Science And Technology Solutions Solutions for Class 9 Science Chapter 15 Life Processes In Living Organisms are provided here with simple step-by-step explanations. These solutions for Life Processes In Living Organisms are extremely popular among class 9 students for Science Life Processes In Living Organisms Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science And Technology Solutions Book of class 9 Science Chapter 15 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Science And Technology Solutions Solutions. All Science And Technology Solutions Solutions for class 9 Science are prepared by experts and are 100% accurate.
Page No 178:
Question 1:
Match the pairs and explain.
| 'A' | 'B' |
|
1. Growth of pollen tube towards ovule
2. Growth of shoot system
3. Growth of root system
4. Growth towards water
|
a. Gravitropic movement b. Chemotropic movement c. Phototropic movement d. Growth-irrelevant movement e. Hydrotropic movemen |
Answer:
| 'A' | 'B' |
|
1. Growth of pollen tube towards ovule
2. Growth of shoot system
3. Growth of root system
4. Growth towards water
|
b. Chemotropic movement c. Phototropic movement a. Gravitropic movement e. Hydrotropic movement |
Page No 178:
Question 2:
The milk was on the stove. Rasika was engrossed watching television. She smelled something burning. She ran towards the kitchen. The milk was boiling over. She held the vessel with her bare hands but, screaming, she let it go at once. This activity was controlled by ................... cells. Special ends of .................... in these cells collected the information, from where it was transferred to the .................... and then towards the terminal end of the .................... The chemicals produced at the terminal end passed through the minute space i.e. ................... . In this way, .................... were conducted in the body and the process of .................... was completed by conducting the impulses from .................... to ..................
(Nerve, muscle cell, impulse, dendrite, synapse, axon, reflex action, cell body)
Answer:
The milk was on the stove. Rasika was engrossed watching television. She smelled something burning. She ran towards the kitchen. The milk was boiling over. She held the vessel with her bare hands but, screaming, she let it go at once. This activity was controlled by nerve cells. Special ends of dendrites in these cells collected the information, from where it was transferred to the cell body and then towards the terminal end of the axon. The chemicals produced at the terminal end passed through the minute space i.e. synapse. In this way, impulse were conducted in the body and the process of reflex action was completed by conducting the impulses from nerve to muscle cells.
Page No 178:
Question 3:
Root pressure, Transpiration, Nerve cell, Human brain, Reflex action
Answer:
b. Transpiration is the loss of water in the form of vapours from the leaves of a plant. The rate of transpiration is affected by number of external and internal factors.
Internal factors:
(i) Leaf area: The greater the leaf area the higher will be the water loss due to transpiration.
(ii) Leaf structure: Presence of thick cuticle, wax layer, compact mesophyll cells reduces the rate of transpiration.
(iii) Root-shoot ratio: Low root-shoot ratio decreases rate of transpiration.
External factors:
(i) Atmospheric humidity: The higher the relative humidity lower will be the rate of transpiration.
(ii) Temperature: Rise in the atmospheric temperature increased the rate of transpiration.
(iii) Wind velocity: High wind velocity increases the transpiration rate.
(iv) Water supply: Deficiency of water in soil decreases the rate of transpiration.
Importance of transpiration:
(i) The rate of transpiration affects the rate of absorption of water by the roots.
(ii) Transpiration creates a suction pressure for the upward movement of water in tall trees.
(iii) It helps in the distribution of water throughout a plant.
(iv) Plants get rid of excess water by transpiration. It helps to keep the surface of the leaves cool.
c. Nerve cell- Nerve cells are also known as neurons.
A neuron consists of 3 parts.
(i) Cell body − It contains a nucleus and cytoplasm.
(ii) Axon − It is a long part arising from the cell body. It transmits impulses away from the cell body.
(iii) Dendrites − These are short, branched parts arising from the cell body. They receive the nerve impulses.
d. Human brain-
The human brain is the main coordinating centre of the body. It is a part of the central nervous system and receives information from the other parts of the body and interprets them. The human brain can be divided into three distinct regions.
(i) Forebrain: It consists of cerebrum, thalamus and hypothalamus. The forebrain is the main site of learning, intelligence and thinking. It also has sensory and motor sites which control all the voluntary movements. Hypothalamus is concerned with things like body temperature, urge to eat, drink, etc.
(ii) Midbrain: It consists of regions concerned with the sense of sight, hearing, etc. It also transmits motor impulses to the limbs.
(iii) Hindbrain: It controls most of the involuntary actions like heartbeat, blood pressure, etc. Cerebellum maintains the posture and equilibrium of the body.
e. Reflex action- The automatic action or response provoked by a stimulus is known as reflex action. The sensory nerves that detect the stimulus are connected to nerves that move the muscles. Such a connection is called a reflex arc. The reflex arc connections meet in a bundle in the spinal cord. The signal and the response that has taken place reach the brain but the brain does not coordinate the reflex response. For example, we withdraw our hands on touching any hot article.
Page No 178:
Question 4:
Pituitary, Thyroid, Adrenal, Thymus,Testis, Ovary
Answer:
(i) Prolactin- Growth of mammary glands and formation of milk in them
(ii) TSH- Synthesis and release of thyroid hormones
(iii) Adrenocorticotrophic hormone (ACTH)- Stimulates synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex
(iv) Vasopressin- Stimulates reabsorption of water from the distal tubules, and hence, prevents loss of water through urine (diuresis); therefore, also called anti-diuretic hormone (ADH)
b. Thyroid- Thyroid gland secretes the hormone, thyroxine (a derivative of amino acid tyrosine). Functions of thyroxine include:
(i) Control of BMR (Basal metabolism rate)
(ii) Control of working of kidney and urine formation
(iii) Regulation of physical, mental, and sexual growth
(iv) Regulation of growth of CNS and bones
(v) Regulation of carbohydrate and fat metabolism
c. Adrenal- Adrenal gland secretes 3 types of hormones- catecholamines, mineralocorticoids and glucocorticoids.
(i) Catecholamine (adrenaline and nor adrenaline)- They are also known as emergency hormones or hormones of fight or flight.
- Increases alertness, pupilary dilation, piloerection (raising of hair)
- Increases heart beat, respiration rate
- Stimulates the breakdown of glucose, lipids and proteins
(ii) Glucocorticoid: stimulates gluconeogenesis, lipolysis and proteolysis and inhibits uptake and utilisation of amino acids
(iii) Mineralocorticoid: Example − Aldosterone- Acts on renal tubule and stimulates reabsorption of Na+ and water
- Stimulates excretion of K+
- Maintains electrolysis, osmotic pressure and blood pressure
- Androgenic steroids plays a role in the growth of axial, facial and pubic hair during puberty
d. Thymus- Thymus secretes peptide hormone called thymosins. Thymosins play an important role in the differentiation of T-lymphocytes (Cell Mediated Immunity) and promotes production of antibodies (Humoral Immunity). Thymus is degenerated in old people, hence, their immune response becomes weak.
e. Testes- Testis secrete hormones called androgens. Functions of androgens include:
- Development, maturation and functioning of the male accessory sex organs like vas deferens and seminal vesicles
- Stimulate muscular growth, growth of facial hair, low pitch voice, etc.
- Stimulatory role in spermatogenesis
- Act on the CNS and influence male sexual behaviour (libido)
- Anabolism of proteins and carbohydrates
f. Ovary- Ovary secretes the hormones oestrogen and progesterone.
Functions of oestrogen:
- Growth and functioning of the female secondary sex organs
- Development of growing follicles and mammary glands
- Regulates female secondary sex characters (Examples − high pitch voice)
Functions of progesterone:
- Acts on mammary glands and stimulates formation of alveoli-like structures storing milk
- Milk secretion
Page No 178:
Question 5:
Human endocrine glands, Human brain, Nephron, Nerve cell, Human excretory system.
Answer:
a. Human endocrine glands​
b. Human brain​
c. Nephron
d. Nerve cell
e. Human excretory system
Page No 178:
Question 6:
a. Explain chemical co-ordination in humans and give the names and functions of some hormones.
Answer:
a. Coordination in humans occurs in two levels i.e. nervous coordination and chemical coordination. The coordination which occurs with the help of hormones is called chemical coordination. Hormones are the organic chemicals produced by the body, which are released into the blood. The key feature of the hormones is that they are secreted by the ductless glands. The glands that secrete hormones do not have ducts. Hormones are released directly into the bloodstream and reach the target organ. The endocrine system works in association with nervous system to control and coordinate our bodies.
Characteristics of Hormones
- Hormones are the organic chemicals that are secreted in response to environmental changes in or outside the body.
- Hormones are secreted by ductless glands and transported along with the blood stream to the site of their action. The site of their production and the organ of their influence are different.
- They can be amino-acid derivatives, proteins, or steroids.
- Being low molecular weight substances, they can easily diffuse through the cell membrane.
- They are produced in small quantities and are effective in extremely lower concentrations.
- Abnormal production of hormones (be it less or more) affects the body in a negative manner.
- Prolactin- Growth of mammary glands and formation of milk in them.
- TSH- Synthesis and release of thyroid hormones.
- Adrenocorticotrophic hormone (ACTH)- Stimulates synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex.
- Vasopressin- Stimulates reabsorption of water from the distal tubules, and hence, prevents loss of water through urine (diuresis); therefore, also called anti-diuretic hormone (ADH).
- Control of BMR (Basal metabolism rate)
- Control of working of kidney and urine formation
- Regulation of physical, mental, and sexual growth
- Regulation of growth of CNS and bones
- Regulation of carbohydrate and fat metabolism
b.
Excretion in plants |
Excretion in animals |
1. Plants do not have specialised structures for excretion. |
1. Animals have specialised structures like nephrons for excretion. |
2. Process of excretion occurs through stomata and lenticels. |
2. Process of excretion occurs through kidney, skin, lungs etc. |
3. Waste is produced in the form of CO2 and O2. |
3. Waste is produced in the form of nitrogenous waste like urea, uric acid and ammonia. |
c. Since plants do not have nervous and muscular system like animals, coordination in plants occurs in response to particular stimuli. Tropism/tropic movement is the term used for the movement or growth of any plant part in response to an external stimulus.
These tropic movements can be of various types like:
Phototropism: The growth movement in plants in response to light stimulus is known as phototropism. For example, the flower head of a sunflower is positively phototropic as it moves from East to West, along with the movement of the Sun.
Geotropism: The growth movement in plants in response to the force of gravity is known as geotropism. In geotropism, the roots of the plant always grow downwards, while the shoots always grow upwards, away from the earth.
Chemotropism: The growth movement in plants in response to chemical stimuli is known as chemotropism. For example, the growth of pollen tube towards the ovule in the ovary (through the stigma and style) is an example of positive chemotropism.
Hydrotropism: The growth movement in plants in response to water is known as hydrotropism. For example, the roots of some plants grow towards the water source, even when the water source is not present directly below it.
Thigmotropism: The growth movement in plants in response to a touch stimulus or contact with a solid object is known as thigmotropism. For example, in some plants, the coiling of tendrils occurs when they come in contact with objects for support.
Page No 178:
Question 7:
a. What is meant by co-ordination?
Answer:
a. Coordination is defined as the working together of various organs of the body of an organism in a proper manner to produce appropriate reaction to a stimulus is called coordination. Coordination is achieved by different mechanisms in plants and humans.
Coordination in humans:
In humans coordination is achieved by two systems-
Nervous system
Endocrine system
The human nervous system is comprised of two parts- Central neural system (CNS) and Peripheral neural system (PNS).
The CNS is composed of brain and spinal cord.
The PNS is composed of nerves associated with CNS. These nerves are of two types- afferent and efferent.
Afferent fibres: Transmit impulses from tissues to CNS
Efferent fibres: Transmit impulses from CNS to tissues
Chemical coordination in humans is achieved by hormones. Hormones are the organic chemicals produced by the body, which are released into the blood. The key feature of the hormones is that they are secreted by the ductless glands. The glands that secrete hormones do not have ducts. Hormones are released directly into the blood stream and reach the target organ. The endocrine system works in association with nervous system to control and coordinate our bodies.
Coordination in plants:
Since plants do not have nervous and muscular system like animals, coordination in plants occurs in response to particular stimuli. Tropism/tropic movement is the term used for the movement or growth of any plant part in response to an external stimulus.
These tropic movements can be of various types like:
Phototropism: The growth movement in plants in response to light stimulus is known as phototropism. For example, the flower head of a sunflower is positively phototropic as it moves from East to West, along with the movement of the Sun.
Geotropism: The growth movement in plants in response to the force of gravity is known as geotropism. In geotropism, the roots of the plant always grow downwards, while the shoots always grow upwards, away from the earth.
Chemotropism: The growth movement in plants in response to chemical stimuli is known as chemotropism. For example, the growth of pollen tube towards the ovule in the ovary (through the stigma and style) is an example of positive chemotropism.
Hydrotropism: The growth movement in plants in response to water is known as hydrotropism. For example, the roots of some plants grow towards the water source, even when the water source is not present directly below it.
Thigmotropism: The growth movement in plants in response to a touch stimulus or contact with a solid object is known as thigmotropism. For example, in some plants, the coiling of tendrils occurs when they come in contact with objects for support.
b. The removal of waste products from the body is known as excretion. In the human body, kidneys, lungs and skin perform the function of excretion. Lungs remove carbon dioxide as waste. Skin helps in the removal of waste in the form of sweat. However, the major organ involved in excretion is the urinary system, which contains the kidneys to filter the blood and form urine.
In human beings, excretion is performed by the excretory system consisting of a pair of kidneys, a pair of ureters, a urinary bladder and urethra.
The urine is formed in kidneys and passes on to the urinary bladder via the ureters. The urinary bladder stores the urine until it is excreted through the urethra.
The kidney contains numerous filtration units called the nephrons. Nephron is the structural and functional unit of the kidney. The nephrons consist of a network of capillaries associated with a cup-shaped end of a tube in which the filtered urine is collected. When the blood passes through the tube, some substances such as glucose, amino acids, salts, and water are selectively reabsorbed. The final filtrate is collected in the collecting tubule and eventually enters the ureters.
The other organs which are involved in the excretory process include:
(i) Lungs: They remove CO2 and water. About 18 L of carbon dioxide is eliminated per day with the help of lungs.
(ii) Liver: It excretes bile pigments (such as bilirubin, biliverdin), vitamins, cholesterols and drugs along with digestive wastes.
(iii) Skin: Sweat and sebaceous glands present on the skin eliminate substances such as sterols, hydrocarbons, wax sebum, etc.
c. Excretion in plants results in the production of various kinds of excreta which are waste for the plant but are equally important for human use. The following examples are helpful in proving the above fact:
1. Oxygen which is an excretory product of photosynthesis is an absolute requirement for human beings to survive on earth.
2. Tannin is a waste plant product which is stored in leaves and bark. it is used in making tea all over the world.
3. Plants store waste products in their leaves and barks which are shed off regularly. These shed offs are used to make manure.
4. Essential oils are also waste products of plants which are stored in their leaves. These essential oils are used for various purposes by us.
d. Transportation is a life process where substances synthesised or absorbed in one part of the body are carried to other parts of the body. The transportation system in plants moves the energy stored in leaves to different parts. It also helps in moving raw materials absorbed from the roots to various organs of the plant. However, these are entirely different pathways. The transportation system in plants consists of two different types of conducting tissues. Xylem conducts water and minerals obtained from soil (via roots) to the rest of the plant. Phloem transports food materials from the leaves to different parts of the plant body.
Transportation of water
The first step in transportation of water is absorption of water by roots of plants. As the water is absorbed by the roots from the soil and moved to the vascular system, it has to be transported to various parts of the plant. Two forces responsible for transporting the water up in a plant are root pressure and transpiration pull.
Root Pressure is the positive pressure created inside the xylem when water follows the ions transported along the concentration gradients into the vascular system. However, majority of water is transported through transpiration pull.
Transpiration pull is the pull of water as a result of tension created by transpiration is the major driving force of water movement upwards in a plants. It accounts for loss of 99% of water taken by the plant and this loss is mainly through stomata. As the water is released by leaves into the atmosphere, the water level in the epidermal layer decreases. To compensate this water loss, water is brought to the leaves through xylem. Transpiration helps in the absorption of water and minerals to all the parts of the plants.
Transportation of food
The transportation of food from the leaves to other parts of the plant occurs in the vascular tissue, phloem and this process of transporting food is known as translocation. The phloem also transports amino acids and other substances to storage organs of the plant (along with the growing organs) such as roots, fruits, and seeds. The phloem consists of companion cells, sieve tubes, phloem parenchyma, and fibres.
The translocation of food occurs in the sieve tubes with the help of companion cells.
Translocation in the phloem, unlike the xylem, is achieved by utilizing energy from ATP. For example, a food material such as sucrose is transported into the phloem tissue using ATP energy. As a result, the osmotic pressure in the tissue increases, causing the water to move into it. This pressure moves the material in the phloem to the tissues, which have less pressure. This is helpful in moving materials according to the requirements of the plant.
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