Class 10 Science Chapter 6 Board Questions

Cerebellum in hind brain controls the posture and balance of the body.

The growth of pollen tube towards a chemical produced by ovule during fertilization of flower is an example of chemotropism.

The two components of the central Nervous System in human are brain and spinal cord.

Gustatory receptors are located in cerebrum of fore brain. Olfactory receptors are located in the olfactory lobe fore brain.

Spinal cord is enclosed in a bony cage called vertebral column.

(i) Roots (ii) Shoot

Insulin helps in regulating blood sugar level. This hormone is secreted by pancreas gland.

Hind-brain coordinates the body movements and posture. It also controls respiration.

Phototropism and Geotropism.

Abscisic acid

(i) Roots (ii) Shoot

Insulin helps in regulating blood sugar level. This hormone is secreted by pancreas gland.

Hind-brain coordinates the body movements and posture. It also controls respiration.

Phototropism and Geotropism.

Abscisic acid

Shoot tip in plants and pituitary gland in man.

Shoots will bend towards the light and roots away from the light.

The plant hormone which helps or promote:
(i) Cell division- Cytokinin
(ii) Growth of stem- Gibberellins

The main hormone secreted by thyroid gland is thyroxine. It regulated the metabolism of carbohydrates, fats and proteins in the body so as to provide the best growth balance.

The two tissues that provide control and coordination in multicellular animals are nervous and muscular tissues.

Pituitary gland secretes the growth hormone.

Movement on the touch sensitive plant.

Iodised salt contains iodine which is necessary for the thyroid gland to synthesized thyroxine hormone. Thyroxine regulates carbohydrates, protein and fats metabolism in the body to provide growth balance. Its deficiency causes goitre.

Hormone estrogen in females.

Cerebellum.

Pituitary gland secretes the growth hormone.

Movement on the touch sensitive plant.

Iodised salt contains iodine which is necessary for the thyroid gland to synthesized thyroxine hormone. Thyroxine regulates carbohydrates, protein and fats metabolism in the body to provide growth balance. Its deficiency causes goitre.

Hormone estrogen in females.

Cerebellum.

Roles of ovary:
(i) Ovaries produce female gametes ova.
(ii) It also produces a female sex hormone called estrogen. Estrogen is essential for development of secondary sense organs in female as well as secondary sexual characters like high pitch voice, development of mammary glands.

Roles of ovary:
(i) Ovaries produce female gametes ova.
(ii) It also produces a female sex hormone called estrogen. Estrogen is essential for development of secondary sense organs in female as well as secondary sexual characters like high pitch voice, development of mammary glands.

Neuron is the longest cell present in the human body.

(i) Pituitary gland- Growth hormone.
(ii) Thyroid gland- Thyroxine hormone.

(a) Cerebrum- Forebrain
(b) Medulla- Hindbrain
(c) Cerebellum- Hind brain
(d) Cerebellum- hind brain

Each step/level of the food chain where energy transfer takes place is called a tropic level.
Example:
(i) Plants < Grasshopper < Frog < Snake (ii) Plants < Deer < Hyena < Tiger

The two main organ of CNS are brain and spinal cord. Spinal cord plays a major role in sending command to muscles to act without involving thinking process. This phenomenon is called reflex action.

Testes secretes male sex hormone called testosterone. The function of testosterone is to regulate male accessory sex organs and secondary sexual characters like moustache, beard and voice.

Hormones secreted by pituitary gland along with their functions are:
(i) Growth hormone: It regulates growth and development of bones and muscles.
(ii) Trophic hormone: It regulates secretion of hormones from of other endocrine glands.
(iii) Prolactin hormone: It regulates the function of mammary gland in females.
(iv) Vasopressin hormone: It regulate water and electrolyte balance in the body.
(v)Oxytocin hormone: It regulates ejection of milk during lactation.

Auxin diffuses towards shady side. Causes elongation on one side resulting in bending of growing shoot. The hormone responsible for bending is auxin and the movement is phototropic movement.

Nastic movement is the non-directional movement of turgor or growth where the movement is determined by the structure of the responding organ irrespective of the direction of stimulus which is generally diffuse.
Example:
Bending and drooping of leaves on touching in touch-me-not plant.

Curvature movements are changes in orientation of different plant parts in relation to one another like bending, twisting and elongation. They are of two type turgor and growth movement.
Example: Telegraph plant.

The cause of shoots of the plant bending towards light due to the directional growth or movement of a plant organ in response to an external stimulus known as phototropism.

A change in the environment of a living organism evolves an appreciate movement in response. The movement to be made depend on the event that’s why triggering it. Such control movement must be connected to various events in the environment. Thus living organism must use system providing control and coordination.

The three major regions or parts of the human brain are Fore brain, Mid brain and Hind brain. A part of the hind brain called the cerebellum maintains posture equilibrium of the body.

(a) Voluntary actions are the actions which need thinking and are performed knowingly that’s why are controlled by conscious though.
Example Speaking to a friend, writing a letter, etc.
Involuntary actions are not under the control of the will of an individual and are automatic response to a stimulus which is not under the voluntary control of the brain. Examples. Touching a hot plate unknowingly

(b) Involuntary actions: Beating of heart, salivation in the mouth on viewing a tasty food.

(i) He is suffering from diabetes. Deficiency of insulin causes diabetes.
(ii) Pancreas secretes insulin. Insulin helps in regulating blood sugar.
(iii) When the sugar level in blood increases it is detected by the cells of pancreas which responds by producing more insulin. As the blood sugar level falls, insulin secretion is reduced.

(a) The brain sits inside a bony box. Inside the box the brain is contained in a fluid filled balloon which provides further shock absorption.
(b) Two main parts of hind brain are Medulla and cerebellum.
There functions are:
Medulla: Involuntary actions such as blood pressure, salivation and vomiting are controlled by medulla.
Cerebellum: It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

(a) Cytokinin is present in greater concentration in the area of rapid cell division.
(b) An example of a plant growth promoter is gibberellins and example of a plant growth inhibition is Abscisic acid.

Pancreas secretes a hormone when blood sugar rises in our body. Insulin is the hormone released by this organ and the name of the enzyme is pancreatic juice.

When a growing plant detects light auxin, synthesises at the shoot tip to help the cells to grow longer. When light comes from one side, auxin diffuses toward the shady side of shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from the light and the plant appears to bend towards light.

When a tendril comes in contact with any support the part of the tendril in contact with the object does not grow as rapidly as the part away from the object. These cause the tendril to circle around the object and thus cling to it.

A hormone called auxin is synthesised at the shoot tip. When a growing plant detects light, auxin synthesis at the shoot tip to help the cells to grow longer. When light comes from one side, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light and the plant appears to bend towards light.

Three endocrine glands with their function in human body are as follows:
(i) Thyroid gland
Function: It secretes a hormone called thyroxine which regulates the metabolism of carbohydrates, fats and proteins in the body and so provide the best balance for growth.
(ii) Adrenal glands
Function: It secretes two hormone adrenalin and corticoid hormones which regulates blood pressure, heart beat, breathing rate, carbohydrates metabolism and mineral balance.
(iii) Pancreas
Function: It secretes two hormone insulin and glucagon. Insulin hormone lower the blood glucose. Glucagon hormone increases the blood glucose.

Hind brain controls the involuntary actions.
Cerebellum controls the coordination of body movement and posture.
Medulla oblongata regulates center for swallowing, coughing, sneezing and vomiting.

Chemotropism is the movement of a part of the plant in response to a chemical stimulus. It can positive chemotropism and negative chemotropism.
Example: The growth of the pollen tube towards a chemical which is produced by an ovule during the process of fertilisation in a flower.
Two plant hormones with their functions are as follows:
Auxins promote cell elongation, root formation, cell division, respiration and other physiological process like protein synthesis, etc.
Gibberellins stimulates stem elongation, seed germination and flowering.

The structural and functional unit of nervous system i.e. neuron with their functions are as follows:
(i) Cell body: Stimulus received from dendrite is changes into impulse in the cyton.
(ii) Dendrites: They receive sensation or stimulus which may be physical, chemical, mechanical or electrical. They pass the stimulus to the cyton.
(iii) Axon: It conduct impulse away from the cell body.

Phototropism is the directional growth movement of curvature of plant organs in response to unidirectional exposure to light.
Phototropism in plants:
Plants bend toward light when they are exposed to it. The aerial shoots usually grow toward light while some aerial roots grow away from light. This response to controlled by the differential distribution of the plant growth substance auxin in the illuminated part which cause differential growth of the root and shoot.
Activity to demonstrate phototropism:
A conical flask with water is taken and neck of which is covered by a wire mesh 2 or 3 freshly germinated bean seeds, are kept on the wire mesh. A cardboard box so that open side of the box receives light from a window. After 2-3 days it will be seen that shoots bend toward light and roots away from light.

Hydrotropism is the directional growth of a plant part is response to water.
Example root shows hydrotropism as they grow towards water in the soil and are positively hydrotropic.
An experiment to demonstrate hydrotropism are as follows:
(i) A porous pot filled with water is taken and is inserted in a tub filled with dry sand.
(ii) A freshly germinated pea seedling is sowed in a sand.
(iii) As water is not available in sand the root growing will bend towards the porous pot filled with dry sand.
(iv) A hydrotropic curvature of the root is observed as it grows towards water.
(v) This bending of roots shows the movement in response toward water.

Hormone are the chemical substances which coordinate and control the activities of living organism and also their growth. The term hormone was introduced by Bayliss and Startling function
(i) Thyroxine hormone regulates the metabolism of carbohydrates, fats and protein in the body so as to provide the best growth balance.
(ii) Insulin hormone helps in regulating sugar level in blood.

(a) Two main constituent of the Central Nervous System in human beings are the brain and spinal cord.
(b) The different organs of our body work in coordination when we perform any activity. For example, when we are taking food, our eyes help in locating the food, our nose detect the smell, our hand brings the food, the teeth and jaw muscles chew the food and saliva starts the digestion process.
So, control and coordination is essential in maintaining a state of stability and a steady state between the internal condition of an organism and the external environment.

Reflex action: It is defined as an unconscious automatic and involuntary response of effectors i.e. muscles and glands to stimulus which is control through the spinal cord.
Mechanism of Reflex action. It involves the following steps:
(i) Receptors organ like skin perceive the stimulus and activates a nerve impulse.
(ii) Sensory organ carries message in the form of sensory impulse to the spinal cord.
(iii) The spinal cord act as modulator. The neurons of spinal cord transmit the sensory nerve impulse to motor neuron.
(iv) Motor nerve conducts these impulses to the effectors like leg muscles which responds by pulling back the organ away from the harmful stimulus.

Hormones are the chemical substance which coordinates and control the activities of living organism and also their growth. The hormone secreted by thyroid is thyroxine. Its function is to regulate the metabolism of carbohydrates, fast and protein in the body so as to provide the best balance for growth. The use of iodised salt is advised to us because iodine is necessary for the thyroid gland to produce thyroxine hormone. Thyroxine regulates carbohydrates, protein and fat metabolism which is required for growth. Deficiency of iodine in the body causes disorder like swollen neck and disease called Goitre.

The animal or plant hormone which is associated with the following are as follow:
(i) Increased sugar level in blood- Insulin hormone
(ii) Changes at puberty in boys- Testosterone hormone
(iii) Inhibits growth of plants- Abscisic Acid
(iv) Rapid development of fruits- Cytokinin
(v) Dwarfism- Growth hormone
(vi) Goitre- Thyroxine hormone

Insulin is a hormone that regulates our blood sugar level by converting it into glycogen which can be stored. Hence of there is more levels of sugar in blood then more insulin is produced and if the sugar level is less than insulin production is also reduced. This is because of feedback mechanism where the blood sugar itself acts as a feedback for more or reduced insulin synthesis.

Feedback system is a regulatory mechanism in which presence of certain level of hormone promotes or inhibits its further formation.
Regulation of thyroxine production by its concentration in blood is an example of hormonal feedback system. If the level of thyroxine is more in the blood, this is detected by hypothalamus, which stops producing thyroid stimulating hormone. Non availability of TSH results in failure of thyroid to produce thyroxine in blood. But if concentration is low in the blood, hypothalamus produce TSH which then passes into circulatory system and reaches thyroid gland. Thyroid now begins to secrete more thyroxine.

Plants do not have nervous system and muscles. Even then they exhibit well-coordinated and controlled movements. Plants possess chemical coordination. They respond to stimuli by secreting chemical substance called as plant growth regulators. They either stimulate or retard growth. Five major type of plant growth hormone are auxin, gibberellins, Cytokinin, Abscisic acid and ethylene. Certain changes in the orientation of plant parts in relation to other parts caused by intrinsic or external stimuli are non-directional, growth independent movements. They are referred as nastic movements. Thus, plants show movements due to growth or change in turgor pressure.

(a) Role of plant hormones:
Chemical control in the plant is performed through plant hormones. They help to coordinate growth development and responses to the environment.
Plant hormones auxin and Cytokinin helps in cell division.
(b) When growing plants detect light a hormone called auxin, synthesised at the shoot tip helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of shoot which is away from light.

(a) Gland that secretes:
(i) Insulin- Pancreas
(ii) Thyroxine- Thyroid gland
(b) The timing and amount of hormone secreted are regulated by the Feedback mechanisms. For example:
(i) High glucose level in blood induces the pancreatic cells to produce more insulin which converts glucose to glycogen.
(ii) Low glucose level in the blood does not induce the pancreatic cells to produce insulin so that less conversion of glucose to glycogen occurs.

(a) (i) Voluntary actions are controlled by cerebellum.
(ii) Involuntary actions are controlled by mid-brain.
(b) Peripheral nervous system facilitates the communication between central nervous system and other body parts.
Components of peripheral nervous system are:
(i) Cranial Nerve: Originating from brain.
(ii) Spinal Nerve: Originating from spinal cord.

Synapse is the gap/junction between two successive neurons. All information from the environment is detect by the specialized tips the dendrites of some nerve cells present in tissues and organs. These are called receptors. They are located in our sense organ like, nose, tongue, skin, eye, and inner ear.
Sensory receptors are of different types. Photoreceptors, phonoreceptors, olfactoreceptors, gustatoreceptors, thermoreceptors and so on. They detect light, sound, smell, taste, heat, and cold respectively.
The above mentioned receptors initiate electrical impulses to be picked up by sensory nerves. This impulse travels from the dendrite to the cell body, and then along the axon to its end. Axon ending of one neuron are placed close to dendrites of the next neuron. This junction is called synapse or gap. As soon as the impulse reaches the end of neuron it sets off release of some chemicals. These chemicals cross the gap or synapse and start a similar electrical impulse in dendrites of neuron. Finally, the 9impulses reaches a muscle or a gland.

Brain and spinal cord are the two components of central nervous system. Human brain is protected by a bony skull, also called as cranium. Internal to the skull it is covered from outside by three membranes called meninges there is a fluid called as cerebrospinal fluid. Beneath the membrane brain is divided into three major parts namely fore-brain, midbrain and hind brain.
Brain is considered as highest coordinating center of the body.
Its three region are given below:
(a) Fore brain is the main thinking part of the brain. It has different regions or areas such as:
(i) Sensory area: It receives sensory impulses from various receptors.
(ii) Auditory area: It is concerned with hearing.
(iii) Olfactory area: It is concerned with smell.
(iv) Gustatory area: It is concerned with taste.
(v) Optic area: It is concerned with sight.
(vi) Association area: This area interprets various sensory information and makes decision how to respond.
(vii) Motor area: Decision made by association area are passed on to this area which control the movement of voluntary muscles.
(b) Mid brain comprises of four lobes. So it is also known as copra quadrigemina. Actions of involuntary muscles are controlled by the midbrain and hind brain.
(c) Hind brain comprises of cerebellum, pons varolii and medulla oblongata. Cerebellum is the second largest part of the brain that coordinate muscles activity of the body as well as maintains body equilibrium or posture. Pons connects cerebellum and medulla oblongata and function as a reply centre among different parts of brain. Medulla oblongata lies below cerebellum and continuous behind spinal cord. Involuntary actions like blood pressure, salivation and vomiting are controlled by the medulla in the hind brain.

The stimulus oriented movement of plant or plant part is called tropism. The direction of movement is related to the direction of stimulus. These movements are always growth orientated movements. They are different types namely phototropism, hydrotropism, geotropism, thigmotropism and chemotropism.
(i) Phototropism is a directional growth movement which occurs in response to unidirectional exposure to light. The region of photoreception is shoot apex where auxin is produced. Auxin moves from illuminated region to the shaded region. This causes more growth on the dark side of stem causing it to bend towards the source of light. Movement of shoot toward light is called phototropism.
(ii) Roots are positively geotropic and negatively phototropic. Shoots are positively phototropic and negatively geotropic.
(iii) Growth of pollen tube inside the style, ovary and ovule in response to the chemicals produced by them is an example of chemotropism.

(a) Hormones are chemical information molecule that are required in minute quantities and are directly poured in the blood stream by the gland. They act on a specific organ called target organ. So their site of production varies from site of action.
Their characteristic are:
(i) They are poured into blood stream.
(ii) Are generally proteinaceous or steroid.
(iii) There secretion is regulated by feedback mechanism.
(iv) Their site of action and secretion is different.
(b) (i) Dwarfism
(ii) Gigantism.
(iii) Diabetes
(iv) Goitre

(a) When blood sugar level rises in blood, a hormone named insulin is produced by cells of islets of Langerhans in the organ Pancreas. Pancreas also produced pancreatic juice which contains pancreatic enzymes such as trypsin, pancreatic amylase and pancreatic lipase. Insulin promotes glucose absorption by individual cells and absorption and formation of glycogen in liver and muscles. This reduces glycose level in blood. As soon as the blood sugar comes to normal the pancreatic cells stops secretion of insulin.
Pancreas secretes slightly alkaline pancreatic juice which contains three major following enzymes:
(i) Trypsin which digests proteins.
(ii) Lipase which digests fats.
(iii) Amylase which digests carbohydrates.
(b) An organism has different organs which perform various functions. The survival of an organism depends on integrated and coordinated function of these organs. Nervous and endocrine system of an organism make them work together like parts of one machine to accomplish homeostasis or coordination.

Plants possess chemical coordination. They respond to stimuli by secreting achemical substance called as plant growth relators. They either stimulate or retard growth. Five major types of plant growth hormone are auxin, gibberellins, cytokinins, abscisic acid and ethylene.
These plant are growth regulator also known as phytohormones.
They are synthesised at the shoot aspics, leave, developing embryos, root tips etc.