11. The Regulators of Life SCHOOL SECTION 259

Transcription

1 11. The Regulators of Life SCHOOL SECTION 259

2 SCIENCE & TECHNOLOGY MT EDUCARE LTD. Q.I (A) Choose the correct alternatives and rewrite the complete sentences : is necessary to obtain energy from glucose and fatty acid. (a) Oxygen (b) Hydrogen (c) Water (d) Nitrogen 2. In certain sensitive plants like Mimosa, movement is in response to the stimulus of.... (a) gravity (b) air (c) light (d) touch 3. The movement of the plant in response to the stimulus of light is called... movement. (a) gravitropic (b) hydrotropic (c) phototropic (d) chemotropic 4. When light falls on a part of growing plant, a hormone called... is synthesized at the tip of the shoot. (a) auxin (b) abscissic acid (c) gibberellins (d) cytokinins 5. The movement of the root system towards the stimulus of gravity is called... movement. (a) gravitropic (b) hydrotropic (c) phototropic (d) chemotropic 6. The movement of the root system towards the stimulus of water is called... movement. (a) gravitropic (b) hydrotropic (c) phototropic (d) chemotropic hormones help in the growth of the stem. (a) Auxins (b) Abscissic acid (c) Gibberellins (d) Cytokinins hormones promote cell division. (a) Auxins (b) Abscissic acid (c) Gibberellins (d) Cytokinins is a plant hormone which inhibits growth wilting of leaves. (a) Auxin (b) Abscissic acid (c) Gibberellins (d) Cytokinins 10. The... is the main thinking part of the brain. (a) cerebrum (b) cerebellum (c) medulla oblongata (d) spinal cord 11. The brain can stay alive for... without oxygen. (a) 4-6 hours (b) 5-6 hours (c) 24 hours (d) 4-6 minutes Answers : 1. Oxygen 2. touch 3. phototropic 4. auxin 5. gravitropic 6. hydrotropic 7. Gibberellins 8. Cytokinins 9. Abscissic acid 10. forebrain or cerebrum minutes. Q.I (B) Fill in the blanks : *1.... do not possess a nervous system. *2. Response to the stimulus of touch is called... whereas response to the stimulus of chemicals is called as SCHOOL SECTION

3 MT EDUCARE LTD. SCIENCE & TECHNOLOGY *3. Brain is the main... centre of the body. *4. The loss of water from the plants is known as refers to the systematic regulation of various activities means the orderly execution of the activities. 7. Transpiration takes place in the leaves through the The food is mixed with the... in the saliva secreted by the salivary glands. 9. The movement or growth of any part of a plant in response to an external stimulus is called The plants use... means to transfer information from one cell to another. 11. The nerves are composed of neurons and The neurons are specialized cells capable of transmitting neurons conduct impulses from the sense organs to the brain and spinal cord neurons conduct impulses from the brain and spinal cord to the effector organs neurons perform the integrative functions of the nervous system keeps the CNS well nourished and also protects it by absorbing mechanical shocks. 17. The chemical control is brought about by chemical substances called The hormones are secreted by the... glands. 19. Endocrine glands are also known as the... glands. 20. Hormones are also referred to as Insect... is under hormonal control. 22. In frogs... secretion stimulates the metamorphosis from tadpole to adult frog. 23. In the..., hormones induce colour changes and are influential in regulating development. 24. The left hemisphere of the brain has... more neurons than the right hemisphere of blood flows through the brain every minute. 26. In certain coelenterates like..., the nervous system is at a very primitive stage of developments. Answers : 1. Plants 2. seismonastic movement, chemotropism 3. thinking 4. transpiration 5. Control 6. Co-ordination 7. stomatal openings 8. enzymes 9. tropism or tropic movement 10. electrochemical 11. neuroglia 12. electrochemical impulses 13. Sensory 14. Motor 15. Association 16. Cerebrospinal fluid (CSF) 17. hormones 18. endocrine 19. ductless 20. chemical messengers 21. metamorphosis 22. thyroid 23. arthropods millions ml 26. hydra. SCHOOL SECTION 261

4 SCIENCE & TECHNOLOGY MT EDUCARE LTD. Q.I (C) Match the following : 1. Column I Column II (i) Seismonastic movement (a) Stimulus of gravity (ii) Phototropic movement (b) Stimulus of chemicals (iii) Gravitropic movement (c) Stimulus of light (iv) Hydrotropic movement (d) Stimulus of touch (v) Chemotropic movement (e) Stimulus of water Ans. (i - d), (ii - c), (iii - a), (iv - e), (v - b). 2. Column I Column II (i) Folding of leaflets in Mimosa (a) Chemotropism pudica (ii) Growth of pollen tube towards (b) Seismonastic the ovules (iii) Bending of plant towards light (c) Hydrotropism (iv) Movement of roots towards water (d) Phototropism Ans. (i - b), (ii - a), (iii - d), (iv - c). 3. Column I Column II (i) Gibberellins (a) Promoting cell division in fruits and seeds (ii) Cytokinins (b) Tip of shoot to grow longer (iii) Abscissic acid (c) Promoting growth of stem (iv) Auxins (d) Wilting of leaves Ans. (i - c), (ii - a), (iii - d), (iv - b). 4. Column I Column II (i) Lotus plant (a) Curl inwards at the touch of an insect, trapping it (ii) Tube rose plant (b) Open in morning (iii) Tentacles of Drosera (c) Bursts open scattering the seeds. (iv) Fruit of Balsam plant (d) Open at night Ans. (i - b), (ii - d), (iii - a), (iv - c). 5. Column I Column II (1) CNS (a) Comprises of nerves present in involuntary organs like heart, stomach, lungs, etc. (2) PNS (b) Comprises of the ductless glands secreting hormones (3) ANS (c) Comprises of brain and spinal cord (4) Endocrine system (d) Comprises of cranial nerves and spinal nerves Ans. (i - c), (ii - d), (iii - a), (iv - b). 6. Column I Column II (i) Taste buds at the tip of the tongue (a) Detect salty and sour tastes (ii) Olfactory receptors (b) Detect bitter tastes (iii) Taste buds at the back of the (c) Sense of smell tongue (iv) Taste buds at the sides of the (d) Detect sweet tastes tongue Ans. (i - d), (ii - c), (iii - b), (iv - a). 262 SCHOOL SECTION

5 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 7. Column I Column II (i) Medulla oblongata (a) Reflex arc (ii) Spinal cord (b) Main thinking part of brain (iii) Cerebellum (c) Involuntary activities like breathing, blood flow, etc. (iv) Cerebrum (d) Voluntary movements and maintaining balance of the body Ans. (i - c), (ii - a), (iii - d), (iv - b). Q.I (D) State whether the following statements are true or false. If false write the corrected statement : 1. The loss of water from the plants is known as translocation. Ans. False. The loss of water from the plants is known as transpiration. 2. Transpiration takes place in the leaves through stomatal openings. Ans. True. 3. There is growth involved in the seismonastic movement exhibited by plants. Ans. False. There is no growth involved in the seismonastic movement exhibited by plants. 4. Unlike animals, plants do not have a nervous system or muscular system. Ans. True. 5. When light falls on growing plants, the hormone auxin is synthesized at the tip of the root. Ans. False. When light falls on growing plants, the hormone auxin is synthesized at the tip of the shoot. 6. Plants possess specialized tissue for conduction of information of touch to bring about movement. Ans. False. Plants use electrochemical means to transfer the information. 7. The central nervous system comprises of all the nerves. Ans. False. The CNS comprises of brain and the spinal cord. 8. The neuroglia are supportive cells which assist the neurons in their function. Ans. True. 9. All the information from our environment is picked up by axons of a neuron. Ans. False. All the information from our environment is picked up by the specialized tips of dendrites of a neuron. 10. Muscle cells possess special kinds of proteins which help them change their shape. Ans. True. 11. Sensory neurons conduct impulses from sense organs to the brain and spinal cord. Ans. True. 12. Motor neurons conduct impulses from effector organs like muscles and glands to brain and spinal cord. Ans. False. Motor neurons conduct impulses from brain and spinal cord to effector organs. 13. Human brain, on an average, weighs gram. Ans. True. 14. Cranial nerves arise from spinal cord. Ans. False. Cranial nerves arise from the brain whereas spinal nerves arise from the spinal cord. 15. The forebrain or the cerebrum is the main thinking part of the brain. Ans. True. SCHOOL SECTION 263

6 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 16. Nerve impulses are slower and long lasting whereas hormonal action is rapid and of short duration. Ans. False. Nerve impulses are rapid and of short duration and hormonal action is much slower and long lasting. 17. The medulla oblongata is a component of the mid brain. Ans. False. The medulla oblongata is a component of the hind brain. 18. The medulla oblongata controls vital involuntary activities like blood flow, breathing, sneezing, etc. Ans. True. 19. Affarent nerves carry impulses from the brain to the sensory organs. Ans. False. Affarent nerves carry impulses from the sensory organs to the nerves. Q.I (E) Find the odd man out : 1. Digestion, Transpiration, Circulation, Excretion. Ans. Transpiration. It is a process which takes place in plants whereas the rest are processes occurring in animals. 2. Seismonastic, Phototropic, Chemotropic, Hydrotropic Ans. Seismonastic. It is a growth independent movement whereas rest are growth dependent movements. 3. Gibberellins, Auxins, Cytokinins, Thyroxine. Ans. Thyroxine. It is a growth hormone in animals whereas the rest are growth hormones in plants. 4. Spinal cord, Cerebrum, Cerebellum, Medulla oblongata. Ans. Spinal cord. It is not a part of the brain, whereas the rest are the three regions of the brain. 5. Dendrite, Cell body, Axon, Synapse. Ans. Synapse. It is a microscopic gap between two neurons whereas the rest are main parts of the neuron. 6. Auxin, Gibberellins, Insulin, Abscissic acid. Ans. Insulin. It is a hormone in animals whereas the rest are hormones in plants. Q.I (F) Write the correlated terms : 1. Loss of water : Transpiration :: Ascent of sap :.... Ans. Translocation. 2. Movement of shoot system : Phototropic :: Movement of root system :.... Ans. Gravitropic and hydrotropic. 3. Brain : Cranium :: Spinal cord :.... Ans. Vertebral column. 4. Cavities of the brain : Ventricles :: Cavity of the spinal cord :.... Ans. Central canal. 5. Central nervous system : Brain and spinal cord :: Peripheral nervous system :.... Ans. Nerves. 6. Involuntary activities : Medulla oblongata :: Balance of the body :.... Ans. Cerebellum. 7. Tip of the tongue : Sweet taste :: Back of the tongue :.... Ans. Bitter taste. 8. Bending of stem towards light : Phototropism :: Growth of pollen tube towards ovules :.... Ans. Chemotropism. 9. Growth of the stem : Gibberellins :: Wilting of leaves :.... Ans. Abscissic acid. 264 SCHOOL SECTION

7 MT EDUCARE LTD. SCIENCE & TECHNOLOGY Q.II (A) Name the following : *1. Growth of plant in response to external factors. Ans. Tropism. *2. Maintenance of steady state by different systems in an organism. Ans. Homoeostasis. *3. Cells those assist the neurons in their function. Ans. Neuroglia. *4. The small gap between the consecutive neurons. Ans. Synapse. *5. Part of the brain that co ordinates the voluntary movements. Ans. Cerebellum. 6. The bony structure protecting the brain. Ans. Cranium (skull). 7. The bony structure protecting the spinal cord. Ans. Vertebral column (Backbone). 8. Protective membranes in the space between the soft CNS and bone. Ans. Meninges. 9. Cavities present on the different parts of the brain. Ans. Ventricles. 10. Long cavity present in the spinal cord. Ans. Central canal. 11. Fluid present in the cavities of brain, spinal cord and space between meninges. Ans. Cerebrospinal fluid. Q.II (B) Define the following : 1. Homoeostasis. Ans. The maintenance of the steady state by different systems of an organism for its optimal functioning because of a perfect co-ordination is called homoeostasis. 2. Tropism OR Tropic movements. Ans. The movement or growth of any part of a plant in response to an external stimulus is called tropism or tropic movements. 3. Reflex action. Ans. Any sudden action in response to some happening in the environment, without thinking about it or without feeling in control of our reactions is called reflex action. Q.III (A) Give scientific reasons : *1. Roots of plants go away from light. Ans. 1. The roots of plants respond to the stimulus of gravity and water. 2. These responses are called gravitropic and hydrotropic movements respectively. 3. Plants absorb water in which minerals are dissolved, from the soil with the help of their roots. 4. Therefore, roots of plants go away from light. *2. Hormones secreted by the endocrine glands are present everywhere in the body. Ans. 1. The chemical control is brought about by chemical substances called hormones. 2. These hormones are secreted by endocrine glands or ductless glands. 3. These glands do not have any duct to store or transport their secretions. 4. Thus, on production these hormones are directly released into the blood stream. SCHOOL SECTION 265

8 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 5. Due to this, the hormones reach everywhere in the body, though the gland secreting them is located in a particular place. 6. Therefore, hormones secreted by the endocrine glands are present everywhere in the body. *3. Insulin plays an important role in controlling the sugar level of blood. Ans. 1. Insulin is a hormone which controls the sugar level of blood. 2. It is very important that insulin should be secreted according to the amount of sugar in the blood. 3. The required quantity of insulin released and the time of released are regulated by feedback mechanisms. 4. When the sugar level of blood rises, it it detected by the cells of the pancreas which respond to the situation by producing more insulin so that the sugar level comes back to normal. 5. On the other hand, as the sugar level of the blood falls, the secretion of insulin is reduced. 6. Therefore, insulin plays an important role in controlling the sugar level of blood. 4. Tendril entwines itself around the object and clings to it. Ans. 1. Tendrils are sensitive to touch. 2. When they come in contact with any object, the portion of the tendril which is in contact, becomes sluggish whereas growth is faster at the other portion. 3. This causes the tendril to entwine itself around the object and thus cling to it. 5. Reflex arcs are evolved in animals. Ans. 1. In animals, the thinking process of the brain is a bit slow. 2. In many animals, specially lower animals the complex neuron network needed for thinking is not there or is not well developed. 3. Hence reflex arcs have been evolved as efficient ways of functioning in the absence of the true thought process. 4. However, in spite of the presence of complex neuron networks, reflex arcs continue to be more efficient for quick responses. Q.III (B) Answer the following questions in short : 1. State the characteristic features of living organisms. Which characteristic feature is less conspicuous in plants? Ans. 1. Living organisms are made up of cells. 2. They need nutrition. 3. They grow and develop up to certain limits. 4. They receive stimuli from the environment and respond to the same. 5. They reproduce. 6. They show structural and functional organization. 7. They show ability to adapt to changes in their environment. Out of these features, showing the ability to adapt to the changes in their environment is less conspicuous in plants. 2. How do we taste food? Ans. 1. There are distinct regions on the tongue where main tastes are detected or recognized. 2. Taste buds at the tip of the tongue detect sweet tastes, those at the back detect bitter tastes and those at the side of the tongue detect salty and sour tastes. 3. The taste buds on the tongue transmit the different taste information as a message to the brain. 4. Brain processes the information and tells us what food is actually in our mouth. 266 SCHOOL SECTION

9 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 3. How do we smell? Ans. 1. Smells enter the back of the nose when you inhale. They also rise up from the back of the mouth as we eat, which is why smell is such an important part of tasting and enjoying food. 2. This is the reason why food tastes odd when we have a cold as the nasal organs become inflamed and the sense of smell is temporarily smothered. 4. How does our memory work? Ans. 1. Sensory memory is brief, it tells us what is happening around us. 2. Short term memory lasts only for 30 seconds. Eg. We remember a phone number and dial it and then it vanishes. 3. Long term memory is for the things that we have carefully learned and memorized. *5. Classify the following as voluntary and involuntary movements. 1. Coughing 2. Food getting digested 3. Moving a table 4. Kicking a ball 5. Beating of heart 6. Release of hormones into blood 7. Flying a kite. Ans. 1. Coughing Involuntary 2. Food getting digested Involuntary 3. Moving a table Voluntary 4. Kicking a ball Voluntary 5. Beating of heart Involuntary 6. Release of hormones into blood Involuntary 7. Flying a kite Voluntary. 6. Give examples of growth independent movements in plants. Ans. 1. Closing of leaflets of mimosa plant when touched. 2. Opening of lotus in the morning and tuberose at night. 3. Insectivorous plants like drosera curl inwards at the touch of an insect and trap the insect. 4. The explosive fruit of balsam plant bursts open at an appropriate time thus scattering the seeds. 7. How does the Venus flytrap traps insects? Ans. 1. The Venus flytrap has a trap which looks an smells like a flower to insects. 2. When insects land on it, they touch a trigger hair which slams the trap shut and they are then digested by the plant. 8. How are neurons classified? State their functions. Ans. 1. Neurons are of three types i.e. sensory neuron, motor neuron and association neuron. 2. Sensory neurons conduct impulses from the sense organs to the brain and spinal cord. 3. Motor neurons conduct impulses from the brain and spinal cord to the effector organs like muscles and glands. 4. Association neurons perform integrative functions of the nervous system. 9. How are nerves categorized based on their functions? Ans. 1. On the basis of their functions, the nerves are categorized as afferent nerves and efferent nerves. 2. Afferent nerves carry impulses from the sensory organs to the brain. 3. Efferent nerves carry impulses from the brain to the sensory organs. Q.III (C) Write short notes for the following : *1. Reflex action. Ans. 1. Any sudden change in response to some happening in the environment, is called as reflex action. SCHOOL SECTION 267

10 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 2. We react to such a situation without thinking about it or without feeling in control of our reactions. 3. Example : When we touch a vessel containing very hot tea, immediately the hand is withdrawn. 4. In this case, the nerves that detect pain are connected to the nerves that bring about the action of the muscle, hence the action is completed quickly. 5. Nerves from all over the body meeting in a bundle in such a connection is called as the spinal cord. 6. Hence reflex arcs are formed in the spinal cord, although the messages reach the brain. *2. Co-ordination in plants. Ans. 1. Plants do not have a nervous system or muscular system. 2. The movements exhibited by plants are mainly in response to the stimulus. 3. In certain sensitive plants like Mimosa, movement is in response to the stimulus of touch. This movement is known as seismonastic movement. There is no growth involved in this movement. 4. On the other hand, the movement of a seedling is because of growth. If growth is prevented, it does not exhibit any movement. 5. Thus, we conclude that plants exhibit two types of movement, one which is growth dependent movement and the other which is growth independent movement. Q.IV (A) Distinguish between : *1. Voluntary movements and Involuntary movements. Ans. Voluntary movements Involuntary movements 1. Movements which are under our control are called voluntary movements. 2. Voluntary movements require thinking. 3. Voluntary movements are controlled by cerebellum. 4. Eg. Moving a table, kicking a ball, walking, clapping hands etc. 2. Growth dependent movements and Growth independent movements. Ans. Growth dependent movements Growth independent movements 1. Growth dependent movements result in growth of the plants. 2. Growth dependent movements are also called as tropic movements. 3. Growth dependent movements are in response to the stimulus of light, water, gravity etc. 4. Eg. Bending of stem towards light, movement of roots towards gravity and water. 1. Movements which are not under our control are called involuntary movements. 2. Involuntary movements do not require thinking. 3. Involuntary movements are controlled by midbrain and hindbrain. 4. Eg. Blood flow, breathing, sneezing etc. 1. Growth independent movements do not result in growth of the plants. 2. Growth independent movements are also known as nastic movements. 3. Growth independent movements are in response to the stimulus of touch. 4. Eg. Closing of leaflets in mimosa plant, shutting of Venus flytrap. 268 SCHOOL SECTION

11 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 3. Central nervous system and Peripheral nervous system. Ans. Central nervous system Peripheral nervous system 1. Central nervous system is composed of brain and spinal cord. 2. Central nervous system is located in the centre of the body. 4. Cerebrum and Cerebellum. Ans. Cerebrum 1. Cerebrum is the part of forebrain. 2. Cerebrum is responsible for thinking and interpreting sensory information. Q.IV (B) Draw a neat and labelled diagram of the following : 1. Human brain showing different areas and their responsibilities. Ans. Movement area Touch area Thought area 1. Peripheral nervous system is composed of all the nerves. 2. Peripheral nerves are spread throughout the body. Cerebellum 1. Cerebellum is the part of hindbrain. 2. Cerebellum is responsible for coordinating the voluntary movements and also maintaining the balance of the body. Hearing area Speed Vision area 2. V.S. of human brain. Ans. Corpus callosum Cerebrum Pineal body Pituitary gland Pons varolii Medulla oblongata Arbor vitae Cerebellum SCHOOL SECTION 269

12 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 3. Neuron. Ans. Dendrites Cyton (cell body) Nucleus Axon 4. Neuromuscular junction. Ans. Axon Neuromuscular junction Muscle fiber Capillary Mitochondrion 5. Chemotropism (Growth of Pollen tube towards the ovules). Ans. Pollen grain (germinating) Pollen tube Zygote formation (a) Ovum (b) 270 SCHOOL SECTION

13 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 6. Reflex arc. Ans. Spinal chord (CNS) Message to brain Sensory neuron Receptors-heat pain Receptors in skin Motor neuron Relay neuron Effector-muscle in arm Q.V Answer the following in detail : 1. What is co ordination? Explain its importance. Ans. 1. Co ordination means orderly execution of the activities, so that an organism shows proper growth and development. 2. For example, man sees food, hand picks it up and puts it into the mouth. The morsel of food is chewed in the mouth with the help of teeth assisted by the tongue. The food is mixed with the enzymes in the saliva secreted by salivary glands. 3. For further biochemical reactions, the food is sent to stomach and the complex food materials are broken down into simple forms such as glucose, amino acids and fatty acids. 4. The simple digested food is absorbed into blood through intestines and undigested food is excreted. 5. Thus digestion, absorption, circulation, excretion are interdependent. 6. Oxygen is necessary to obtain energy from glucose and fatty acid. Oxygen is supplied by the process of respiration. 7. Thus, various organ systems function in a synchronized manner. Coordination is necessary between organs and organ systems that bring about all the inter-related life processes. 8. Any disturbance at any stage due to lack of co-ordination can leave the desired process incomplete. 9. Thus for successful completion of desired process, there has to be perfect co ordination between different systems and / or organs involved at every step. 2. What is homoeostasis? How is it maintained in an individual s body? Ans. 1. The maintenance of the steady state by different systems of an organism for its optimal functioning because of a perfect co ordination is called homoeostasis. 2. Control and co ordination provide stability and maintenance of the steady state i.e. creation of a relatively constant environmental condition within any organism. 3. In an individual s body perfect co ordination between internal activities of the body caused due to water or enzyme level and temperature etc. and similar such external environmental stimuli must be there to achieve homoeostasis (e.g. In summer, with excessive sweating we feel more thirsty.) 4. In animals, nervous system along with hormones bring about co ordination. 5. In plants, due to lack of nervous system only hormones bring about chemical co ordination. SCHOOL SECTION 271

14 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 3. What is tropic movement? Describe the different types of tropic movements. Ans. The movement or growth of any part of a plant in response to an external stimulus is called tropism or tropic movement. Tropic movements are of three types : 1. Phototropic movement (Phototropism) : The movement of a plant in response to the stimulus of light is called phototropism. E.g. the shoot system of any plant responds towards the stimulus of light i.e. it grows in the direction of source of light. 2. Gravitropic movement (Gravitropism) : The root system of the plants responds to the stimulus of gravity. This movement is called as gravitropic movement. *3. Hydrotropic movement (Hydrotropism) : The root system of the plants responds to the stimulus of water. This movement is called hydrotropic movement. 4. Chemotropic movement (Chemotropism) : It is the movement of a plant part in response to certain chemicals. E.g. the growth of pollen tube towards the ovules. 4. Which are the different parts of the human nervous system? Ans. The human nervous system can be divided into : 1. The Central Nervous System (CNS) : It comprises of the brain and spinal cord and regulates all activities of the body. 2. The Peripheral Nervous System (PNS) : It includes all the nerves. The nerves form a network and spread throughout the body. They are instrumental in connecting all parts of the body to the central nervous system. 3. The Autonomic Nervous Sytem (ANS) : If comprises of all the nerves present in the involuntary organs like heart, stomach, lungs etc. 4. On the basis of their function, the nerves are categorized as afferent and efferent nerves. 5. The nerves are composed of neurons and neuroglia. The neurons are specialized cells capable of creating and transmitting electrochemical impulses. The neuroglia are supportive cells which assist the neurons in their function. 5. Describe the Central Nervous System in human beings. Ans. 1. The central Nervous system is a delicate structure composed of the brain and spinal cord. 2. The brain is protected by a bony structure called cranium or skull and the spinal cord is protected by the vertebral column or the back bone. 3. In between the soft CNS and the bone are present protective membranes called the meninges. 4. There are cavities present on the different parts of brain known as ventricles, while the long cavity of the spinal cord is called central canal. 5. The ventricles, central canal and the space between the meninges are filled with cerebrospinal fluid (CSF). 6. The CSF keeps the CNS well nourished and also protects it from absorbing mechanical shocks. 7. The brain is a complex organ divided into three regions : the forebrain, midbrain and hindbrain. 8. The forebrain or cerebrum is the main thinking part of the brain. It has regions which receive the sensory impulses from various receptors. The areas for smell, hearing, vision etc. are separate. 272 SCHOOL SECTION

15 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 9. Even there are different areas where the sensory information is received and interpreted and put together with the information received from other receptors as well as the information that is already stored in the brain. Such centres are known as association centres. 10. Involuntary activities like blood flow, breathing, sneezing etc. are controlled by Medulla oblongata, a component of the hind brain. 11. Another component of the hind brain is cerebellum. It is responsible for co-ordinating the voluntary movements and also maintaining the balance of our body. Eg. riding a bicycle, picking up an object from the floor, running along a straight line etc. 12. Spinal cord is an important part of the CNS which extends through the vertebral column. It controls the reflex actions. 13. Each side of our brain controls the opposite side of the body. Usually the left side of the brain controls speaking, writing and logical thought. The right side of the brain controls artistic abilities. *6. Describe chemical co ordination in animals. Ans. 1. The chemical control is brought about by chemical substances called hormones. 2. These hormones are secreted by endocrine glands also known as the ductless glands. 3. On production these hormones are directly released into the blood stream, due to this the hormones reach every where in the body though the gland secreting them is located in a particular place. 4. The endocrine system shares its responsibility of control and co ordination with the nervous system. Both systems work in co-operation to integrate and control various body activities. 5. The significant difference between the two systems is that the nerve impulses are rapid and are usually of short duration while the hormonal action is much slower and longlasting. 6. Eg. Suppose some animal like rabbit is caught in a scary situation, its body has to be prepared either to fight with the situation or to run away from there. Both are extremely complicated activities that will utilize a great deal of energy in controlled ways. 7. If the body of the rabbit has to trust only the electrical impulses through nerve cells, then the tissues instructed to get prepared for the activity would be limited. On the other hand, if chemical signals were to be sent, it would reach each and every cell of the body and render a wide range of changes that are needed. 8. In chemical co-ordination, the hormones are secreted according to the requirement. The required quantity of hormone released and the time of release is regulated by feedback mechanisms. Example : When the sugar level of blood rises, it is detected by the cells of the pancreas which respond to the situation by producing more insulin. As the sugar level of the blood falls, the secretion of insulin is reduced. 7. Describe the conduction of nerve impulse. Ans. 1. Nerves are composed of neurons and neuroglia. The neurons are specialized cells capable of creating and transmitting electrochemical impulses. 2. All the information from our environment is picked up by the specialized tips of dendrites of a neuron. 3. This sets off a chemical reaction producing an electrical impulse which travels from dendrite to cell body, from there through the axon (nerve fibre) to its end. SCHOOL SECTION 273

16 SCIENCE & TECHNOLOGY MT EDUCARE LTD. 4. At the end of the first axon, the electrical impulse induces release of some chemicals. 5. These chemicals produced go across the small gap (synapse) of 2-20nm between the neurons and start a similar electrical impulse in the dendrite of the next neuron. 6. The impulses travel in body in the above manner from the neurons and are delivered to the muscle cell or glands. 7. When an action or movement has to be brought about, the muscle tissue does the final job. Muscle cells possess special kinds of proteins which are capable of bringing about change in their shape and make the cell capable to respond to the nervous electrical impulses. 8. Describe the movements in plants which are growth independent. Ans. 1. Certain movements of plants do not result in their growth and are termed as growth independent movements. 2. Hormones bring about various movements in plants in response to the changes occuring in their surroundings. 3. These movements also happen at a place different from the place of touch. This means that the information that a touch has occured has been communicated. Eg. Closing of leaflets of Mimosa on touch. 4. Plants use electrochemical means to transfer information from cell to another as there is no specialized tissue for the conduction of information. 5. Then the movement is brought about as the plant cells change their shapes by altering the amount of water in them. By this the cells either swell or shrink and thus change their shape. 6. Some other movements seen in plants which are growth independent are - lotus opens in the morning and the tube rose opens at night, the tentacles on the leaves of the insectivorous plants like Drosera curl inwards at the touch of an insect and trap the insect, the explosive fruit of balsam plant bursts open at appropriate time thus scattering the seeds. 7. The Venus flytrap which looks and smells like a flower to insects. When they land on it they touch a trigger hair which slams the trap shut and they digested by the plant. 9. Describe the growth dependent movements in plants. Ans. 1. The movement or growth of any part of a plant in response to an external stimulus is called tropism or tropic movements. 2. The shoot system of any plant responds towards the stimulus of light i.e., it grows in the direction of source of light. When a potted plant is kept near the window in a room, the stem bends slightly towards the window. This movement exhibited by the plant is called phototropic movement. 3. When light falls on a part of growing plant, a hormone called auxin which is synthesized at the tip of the shoot helps the cells to grow longer. As the light is falling on one side of the plant, this hormone auxin diffuses towards the shady side of the shoot and stimulates the cells to grow longer. 4. On the other hand, the root system of the plants responds to the stimulus of gravity and water. These responses are called gravitropic and hydrotropic movements respectively. 5. The movement of plant part in response to certain chemicals. Eg. The growth of pollen tubes towards the ovules. 274 SCHOOL SECTION

17 MT EDUCARE LTD. SCIENCE & TECHNOLOGY Q.VI Answer the following questions in one sentence each : 1. Name the sense organs. Ans. The sense organs are eyes, nose, ears, tongue, skin. 2. Where do you find the gustatory and olfactory receptors? Ans. Gustatory receptors are located on the tongue and olfactory receptors are located in the nose. 3. What do the gustatory and olfactory receptors detect? Ans. Gustatory receptors detect tastes and olfactory receptors detect smell. 4. How are life processes controlled in unicellular amoeba? Ans. In unicellular amoeba, there is no nervous system. The cell is sensitive enough to control its own life processes or activities. 5. How is the nerve cord formed in annelidans like earthworm? Ans. In annelidans like earthworm a number of nerve cells come together and form a cluster. These clusters are joined together to form a beaded structure called the nerve cord. 6. What is short term memory? Ans. Short term memory lasts only for 30 seconds. Eg. Remember a phone number and dial it and then it vanishes from memory. 7. What is long term memory? Ans. Long term memory is the memory for things that we have carefully learned and memorized. 8. What is a neuron? Ans. Neuron is a specialized cell capable of creating and transmitting electrochemical impulses. 9. What is the function of hormones in arthropods? Ans. In arthropods, hormones induce colour changes and are influential in regulating development. SCHOOL SECTION 275

18 SCIENCE & TECHNOLOGY MT EDUCARE LTD. ACTIVITY BASED QUESTIONS ACTIVITY : 11.1 Q. Take out from the refrigerator the polyethylene bag in which vegetables are kept. After 5 minutes, remove the vegetables from the bag and feel the inside of the bag. What is your observation? Ans. The inside of the bag feels moist. This is due to loss of water from the vegetables. This loss of water is called transpiration. ACTIVITY : 11.2 Take a shallow bottle with a wide mouth. Put some moist cotton in it. Place a few sprouted seeds on it. Q. Observe the directions of growth of radicle and plumule. Ans. The radicle grows downwards and the plumule grows upwards. Pick up one of the sprouts and place it in such a way that the radicle is towards the source of light and the plumule is away from light. Q. Observe the directions of growth daily. Ans. The radicle bends downwards and the plumule bends towards light. Q. What do you conclude from your observations? Ans. The radicle is the part which forms roots so it bends downwards towards the stimulus of gravity and water whereas the plumule is the part which forms the stem so it bends towards the source of light. ACTIVITY : 11.3 Look for Mimosa plants in the garden or along the hedges. Touch the leaves of this plant. Q. What do you observe? What happens to them? Ans. The leaflets of Mimosa plant fold and droop down. Q. After half an hour, observe the same plant. Note down you observation. Ans. The leaflets again unfold and return to their normal position. ACTIVITY : 11.4 Q. An inter-house Basketball match is in progress at your school s court. List a few actions of the players where you observe control and coordination in their movements. Ans. Control and co-ordination is observed in dodging the ball, jumping, running, passing it to the team mate and dribbling the ball. ACTIVITY : 11.5 Q. Your pet dog Dollar is comfortably taking a nap. Go near him and drop a stainless steel spoon on the floor. What do you observe? Ans. The dog startles and wakes up and his ear pinnae are raised. 276 SCHOOL SECTION

19 MT EDUCARE LTD. SCIENCE & TECHNOLOGY ACTIVITY : 11.6 Q. List the endocrine glands present in human beings. Where are they positioned in our body? Consult books in the library to find out about their functions. Ans. Sr. No Endocrine glands Hypothalamus Pituitary (Master gland) Thyroid Adrenal Pancreas Ovary (In females) Testis (In males) Pineal Thymus Brain Location Base of forebrain Lower part of the neck A pair of cap shaped organs above each kidney In the curve of the small intestine Lie on the lateral walls of the pelvis In the scrotum Near the center of the brain, between the two hemispheres Behind the sternum and above the trachea and heart Hormones Releasing hormones Growth hormones Trophic hormones Prolactin Vasopressin Oxytocin Thyroxine Adrenaline and Cortisone Insulin and glucagon Oestrogen and Progesterone Testosterone Melatonin Thymosin Functions Regulation of the secretion of hormones from the pituitary gland. Development of bones and tissues. Regulation of the secretion of hormones from other endocrine glands. Regulation of the function of mammary glands. Regulation of water and electrolyte balance. Stimulates contractions of smooth muscles, helps in child birth and lactation. Regulates rate of growth and metabolism. Regulation of blood pressure, heart rate. Carbohydrate metabolism and mineral balance. Regulates sugar metabolism. Development of secondary sexual characters. Eg. Development of breasts in female. Regulation of menstrual cycle. Development of secondary sexual characters in male. (Masculine features such as growth of moustaches and beard.) Its regulates the wake/sleep patterns and seasonal functions. It stimulates the activity of the T- lymphocytes which are responsible for invading organisms and killing them. SCHOOL SECTION 277

20 SCIENCE & TECHNOLOGY MT EDUCARE LTD. HOTS QUESTIONS & ANSWERS 1. The plant which has fruits is seen bending towards sunlight. This response of the plant to light is because of a hormone which is responsible for... (a) helping the cells of the shoot to grow longer. (b) helping the cells of the fruit to divide. (c) helping the inhibition of growth of the part of the plant which is directly in contact with the sunlight. Ans. Helping the cells of the shoot to grow longer. 2. State whether afferent or efferent nerves would be responsible for passing the impulses between the brain and sensory organs or muscles or other body organs. (a) My finger got burnt while cooking. (b) The wild life photographer started running after the lion suddenly jumped before him from nowhere. Ans. (a) Afferent nerve carried the impulse from finger to the brain. (b) Efferent nerve carried the impulse from brain to the muscles of the leg. 3. In some of the plants, as a response to a stimulus, a small part of a plant such as a leaf, alters its shape. Explain. Ans. Various stimuli such as touch or an insect make some of the plants respond by altering its shape. The information about the stimulus is passed on from one cell to another with the help of electrical or chemical means. Then, the alteration in shape or movement is brought about by changing the amount of water inside the cells i.e. either by swelling or shrinking, thus changing the shape. Hormones are mainly responsible cause for these movements in the plant as a response to the stimuli. 4. Look at the following actions. Write the name of that part of the brain which controls them. (a) Riding a bicycle (b) Sneezing (c) Thinking (d) Speaking (e) Artistic abilities. Ans. (a) Hind brain Cerebellum. (b) Hind brain Medulla oblongata. (c) Fore brain Cerebellum. (d) Left part of the brain. (e) Right part of the brain. 5. Classify the following actions into voluntary and involuntary. (a) Mr. Ajay s blood pressure shot up after a fight with his neighbour. (b) Shantanu was forced by his friends to tell a lie. Ans. (a) Involuntary. (b) Voluntary. 278 SCHOOL SECTION

21 MT EDUCARE LTD. SCIENCE & TECHNOLOGY 6. The following statement is false. What is the truth? Why? In human beings, in order to facilitate the secretion of hormones, endocrine glands are placed in ducts. Ans. Endocrine glands are ductlesss glands. They are also called as glands of secretion. The hormone is secreted directly into the blood stream. This provision is made to facilitate the transport of hormone to all the parts of the body in order to activate necessary body organs in a short duration. The hormone secreted is called as chemical messenger. 7. Evaluate the following situations and state if the movements were controlled by central and peripheral nervous system or autonomous nervous system : (a) Ram bent down to pick up his books on the floor. (b) My heart started beating very rapidly. (c) He blinked when he had to face a sudden flash of light. (d) Shyam was flying kite. (e) Seema s stomach was upset after eating stale food. Ans. (a) Central and peripheral nervous system. (b) Autonomous nervous system. (c) Autonomous nervous system. (d) Central and peripheral nervous system. ( e) Autonomous nervous system. 8. Imagine that you are given powers to bring out changes in the system of plants. What should be done to... (a) stop the growth of the root towards water? (b) expedite the process of cell division? Ans. (a) Remove the hormone auxin which is responsible for the growth and induce Abscissic acid which inhibits the growth of a plant. (b) Induce the hormone cytokinins which promotes the cell division. 9. Give three names of animals in accordance with the advancement of their nervous system. Justify. Ans. (a) Amoeba. There is no nervous system at all. The cell carries out all the functions. (b) Any member of the family of annelids in which a number of nerve cells come together to form a cluster called nerve cord. (E.g. Earthworm) (c) Human beings in which a well developed nervous system is present consisting of CNS (Central nervous system), PNS (Peripheral nervous system), ANS (Autonomous nervous system). 10. What would happen if... (a) leaves a plant are coated with paint. (b) animals loose the capacity of reflex action. (c) plants lack Abscissic acid. (d) peripheral and autonomous nervous systems are detached from each other and from Central nervous system. SCHOOL SECTION 279

22 SCIENCE & TECHNOLOGY MT EDUCARE LTD. (e) there appears malfunctioning in the mid and hind brain which controls involuntary action in the body of animals. Ans. (a) The stomata would get blocked. Transpiration of water and gases would not happen resulting into death of the plant. (b) They would not be able to defend themselves from emergencies resulting into injury or death. (c) Abscissic acid is a hormone responsible for inhibiting growth of the plant. The plants would grow limitlessly. The leaves would not wilt. (d) There would not be any co-ordination in the body of the animals and their existence would be impossible. ( e) The heart would stop as its beating is an involuntary action. The animals would be dead. 11. The movement of a plant organ in response to the stimulus of contact is called thigmotropism. It is seen in plants which climb by means of tendrils which are sensitive to the contact stimulus. Tendrils are found in plants like Cucurbita and grapevine. Only the apical part of the tendril is sensitive to contact. Questions : (a) What is thigmotropism? (b) Which plants show thigmotropism? (c) Give the names of any two plants which show tendrils. (d) Which part of the tendril is sensitive to contact? Ans. (a) The movement of a plant organ in response to the stimulus of contact is called thigmotropism. (b) Thigmotropism is seen in plants which climb by means of tendrils. (c) Plants such as Cucurbita and grapevine show tendrils. (d) The apical part of the tendril is sensitive to contact. 12. Name the plant hormone : (a) Which inhibits growth and causes wilting of leaves? (b) Which promotes cell division? Ans. (a) Abscissic acid. (b) Cytokinins. 280 SCHOOL SECTION

23 MT EDUCARE LTD. SCIENCE & TECHNOLOGY Found in Plants Movement is CONCEPT MAP Control and Co-ordination helps in Found in Animals Movement is controlled by Growth dependent Growth independent Nerves Chemicals lead to hormones from Spinal cord Brain Endocrine glands sometimes influence the action of comprises of controls Forebrain Mid brain Hind brain responsible for Reflex Action Voluntary Action Involuntary Action SCHOOL SECTION 281

24 S.S.C. Marks : 20 CHAPTER 11 : REGULATORS OF LIFE SCIENCE Duration : 1 hr. Q.I [A] Fill in the blanks : do not possess a nervous system. 2. Response to the stimulus of touch is called... whereas response to the stimulus of chemicals is called as Brain is the main... centre of the body. 4. The loss of water from the plants is known as.... Q.I [B] Match the columns : 2 Column A Column B 1. Gibberellins (a) Promoting cell division in fruits and seeds 2. Cytokinins (b) Tip of shoot to grow longer 3. Abscissic acid (c) Promoting growth of stem 4. Auxins (d) Wilting of leaves Q.I [C] Name the following : 3 1. Maintenance of steady state by different systems in an organism. 2. Cells those assist the neurons in their function. 3. The small gap between the consecutive neurons. Q.II Give scientific reasons : (Any Two) 4 1. Roots of plants go away from light. 2. Hormones secreted by the endocrine glands are present everywhere in the body. 3. Insulin plays an important role in controlling the sugar level of blood. Q.III Answer the following questions : (Any Two) 4 1. Write a note on Reflex action. 2. Write a note on Co-ordination in plants. 3. Distinguish between Voluntary and Involuntary movements. 4. What is tropic movement? Describe the different types of tropic movements. Q.IV Answer the following : (Any One) 5 1. Describe chemical co-ordination in animals. 2. Describe the conduction of nerve impulse. Best Of Luck