9th Science 2 – Ch.15. Life Processes PDF

9th Science 2 – Ch.15. Life Processes in Living Organisms Exercise Question & Answers Q.1. Match the columns:- ‘A’ ‘B’ 1. Growth of pollen tube towards ovule – b. Chemotropic Movement 2. Growth of shoot syste...

9th Science 2 – Ch.15. Life Processes in Living Organisms Exercise Question & Answers Q.1. Match the columns:- ‘A’ ‘B’ 1. Growth of pollen tube towards ovule – b. Chemotropic Movement 2. Growth of shoot system – c. Phototropic Movement 3. Growth of root system – a. Gravitropic Movement 4. Growth towards water – e. Hydrotropic Movement Q.2. Complete the paragraph with words from the brackets. (Nerve, muscle cell, impulses, dendrite, synapse, axon, reflex action, cell body) 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, impulses were conducted in the body and the process of reflex action was completed by conducting the impulses from nerve to muscle cell. Q.3. Explain the following:- (a) Root Pressure (i) Root cells are in contact with water and minerals in the soil. (ii) Water and minerals enter the cells on the root surface due to differences in concentration. (iii) As a result, these cells become turgid. These turgid cells exert pressure on the adjacent cells. This is called ‘root pressure’. (iv) Under the effect of this pressure, water and minerals reach the xylem of the roots and to reduce this difference in concentration they are continuously pushed forward. (v) As a result of this continuous movement, a water column is formed, which is continuously pushed ahead. (vi) This pressure is sufficient to lift the water up in shrubs, small plants and small trees. (b) Transpiration (i) Plants give out water in the form of vapour through the stomata on their leaves. (ii) Two cells called guard cells are present around the stomata. These cells control the opening and closing of stomata. Transpiration occurs through these stomata. (iii) Water is released into the atmosphere by leaves through the process of evaporation. (iv) As a result, water level in the epidermal layer of the leaf decreases. (v) Water is brought up to the leaves through the xylem so as to compensate for the lost water. (vi) Transpiration helps in absorption of water and minerals and distribution to all parts of the plant whereas root pressure performs the important role of pushing the water up during the night time. (c) Nerve Cell (i) Special types of cells which conduct impulses from one place to another in the body are called neurons. (ii) Neurons are the structural and functional units of the nervous system. (iii) Nerve cells, the largest cells in the human the body, may measure up to a few metres in length. (iv) Nerve cells have the ability to generate and conduct electrochemical impulses. (v) The cells that support the nerve cells and help in their functioning are called neuroglia. (vi) Nerve cells and neuroglial cells together form the nerves (d) Human Brain (i) The organization of the brain is extremely delicate and highly evolved. (ii) The brain is the main controlling part of the nervous system and it is safely located in the cranial cavity. (iii) The spinal cord is protected by the vertebral column. (iv) In the space between the delicate central nervous system and its bony covering are the protective layers called the meninges. (v) Cavities present in various parts of the brain are called ‘ventricles’ whereas the long tubular cavity of the spinal cord is called the ‘central canal’. (vi) The ventricles, central canal and spaces between the meninges are filled with cerebro-spinal fluid. This fluid supplies nutrients to the central nervous system and protects it from shock.  (vii) The brain of an adult human weighs about 1300 – 1400 grams and consists of approximately 100 billion neurons. (e) Reflex Action (i) An immediate and involuntary response given to a stimulus from the environment is called a reflex action. (ii) Sometimes we react to an incident without any thinking on our part or control over the reaction. (iii) This is a response given to a certain stimulus from the surroundings. (iv) In such situations, proper control and co-ordination is achieved even without intervention of the brain. Q.4. Name the hormones of the following endocrine glands and the function of each:- Gland Hormone Function – Growth Hormone - Stimulates growth of bones –Adrenocorticotropic hormone - Stimulates adrenal gland – Thyroid stimulating hormone - Stimulates thyroid gland – Prolactin - Stimulates milk production Pituitary Gland – Follicle stimulating hormone - Controls growth of gonads – Luteinizing hormone - Controls menstrual cycle and ovulation – Oxytocin - Contracts uterus during parturition. – Antidiuretic hormone - Regulates water-level in the body - Controls growth of body and metabolic – Thyroxine activities Thyroid - Controls calcium metabolism and – Calcitonin calcium level in blood – Adrenaline and Nor- - Controls behaviour during crisis and adrenaline emotional situations Adrenal Glands - Stimulates heart and its conducting tissue and metabolic processes.  – Corticosteroid - Maintains balance of Na+ and K+ and stimulates metabolism Controls the cells which give rise to Thymus – Thymosine immunity Stimulates growth of secondary sexual Testis – Testosterone characterstics like beard, mustache, hoarse voice, etc. in men -Stimulates growth of endometrium – Oestrogen -Stimulates growth of secondary sexual characterstics in women Ovary – Progesterone -Prepares the endometrium for conception and maintains the pregnancy. Q.5. Draw and label diagrams of:- (a) Human Endocrine Glands (b) Human Brain (c) Nephron (d) Nerve Cell  (e) Human Excretory System Q.6. Answer the following:- (a) Explain chemical co-ordination in humans and give the names and functions of some hormones. (i) Control and co-ordination in our body is also brought about with the help of certain chemical substances called hormones. (ii) Hormones are secreted by endocrine glands. These glands are also called ductless glands. (iii) These glands do not have any arrangement of their own to either store or carry their secretions. (iv) Hence, as soon as hormones are produced, they are directly released into the blood circulation. (v) Thus, though these endocrine glands are present at specific locations in our body, their secretions reach all parts of the body via blood. (vi) Examples of some Hormones:- a. Prolactin – stimulates milk production b. Luteinizing Hormone (LH) – controls menstrual cycle and ovulation c. Thyroxine – controls growth and metabolism d. Testosterone – Stimulates the growth of secondary sexual characterstics (beard, mustache, hoarse voice, etc.) in men (b) Explain the difference between the excretory system of humans and plants. Excretion in Plants Excretion in Humans a. Humans have an specialized 1. Plants do not have specialized structure such as Nephrons and structures or systems for Kidneys and an Excretory excretion. System. 2. Process of excretion occurs b. Process of excretion occurs through stomata. through kidney, skin, lungs, etc. 3. Waste is produced in the form c. Waste is produced in the form of CO2 and O2. of urea, ammonia, and uric acid. (c) Explain co-ordination in plants with the help of suitable examples. (i) Since plants do not have nervous and muscular system like animals, coordination in plants occurs in response to particular stimuli. (ii) Tropism/tropic movement is the term used for the movement or growth of any plant part in response to an external stimulus. (iii) These tropic movements can be of various types like: a. Phototropism: The growth movement in plants in response to light. Eg. growth of shoots towards the sun. b. Gravitropism: The growth movement in plants in response to the force of gravity. Eg. growth of roots downwards in the soil. c. Chemotropism: The growth movement in plants in response to chemical stimuli. Eg. the growth of pollen tube towards the ovule. d. Hydrotropism: The growth movement in plants in response to water. Eg. growth of roots towards water sources. e. Thigmotropism: The growth movement in plants in response to a touch stimulus or contact with a solid object. Eg. in some plants, the coiling of tendrils occurs when they come in contact with objects for support. (iv) All these examples are related to growth and hence are known as ‘growth relevant movements’. (v) Some specific movements of the plants do not lead to the plant’s growth. Such movements are called ‘growth irrelevant movements’. (vi) As a response to changes in the surroundings, plant hormones bring about various movements in plants. (vii) Eg. Venus Fly Trap, Mimosa Plant, etc. Q.7. Explain with examples:- (a) What is meant by co-ordination? (i) Several different organ systems function in multicellular organisms. (ii) Their life goes on smoothly if there is co-ordination between the different organ systems or organs and the stimuli in the surrounding. (iii) Depending upon this, we can say that systematic regulation of different processes can be called control and bringing about the different processes in the proper sequence can be called co- ordination. (iv) If any activity in the body is to be completed successfully, proper co- ordination between different systems and organs participating at different steps of that activity is necessary. (v) If due to lack of co-ordination or some other factor, there is confusion at any step the activity may not get completed. (vi) There should not be any randomness at any step. (vii) There needs to be proper co-ordination between internal activities of the body resulting from various factors like body temperature, water- level, enzyme-level, etc. or stimuli arising in the surrounding environment. (viii) Proper co-ordination between various systems of an organism helps to maintain a state of equilibrium called ‘homeostasis’ which is necessary for the optimal efficiency of the body. (b) How does excretion occur in human beings? (i) Removal of these wastes from the body is very important and it is the excretory system that carries out this function. (ii) The human excretory system consists of a pair of kidneys, a pair of ureters, the urinary bladder and the urethra. (iii)Urine is formed by the kidneys by separating the waste and unwanted excess substances from the blood. (iv) The urine is formed in kidneys and passes on to the urinary bladder via the ureters. (v) The urinary bladder stores the urine until it is excreted through the urethra. (vi) The kidney contains numerous filtration units called the nephrons. (vii) Nephron is the structural and functional unit of the kidney. (viii)The nephrons consist of a network of capillaries associated with a cup-shaped end of a tube in which the filtered urine is collected. (ix) When the blood passes through the tube, some substances such as glucose, amino acids, salts, and water are selectively reabsorbed.  (x) The final filtrate is collected in the collecting tubule and eventually enters the ureters. (xi) The other organs which are involved in the excretory process include: a. Lungs: They remove CO2 and water. b. Liver: It excretes bile pigments, vitamins, cholesterols and drugs along with digestive wastes. c. Skin: Sweat and sebaceous glands present on the skin eliminate substances such as sterols, hydrocarbons, wax sebum, etc. (c) How is excretion in plants useful to human beings? (i) 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. (ii) The following are some ways in which excretion in plants is useful to humans:- a. Oxygen which is an excretory product of photosynthesis is vital for respiration in humans. b. Tannin, a waste plant product which is stored in leaves and bark, is used to make tea. c. Plants store waste products in their leaves and barks which are shed off regularly. These shed offs are used to make manure. d. Essential oils are also waste products of plants which are stored in their leaves. These essential oils are used for various purposes by us. e. Gum and latex excreted by plants is also of various use for humans. (d) Describe the transportation system in plants. (i) Most animals move from place to place but plants do not. There are many dead cells in the plant body. (ii) They need less energy as compared to animals. (iii) Plants need inorganic substances like nitrogen, phosphorus, magnesium, manganese, sodium, etc. (iv) Soil is the nearest and richest source of these substances. (v) Roots of plants absorb these substances from the soil and transport them. (vi) There are specific types of tissues to perform this function. (vii) The xylem conducts the water whereas the phloem conducts the food. (viii) All parts of the plant are connected with these conducting tissues. a. Root Pressure: i. Under the effect of root pressure caused by the turgid cells, water and minerals reach the xylem of the roots and to reduce this difference in concentration they are continuously pushed forward. ii. As a result of this continuous movement, a water column is formed, which is continuously pushed ahead. b. Transpiration: i. Water is released into the atmosphere by leaves through the process of evaporation. ii. As a result, water level in the epidermal layer of the leaf decreases. iii. Water is brought up to the leaves through the xylem so as to compensate for the lost water. iv. Transpiration helps in absorption of water and minerals and distribution to all parts of the plant whereas root pressure performs the important role of pushing the water up during the night time.