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Diversity: It refers to the variety and variability among living organisms from all sources

including land, water, and other ecosystems.

Classification

 It refers to the identification, naming, and grouping of organisms into a formal

system based on similarities in internal and external structures or evolutionary

history

 It helps in organising the diversity of life forms in detail.

 Characteristic - A feature that helps identify or describe a person or a thing

 There are certain characteristics that are considered more fundamental than others.

These fundamental characteristics make broad divisions in living organisms.

Principles of classification

 Nature of cell (Fundamental characteristic): On the basis of the nature of

cell, living organisms are classified as: prokaryotes and eukaryotes

 Cellularity: On the basis of cellularity, organisms are classified as: unicellular

and multicellular

 Mode of nutrition: On the basis of mode of nutrition, organisms are classified as:

 Autotrophs and heterotrophs

Classification and evolution

 Primitive organism or lower organism has a simple body structure and ancient

body design

 Advanced organism or higher organism has a complex body structure and

organisation

 Evolution - The process of gradual and continuous change in primitive or simple

organisms to give rise to advanced organisms

 Biodiversity - The variety of life forms present in various ecosystems

Hierarchy of classification

 The hierarchical arrangement of various taxonomical categories in descending order

is: Kingdom  Phylum (for animals)/ Division (for plants)  Class 

Order  Family  Genus  Species.Mnemonic to learn this hierarchy: Kids Prefer Cheese Over Fried Green Spinach

 Species is the basic unit of classification

 Carolus Linnaeus developed the hierarchy of classification. He also brought out

the famous book Systema Naturae

 Linnaeus also developed the concept of binomial nomenclature

 Binomial nomenclature refers to the naming of species. In this system, the name of a

species is made up of two words: the genus name and the species name. E.g. Rosa

indica

 R.H. Whittaker (in 1969) proposed a five-kingdom classification of living organisms

 The five kingdoms proposed by Whittaker are: Monera, Protista, Fungi, Plantae,

and Animalia.

1. Kingdom Monera: It includes mainly bacteria, blue-green algae, or

cyanobacteria

Important features of monera:

 Absence of well-defined nuclear or membrane-bound organelles- prokaryotic

organisms.

 All of them are unicellular

 Can be autotrophic or heterotrophic

2. Kingdom Protista: It Includes protozoans such as, Amoeba, Paramecium, diatoms

etc

Important features of protista:

 Unicellular, eukaryotic organism

 Can be autotrophic or heterotrophic

3. Kingdom Fungi

Commonly known fungi are Yeast, mushroom, Penicillium, Aspergillus, etc.

Important features of fungi:

 Multicellular eukaryotic organisms

 Always heterotrophic (saprophytes)

 Cell wall made of chitin is present

4. Kingdom Plantae

Important features of plantae:

 Multicellular eukaryotic organisms Most of the plants contain chlorophyll. Hence, they are autotrophic

 Cell wall made of cellulose is present

5. Kingdom Animalia

Important features of animalia:

 Multicellular eukaryotic organisms

 Chloroplast is absent. Hence, they have heterotrophic mode of nutrition

 Cell wall is absent

Kingdom Plantae: It includes five divisions:

1. Division Thallophyta: Includes Spirogyra, Cladophora, Ulva

Characteristic feature of Thallophyta:

 Plant body is not differentiated into true root, stem, and leaves

2. Division Bryophyta (also called amphibians of plant kingdom):

Includes mosses, Riccia, Marchantia

Characteristic feature of Bryophyta:

 Specialised vascular tissues (such as xylem) for the conduction of water are

absent

 Body is differentiated into stem and leaf-like structures

 Naked embryo i.e. spores are present.

3. Division Pteridophyta: Includes ferns, Marsilea, Equisetum

Characteristic feature of Pteridophyta

 Specialised vascular tissues for the conduction of water are present.

 Naked embryo i.e. spores are present

Cryptogams: Plants that do not have well differentiated reproductive organs and produce

naked embryo (spores) are called cryptogams. Thallophyta, Bryophyta and Pteridophyta all

possess naked embryo.

Phanerogams: Plants that have well developed reproductive organs that finally make

seeds are called Phanerogams. Gymnosperms and angiosperms belong to Phanerogams.

4. Division Gymnospermae: Includes Pinus, cedar, fir, Juniper, Cycas, etc

Characteristic feature of Gymnospermae:

 Seed bearing, non-flowering plants.  Bear naked seeds, not enclosed inside fruits.

5. Division Angiospermae: Includes all flowering plants

Characteristic feature of Angiospermae:

 Flowering plants in which seeds are enclosed inside fruits.

 Seeds develop inside the ovary, which develops into a fruit

 Major groups of Angiosperms

 Monocotyledons: Seeds that have one cotyledon. E.g. maize, wheat etc

 Dicotyledons: Seeds that have two cotyledons. E.g. Sunflower, gram etc

Kingdom Animalia

Kingdom Animalia can be divided into two major groups on the basis of the presence or

absence of notochord: non-chordata and chordata

 Non-chordata can be further divided into the following phyla:

i. Phylum Porifera: Includes sponges such as Spongilla, Euplectella, etc

Characteristic feature of Porifera:

 Cellular level of organisation

 Mainly found in marine habitats

 Posses canal system for circulating water.

ii. Phylum Coelenterata: Includes organisms such as hydra, sea anemone, etc.

Characteristic feature of Coelentrata:

 Tissue level of organisation

 Body cavity (coelom) is absent

 Diploblastic i.e body is made of two layers of cells.

iii. Phylum Platyhelminthes: Includes flatworms, liver flukes and planarians

Characteristic feature of Platyhelminthes:

 Bilateral symmetry

 Triploblastic i.e. three layers of cells are present

 Body cavity is absent

iv. Phylum Nematoda (Aschelminthes): Includes roundworms - Ascaris

Characteristic feature of Nematoda:

 Bilaterally symmetrical

 Triploblastic  Pseudocoelom (false coelom) is present

v. Phylum Annelida: Includes segmented worms such as earthworms and leeches

Characteristic feature of Annelida:

 Bilaterlly symmetrical

 Triploblastic

 Body is segmented

vi. Phylum Arthropoda: Includes crabs, prawns, insects, spiders, scorpions, etc

Characteristic feature of Arthropoda:

 Largest group of the animal kingdom.

 Bilaterally symmetrical and segmented

 Coelomic cavity is blood-filled

 Presence of Jointed legs

vii. Phylum Mollusca: Includes snails, octopus, Pila, etc

Characteristic feature of Mollusca:

 Bilaterally symmetrical, little segmentation

 Coelomic cavity is reduced

 Open circulatory system and kidney-like organ for excretion is present.

viii. Phylum Echinodermata: Includes marine animals such as starfishes, sea

urchins, etc

Characteristic feature of Echinodermata:

 Spiny skinned organisms

 Free living marine organisms

 Triploblastic and coelomate

 Skeleton is made of calcium carbonate

 Chordata can be further divided into sub-phyla Protochordata and Vertebrata

(1) Protochordata: Includes Herdmania and Amphioxus

Characteristic feature of Protochordata

 Triploblastic, and have a coelom cavity

 Bilaterally symmetrical

 Notochord at some stages of life is present. Notochord is a flexible rod-like structure that forms the supporting axis of the body in the

chordates.

(2) Vertebrata: The sub-phylum Vertebrata is further divided into five classes:

i. Class Pisces: Includes all fishes

Characteristic feature of Pisces:

 Exclusively aquatic animals

 Body is streamlined and covered with scales

 They are cold blooded animals

 Heart is two chambered

 Skeleton is bony or cartilaginous

 Oviparous, they lay eggs in water.

ii. Class Amphibia: Includes frogs, toads, and salamanders

Characteristic feature of Amphibia:

 Scales are absent

 Cold blooded animals

 Heart is three chambered

 Oviparous, they lay eggs in water

 These animals have a dual mode of life (in water and land); respire through gills,

skin, and lungs

iii. Class Reptilia: Includes reptiles such as lizard, snake, turtle, etc

Characteristic feature of Reptilia:

 Cold blooded animals

 Most of them have three chambered heart (Crocodiles have four chambered

heart)

 Skin is covered with scales

 These animals are completely terrestrial. They breath through lungs

 Lay eggs on land (oviparous)

iv. Class Aves: Includes all birds

Characteristic feature of Aves:

 Warm-blooded animals with four chambered heart

 They breathe through lungs

 Have feathers and forelimbs modified for flight Exclusively egg-laying animals

v. Class Mammalia: Includes kangaroo, rat, dolphin, elephant, horse, human,

tiger, etc

Characteristic feature of Mammalia:

 Warm-blooded animals with four chambered heart

 Most of them are viviparous except for platypus and Echidna. They both are

oviparous

 These animals have milk-producing glands (mammary glands) to nourish their

young ones

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Question 1. What are the advantages of classifying organisms?

Answer : There are many advantages of classifying organisms which are given as below

1. Classifying organisms helps us in recognising the basic arrangement of a hierarchical structure among diverse species.

2. It tells us about the resemblances and relationships between various organisms thus facilitating studies or research of wide variety associated with organisms effortlessly.

3. It helps in understanding the evolution of organisms, as it gives us most of the information permitting a reconstruction of phylogeny of life.

4. It has major role in agriculture, public health and environmental biology. Exact identification of harmful pests, disease vectors makes possible to control diseases much easier.

5. Several ornamental plants have been introduced by horticulturists due to proper identification and nomenclature.

6. It also gives us a fair idea about the vast number of life forms and we are able to understand diversity among living organisms in a much better way.

7. It helps in placement of different organisms in a definite taxonomic group which is the basic requirement of biological sciences.

8. It forms the basis for Taxonomy in biological sciences, which is a science of identifying, grouping, and naming organisms according to their established natural relationship.

9. Classification of organism has facilitated science of genetic engineering to a great extent

Question 2. How would you choose between two characteristics to be used for developing a hierarchy in classification?

Answer : For developing a hierarchy of classification, we choose the fundamental characteristic among several other characteristics. These fundamental characteristics are independent of any other characteristics in their effects on the form and function of the organism. The characteristics in the next level would be dependent on the previous one and would decide the variety in the next level. In this way, we can build up a whole hierarchy of mutually related characteristics to be used for classification. For example, plants differ from animals in many ways such as body design, photosynthesis, the absence of locomotion, chloroplasts, cell wall, etc. But, out of these, only locomotion is considered as the basic or fundamental feature that is used to distinguish between plants and animals. This is because the absence of locomotion in plants gave rise to many structural changes such as the presence of a cell wall for protection, and the presence of chloroplast for photosynthesis (as they cannot move around in search of food like animals). Thus, all these features are a result of locomotion. Therefore, locomotion is considered to be a fundamental characteristic. By choosing the basic or fundamental characteristic, we can make broad divisions in living organisms as the next level of characteristic is dependent on these. This goes on to form a hierarchy of characteristics.

Question 3. Explain the basis for grouping organisms into five kingdoms.

Answer : Robert .H. Whittaker in 1959 proposed a five kingdom classification of living organisms on the basis of Linnaeus’ system of classification encorporating cell structure, mode and source of nutrition and body organisation as main features. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae, and Animalia

The basis for grouping organisms into five kingdoms is as follows :

(i) On the basis of the presence or absence of membrane-bound organelles, all living organisms are divided into two broad categories of eukaryotes and prokaryotes. This division lead to the formation of kingdom Monera, which includes all prokaryotes.

(ii) Then, eukaryotes are divided as unicellular and multicellular, on the basis of cellularity. Unicellular eukaryotes form kingdom Protista, and multicellular eukaryotes form kingdom Fungi, Plantae, and Animalia.

(iii) Animals are then separated on the basis of the absence of a cell wall.

(iv) Since fungi and plants both contain a cell wall, they are separated into different kingdoms on the basis of their modes of nutrition. Fungi have saprophytic mode of nutrition, whereas plants have autotrophic mode of nutrition. This results in the formation of the five kingdoms

Question 4. What are the major divisions in the Plantae? What is the basis for these divisions?

Answer : The kingdom Plantae is divided into five main divisions: Thallophyta, Bryophyta, Pteridophyta, Gymnosperms, and Angiosperms.

The classification depends on the following criteria:

• Differentiated or Undifferentiated plant body

• Presence /absence of vascular tissues

• With/without seeds

• Naked seeds/ seeds inside fruits

Classification Of Plants

(i) The first level of classification depends on whether a plant body is well differentiated or not. A group of plants that do not have a well differentiated plant body are known as Thallophyta.

(ii) Plants that have well differentiated body parts are further divided on the basis of the presence or absence of vascular tissues. Plants without specialised vascular tissues are included in division Bryophyta, whereas plants with vascular tissues are known as Tracheophyta.

(iii) Tracheophyta is again sub-divided into two divisions Pteridophyta and Phanerogams on the basis of the absence/presence of seed formation.

(iv) Pteridophyta plants do not produce seeds

(iv) Phanerogams plants have well developed reproductive organs that finally produce seeds.

(v) Phanerogams group is further sub- divided on the basis of whether the seeds are naked or enclosed in fruits. This classifies them into gymnosperms and angiosperms.

Gymnosperms are seed bearing, non-flowering plants, whereas angiosperms are flowering plants in which the seeds are enclosed inside the fruit.

Question 5. How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?

Answer :Criteria for deciding divisions in plants are:

(i) Differentiated/ Undifferentiated plant body

(ii) Presence/ absence of vascular tissues

(iii) With/without seeds

(iv) Naked seeds/ seeds inside fruits

Criteria for deciding subgroups among animals are:

Kingdom Animalia is divided into two major groups on the basis of the presence or absence of a notochord.

Non-chordates do not possess a notochord, while all members of the phylum chordates possess a notochord.

Non-chordate is further divided into subgroups on the basis of the following features:

On the basis of the above features, non-chordates are divided into the following subgroups:

Porifera, Coelenterate, Platyhelminthes, Nematodes, Annelids, Molluscs, Arthropoda, and Echinodermata

All members of the phylum chordate possess a notochord. However, some animals such as Balanoglossus, Amphioxus, Herdmania, etc. have a notochord, which is either absent or does not run the entire length of the animal’s body. Therefore, these animals are kept in a separate sub-phylum called Protochordata, and the rest of the chordates are included in the sub-phylum vertebrata. The members of the sub-phylum vertebrata are advanced chordates. They are divided into five classes: Pisces, Amphibian, Reptilia, Aves, and Mammalia

Question 6. Explain how animals in Vertebrata are classified into further Subgroups ?

Answer : Vertebrata : These animals have a true vertebral column and internal skeleton, allowing a completely different distribution of muscle attachment points to be used for movement. Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented, with complex differentiation of body tissues and organs. All chordates possess the following features:

(i) They have a notochord

(ii) They have a dorsal nerve cord

(iii) They are triploblastic

(iv) They have paired gill pouches

(v) They are coelomate.

Vertebrates are grouped into five classes

(i) PISCES (ii) AMPHIBIA (iii) REPTILIA (iv) AVES (v) MAMMALIA

Vertebrates Classification

Question 7. How do poriferan animals differ from coelenterate animals?

Answer :

Differences between Poriferan animals and Coelenterate animals

Porifera	Coelenterate
They are mostly marine, non-motile and found attached to rocks. They show cellular level of organization Examples - Spongilla, Euplectella etc	They are excusively merine animals that either leave in colonies or have a solitary life span. They show tissues level of organisation Examples - Hydra, Sea Anemone, Corals etc.

Question 8. How do annelid animals differ from arthropods?

Answer :

Differences between Annelid animals and Arthropods

Annelid animals	Arthropods animals
The circulatory system of Annelid animals is closed The body is divided into several identical segments	The Arthropods have an open circulatory system The body is divided into few specialized segments

Question 9. What are the differences between amphibians and reptiles?

Answer :

Differences between Amphibians and Reptiles

Amphibians	Reptiles
They have dual mode of life. Scales are absent. They lay eggs in water.	They are completely terrestrial. The skin is covered with scales. They lay eggs on land.

Question 10. What are the differences between animals belonging to the Aves group and those in the mammalian group?

Answer :

Differences between Aves group and Mammalian group

Aves group	Mammalian group
Most birds have feathers and they possess a beak. They lays eggs, hence are oviparous.	They do not have feathers and beak is also not present. Some of them lay eggs and some give birth to young hence they are both viviparous and oviparous

Diversity: It refers to the variety and variability among living organisms from all sources

including land, water, and other ecosystems.Classification It refers to the identification, naming, and grouping of organisms into a formalsystem based on similarities in internal and external structures or evolutionaryhistory It helps in organising the diversity of life forms in detail. Characteristic - A feature that helps identify or describe a person or a thing There are certain characteristics that are considered more fundamental than others.These fundamental characteristics make broad divisions in living organisms.Principles of classification Nature of cell (Fundamental characteristic): On the basis of the nature ofcell, living organisms are classified as: prokaryotes and eukaryotes Cellularity: On the basis of cellularity, organisms are classified as: unicellularand multicellular Mode of nutrition: On the basis of mode of nutrition, organisms are classified as: Autotrophs and heterotrophsClassification and evolution Primitive organism or lower organism has a simple body structure and ancientbody design Advanced organism or higher organism has a complex body structure andorganisation Evolution - The process of gradual and continuous change in primitive or simpleorganisms to give rise to advanced organisms Biodiversity - The variety of life forms present in various ecosystemsHierarchy of classification The hierarchical arrangement of various taxonomical categories in descending orderis: Kingdom  Phylum (for animals)/ Division (for plants)  Class Order  Family  Genus  Species.Mnemonic to learn this hierarchy: Kids Prefer Cheese Over Fried Green Spinach Species is the basic unit of classification Carolus Linnaeus developed the hierarchy of classification. He also brought outthe famous book Systema Naturae Linnaeus also developed the concept of binomial nomenclature Binomial nomenclature refers to the naming of species. In this system, the name of aspecies is made up of two words: the genus name and the species name. E.g. Rosaindica R.H. Whittaker (in 1969) proposed a five-kingdom classification of living organisms The five kingdoms proposed by Whittaker are: Monera, Protista, Fungi, Plantae,and Animalia.1. Kingdom Monera: It includes mainly bacteria, blue-green algae, orcyanobacteriaImportant features of monera: Absence of well-defined nuclear or membrane-bound organelles- prokaryoticorganisms. All of them are unicellular Can be autotrophic or heterotrophic2. Kingdom Protista: It Includes protozoans such as, Amoeba, Paramecium, diatomsetcImportant features of protista: Unicellular, eukaryotic organism Can be autotrophic or heterotrophic3. Kingdom FungiCommonly known fungi are Yeast, mushroom, Penicillium, Aspergillus, etc.Important features of fungi: Multicellular eukaryotic organisms Always heterotrophic (saprophytes) Cell wall made of chitin is present4. Kingdom PlantaeImportant features of plantae: Multicellular eukaryotic organisms Most of the plants contain chlorophyll. Hence, they are autotrophic Cell wall made of cellulose is present5. Kingdom AnimaliaImportant features of animalia: Multicellular eukaryotic organisms Chloroplast is absent. Hence, they have heterotrophic mode of nutrition Cell wall is absentKingdom Plantae: It includes five divisions:1. Division Thallophyta: Includes Spirogyra, Cladophora, UlvaCharacteristic feature of Thallophyta: Plant body is not differentiated into true root, stem, and leaves2. Division Bryophyta (also called amphibians of plant kingdom):Includes mosses, Riccia, MarchantiaCharacteristic feature of Bryophyta: Specialised vascular tissues (such as xylem) for the conduction of water areabsent Body is differentiated into stem and leaf-like structures Naked embryo i.e. spores are present.3. Division Pteridophyta: Includes ferns, Marsilea, EquisetumCharacteristic feature of Pteridophyta Specialised vascular tissues for the conduction of water are present. Naked embryo i.e. spores are presentCryptogams: Plants that do not have well differentiated reproductive organs and producenaked embryo (spores) are called cryptogams. Thallophyta, Bryophyta and Pteridophyta allpossess naked embryo.Phanerogams: Plants that have well developed reproductive organs that finally makeseeds are called Phanerogams. Gymnosperms and angiosperms belong to Phanerogams.4. Division Gymnospermae: Includes Pinus, cedar, fir, Juniper, Cycas, etcCharacteristic feature of Gymnospermae: Seed bearing, non-flowering plants.  Bear naked seeds, not enclosed inside fruits.5. Division Angiospermae: Includes all flowering plantsCharacteristic feature of Angiospermae: Flowering plants in which seeds are enclosed inside fruits. Seeds develop inside the ovary, which develops into a fruit Major groups of Angiosperms Monocotyledons: Seeds that have one cotyledon. E.g. maize, wheat etc Dicotyledons: Seeds that have two cotyledons. E.g. Sunflower, gram etcKingdom AnimaliaKingdom Animalia can be divided into two major groups on the basis of the presence orabsence of notochord: non-chordata and chordata Non-chordata can be further divided into the following phyla:i. Phylum Porifera: Includes sponges such as Spongilla, Euplectella, etcCharacteristic feature of Porifera: Cellular level of organisation Mainly found in marine habitats Posses canal system for circulating water.ii. Phylum Coelenterata: Includes organisms such as hydra, sea anemone, etc.Characteristic feature of Coelentrata: Tissue level of organisation Body cavity (coelom) is absent Diploblastic i.e body is made of two layers of cells.iii. Phylum Platyhelminthes: Includes flatworms, liver flukes and planariansCharacteristic feature of Platyhelminthes: Bilateral symmetry Triploblastic i.e. three layers of cells are present Body cavity is absentiv. Phylum Nematoda (Aschelminthes): Includes roundworms - AscarisCharacteristic feature of Nematoda: Bilaterally symmetrical Triploblastic  Pseudocoelom (false coelom) is presentv. Phylum Annelida: Includes segmented worms such as earthworms and leechesCharacteristic feature of Annelida: Bilaterlly symmetrical Triploblastic Body is segmentedvi. Phylum Arthropoda: Includes crabs, prawns, insects, spiders, scorpions, etcCharacteristic feature of Arthropoda: Largest group of the animal kingdom. Bilaterally symmetrical and segmented Coelomic cavity is blood-filled Presence of Jointed legsvii. Phylum Mollusca: Includes snails, octopus, Pila, etcCharacteristic feature of Mollusca: Bilaterally symmetrical, little segmentation Coelomic cavity is reduced Open circulatory system and kidney-like organ for excretion is present.viii. Phylum Echinodermata: Includes marine animals such as starfishes, seaurchins, etcCharacteristic feature of Echinodermata: Spiny skinned organisms Free living marine organisms Triploblastic and coelomate Skeleton is made of calcium carbonate Chordata can be further divided into sub-phyla Protochordata and Vertebrata(1) Protochordata: Includes Herdmania and AmphioxusCharacteristic feature of Protochordata Triploblastic, and have a coelom cavity Bilaterally symmetrical Notochord at some stages of life is present. Notochord is a flexible rod-like structure that forms the supporting axis of the body in thechordates.(2) Vertebrata: The sub-phylum Vertebrata is further divided into five classes:i. Class Pisces: Includes all fishesCharacteristic feature of Pisces: Exclusively aquatic animals Body is streamlined and covered with scales They are cold blooded animals Heart is two chambered Skeleton is bony or cartilaginous Oviparous, they lay eggs in water.ii. Class Amphibia: Includes frogs, toads, and salamandersCharacteristic feature of Amphibia: Scales are absent Cold blooded animals Heart is three chambered Oviparous, they lay eggs in water These animals have a dual mode of life (in water and land); respire through gills,skin, and lungsiii. Class Reptilia: Includes reptiles such as lizard, snake, turtle, etcCharacteristic feature of Reptilia: Cold blooded animals Most of them have three chambered heart (Crocodiles have four chamberedheart) Skin is covered with scales These animals are completely terrestrial. They breath through lungs Lay eggs on land (oviparous)iv. Class Aves: Includes all birdsCharacteristic feature of Aves: Warm-blooded animals with four chambered heart They breathe through lungs Have feathers and forelimbs modified for flight Exclusively egg-laying animalsv. Class Mammalia: Includes kangaroo, rat, dolphin, elephant, horse, human,tiger, etcCharacteristic feature of Mammalia: Warm-blooded animals with four chambered heart Most of them are viviparous except for platypus and Echidna. They both areoviparous These animals have milk-producing glands (mammary glands) to nourish theiryoung ones *  * 

It refers to the variety and variability among living organisms from all sources