What is this method known as?
(d) Name two marine organisms which also reproduce by the same method as yeast but form colonies.

Answer:

(a) The bread mould reproduces by spore formation. It is an asexual mode of reproduction.

(b) Yeast is a microorganism which is classified as a fungus. It is eukaryotic and reproduces by budding. In yeast, a bud first appears outside its cell wall. Immediately the parent nucleus divides itself into two in such a way that one of its parts moves into the bud. Then the bud detaches itself from the parent cell to form a new yeast cell.
Figure: Reproduction in yeast

(c) Hydra reproduces by the same method as yeast, i.e. budding.
        
(d) Sponges and corals are the two marine animals that reproduce by the same method as yeast i.e., budding; however, they form colonies.

Page No 143:

Question 37:

(a) What is meant by 'grafting' as a means of propagation in plants?
(b) Define 'stock' and 'scion'.
(c) Describe the grafting method for the artificial propagation of plants with the help of labelled diagrams.
(d) Name two fruit trees which are usually propagated by grafting method.
(e) State two advantages of grafting method of artificial propagation of plants.
(f) What is the difference between the cuttings method and grafting method for the artificial propagation of plants?

Answer:

(a) Grafting is a method of artificial propagation in which the stem of two plants are cut, one with and the other without roots. These stems are then joined together to form a single plant.

(b) The lower portion of the graft, i.e. the stem with roots is termed as a stock. The upper portion of the graft, i.e. the stem without roots is termed as a scion.

(c) In grafting, two plants of the desired traits are chosen. First, the plant that has been chosen as the scion is cut slantingly, then the stock is also cut in the same manner. After that, the scion is placed over the stock and tightly fitted together. Either they are tied by a piece of cloth or covered using a polythene sheet.



(d) Apple and orange trees are propagated by the method of grafting.

(e) The first advantage of this method of propagation is that plants with desired characteristics are obtained. Also, with this method, young stems can be made to flower and bear fruits quickly.

(f)

Cutting Grafting
In cutting, only one plant is involved. In grafting, two plants are involved.
New plant formed from cutting, is identical to its parent. The new plant has characteristics of both the parents.

Page No 143:

Question 38:

(a) What is tissue culture?
(b) Name any four types of ornamental plants which are being produced by tissue culture technique.
(c) What is the importance of DNA copying in reproduction? Explain with an example.
(d) How does reproduction help in providing stability to population of species?
(e) Why is variation during reproduction beneficial to the species but not necessarily for the individual?

Answer:

(a) Tissue culture is the process of propagating new plants, in a suitable growth medium, from a small piece of a plant's tissue, that is obtained from the growing tip of that plant.

(b) Orchids, Dahlia, carnation and Chrysanthemum are propagated by the method of tissue culture.

(c) DNA copying refers to the replication of DNA at the time of cell division. It is important for transfer of genes of parent(s) to the progeny. This ensures continuity of existence of a species. It also plays a very important role in giving rise to slight variations in offsprings from the parents. During replication, some variations are incorporated in the DNA, as no biochemical process is 100 % efficient. This process becomes specifically important in the organisms that reproduce asexually, as in such organisms, only one parent is involved and there is no other source of variation in the DNA of the progeny from the parent. 
Example: Suppose there is some species of bacteria that is capable of surviving in temperate water. Now, consider a situation in which, due to global warming, the temperature of the temperate water bodies raises. If all the bacteria would have been identical, then all of them would have died because of this rise in temperature. However, it does not happen in nature. Due to slight variation in the DNA of progeny, not all the individuals of a species are identical, although they are similar. Some individuals of this species of bacteria, due to this little variation in their DNA, will be capable of surviving in warmer water, thereby ensuring the continuity of species. This is how variations incorporated in DNA during replication are important. 

(d) Reproduction ensures that new offsprings are produced continuously to replace the dying individuals of the population. Thus, it ensures continuity of life and provides stability to the population.

(e) Variation during reproduction ensures that a species can survive and flourish even in adverse conditions. However, these adverse conditions might or might not appear during the life cycle of a specific individual.  Thus, it is beneficial to the species but not necessarily for an individual.

Page No 143:

Question 39:

(a) What is a 'cutting' in respect of plants for propagation purposes?
(b) What care should be taken while making a cutting from a plant?
(c) Describe the cuttings method for the artificial propagation of plants. Illustrate your answer with the help of labelled diagrams.
(d) Name any two plants which are usually propagated by the cuttings method.

Answer:

(a) Cutting is a method of vegetative propagation of plants. It is a means of asexual reproduction.

(b) While cutting a stem from the parent plant it has to be kept in mind that at least a few buds are present on the cutting we want to plant.

(c) In the cutting method, a part of the stem comprising buds on it is cut from the plant using a sharp knife. This stem is then buried in a suitable medium. After some days, the stem develops roots and starts growing into a new plant.
 


(d) Rose and sugarcane are propagated by the cutting method.

Page No 143:

Question 40:

Asexual reproduction is :
(a) a fusion of specialised cells
(b) a method by which all types of organisms reproduce
(c) a method producing genetically identical offspring
(d) a method in which more than one parent are involved

Answer:

(c) a method of producing genetically identical offsprings
Asexual reproduction involves only one parent; therefore, the offsprings are genetically identical.

Page No 143:

Question 41:

One of the following organisms does not reproduce by binary fission. This is :
(a) Amoeba
(b) Plasmodium
(c) Leishmania
(d) Paramecium

Answer:

(b) Plasmodium
It reproduces by multiple fission.

Page No 143:

Question 42:

The micro-organism which reproduces by multiple fission is the one which causes the disease known as :
(a) Kala-azar
(b) marasmus
(c) malaria
(d) amoebiasis

Answer:

(c) malaria
Plasmodium reproduces by multiple fission and causes malaria.

Page No 143:

Question 43:

The protozoan having a flagellum at its one end is :
(a) Amoeba
(b) Paramecium
(c) Hydra
(d) Leishmania

Answer:

(d) Leishmania
Leishmania is the protozoan that has flagellum at its one end.

Page No 143:

Question 44:

In the list of organisms given below, those which reproduce by the asexual method are :
(i) banana
(ii) yak
(iii) yeast
(iv) Amoeba

(a) (ii) and (iv)
(b) (i), (iii) and (iv)
(c) (i) and (iv)
(d) (ii), (iii) and (iv) 

Answer:

(b) (i), (iii) and (iv)
Banana, yeast and Amoeba reproduce asexually. Banana reproduces by vegetative propagation, yeast propagates by the method of budding and Amoeba propagates by binary fission.

Page No 143:

Question 45:

One of the following organisms does not reproduce by budding. This is :
(a) Sponge
(b) Yeast
(c) Hydra
(d) Planaria

Answer:

(d) Planaria
It reproduces by regeneration.

Page No 143:

Question 46:

The disease kala-azar is caused by a micro-organism known as :
(a) Planaria
(b) Leech
(c) Leishmania
(d) Plasmodium

Answer:

(c) Leishmania
It is a protozoan which causes kala-azar.

Page No 143:

Question 47:

Reproduction is essential for living organisms in order to :
(a) keep the individual organ alive
(b) fulfil their energy requirements
(c) maintain growth
(d) continue the species for ever

Answer:

(d) continue the species forever
Reproduction provides the means of producing new offsprings, so that a species can continue surviving on earth forever.

Page No 143:

Question 48:

The unicellular organism which reproduces by budding is :
(a) Spirogyra
(b) Hydra
(c) Planaria
(d) Yeast

Answer:

(d) Yeast
Yeast is the unicellular organism which reproduces by budding.

Page No 143:

Question 49:

A multicellular organism which reproduces by budding is :
(a) Amoeba
(b) Yeast
(c) Leishmania
(d) Hydra

Answer:

(d) Hydra
Hydra is a multicellular organism. It reproduces by budding.



Page No 144:

Question 50:

The offsprings formed by asexual reproduction method have greater similarity among themselves because :
(i) asexual reproduction involves only one parent
(ii) asexual reproduction involves two parents
(iii) asexual reproduction involves gametes
(iv) asexual reproduction does not involve gametes

(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (i) and (iv)

Answer:

(d) (i) and (iv)
The offsprings formed by the method of asexual reproduction have greater similarity among themselves. This is because asexual reproduction involves only one parent and does not require gametes.

Page No 144:

Question 51:

A simple multicellular animal having tentacles which lives in freshwater usually reproduces by the asexual process of :
(a) binary fission
(b) spore formation
(c) budding
(d) fragmentation

Answer:

(c) Budding
Hydra is a simple multicellular animal that has tentacles and lives in freshwater. It reproduces by budding.

Page No 144:

Question 52:

One of the following does not reproduce by spore formation method. This is :
(a) Rhizopus fungus
(b) Penicillium fungus
(c) Yeast fungus
(d) Mucor fungus

Answer:

(c) Yeast fungus
Yeast reproduces by budding.

Page No 144:

Question 53:

The factors responsible for the rapid spreading of bread mould on slices of bread are :
(i) presence of large number of spores in air
(ii) presence of large number of thread-like branched hyphae
(iii) presence of moisture and nutrients
(iv) formation of round shaped sporangia

(a) (i) and (iii)
(b) (ii) and (iv)
(c) (i) and (ii)
(d) (iii) and (iv)

Answer:

(a) (i) and (iii)
The factors responsible for the rapid spreading of bread mould on slices of bread are the presence of a large number spores in air and the presence of moisture and nutrients in bread that act as food for the fungi.

Page No 144:

Question 54:

One of the following reproduces by forming spores. This in :
(a) Fern
(b) Planaria
(c) Spirogyra
(d) Potato

Answer:

(a) Fern
Fern is a non-flowering plant which reproduces by forming spores.

Page No 144:

Question 55:

Asexual reproduction through budding takes place in :
(i) Amoeba and Yeast
(ii) Yeast and Hydra
(iii) Hydra and Plasmodium
(iv) Corals and Sponges

(a) (i) and (ii)
(b) only (ii)
(c) (i) and (iii)
(d) (ii) and (iv)

Answer:

(d) (ii) and (iv)
Yeast, Hydra, corals and sponges reproduce by budding.

Page No 144:

Question 56:

A feature of reproduction that is common to Amoeba, Yeast and Bacterium is that :
(a) they are all multicellular
(b) they are all unicellular
(c) they reproduce only sexually
(d) they reproduce asexually

Answer:

(b) they are all unicellular and (d) they reproduce asexually
Amoeba, yeast and bacterium are unicellular organism that reproduce asexually.

Page No 144:

Question 57:

One of the following organisms does not reproduce by fission. This is :
(a) Amoeba
(b) Leishmania
(c) Planaria
(d) Plasmodium

Answer:

(c) Planaria
It reproduces by regeneration.

Page No 144:

Question 58:

An organism which may be considered to be a kind of plant and reproduces by budding is :
(a) Paramecium
(b) Bread mould
(c) Hydra
(d) Yeast

Answer:

(d) Yeast
Yeast is a fungus and is considered as a non green plant. It reproduces by budding.

Page No 144:

Question 59:

An animal which reproduces by the process of budding is :
(a) Plasmodium
(b) yeast
(c) Hydra
(d) Planaria

Answer:

(c) Hydra
It is a multicellular organism that reproduces by budding.

Page No 144:

Question 60:

In Spirogyra, asexual reproduction takes place by :
(a) division of a cell into two cells
(b) breaking up of filaments into smaller bits
(c) division of a cell into many cells
(d) formation of a large number of buds

Answer:

(b) breaking up of filaments into smaller bits
In Spirogyra, reproduction takes place by fragmentation that involves breaking down the filaments into smaller bits.

Page No 144:

Question 61:

The ability of a cell to divide into several cells during reproduction in Plasmodium is called :
(a) budding
(b) fragmentation
(c) binary fission
(d) multiple fission

Answer:

(d) multiple fission
The ability of a cell to divide itself into several cells during reproduction is called multiple fission.

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Question 62:

In Rhizopus fungus, the fine thread-like structures spread on the whole surface of slice of bread are called :
(a) rhizoids
(b) stems
(c) roots
(d) hyphae

Answer:

(d) hyphae
Hyphae are the fine thread-like structures of the fungi that are spread on the whole surface of a slice of bread.

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Question 63:

Vegetative propagation refers to the formation of new plants from the following existing organs of the old plants :
(a) stems, roots and flowers
(b) stems, roots and leaves
(c) stems, flowers and fruits
(d) stems, leaves and flowers

Answer:

(b) stems, roots and leaves
Plants can reproduce through their stems (like grass), roots (like guava) and leaves (like Bryophyllum).

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Question 64:

The two organisms which can regenerate fully from their cut body parts are :
(a) Paramecium and Hydra
(b) Hydra and Amoeba
(c) Planaria and Leishmania
(d) Hydra and Planaria

Answer:

(d) Hydra and Planaria
Hydra and Planaria reproduce through regeneration. They can regenerate fully from their cut body parts.

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Question 65:

The two types of organisms which produce colonies by the process of budding are :
(a) Hydra and Corals
(b) Yeast and Sponges
(c) Corals and Sponges
(d) Hydra and Yeast

Answer:

(c) Corals and sponges
In corals and sponges, the buds remain attached to their parents permanently, and form colonies.

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Question 66:

Spore formation is the most common asexual method of reproduction in :
(a) protozoa
(b) tubers
(c) fungi
(d) algae

Answer:

(c) fungi
Fungi reproduce asexually through the formation of spores.



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Question 67:

An alga which reproduces by the asexual reproduction method called fragmentation is :
(a) Rhizopus
(b) Salmonella
(c) Plasmodium
(d) Spirogyra

Answer:

(d) Spirogyra
It reproduces by the method of fragmentation in which the filament is broken down into small pieces.

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Question 68:

The organisms which can reproduce by fragmentation are :
(a) Corals and Sponges
(b) Corals and Spirogyra
(c) sea anemone and Spirogyra
(d) Sponges and Sea anemones

Answer:

(c) seas anemone and Spirogyra
They reproduce asexually by the method of fragmentation.

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Question 69:

Binary fission describes the type of reproduction where the organism divides to form :
(a) many spores
(b) two daughters
(c) many buds
(d) two hyphae

Answer:

(b) two daughters
In binary fission, a single-celled organism divides into two daughter cells that are identical to their parent.

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Question 70:

The cut part of a plant stem (without roots) which is used in grafting is called :
(a) stock
(b) stump
(c) scion
(d) graft

Answer:

(c) scion
Scion is the upper part of the graft, which does not have roots.

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Question 71:

The cut part of plant stem (having roots and fixed to ground) which is used in the process of grafting is known as :
(a) stock
(b) scion
(c) cutting
(d) bud

Answer:

(a) stock
Stock is the lower part of the graft, which is fixed to the ground and has roots.

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Question 72:

Multiple fission occurs in one of the following. This is :
(a) bread mould
(b) kala-azar parasite
(c) flatworm
(d) malaria parasite

Answer:

(d) malaria parasite
Plasmodium, which causes malaria, reproduces by â€‹multiple fission.

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Question 73:

An organism having a whip-like structure at one end which reproduces by the process of binary fission is :
(a) Hydra
(b) Paramecium
(c) Leishmania
(d) Plasmodium

Answer:

(c) Leishmania
Leishmania, which has a flagellum or whip-like structure at one end, reproduces by binary fission.

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Question 74:

A tiny animal having tentacles which reproduces by growing buds on the sides of its body is :
(a) Planaria
(b) Yeast
(c) Amoeba
(d) Hydra

Answer:

(d) Hydra
Hydra
is a tiny animal that has tentacles on one end, and reproduces by the method of budding.

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Question 75:

An organism which can reproduce by two asexual reproduction methods one similar to the reproduction in yeast and the other similar to the reproduction in Planaria is :
(a) Spirogyra
(b) Bryophyllum
(c) Hydra
(d) Sea anemone

Answer:

(c) Hydra
Hydra
can reproduce by the method of budding similar to yeast, and also by regeneration as in the case of Planaria.

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Question 76:

Stock and scion are involved in the artificial propagation method known as :
(a) tissue culture
(b) layering
(c) grafting
(d) cuttings

Answer:

(c) grafting
Stock and scion are the two parts of a graft.

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Question 77:

In asexual reproduction, two offsprings having the same genetic material and the same body features are called :
(a) callus
(b) twins
(c) clones
(d) chromosomes

Answer:

(c) clones
The genetically identical offsprings formed by asexual reproduction are called clones.

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Question 78:

The method of asexual reproduction in plants in which callus is produced is :
(a) micropropagation
(b) vegetative propagation
(c) regeneration
(d) fragmentation

Answer:

(a) micropropagation
Micropropagation is a tissue culture method of asexual reproduction in plants, in which callus is formed.

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Question 79:

A Planaria worm is cut horizontally in the middle into two halves P and Q such that the part P contains the whole head of the worm. Another Planaria worm is cut vertically into two halves R and s in such a way that both the cut pieces R and S contain half head each. Which of the cut pieces of the two Planaria worms could regenerate to form the complete respective worms?
(a) only P
(b) only R and S
(c) P, R and S
(d) P, Q, R and S

Answer:

(d) P, Q, R and S
In Planaria, each body piece can regenerate into a new individual.

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Question 80:

There are four tiny organisms A, B, C and D. The organism A is a parasitic protozoan which causes a disease known as kala-azar. The organism B is a microscopic single-celled animal which causes malaria disease in human beings. The organism C is a unicellular animal which can change its body shape according to need, it has no fixed shape. The organism D is also a unicellular animal which is slipper-shaped having a large number of tiny hair all around its body.
(a) Name the organisms A, B, C and D
(b) Name one characteristic body feature of organism A.
(c) Name the insect which carries organism B and transmits it from one person to another.
(d) What name is given to the asexual method of reproduction of (i) organism A, and (ii) organism B?
(e) Where do organisms C and D live?

Answer:

(a) The organism A is Leishmania, B is Plasmodium, C is Amoeba and D is Paramecium.
(b) One body feature of organism A is that it has a whip-like structure called flagellum at one end.
(c) Female Anopheles mosquito carries the organism B and transmits it from one person to another.
(d) (i) Organism A reproduces by binary fission.
(ii) Organism B reproduces by multiple fission.
(e) Organisms C and D are found in ponds.

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Question 81:

Two very small organisms X and Y both reproduce by the method of budding. Organism X is industrially very important because it is used in making alcohol from sugar. It is also used in making bread. Organism Y Lives in freshwater. If organism Y gets cut into a number of parts accidently, each cut part can grow to form complete organism.
(a) What are organisms X and Y?
(b) What is the name of the process in which X converts sugar into alcohol?
(c) To which class of organisms does X belong?
(d) Name an important body feature of organism Y.
(e) Which organism is multicellular and which one is unicellular?

Answer:

(a) The organism X is yeast and organism Y is Hydra.
(b) The process by which the organism X converts sugar into alcohol is fermentation.
(c) Organism X is a fungus; hence, it belongs to the category of non-green plants.
(d) Organism Y is a multicellular organism and comprises tentacles at one end.
(e) Organism X is unicellular, and the organism Y is multicellular.



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Question 82:

When a moist slice of bread was kept aside for a few days then some organism grew on it to form a white cottony mass which later turned black. When this slice of bread was observed through a magnifying glass, then fine thread-like projections and thin stems having bulb-like structures at the top were seen.
(a) What is the common name and scientific name of the organism which grew on the moist slice of bread?
(b) How did this organism grow on the moist slice of bread automatically?
(c) What are the fine, thread-like projections on the surface of slice of bread known as?
(d) What name is given to the knob-like structures and what do they contain?
(e) What is the name of this method of reproduction?
(f) Name one unicellular organism which reproduces by this method.
(g) Name tow non-flowering plants which reproduce by this method.

Answer:

(a) The common name of the organism is bread mould, and its scientific name is Rhizopus.
(b) Spores of fungus are present in the air in their inactive form. When these spores get the favourable condition like a moist bread, they germinate and grow into new organisms.
(c) The fine, thread-like projections on the surface of the bread are known as hyphae.
(d) The knob-like structures are sporangium, which contain the spores.
(e) This method of reproduction is known as spore formation.
(f) Mucor fungus reproduces by the method of spore formation.
(g) Ferns and mosses are two non-flowering plants which reproduce by this method.

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Question 83:

A scientist removed some cells from the growing point of a plant and placed it in a suitable medium leading to the formation of a shapeless lump of mass X. X is then transferred to another medium which stimulates it to develop roots. When X with developed roots is placed in a yet another medium, then it develops shoots to form tiny plantlets. These plantlets can then be transplanted in pots or soil where they can grow to form mature plants.
(a) What is the shapeless lump of mass X known as?
(b) What name is given to this method of producing new plants?
(c) The growth medium used in this method contains plant nutrients in the form of a 'jelly'. Name this jelly.
(d) What is the general name of chemicals used to stimulate the growth of plant cells and development of roots and shoots?
(e) Name any two plants which are produced by this method.
(f) State any two advantages of this method of producing plants.
(g) What is the other name of this method [other then that given in (b) above]?

Answer:

(a) The shapeless lump of mass X is known as callus.
(b) This method of producing new plants is known as tissue culture.
(c) The jelly is called agar.
(d) The chemicals used to stimulate the growth of plant cells and fasten the development of roots and shoots are called plant hormones.
(e) Orchids and dahlia are two flowering plants that are propagated by this method.
(f) The main advantage of this technique is that it is extremely fast, and the plantlets are obtained in a few weeks. Secondly, this method produces disease-free plantlets.
(g) The other name of this technique is micropropagation.

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Question 84:

The stem of a fruit tree X fixed in soil is cut in a slanting way. The upper part of stem of another fruit tree Y of different variety of same species is also cut in a slanting way. The cut stem of tree Y, without roots but having some leaves, is placed over the rooted cut stem of tree X in such a way that their cut surfaces fit together properly. While joining the two cut stems, care is taken to make sure that the layer Z of one cut stem is in contact with layer Z of the other cut stem. The joint of cut stem is bound tightly with a piece of cloth and covered properly with polythene. Soon the cut heals and the two stems grow together and become one fruit tree producing leaves, flowers and fruits.
(a) What is the name of this method of producing plants or trees?
(b) What name is given to the cut stem of tree X having roots?
(c) What name is given to the cut stem of tree Y which has no roots but has some leaves?
(d) Name the layer Z.
(e) Why should the layer Z of one cut stem be in contact with the layer Z of the other cut stem?
(f) Name any four fruit trees which are usually bred by this technique.
(g) State any one advantage of producing fruit trees by this technique.

Answer:

(a) This method of propagating plants or trees is known as grafting.

(b) The segregated stem of tree X is termed as stock.

(c) The segregated stem of tree Y that is devoid of roots, is termed as scion.

(d) The layer Z is called the cambium layer.

(e) The cambium layer (Z) of both the stems should be joined, as they are responsible for the growth of a new tree.

(f) Four trees which are propagated by this method are apple, pineapple, orange and grapes.

(g) The main advantage of cultivating plants by this method is that the graft will have the most desirable features of both the parts, i.e. the stock and the scion.

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Question 85:

A small part of the shoot of a plant is removed with a sharp knife. When the lower end of this small part of  the shoot is buried in moist soil, it gradually develops roots and shoots and grows to become a new plant.
(a) What is the name of this method of propagating plants?
(b) What care should be taken while removing a small part of the shoot from the parent plant with a knife?
(c) Name any two plants which provide us with food directly or indirectly and are grown by this method.
(d) Give one advantage of this method of producing new plants.
(e) State whether it is a sexual method of reproduction or an asexual method. Why?
(f) What special name can be given to the genetically identical new plants produced by this technique?

Answer:

(a) This method of propagating plant is known as cutting.
(b) While removing a small part of the shoot from the parent plant using a knife, one has to be careful about the fact that the shoot has some buds on it.
(c) Sugarcane and banana are those two plants which are propagated by this method, and are consumed as food.
(d) Using this method, many new plants can be produced from one plant. This is one of the advantages of this method.
(e) This is an asexual method of reproduction, as it involves only one parent and no gamete formation.
(f) The genetically identical plants produced by this method are called clones.

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Question 86:

When the branches of a plant growing in the field are pulled towards the ground and a part of them is covered with moist soil (leaving the tips of the branches exposed above the ground), then after some time new roots develop from the parts of branches buried in the soil. On cutting these branches from the parent plant, new plants are produced from the cut parts of branches which had developed roots.
(a) What is this method of propagation of plants known as?
(b) What type of branches should a plant have to be able to be propagated by this method?
(c) Name any two plants which are grown for their flowers and propagated by this method.
(d) Name any two plants which are grown for their fruits and propagated by this method
(e) Name one plant which gets propagated by this method naturally by forming runners (soft horizontal stems running above the ground).

Answer:

(a) This method of propagating plants is known as layering.
(b) To get propagated by this method, a plant should have soft horizontal branches.
(c) Jasmine and China rose are the two plants that are propagated by this method for their flowers.
(d) Guava and lemon are the two plants that are propagated by this method for their fruits.
(e) Strawberry gets propagated naturally by this method by forming runners.



Page No 147:

Question 87:

A worm X found in freshwater and slow-moving streams has been accidently cut into three pieces. It was observed that in due course of time, each cut piece of the worm develops to become a complete worm by growing all the missing parts.
(a) Name the worm X which can exhibit this phenomenon of making complete worm from its cut body parts.
(b) Name another organism Y which possesses the same characteristic of growing fully from its cut body parts.
(c) What is the name of this process in which a complete organism is formed from its cut body part.
(d) State whether X and Y are unicellular and/or multicellular organisms.
(e) Can a dog be produced completely form its cut body part (say, a cut tail) just like organisms X and Y? Why?

Answer:

(a) The worm X is Planaria.

(b) The organism Y which posses the same characteristic as of X is Hydra.

(c) The process in which a complete organism is formed from a lost body part of its parent is regeneration.

(d) X and Y are multicellular organisms.

(e) A dog cannot be produced from a lost body part like its tail, as this animal has a high degree of organisation in its body. 

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Question 88:

A thickened underground stem X of a plant which is swollen with stored food has a number of points Y on its surface. When the old stem X is planted in the soil of a field in the next growing season, then each point Y present on its surface grows into a new plant.
(a) What is the general name of the underground stems like X?
(b) Give one example of X.
(c) What are points Y present on X known as?
(d) Is it necessary to plant the whole of stem X in the ground to obtain its new plants? Explain your answer.
(e) What is the name of this method of reproduction of plants?
(f) What is the advantage of growing new plants from the underground stems like X?

Answer:

(a) Tuber is the general name of those underground stems like X.

(b) Potato is an example of X.

(c) The points Y present on X are known as buds.

(d) No, it is not necessary to plant the entire stem X in the ground. This stem has many buds (Y) on it that form the vegetative organ of reproduction.

(e) This method of reproduction is termed as vegetative propagation.

(f) The main advantage of this method is that it is comparatively faster to growing plants from seeds.

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Question 89:

A filamentous alga X is found in ponds, lakes and slow-moving streams. The filament of this alga simply breaks into two (or more) pieces on maturing and each piece then grows to become a complete new alga.
(a) Name an alga which X is likely to be.
(b) What is the colour of X?
(c) What is the method of forming new algae by the breaking of parent alga known as?
(d) An Amoeba also breaks up to form two daughter Amoebae. What is the difference in the splitting of Amoeba and splitting of this alga as a method of reproduction?
(e) Name one marine animal which reproduces in the same way as alga X.

Answer:

(a) The alga X is likely to be Spirogyra.

(b) The alga is green in colour.

(c) This mode of forming new alga from the breaking-up of the parent alga is termed as fragmentation.

(d) The splitting of Amoeba is termed as fission, which occurs only in unicellular organisms. The splitting of alga is termed as fragmentation, which occurs only in multicellular organisms.

(e) Sea anemone reproduces in the same way as the alga X.

Page No 147:

Question 90:

When a broken piece of the stem of a plant X is planted in the soil, a new plant grows from it in a week's time. The leaves of plant X also have many small entities Y in their margins which can fall to the ground alone or alongwith leaves and grow into new plants.
(a) Name a plant which X could be.
(b) What are the entities Y present on the leaves of X known as?
(c) Name a plant other than X which can be reproduced from its leaves.
(d) Name a common plant grown in many homes which can be propagated from its broken stems like plant X.
(e) Name a kind of dormant organs present in dry stems of old grass plants lying in the fields which get activated and produce green grass plants after the rains.

Answer:

(a) The plant X is Bryophyllum.

(b) The entities, Y, present on the leaves of X are known as buds.

(c) Other than X, Begonia can also be reproduced by its leaves.

(d) Money plant can be propagated from its broken stem similar to plant X.

(e) Buds are present in the dry stems of the old grass lying in the fields. These buds get activated after a spell of shower, and  start producing new grasses.



Page No 168:

Question 1:

Where are a plant's sex organs located?

Answer:

A plant's sex organs are located in its flower.

Page No 168:

Question 2:

What is the function of a flower?

Answer:

The function of a flower is to carry out sexual reproduction in plants through the formation of male and female gametes. Flowers ensure that the gametes fertilise to form seeds that further help in reproduction of plants.

Page No 168:

Question 3:

What are the reproductive organs in a flower?

Answer:

Stamen and carpel are the reproductive organs of a flower.

Page No 168:

Question 4:

What is the name of :
(a) male part of a flower?
(b) female part of a flower?

Answer:

(a) The male part of a flower is called stamen.
(b) The female part of a flower is called carpel.

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Question 5:

What is the name of female organ of a flower (other than carpel)?

Answer:

Pistil is the other name of the female organ of a flower.

Page No 168:

Question 6:

What is the other name of sex cells?

Answer:

The other name of sex cells is gametes.

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Question 7:

What is the name of sex cells (other than gametes)?

Answer:

The male sex cells are called sperms and the female reproductive cells are called eggs.

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Question 8:

Name the male and female gametes in animals.

Answer:

The male gametes are called sperms and the female gametes are called ovum or eggs.

Page No 168:

Question 9:

Where is the male gamete formed :
(i) in humans?
(ii) in flowering plants?

Answer:

(i) In humans, the male gametes are formed in the testes.
(ii) In flowering plants, the male gametes are formed in the anther of the stamen.

Page No 168:

Question 10:

Where is the female gamete formed :
(i) in humans?
(ii) in flowering plants?

Answer:

(i) In humans, the female gametes form in the ovaries.
(ii) In flowering plants, the female gametes form in the ovary of the pistil.

Page No 168:

Question 11:

Name two animals which undergo external fertilisation and two animals which undergo internal fertilisation?

Answer:

Fish and frog undergo external fertilisation.
Human and lion undergo internal fertilisation.

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Question 12:

Define sexual reproduction.

Answer:

The method of reproduction in which the male sex cell fuses with the female reproductive cell, to produce a zygote which develops into a new organism, is termed as sexual reproduction.

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Question 13:

Do all organisms give birth to individuals like humans?

Answer:

No, all organisms do not give birth to individuals like humans. Some animals lay eggs. For e.g., hen, duck, most snakes.

Page No 168:

Question 14:

Write the full forms of the following as they occur in biology :
(i) STD
(ii) AIDS
(iii) HIV

Answer:

(i) STD: Sexually Transmitted Diseases
(ii) AIDS: Acquired Immunodeficiency Syndrome
(iii) HIV: Human Immunodeficiency Virus

Page No 168:

Question 15:

What is the causative organism for the following diseases?
(i) Gonorrhoea
(ii) Syphilis
(iii) AIDS

Answer:

(i) Gonorrhoea is caused by bacteria.
(ii) Syphilis is caused by bacteria.
(iii) AIDS is caused by virus.

Page No 168:

Question 16:

What are the organs in humans which produce the gametes?

Answer:

In males, testes produce male gametes called sperms and in females, ovaries produce female gametes called eggs.

Page No 168:

Question 17:

(a) What are the male sex cells in humans called?
(b) Name the organ which produces male sex cells.

Answer:

(a) The male sex cells in humans are called sperms.
(b) Testes produce male sex cells.

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Question 18:

(a) What are the female sex cells in humans called?
(b) Name the organ which produces female sex cells.

Answer:

(a) The female sex cells in humans are called ova or eggs.
(b) Ovaries produce the female sex cells.

Page No 168:

Question 19:

Which part of the human body :
(a) produces sperms?
(b) produces ova?
(c) passes sperms from a man to a woman?

Answer:

(a) Testes produce sperms in the human body.
(b) Ovaries produce ova.
(c) The penis passes the sperms from a man to a woman.

Page No 168:

Question 20:

(a) What do the testes in a man produce?
(b) What do the ovaries in a woman produce?

Answer:

(a) The testes of a man produce male gametes called sperms.
(b) The ovaries of a woman produce female gametes called eggs or ova.

Page No 168:

Question 21:

(a) Where in the human body does an ovum get fertilised?
(b) Where does a fertilised ovum develop into a baby in the human body?

Answer:

(a) The ovum gets fertilised in the oviduct or fallopian tube of a female body.
(b) A fertilised ovum gets implanted into the wall of uterus and develops into a baby in the uterus.

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Question 22:

Name the liquid that contains sperms.

Answer:

The seminal fluid or semen is the fluid that contains sperms.

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Question 23:

What is the name of the process in which thickened uterus lining alongwith blood vessels is removed from the body of a human female through vaginal bleeding?

Answer:

Menstruation is the periodic process in which the thickened uterus lining, along with blood vessels, is removed from the body of a female through vaginal bleeding.

Page No 168:

Question 24:

(a) For how much time does menstruation last in human females (or women)?
(b) What is the frequency of menstrual cycle in human females (or women)?

Answer:

(a) The menstruation cycle lasts for 3-5 days in a female.
(b) The frequency of the menstrual cycle is once, every 28 days.

Page No 168:

Question 25:

Fill in the following blanks with suitable words :
(a) Pollen grains contain ............ gametes of a plant.
(b) Ovules contain ......... gametes of a plant.
(c) The ovary of a flower becomes ....... after fertilisation.
(d) The ovule becomes a .......... after fertilisation.
(e) Flowering plants reproduce by ...........method of reproduction.
(f) The female organ of reproduction in the flower is the...........
(g) The male organ of reproduction in the flower is the.......... .
(h) The name of the structure in the flower in which the male gamete is formed is...........
(i) The.......... at the base of the carpel contains egg cells.
(j) The term used to refer to the transfer of pollen from the stamen of one flower to the carpel of another flower of the same species is...........
(k) The cells involved in sexual reproduction are called .............
(l) Fusion of gametes gives rise to a single cell called ............
(m) The process of fusion of gametes is called .............
(n) A multicellular animal starts its life from a ........... through sexual reproduction.
(o) The union of a sperm nucleus with an egg nucleus is known as.......... and results in a .........egg.
(p) The menstrual cycle is controlled by.............

Answer:

(a) Pollen grains contain male gametes of a plant.
(b) Ovules contain female gametes of a plant.
(c) The ovary of a flower becomes a fruit after fertilisation.
(d) The ovule becomes a seed after fertilisation.
(e) Flowering plants reproduce by the sexual method of reproduction.
(f) The female reproductive organ of a flower is carpel.
(g) The male sex organ of a flower is stamen.
(h) The structure of a flower in which the male gamete is formed is pollen.
(i) The ovary at the base of the carpel contains egg cells.
(j) The term used to refer to the transfer of pollen from the stamen of one flower to the carpel of another flower of the same species is pollination.
(k) The cells involved in sexual reproduction are called gametes.
(l) Fusion of gametes gives rise to a single cell called zygote.
(m) The process of fusion of gametes is called fertilisation.
(n) A multicellular animal starts its life from a zygote in sexual reproduction.
(o) The union of a sperm nucleus with an egg nucleus is known as fertilisation and it results in a diploid egg.
(p) The menstrual cycle is controlled by hormones.



Page No 169:

Question 26:

(a) What are gametes?
(b) In which sort of reproduction are gametes involved?
(c) What is formed when two gametes fuse?
(d) What is this act of fusion called?

Answer:

(a) The sex cells or reproductive cells, which fuse together to reproduce a new organism, are called gametes.

(b) Gametes are involved in sexual reproduction.

(c) Two gametes fuse to form a zygote.

(d) The act of fusion of gametes is called fertilisation.

Page No 169:

Question 27:

(a) Write the names of (a) male sex hormone, and (b) female sex hormones.
(b) What name is given to the fusion of sperm and ovum?
(c) Name the tissue through which the foetus gets all the requirements form the mother's body.

Answer:

(a) (i) Testosterone is the male sex hormone.
     (ii) Oestrogen is the female sex hormone.

(b) The fusion of sperm and ovum is termed as fertilisation.

(c) A foetus fulfils all its requirements from the mother's body through the tissue called placenta.

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Question 28:

(a) Draw a neat sketch of the stamen of a flower. Mark in it filament and anther.
(b) Draw a neat sketch of the carpel of a flower. Mark in it stigma, style and ovary.
(c) What is made in (i) anther, and (ii) ovary, of a flower?

Answer:

(a) Stamen of a flower

(b) Carpel of the flower



(c) (i) Male gametes called pollen grains are produced in the anther.
    (ii) Female gametes called eggs are produced in the ovary.

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Question 29:

(a) Explain the terms 'self pollination' and 'cross-pollination'?
(b) How do the insects help in cross-pollination?
(c) How is the process of pollination different from fertilization?

Answer:

(a) In self pollination, pollens from the anther are transferred to the stigma of the same flower or another flower of the same plant.
In cross pollination, pollens from the anther of one flower are transferred to the stigma of the another flower of another plant but of the same species.

(b) When an insect sits on a flower, the pollens from the anther stick to their wings and limbs. The same insect when sits on another flower, the pollens from its body get transferred to the stigma of that flower thereby affecting pollination.

(c) Pollination is the transfer of male gametes onto the female gametes, while fertilisation is the fusion of these two gametes.

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Question 30:

(a) Explain the term 'fertilisation'.
(b) Give some examples of different modes of fertilisation in nature?
(c) What type of fertilisation takes place in (i) fish, and (ii) birds?

Answer:

(a) Fertilisation is the fusion or union of male and female gametes to form a zygote.

(b) There are two modes of fertilisation, i.e., external fertilisation as seen in case of fishes and frogs, and internal fertilisation that happens in humans, dogs, etc.

(c) (i) In fish, external fertilisation takes place.
    (ii) In birds, internal fertilisation takes place.

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Question 31:

(a) What are the male and female gonads in human beings? Mention their functions.
(b) State the advantages of sexual reproduction over asexual reproduction.

Answer:

(a) The male gonads are the testes; they produce sperms. The female gonads are ovaries and they produce eggs or ova.
(b) In sexual reproduction, a variation appears in the offsprings due to blending of two kinds of genetic material, one from each parent, whereas in case of asexual reproduction, only one parent is involved in the reproduction of a new organism, such that the chances of appearance of variations in the progeny are minimized and variations are caused only due errors in replication of DNA.  

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Question 32:

Describe the various steps involved in the sexual reproduction in animals. Draw labelled diagrams to show the fertilisation of an ovum (or egg) by a sperm to form a zygote.

Answer:

The various steps involved in the sexual reproduction in animals are as follows:

  • Male gametes called sperms are produced by the male parent.
  • Female gametes called eggs are produced by the female parent.
  • The sperm fuses with the egg to form zygote. This process is termed as fertilisation.
  • The zygote divides repeatedly to form a large number of cells. Ultimately it grows and develops into a baby.

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Question 33:

Why does menstruation occur? Describe the menstrual cycle in human females (or women).

Answer:

Menstruation occurs due to the rupture or removal of the inner, thick and soft lining of the uterus when fertilisation does not take place.

The menstrual cycle:

  • After a female attains puberty, every month one of the ova in the ovaries matures and gets released, once in every 28 days, by the process of ovulation.
  • The lining of the uterus becomes thick and spongy before ovulation in order to receive the fertilised egg. If the egg is not fertilised, this lining of the uterus breaks and comes out of the vagina in the form of blood and tissue; this flow of tissue and blood from vagina is known as menstrual flow.
  • This occurs on the 14th day of ovulation and lasts for 3-5 days.
  • After this flow stops, the uterus starts preparing itself, again for the fertilised egg. If it does not receive the fertilised egg, the same set of events are repeated.

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Question 34:

(a) Write the various steps involved in the sexual reproduction in plants.
(b) Name two plants which reproduce by sexual reproduction method and two plants which reproduce by asexual reproduction methods.

Answer:

(a) The various steps involved in the sexual reproduction in plants are as follows:

  • Male and female gametes are formed in the anther and the ovule respectively.
  • Male gametes fertilise female gametes present in the ovules.
  • The fertilised eggs grow and develop into seeds.
  • These seeds germinate under favourable conditions to form plants.
(b) Sexual reproduction takes place in mango and rose plants. Ferns and mosses propagate by asexual reproduction.

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Question 35:

(a) What type of plants reproduce by sexual reproduction method?
(b) What is a seed? What are the parts of a seed? Explain with the help of a labelled diagram.

Answer:

(a) The plants with flowers i.e. flowering plants, reproduce by sexual reproduction.

(b) Seed is the reproductive unit of a plant. The various parts of a seed are plumule, radicle and cotyledon.

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Question 36:

(a) What is puberty? Who attains puberty at an earlier age in human beings : male or female (boy or girl)?
(b) Mention two functions each of (i) human testes, and (ii) human ovaries.

Answer:

(a) Puberty is the age at which males and females attain sexual maturity. In human beings, females attain puberty earlier than males.

(b) (i) Testes produce male gametes (sperms) and the hormone testosterone which is responsible for secondary sexual changes in males. 
(ii) Ovaries produce female gametes (ova or egg) and the hormone oestrogen which is responsible for secondary sexual changes in females.

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Question 37:

(a) What is gestation period? How much is the gestation period in humans?
(b) Name one method of contraception which also protects against sexually transmitted diseases.
(c) Name one sexually transmitted disease for which no definite cure has been found so far. What is the causative organism of this disease?

Answer:

(a) The period of pregnancy is called the gestation period. It is of 9 months in humans.

(b) Barrier methods (e.g., condom)  is one method of contraception, which also protects from sexually transmitted diseases.

(c) AIDS is a sexually transmitted disease for which no definite cure has been found so far. HIV is the causative organism of this disease.

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Question 38:

What are the three types of methods used for birth control (or regulating child birth)? Give one example of each type.

Answer:

The three types of methods used for birth control are:

  • Barrier method, e.g., condom
  • Chemical method, e.g., oral pills
  • Surgical method, e.g., vasectomy

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Question 39:

(a) What is the name of surgical method of birth control in human males in which the sperm ducts are cut and ligated (tied) at both ends?
(b) What is the name of surgical method of birth control in human females in which the oviducts are cut and ligated (tied) at both ends?
(c) Name the contraceptive device used by the human males which acts as a sheath over the male organ and traps the sperms in it.
(d) Name the contraceptive device used by human females which is put over the cervix.

Answer:

(a) The surgical method of birth control in human males in which the sperm ducts are cut and ligated (tied) at both ends is called vasectomy.

(b) The surgical method of birth control in human females in which the oviducts are cut and ligated (tied) at both ends is called tubectomy.

(c) The contraceptive device used by human males which acts as a sheath over the male organ and traps the sperms in it is called a condom.

(d) The contraceptive device used by human females which is put over the cervix is known as diaphragm.



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Question 40:

(a) Describe the surgical methods of birth control (i) for men, and (ii) for women.
(b) Name two devices used in the barrier method of birth control.

Answer:

(a) (i) The surgical method of birth control for men is called vasectomy in which a small portion       of the vas deferens is cut and loose ends are ligated (sealed) to prevent sperms from       coming out.
      (ii) The surgical method of birth control for women is called tubectomy in which a portion of        oviducts are cut and their ends are ligated to prevent the release of eggs.
(b) The two devices used in the barrier method of birth control are condoms and diaphragms.

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Question 41:

(a) What is meant by contraception? What are the different methods of contraception?
(b) What is done in the contraception method known as (i) vasectomy, and (ii) tubectomy?
(c) If a woman is using copper-T for contraception, will it protect her from sexually transmitted diseases?

Answer:


(a) Contraception is defined as the prevention of pregnancy in females by preventing fertilisation. The barrier method, chemical method and surgical method are some of the methods of contraception.

(b) (i) The surgical method of birth control for men is called vasectomy, in which a small         portion of the vas deferens is cut and their ends are ligated (sealed) to prevent sperms         from coming out.
     (ii) The surgical method of birth control for women is called tubectomy, in which a portion         of the oviducts are cut and their ends are ligated to prevent the release of eggs.

(c) No, using copper-T will not protect a woman from sexually transmitted diseases (STDs).

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Question 42:

(a) What are sexually transmitted diseases? Give two examples of sexually transmitted diseases.
(b) Which method of contraception prevents fertilised egg from being implanted in the uterus?

Answer:

(a) The diseases that are spread through sexual contact with an infected person is termed as a sexually transmitted disease. Examples: AIDS and syphilis.

(b) IUCD such as copper-T prevents fertilised egg from being implanted into the uterus.

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Question 43:

(a) What substances are contained (i) in oral pills, and (ii) in vaginal pills, used as contraceptives? How do they work?
(b) How does copper-T prevent pregnancy?
(c) Name the disease caused by HIV.

Answer:

(a) (i) Oral pills have hormones that stop the ovaries from releasing ovum.
     (ii) Vaginal pills have spermicides which kill the sperms.

(b) Copper-T prevents the implantation of fertilised egg in the uterus and, thus, prevents pregnancy.

(c) AIDS is caused by HIV.

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Question 44:

(a) What is the name of surgical method of birth control (or preventing pregnancy) which is carried out (i) in men, and (ii) in women?
(b) Name the part of a seed which (i) contains stored food (ii) grows into root, and (iii) grows into shoot.

Answer:

(a) The  surgical method for birth control (or preventing pregnancy) which is carried out
    (i) in men is known as vasectomy and
    (ii) in women is known as tubectomy.
(b) The part of the seed which 
    (i) contains stored food is called cotyledon
    (ii) grows into roots is called radicle and
   (iii) grows into shoot is called plumule.

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Question 45:

Explain how, offsprings and parents of organisms reproducing sexually have the same number of chromosomes.

Answer:

Gametes of sexually-reproducing animals have half the number of chromosomes as that of the parents. Hence, during fertilisation, when two gametes i.e. male and female gametes, fuse, the offspring produced will have the same amount of DNA or the same number of chromosomes as that of the parent.

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Question 46:

In tobacco plant, the male gametes have 24 chromosomes.
(i) What is the number of chromosomes in the female gamete?
(ii) What is the number of chromosomes in the zygote?

Answer:

(i) The number of chromosomes in a female gamete is equal to the number of chromosomes in a male gamete, i.e., 24.
(ii) The zygote is formed by the fusion of a male and a female gamete. Therefore, the number of chromosomes in a zygote is twice as many as that of a gamete, i.e., 48.

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Question 47:

(a) What would be the ratio of chromosome number between an egg and its zygote?
(b) Distinguish between a gamete and a zygote.

Answer:

(a) The ratio of chromosome numbers between an egg and its zygote is 1 : 2. The number of chromosomes in a zygote is twice the number of chromosomes in an egg.

(b)

Gamete Zygote
A gamete is a sex cell and is of two types: male and female.  A zygote is formed by the fusion of a male and a female gamete.
It has 24 chromosomes. It has 48 chromosomes.

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Question 48:

(a) Fertilisation in humans can occur only once in a month. Why?
(b) What is the scientific name of (i) womb, and (ii) birth canal?

Answer:

(a) A human female produces one egg a month through the process of ovulation therefore, fertilisation can occur only once in a month.
(b) The scientific name of (i) womb is uterus and (ii) birth canal is vagina.

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Question 49:

The diagram shows female reproductive system. Name the parts labelled A to D.
(a) In which part do the sperms enter?
(b) Which part releases the egg?
(c) In which part does fertilisation take place?
(d) In which part does the foetus develop?

Answer:

Part A is the oviduct; B is the ovary; C is the uterus and D is the vagina.

(a) Sperms enter through the vagina (D).
(b) The ovary (B) releases the eggs.
(c) Fertilisation takes place in the oviduct (A).
(d) The foetus develops in the uterus (C).

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Question 50:

Why is it an advantage for the testes to be situated in the scrotal sac outside the main body cavity? Can you think of one disadvantage?

Answer:

The formation of sperm requires a temperature lower than that of the body. Therefore, the testes are situated in the scrotal sac outside the main body cavity providing them a lower temperature.

Their position outside the main body cavity makes the testes prone to injury.

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Question 51:

Which structures in human female are equivalent to the following structures in the male?
(a) testes
(b) vas deferens
(c) penis
In each case say in what respect the structures are equivalent?

Answer:

(a) The ovary. Both make gametes.
(b) The fallopian tubes. Both act as ducts for carrying and transporting gametes.
(c) The Vagina. The penis discharge sperms and the vagina receives it.

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Question 52:

People who die from AIDS are not killed by the virus itself. Explain.

Answer:

HIV affects the immune system of an infected person. This weakens the body making it unable to fight any infection. Therefore, people who die from AIDS are not killed by the virus itself but by other infections.

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Question 53:

(a) What is the life support system of a fetus?
(b) How long does a human baby take to develop before birth?
(c) What is the name of the narrow opening between the uterus and the vagina.

Answer:

(a) The placenta is the life support system of a foetus.
(b) A human baby takes 9 months to develop before birth.
(c) The cervix is the narrow opening between the uterus and the vagina.

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Question 54:

(a) What is meant by 'unisexual flowers' and 'bisexual flowers'? Give two examples of each.
(b) What is pollination? How does pollination occur?
(c) Describe the process of fertilisation in a flower with the help of labelled diagrams.
(d) What changes take place in the flower after fertilisation which lead to the formation of seeds and fruit?

Answer:

(a) Unisexual flowers have only one kind of sex organ, either stamen or pistil, e.g., flowers of papaya and water melon. Bisexual flowers have both stamen and pistil, e.g., flowers of Hibiscus and mustard.

(b) Pollination is the transfer of pollen grains from the stamen to the stigma of the pistil. Pollination occurs when pollen grains are carried from the anther to the stigma by insects, birds, wind or water.

(c) Fertilisation occurs after pollen grains fall on the stigma. Upon falling on the stigma, the pollen grains burst and grow a pollen tube that passes downwards from the style to the ovary containing the ovule. The male gamete present in the pollen moves downward through the pollen tube and reaches the ovule. This gamete fuses with the egg to form a zygote. This process is known as fertilisation.



(d) After fertilisation, the eggs in the ovule grow and develop into zygote. The ovule develops a thick coating and forms the seed, whereas the ovary develops into a fruit.

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Question 55:

(a) Draw a neat diagram of a flower showing its various parts. In this diagram mark stem, receptacle, sepals, petals, stamen and carpel.
(b) What name is given to (i) all the petals of a flower, and (ii) all the sepals of a flower?
(c) What are (i) stamen, and (ii) carpel, in a flower?
(d) What is the other name of carpel of a flower?
(e) What is the name of yellow powdery substance present in the anther of a flower?

Answer:

(a)  A flower

(b) (i) The corolla
     (ii) The calyx

(c) (i) Stamen is the male reproductive organ in a flower.
     (ii) Carpel is the female reproductive organ in a flower.

(d) The other name of carpel is pistil.

(e) The yellow powdery substance present in the anther of a flower are pollen grains.



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Question 56:

(a) What changes are seen in boys at the time of puberty?
(b) Name the organs which produce sperms in human males.
(c) Draw a labelled diagram of the human male reproductive system. With the help of this diagram, describe the working of human male reproductive system?
(d) What is the role of seminal vesicles and prostrate gland in human male reproductive system?

Answer:

(a) Boys at puberty develop hair in their armpits, chest, face and around the pubic region. They become muscular and their voices crack. Penis and testes become large. The testes begins producing sperms.

(b) Testes produce sperms in human males.

(c) Testes are the primary reproductive organs of human males. They are located in the scrotum outside the body. They produce sperms, which engage into a coiled tube called epididymis and get stored there. Sperms are then carried away through the vas deferens, which joins the urethra. On way to the urethra, sperms also receive secretions from the seminal vesicles and the prostrate gland. The urethra carries sperms to the penis, which opens outside the body.



(d) The seminal vesicles and the prostrate gland produce seminal fluid, which then gets mixed with sperms to form semen.

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Question 57:

(a) What changes are seen in girls at the time of puberty?
(b) Name the organs which produce ova (or egg cells) in human females.
(c) Draw a labelled diagram of the human female reproductive system. With the help of this diagram, explain the working of human female reproductive system.
(d) Describe the process of fertilisation in humans and development of embryo briefly.

Answer:

(a) Girls at puberty develop hair in their armpits and around the pubic region. The mammary glands develop and become large. The hips get broadened and extra fat gets deposited on various parts of the body. The ovaries start releasing eggs; the vagina enlarges and menstruation starts.

(b) Ovaries in humans produce ova, which are also known as egg cells.

(c) Ovaries are the primary reproductive organs in females, which produce ovum or egg. Above the ovary lies the oviducts, or fallopian tubes, which are connected to the uterus. The eggs move into the oviduct from the ovaries, where it gets fertilised by a sperm. The fertilised ovum develops into a baby in the uterus. The uterus is connected to the vagina by the cervix. The vagina opens outside the body and receives sperms.



(d) In humans, fertilisation is internal. Sperms are introduced in the vagina by the penis during copulation. The sperms move up through the cervix, enter the uterus and pass into the oviducts. In the oviducts, the egg gets fertilised by one of the sperms. Zygote is formed by the fusion of a sperm and an egg. This zygote divides multiple times to form a hollow ball of the cells called embryo.

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Question 58:

(a) What is ovulation? How often does it happen in human females?
(b) Where does fertilisation take place in human females?
(c) Explain why, fertilisation is possible if mating takes place during the middle of menstrual cycle.
(d) What is meant by implantation?
(e) What is placenta? What is its function?
(f) What joins embryo to placenta in mother's body?

Answer:

(a) Ovulation is the release of an ovum from the ovary. It happens once in 28 days in human females.

(b) Fertilisation takes place in fallopian tubes, or oviducts, in human females.

(c) Fertilisation is possible if mating takes place during the middle of the menstrual cycle because at that time, ovulation occurs and the egg is released.

(d) Implantation is the embedding of the embryo in the thick lining of the uterus.

(e) Placenta is a disc-like tissue that develops between the uterus wall and the embryo. It helps the embryo in meeting its requirements from the mother.

(f) The umbilical cord connects the embryo with the placenta in the mother's body.

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Question 59:

The anther contains :
(a) sepals
(b) ovules
(c) carpel
(d) pollen grains

Answer:

(d) pollen grains

An anther contains male gametes called pollen grains.

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Question 60:

Which of the following is not a part of the female reproductive system in human beings?
(a) ovary
(b) uterus
(c) vas deferens
(d) oviducts

Answer:

(c) vas deferens

The vas deferens is a part of the male reproductive system in humans.

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Question 61:

One of the following is not a part of the human male reproductive system. This is
(a) testis
(b) oviduct
(c) seminal vesicle
(d) prostrate gland

Answer:

(b) Oviduct
The oviduct is a part of the female reproductive system in humans.

Page No 171:

Question 62:

Which of the following is not a sexually transmitted disease?
(a) gonorrhoea
(b) hepatitis
(c) syphilis
(d) AIDS

Answer:

(b) Hepatitis

Hepatitis is not a sexually transmitted disease.

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Question 63:

Which of the following method of contraception protects a person from acquiring a sexually transmitted disease?
(a) oral pills
(b) condom
(c) copper-T
(d) surgery

Answer:

(c) Condom

Condom acts as a physical barrier during intercourse and protects a person from acquiring any sexually transmitted disease.

Page No 171:

Question 64:

In which one of the following birth control methods, a small portion of oviducts of a woman is removed by surgical operation and the cut ends are ligated?
(a) copper-T
(b) tubectomy
(c) vasectomy
(d) diaphragm

Answer:

(b) Tubectomy

The surgical method of birth control in females is termed as tubectomy.

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Question 65:

One of the following is a surgical method which prevents the sperms from reaching the ovum and pregnancy does not occur. This method is :
(a) IUCD
(b) vasectomy
(c) condom
(d) tubectomy

Answer:

(b) Vasectomy

Vasectomy is a surgical method of contraception that stops the sperms from reaching the ovum and thus, prevents pregnancy.

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Question 66:

Fertilisation results immediately in the formation of :
(a) a zygote
(b) an embryo
(c) a placenta
(d) a foetus

Answer:

(a) a zygote

A zygote is formed by the fertilisation of the egg and a sperm cell.

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Question 67:

Which one of the following best describes the function of the umbilical cord? It :
(a) feeds the embryo with digested substances.
(b) conveys nutrients and wastes to and from the embryo respectively
(c) removes waste matter from the embryo to the mother's blood.
(d) supplies oxygenated blood from the mother to the embryo.

Answer:

(b) conveys nutrients and wastes to and from the embryo, respectively.

The exchange of nutrients, oxygen and waste products between the embryo and the mother's body takes place through the umbilical cord.

Page No 171:

Question 68:

The sexually transmitted disease which is caused by bacteria is :
(a) malaria
(b) diarrhoea
(c) gonorrhoea
(d) AIDS

Answer:

(c) Gonorrhoea

Gonorrhoea is caused by bacteria, which spreads through sexual contact.

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Question 69:

AIDS is a deadly disease which is caused by :
(a) a protozoan
(b) a fungus
(c) a bacterium
(d) a virus

Answer:

(d) a virus
AIDS is caused by HIV.



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Question 70:

The advantage that internal fertilisation has over external fertilisation is that in internal fertilisation :
(a) new off-springs are exactly like the parent
(b) production of large numbers of gametes is unnecessary
(c) copulation and fusion of gametes is passive
(d) fewer individuals are produced

Answer:

(c) production of a large number of gametes is unnecessary.

In internal fertilisation, there is no need for the production of a large number of gametes as it provides a safe environment.

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Question 71:

The figure given alongside shows the human male reproductive organs. Which structures make sperms and seminal fluid?
(a) V makes sperms and X makes seminal fluid
(b) W makes sperms and Y makes seminal fluid
(c) X makes sperms and W makes seminal fluid
(d) Y makes sperms and V makes seminal fluid

Answer:

(d) Y makes sperms and V makes seminal fluid
Y represents the testes that produce sperms and V represents the prostrate gland that produces seminal fluid.

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Question 72:

In a flower, the parts that produce male and female gametes are respectively :
(a) sepal and anther
(b) filament and stigma
(c) anther and ovary
(d) stamen and style

Answer:

(c) anther and ovary

The anther produces pollen grains which are male gametes and the ovary produces ovules which are female gametes.

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Question 73:

Which of the following is the correct sequence of events of sexual reproduction in a flower?
(a) pollination, fertilisation, seed, embryo
(b) seed, embryo, fertilisation, pollination
(c) pollination, fertilisation, embryo, seed
(d) embryo, seed, pollination, fertilisation

Answer:

(c) pollination, fertilisation, embryo, seed

The pollens are transferred to the stigma by pollination, the gametes then fuse and under go fertilisation to form the zygote which develops into an embryo and, then, into a seed.

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Question 74:

The characteristics transmitted from parents to offspring are present in :
(a) cytoplasm
(b) ribosome
(c) golgi bodies
(d) genes

Answer:

(d) genes
Genes carry the genetic information and are responsible for the transmission of characteristics from parents to offspring.

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Question 75:

Characters that are transmitted from parents to offspring during sexual reproduction show :
(a) only similarities with parents
(b) only variations with parents
(c) both similarities and variations with parents
(d) neither similarities nor variations with parents

Answer:

(c) both similarities and variations with parents
Offsprings produced by sexual reproduction show similarities as well as variations with parents.

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Question 76:

The number of chromosomes in parents and offsprings of a particular species remains constant due to :
(a) doubling of chromosomes after zygote formation
(b) halving of chromosomes during gamete formation
(c) doubling of chromosomes after gamete formation
(d) halving of chromosomes after gamete formation

Answer:

b) halving of chromosomes during gamete formation

The gametes have half the number of chromosomes. After their fusion, the zygote thus formed has a full set of chromosomes. Therefore, the numbers of chromosomes in parents and offsprings of a particular species remain constant.

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Question 77:

The length of pollen tube depends on the distance between :
(a) pollen grain and upper surface of stigma
(b) pollen grain on upper surface of stigma and ovule
(c) pollen grain in anther and upper surface of stigma
(d) upper surface of stigma and lower part of style

Answer:

(b) pollen grains on upper surface of stigma and ovule.

Pollen grains land on the surface of the stigma. Hence, the pollen tube is formed so that the pollens can reach the ovules present in the ovary.

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Question 78:

Which of the following statements are true for flowers?
(i) flowers are always bisexual
(ii) they contain sexual reproductive organs
(iii) they are produced in all groups of plants
(iv) after fertilisation they give rise to fruits

(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (ii) and (iv)

Answer:

(d) (ii) and (iv)
Plants have sexual reproductive organs such as stamen and pistil. A fruit is formed after fertilisation in plants.

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Question 79:

The correct sequence of organs in the male reproductive system for the transport of sperms is:
(a) testis → vas deferens → urethra
(b) testis → ureter → urethra
(c) testis → urethra → ureter
(d) testis → vas deferens → ureter

Answer:

(a) testis → vas deferens → urethra

Sperms are produced in the testis and then carried away by the vas deferens to the urethra.

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Question 80:

In human males, the testes lie in the scrotum outside the body because it helps in the
(a) process of mating
(b) formation of sperms
(c) easy transfer of sperms
(d) all the above

Answer:

(b) formation of sperms

The testes lie outside the body in the scrotum because sperm production requires low temperature, which is provided by the scrotum.

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Question 81:

Which among the following are not the functions of testes at puberty?
(i) formation of germ cells
(ii) secretion of testosterone
(iii) development of placenta
(iv) secretion of estrogen

(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (iii) and (iv)

Answer:

(d) (iii) and (iv)
The development of the placenta and the secretion of oestrogen is done by human female body organs.



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Question 82:

During adolescence, several changes occur in the human body. Mark one change from the following associated with sexual maturation in boys :
(a) loss of milk teeth
(b) increase in height
(c) cracking of voice
(d) weight gain

Answer:

(c) cracking of voice
Cracking of voice in males is brought about by the male hormone testosterone, which is produced after sexual maturation.

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Question 83:

In human females, an event that indicates the onset of reproductive phase is :
(a) growth of body
(b) change in hair pattern
(c) change in voice
(d) menstruation

Answer:

(d) menstruation
When a female starts to menstruate, it indicates that she is sexually mature and can start her reproductive life.

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Question 84:

The offsprings formed as a result of sexual reproduction exhibit more variations because :
(a) sexual reproduction is lengthy process
(b) genetic material comes from two parents of different species
(c) genetic material comes from two parents of same species
(d) genetic material comes from many parents

Answer:

(c) genetic material comes from two parents of the same species
The sexual reproduction involves two parents of the same species. Thus, both of them contribute to the genetic material of the offspring and bring about the variations.

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Question 85:

One of the following occurs in the reproductive system of flowering plants as well as that of humans. This is :
(a) vas deferens
(b) anther
(c) ovary
(d) style

Answer:

(c) Ovary

The ovary of a flower has ovules and the ovary of a human female has eggs.

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Question 86:

Which among the following statements are true for unisexual flowers?
(i) They possess both stamen and pistil
(ii) They possess either stamen or pistil
(iii) They exhibit cross pollination
(iv) Unisexual flower possessing only stamens cannot produce fruits

(a) (i) and (iv)
(b) (ii), (iii) and (iv)
(c) (ii) and (iii)
(d) (i), (iii) and (iv)

Answer:

(b) (ii), (iii) and (iv)

Unisexual flowers have either male or female sexual organ. Therefore, they cannot self-pollinate and, thus, show cross pollination. The ovary of the female organ develops into a fruit after fertilisation, therefore flowers having stamens cannot produce fruits.

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Question 87:

Which of the following statements are true for sexual reproduction in flowering plants?
(i) it requires two types of gametes
(ii) fertilisation is a compulsory event
(iii) it always results in the formation of zygote
(iv) offsprings formed are clones

(a) (i) and (iv)
(b) (i), (ii) and (iv)
(c) (i), (ii) and (iii)
(d) (ii), (iii) and (iv)

Answer:

(c) (i), (ii) and (iii)

Sexual reproduction in flowers requires two types of gametes, namely pollen grains and ovules. The fusion of the gametes results in the formation of the zygote. This process is termed as fertilisation.

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Question 88:

One of the following process does not lead to the formation of clones. This is :
(a) fission
(b) fertilisation
(c) fragmentation
(d) tissue culture

Answer:

(b) fertilisation

Fertilisation is the fusion of two gametes in a sexual reproduction. It produces genetically different offsprings and does not lead to the formation of clones.

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Question 89:

In the figure given alongside, the parts marked A, B and C are sequentially :
(a) cotyledon, plumule and radicle
(b) plumule, radicle and cotyledon
(c) plumule, cotyledon and radicle
(d) radicle, cotyledon and plumule

Answer:

(c) plumule, cotyledon and radicle

A represents the plumule which forms the shoot. B represents the cotyledon and C represents the radicle which forms the roots.

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Question 90:

The correct sequence of reproductive stages occurring in flowering plants is
(a) gametes, zygote, embryo, seed
(b) zygote, gametes, embryo, seed
(c) seed, embryo, zygote, gametes
(d) gametes, embryo, zygote, seed

Answer:

(a) gametes, zygote, embryo, seed

Gametes of flowers fuse to form a zygote. This zygote develops into an embryo that later forms the seed.

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Question 91:

The part of a seed which grows and develops into root on germination is :
(a) cotyledon
(b) plumule
(c) follicle
(d) radicle

Answer:

(d) radicle

The radicle of a seed forms the root after germination.

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Question 92:

The male gametes in a flower and in a human are produced respectively in :
(a) stigma and ovary
(b) anther and style
(c) ovary and testes
(d) anther and testes

Answer:

(d) anther and testes

In flowers, the anther produces pollen grains. In humans, the testes produces sperms.

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Question 93:

The ratio of number of chromosomes in a human zygote and a human sperm is :
(a) 2 : 1
(b) 3 : 1
(c) 1 : 2
(d) 1 : 3

Answer:

(a) 2 : 1

The number of chromosomes in a human sperm is half the number of chromosomes in a zygote, i.e., their ratio is 2 : 1.

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Question 94:

The normal body cell of an organism contains 28 pairs of chromosomes. The number of chromosomes present in its germ cell will be
(a) 28
(b) 14
(c) 56
(d) 42

Answer:

(b) 14

A germ cell has 14 pairs of chromosomes i.e. half the number of chromosomes present in the normal body cell of an organism.

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Question 95:

The flask-shaped organ A at the centre of a flower is surrounded by a number of little stalks B having swollen tops which lie just inside the ring of petals.
(a) Name A. What are the various parts of A?
(b) Which part of A contains gametes?
(c) Name B. What is the swollen top of B known as?
(d) What does the swollen top of B contain?
(e) Out of A and B, which one is (i) male part, and (ii) female part of the flower?

Answer:

(a) A represents the carpel. The carpel is composed of the stigma, style and ovary.

(b) The ovary contains gametes in the form of ovules.

(c) B represents the stamen. The swollen tip of the stamen is the anther.

(d) The anther has pollen grains.

(e) The stamen (B) is a male part and the carpel (A) is a female part.



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Question 96:

When an insect sits on the flower of a plant then some particles A present in the top of little stalks in the flower attach to its body hair. When this insect now sits on the flower of another similar plant, then particles A attached to the hair of insect are put on the top of a flask-shaped organ at the centre of flower. The particle A grows a long tube B from the top of flask-shaped organ through which C moves down and reaches the bottom part of flask-shaped organ. Here C fuses with the nucleus of D contained in structure E. The fusion of C and D forms a new cell F which grows and develops into a seed of the plant.
(a) What are particles A? What is the process of transferring A from one flower to another flower of similar plant by the insect known as?
(b) What is the name of tube B?
(c) What is C which moves down through the tube B?
(d) Name D and E.
(e) What is F?

Answer:

(a) A represents pollen grains. The process of transferring pollen grains from one flower to another flower of the similar plant by insects is known as cross pollination.

(b) B represents the pollen tube.

(c) C is the male gamete which moves down through the pollen tube (B).

(d) D is the female gamete (or egg). The structure E represents the ovule.

(e) F is the zygote.

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Question 97:

When a human female reaches a certain age then vaginal bleeding occurs for a few days after regular time intervals.
(a) What is this process known as (i) in scientific terms, and (ii) in everyday language?
(b) At what approximate age this process starts in human females? When is the human female said to have attained at this stage?
(c) After how much time is this process repeated? For how many days does this process usually last?
(d) What does the onset of this process in human females signify?
(e) At which particular event in the life of a human female does this process stop temporarily but start again?
(f) At which approximate age of human female does this process stop permanently?

Answer:

(a) The process is termed as (i) menstruation scientifically and (ii) periods in everyday language.

(b) The approximate age for a girl to undergo her first period is between 10 and 12 years. A human female usually attains puberty or sexual maturity at this stage.

(c) This process is repeated after every 28 days and usually lasts for 3 to 5 days.

(d) The onset of this process signifies sexual maturity in human females.

(e) During pregnancy, this process stops temporarily but starts again eventually.

(f) At the age of about 45–50, this process stops permanently.

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Question 98:

X and Y are two human beings. The organ A in the reproductive system of X releases a mature gamete B once a month which goes into a tube-like structure C through a funnel-like opening. The organ D in the reproductive system of Y makes and releases gametes E which pass through a duct F and are introduced by an organ of Y, into the body of X. B and E fuse together in C to form a new cell G. The cell G divides repeatedly to form a ball of cells H which gets embedded in the lining of organ I of reproductive system of X where it grows and develops into a baby.
(a) Name (i) organ A, and (ii) gamete B.
(b) Write two names of tube-like structure C.
(c) Name (i) organ D, and (ii) gamete E.
(d) Write two names of duct F.
(e) Name (i) cell G (ii) ball of cells H, and (iii) organ I.
(f) Out of X and Y, which one is (i) male, and (ii) female?

Answer:

(a) (i) The organ A is the ovary and (ii) the gamete B is an egg.

(b) The tube-like structure C is the oviduct or the fallopian tube.

(c) (i) D represents the testes and (ii) the gamete E represents sperm.

(d) The duct F is the sperm duct or the vas deferens.

(e) (i) The cell G is the zygote, (ii) the ball of cells H is the embryo and (iii) the organ I is the uterus.

(f) (i) X represents female and (ii) Y represents male.

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Question 99:

When a fertilised egg E formed in the oviduct of a human female divides repeatedly to form an embryo, the embryo gets implanted in the thick and soft lining of the uterus. After this a disc-like special tissue T develops between the uterus wall and embryo through which all the requirements of the developing embryo (and foetus) are met from the mother's body, The embryo is connected to the tissue T through a string like structure S.
(a) What is the other name of fertilised egg cell E?
(b) What is the name of tissue T?
(c) Name the string-like structure S.
(d) Name two substances which pass from mother's blood to embryo through tissue T and, one type of substance which passes from embryo to mother's blood.
(e) What happens to S when the baby is born? Why?

Answer:

(a) The fertilised egg cell E is also called the zygote.

(b) The tissue T is the placenta.

(c) The string-like structure S is the umbilical cord.

(d) Oxygen and nutrients pass from the mother's blood to the embryo and carbon dioxide passes from the embryo to the mother's blood through the placenta (T).

(e) When a baby is born, the umbilical cord is still attached to the baby. It is cut and tied to separate the baby from the mother.

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Question 100:

When a female child is born, her ovaries already contain thousands of immature eggs (or ova) contained in immature structures A. On maturing, A bursts open and an egg shoots out of the ovary in a process called B. The process B starts in the females at puberty and occurs again and again after a time period x. Before every occurrence of process B, the inner lining of uterus becomes thick and soft with lots of blood vessels in it. When the egg cell gets fertilised by a sperm, then an event C occurs in the life of mature human female which lasts for time period y leading to the birth of baby. If, however, the egg cell released by the ovary does not get a sperm to fuse with, then the thick and soft inner lining of uterus breaks down and comes out of the female's body in an event called D. The occurrence of event D is controlled by chemical substances E.
(a) What are A?
(b) What is process B?
(c) What is the time period x?
(d) Name the event C.
(e) How much is the time period y?
(f) What is the name of process D?
(g) Name the chemical substances E.

Answer:

(a) A represents immature follicles.

(b) B represents the process of ovulation.

(c) The time period x is 28 days.

(d) The event C is pregnancy.

(e) The time period y is the gestation period, i.e., 9 months.

(f) D represents the process of menstruation.

(g) The chemical substance E is the hormone oestrogen.



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Question 101:

In the surgical method of birth control available for males, the structures A in the reproductive system are cut and ligated (tied up) at both ends. This prevents the reproductive cells B from coming out from the organs C where they are made in the male body. Since B cannot come out from the male body, they cannot fuse with cell D in the body of a female and hence pregnancy is prevented.
(a) What are structures A?
(b) What are cells B?
(c) Name the organs C.
(d) What is cell D?
(e) What is the name of this surgical procedure for birth control available to males?

Answer:

(a) A represents the vas deferens.

(b) B represents sperms.

(c) C represents the testes.

(d) The cell D is the egg or ova.

(e) The surgical method of birth control available to males is called vasectomy.

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Question 102:

In the surgical method of birth control available for human females, the structures P in the reproductive system are cut and ligated (tied up) properly at both ends. This prevents the reproductive cell Q released by an organ R from entering the structures P so that Q is not available to fuse with another reproductive cell S coming from the male reproductive system. In this way, pregnancy is prevented.
(a) What are structures P?
(b) What is cell Q?
(c) Name the organ R.
(d) What is the reproductive cell S?
(e) What is the name of this surgical method of birth control available to females?

Answer:

(a) The structure P is the oviduct.

(b) The cell Q are the eggs or ovum.

(c) The organ R is oviduct.

(d) The reproductive cell S is sperm.

(e) The surgical method of birth control available to females is tubectomy.

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Question 103:

The human males use a device X made of a very thin rubber sheet as a covering on the male organ to prevent pregnancy. This device traps the gametes Y in it. In order to prevent pregnancy, the human females use a device Z which is a circle of rubber with a metal spring around it. The device Z is put inside the vagina to cover the cervix. It stops Y from going into the uterus.
(a) What is device X?
(b) What are Y?
(c) Name the device Z.
(d) What is the general name of these methods of birth control (or preventing pregnancy)?
(e) The use of which contraceptive device, X or Z, can protect the persons from sexually transmitted diseases?

Answer:

(a) The device X is condom.

(b) Y represents sperms.

(c) The device Z is copper-T.

(d) The general name of these methods of birth control is called barrier method or IUCD (Intrauterine Contraceptive Device).

(e) Using condoms (X) during sexual intercourse can protect a person from sexually transmitted disease.

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Question 104:

A woman uses pills A as a method of birth control (or preventing pregnancy). The pills A stop the ovaries from releasing ovum into oviducts. Another woman uses pills B as a method of birth control. The pills B kill the sperms and prevent pregnancy.
(a) What do the pills A contain?
(b) What is the common name of pills A?
(c) What do the pills B contain?
(d) What is the common name of pills B?
(e) What is the general name of these methods of birth control?

Answer:

(a) The pills A contain hormones.

(b) The common name of pills A is oral pills.

(c) The pills B contain spermicides.

(d) The common name of pills B is vaginal pills.

(e) The general name of these methods of birth control is called chemical method.

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Question 105:

A woman uses a device X made of a common metal for preventing pregnancy. This device works by preventing the implantation of fertilised egg cell (or embryo) in the female organ Y.
(a) What are the two names of device X?
(b) Name the organ Y.
(c) Can this method of contraception protect a woman from acquiring a STD?

Answer:

(a) The name of the device Y is copper-T or IUCD.

(b) The organ Y is the uterus.

(c) This method cannot protect a woman from acquiring STDs.

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Question 106:

A, B and C are three common STDs. A and C are caused by bacteria whereas B is caused by a virus D. The virus D reduces the immunity of the infected person to such a low level that the person can die of even very mild diseases.
(a) What could A and C be?
(b) What is B?
(c) Name the virus D?
(d) How can A, B and C be caused?
(e) Out of A, B and C, which one does not have a definite cure as yet?

Answer:

(a) A is gonorrhoea and C is syphilis.

(b) B is AIDS.

(c) The virus D is Human Immunodeficiency Virus (HIV).

(d) A, B and C can be caused by sexual contact with an infected person.

(e) AIDS (B) does not have a definite cure as yet.



Page No 176:

Question 107:

The germ cell A produced by a person X is round in shape and it fuses with another germ cell B having a long tail and produced by a person Y. The fusion of A and B produces a new cell C. The cell C divides repeatedly and grows inside the organ D of person X to form E in which the body features of the unborn baby are not much developed. E grows further to form F in which the various body features of the unborn baby (like hands, legs, head, eyes, and ears, etc.) can be identified. F grows further and ultimately forms a baby. What are A, B, C, D, E and F? Out of the two persons X and Y, which one is male and which one female?

Answer:

A is the ovum.
B is sperm.
C is the zygote.
D is the uterus.
E is the embryo. 
F is the foetus.

The person X is a female and Y is a male.

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Question 108:

Explain why, a human zygote is more likely to grow into an adult than a frog zygote.

Answer:

In humans, fertilisation is internal. The zygote divides and forms the embryo which is implanted in the uterus. This embryo receives all the nutrients and care from the mother's body and develops into an adult.

In frogs, fertilisation is external and the zygote is formed outside the body. Thus, it forms a larva instead of developing directly into an adult.

Page No 176:

Question 109:

In a bisexual flower, inspite of the young stamens being removed artificially, the flower produces fruit. Explain.

Answer:

The ovary of a flower develops into a fruit after fertilisation. The ovary is a part of the carpel. Thus, in spite of the young stamens being removed artificially, the flower produces fruits.

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Question 110:

In what ways is fertilisation in a plant :
(a) similar to fertilisation in a human?
(b) different from fertilisation in a human?

Answer:

(a) The process of fertilisation is similar in plants and humans as both involve male and female gametes and show internal fertilisation.

(b)

Fertilisation in plants Fertilisation in animals
External agents are required for pollination. External agents are not required.
The seed is formed after fertilisation. The human baby is formed after fertilisation.



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