Science Answer the following questions: [5 M]

1.  

1. ​​​​​​​P is a thermoreceptor.
2. Q is a sensory neuron.
3. R is the spinal cord.

2.  

1. S is a relay neuron. The impulse from the spinal cord is passed on to a relay neuron.
2. T is a motor neuron. From the relay neuron, the impulse is passed on to a motor neuron.

3. U is a muscle.
4. Reflex action is the phenomenon in which the hand is pulled away quickly from a hot plate. It is performed automatically by an individual.
5. The effector organ is the muscle of the arm.

1. The glands A are the ovaries.
2. The hormones C and D, secreted by the ovaries, are oestrogen and progesterone, respectively.
3. The glands B are the testes. The hormone E, released by the testes, is testosterone.
4.  

1. The gametes F are ova or eggs. They are produced by the ovaries.
2. The gametes G are sperms. Sperms are produced by the testes.

5. The secretion of hormones C (oestrogen) and D (progesterone) in females and hormone E (testosterone) in males are associated with puberty.

If the plant part moves towards the direction of gravity, it is called positive geotropism. Example – Roots. If the plant part moves against the direction of the gravity it is negative geotropism. Example – Stem
Experiment to show the response of a plant to gravity (geotropism).

1. Thyroxine.
2. Parathromone.
3. Insulin.
4. Adrenaline.

1. The structure P is the spinal cord. It is a cylindrical structure that begins in continuation with the medulla and extends downwards.
2.  

1. The bony cage Q is the vertebral column. The spinal cord is enclosed by the vertebral column.
2. R represents the meninges. The spinal cord is surrounded by membranes called the meninges.

3. X represents the number of pairs of spinal nerves. They are 31 in number.
4. S is the brain. The central nervous system consists of the brain and the spinal cord.
5. The reflex actions involving the spinal cord (P) are known as spinal reflexes.

1. The stimulus A is water.
2. The stimulus B is gravity.
3. The stimulus C is light.
4. The two stimuli responsible for the straight growth of the branches of a fallen tree are B and C, i.e., gravity and light, respectively.

The movement of a plant part in response to water is called hydrotropism. Example: The roots of a plant always go towards water, this is positive hydrotropism.
Experiment to show the response of a plant to water (hydrotropism).

The hormones that control and coordinate the activities in plants are called plant hormones. The four types of plant hormones are:

1. Auxins – It promotes cell enlargement and cell differentiation in plants.
2. Gibberellines – It helps in breaking the dormancy in seeds and buds.
3. Cytokinins – It promotes cell division in plants.
4. Abscisic acid – It promotes the dormancy in seeds and buds.

The pathway taken by nerve impulses in a reflex action is called a reflex arc. It is an automatic response to a stimulus. When a stimulus is given to a receptor, the receptors produce an impulse in the sensory fibre. The sensory fibre carries this message in the form of an electrical stimulus across the synapse. From the synapse, the impulse travels in the motor fibre and stimulates the effector organ to produce the desired response. The correct order for a simple reflex arc is:
(b) → (d) → (a) → (c).

P is adrenal glands.
Q is kidneys.
R is adrenaline hormone.
S is glucose.
Humans have two adrenal glands, which are located on top of the kidneys. They are often called emergency glands. They secrete adrenaline into the bloodstream. It is secreted in large amounts when a person is frightened. Adrenal gland brings about temporary changes in the body which allow glucose from the liver to go into the bloodstream. This provides a lot of energy in a very short time.

1. The organ A is the brain. The brain is located inside the skull of our body at the top of the spinal cord.

2.  

1. B is the cranium. The brain is protected by a bony box in the skull called the cranium.
2. C are meninges. The brain is surrounded by three layers of membranes called the meninges.
3. D is the cerebrospinal fluid. It is present in between the meninges and protects the brain from mechanical shocks.

3. The organ E is the spinal cord. The brain (organ A) and the spinal cord (organ E) together make central nervous system.
4. A person walking barefoot lifts his foot at once on stepping on to a sharp piece of stone. The spinal cord (E) is involved in this action. Those reflexes that involve only the spinal cord are called spinal reflexes.
5. A person closes his eyes at once when he steps out from a darkened room to bright light. The brain (A) is involved in this action. Those reflexes that involve only the brain are known as cerebral reflexes.

1.  

1. W represents the pancreas. It is located just below the stomach in the human body.
2. X represents insulin, which is secreted by the pancreas.

2. The function of insulin (X) is to maintain the sugar level in blood.
3.  

1. Y represents diabetes, which is a disease caused by increased blood sugar level.
2. The person Z is known to be diabetic.

4. A person suffering from diabetes (Y) should control his/her diet, reduce his/ her weight and do regular physical exercises. He/ she should regularly take proper medication to control the sugar level in blood.

1. (i) R is a leaf tendril and (ii) S is a stem tendril.
2. The growth movement exhibited by R and S is thigmotropism.
3. The stimulus involved is touch or contact with other objects.
4. The behaviour of R and S is a tropic movement.
5. Pea plant is an example of plant type P, whereas bitter gourd plant is an example of the type Q.

1. (i)A represents the thyroid gland. It is attached to the wind pipe in the human body.
2. (ii) B represents thyroxine. It regulates the metabolism of carbohydrates, fats and proteins in the body.
3. The non-metal element C is iodine. It is essential for the synthesis of thyroxine hormone by the thyroid gland.
4. Sea foods like fish provide sufficient amount of iodine in the diet of a person.
5.  

1. D represents the disease called goiter. It is characterised by abnormal enlargement of the thyroid gland in the neck.
2. E represents iodised salt. It is advised to use iodine in cooking food in order to prevent goiter.

1. X is the pituitary gland. It is located just below the brain.
2. The chemical substance (Y) released from the pituitary gland is human growth hormone.
3. Under-secretion of growth hormone leads to a condition known as dwarfism. In dwarfism, the person remains very short.
4. Over-secretion of growth hormone causes a condition known as gigantism. In gigantism, the person grows very tall.
5. The pituitary gland (X) is a part of the endocrine system.

1. P is a receptor. The five organs which contain receptors are: Eyes, ears, nose, tongue and skin.
2. Q represents sensory nerves. Sensory nerves bring impulses from sensory organs to the CNS.
3. R is an effector organ. Effectors are part of the human body which can respond to a stimulus according to the instructions sent from the CNS though the motor nerves. Two examples of effector organs are the muscles and glands.
4. S represents motor nerves. Motor nerves carry impulse from the CNS to the effector organs like the muscles or glands.
5. Messages travel in the form of electrical impulses or nerve impulses through sensory nerves (Q) and motor nerves (S).

1. A represents neurons. Neurons are the largest cells in the human body, which look like electric wires.
2.  

1. B represents the axon.
2. C represents the dendrites.

3. The microscopic gap D is known as a synapse. A synapse is a functional junction between a pair of adjacent neurons over which nerve impulses can pass.
4. A neuron transmits messages to and from the central nervous system. It is the structural and functional unit of the nervous system.
5. The three types of neurons are sensory neurons, motor neurons and relay neurons.

1. The part A functions as an endocrine gland. The glands that secrete their secretions directly into the blood are called endocrine glands. Part A of the pancreas secretes insulin (a hormone) directly into the bloodstream.
2. Insulin is a hormone which is secreted by the pancreas. It controls the blood sugar level.
3. Deficiency of insulin in the body can lead to diabetes. Diabetes can be treated by giving injections of insulin.
4. Pancreatic juice contains digestive enzymes like pancreatic amylase, trypsin and lipase. The pancreatic juice goes into the small intestine where complete digestion of food takes place.
5. Digestion is the process where the enzymes present in the pancreatic juice are used to break down the food.

1. Receptor A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus (or a particular type of change in the environment). Example: Photoreceptors and Phonoreceptors. Effector An effector is the part of the body which can respond to the stimulus according to the instructions sent from the nervous system (spinal cord and brain). Example: Muscles and glands.
2. Cerebrum:

1. It is a part of forebrain.
2. It is the main thinking part of the brain. All our thoughts, sensation, actions and movements are controlled by cerebrum.

Cerebellum:

1. It is a part of hindbrain.
2. It helps in maintaining posture and balance of the body. It enables us to make precise and accurate movements.

1. A represents the endocrine system. The endocrine system is composed of glands.
2. C represents hormones. Hormones are the chemical messengers of the body and they travel slowly through the bloodstream.
3. D represents endocrine glands that are made up of tissues. Hypothalamus, thyroid, thymus, pancreas and adrenalglands are some of the endocrine glands present in the human body.
4. B represents the nervous system. It comprises the brain, spinal cord and nerves.
5. E represents nerve fibres. They transmit messages very quickly in the form of electrical impulses.
6. The nervous system (B) controls the working of the endocrine system (A).

1. The part X is the root.
2. The part Y is the shoot.
3. The part X (root) will exhibit positive hydrotropism.
4. The part Y (shoot) could have tendrils on it.
5. The phytohormone, auxin causes the root to exhibit negative phototropism.

1. (i) X is the carpel and (ii) Y is the stamen.
2. (i) A is the stigma, (ii) B is the style and (iii) C is the ovary of the flask-shaped organ.
3. (i) D is the pollen and (ii) E is the anther.
4. F is the pollen tube.
5. The phenomenon of growing a long tube in response to a sugary substance in the process of fertilisation in a flower is known as chemotropism.

The endocrine gland present in the human body are:

1. Pineal gland.
2. Hypothalamus.
3. Pituitary.
4. Thyroid.
5. Parathyroid.
6. Thymus.
7. Pancreas.
8. Adrenal glands.
9. Testes (in males).
10. Ovaries (in females). Pancreas, testes and ovaries function as exocrine glands.

1. Pituitary – Growth.
2. Thyroid – Thyroxine.
3. Pancreas – Insulin.
4. Adrenal – Adrenaline.
5. Testes – Testosterone.

1. From the given question, the chemical substance P is Auxin which is produced at the shoot tip and can diffuse to other plant parts.
2. Auxin moves to the darker side of the plant, causing the cells there to grow large.
3. Auxin has adverse effect on growth rate of roots hence, it decrease the growth rate of roots. Unlike roots, the auxin has positive effect on growth rate of stem hence, it increases the growth rate of stem.
4. Process Q is positive phototropism while process E is negative phototropism. Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism.
5. Chemical substance like P is Auxin, aPhytohormone or plant hormone. Like Auxin, Gibberellin is also an example of phytohormone.

1. Photoreceptors.
2. Thermoreceptors.
3. Phonoreceptors.
4. Olfactory receptors.
5. Gustatory receptors.

Different types of tropisms are:

1. Phototropism: The movement of a plant part in response to light is called phototropism. Its stimulus is light.
2. Geotropism: The movement of a plant part in response to gravity is called geotropism. Its stimulus is gravity.
3. Chemotropism: The movement of a plant part in response to a chemical stimulus is called chemotropism. Its stimulus is chemical.
4. Hydrotropism: The movement of a plant part in response to a water stimulus is called hydrotropism. Its stimulus is water.
5. Thigmotropism: The movement of a plant part in response to a touch stimulus is called thigmotropism. Its stimulus is touch.

1. Thyroxine? The function of this hormone is to control the rate of metabolism of carbohydrates, fats and proteins in the body.
2. Adrenaline? Its function is to regulate heart rate, breathing rate, blood pressure and carbohydrate metabolism.
3. Growth hormone? It controls the growth of the human body.

Phototropism in a plant stem – The bending of a plant stem towards light is an example of phototropism. The plant stem responds to light and bends towards it due to the action of auxin hormone. The auxin hormone is present at the tip of the stem of the growing plant. Auxin prefers to stay in shade away from light so when sunlight falls on the stem from one side, it gets concentrated on the opposite side. Due to more auxin, the shady side of the stem grows to be longer than the side of stem which is facing light, and makes the stem bend towards light.
Diagrams to explain the bending of a plant stem (or shoot) towards light by the action of 'auxin' hormone.

1. Light – Phototropism.
2. Gravity – Geotropism.
3. Chemical – Chemotropism.
4. Water – Hydrotropism.
5. Touch – Thigmotropism.

The main organs of the nervous system are; brain, spinal cord and nerves.

The human nervous system.

A microscopic gap between a pair of adjacent neurons over which nerve impulses pass when going from one neuron to the next is called a synapse. Synapse between two neurons acts as a one way valve which allows electrical impulses to pass in one direction only. This happens as follows: When an electrical impulse coming from the receptor reaches the end of the axon of sensory neuron, then the electrical impulse releases tiny amount of a chemical substance called neuro transmitter substance into the synapse between two adjacent neurons. This substance crosses the synapse and starts a similar electrical impulse in the dendrite of the next neuron. In this way, the electrical impulses passes from one neuron to the next across the synapse.

The central nervous system consists of the brain and spinal cord. The work of the CNS is to direct incoming messages to the motor neurons that are connected to the part of the body which will respond to a stimulus. It is involved in complicated responses where both (brain and spinal cord) work. It enables a person to give a more appropriate and more intelligent response to various situations.

1. The phenomenon shown by the flowers of plants A and B is photonasty.
2. A flower which behaves like the flower of (i) plant A is dandelion and (ii) plant B is moonflower.
3. The leaves of plant C exhibit thigmonasty.
4. A plant whose leaves behave like those of plant C is Mimosa pudica.
5. The plants A and B exhibit the phenomenon based on growth movements.

1. The brain receives information carrying nerve impulses from all the sensory organs of the body.
2. It responds to the impulses brought in by sensory organs by sending its own instructions through motor nerves to the muscles and glands causing them to function accordingly.
3. It correlates the various stimuli from different sense organs and produces the most appropriate and intelligent response.
4. It coordinates the body activities so that the mechanisms and chemical reactions of the body work together efficiently.
5. It stores information so that behavior can be modified according to the past experience.

1. Light.
2. Gravity.
3. Chemical.
4. Water.
5. Touch.