Lakhmir Singh Manjit Kaur Biology 2020 2021 for Class 10 Science Chapter 2

Question 1:

What is the general name of chemical substances which bring about control and coordination in plants?

Answer:

Plant hormones are chemical substances which bring about the control and coordination in plants.

Question 2:

Which plant hormone is responsible for the wilting and falling of leaves?

Answer:

Abscisic acid is responsible for the wilting and falling of leaves.

Question 3:

Which plant hormone makes a stem (or shoot) bend towards light?

Answer:

Auxin is a plant hormone which makes a stem (or shoot) bend towards light sources.

Question 4:

Where is the auxin hormone made in a plant stem?

Answer:

Auxin hormone is made in the cells of the tip of a plant stem.

Question 5:

What is the scientific name of sensitive plant?

Answer:

The scientific name of sensitive plant is Mimosa pudica.

Question 6:

Name one plant hormone that promotes growth and another plant hormone which inhibits growth.

Answer:

Auxin is a plant hormone that promotes growth in plants and abscisic is a plant hormone that inhibits growth.

Question 7:

Name one example of the movement of a plant part which is very quick and can be observed easily.

Answer:

Thigmonasty is the movement of plant, especially prevalent in sensitive plants, which is very quick and can be observed easily. If we touch the leaflets of a sensitive plant, they fold up and droop immediately.

Question 8:

Name the type of chemical substances that control the growth in plants.

Answer:

Plant hormones are the chemical substances that control growth in plants. Auxin, gibberelins, cytokinins and abscisic acid are examples of plant hormones.

Question 9:

What is the stimulus in : (a) phototropism? (b) geotropism? (c) chemotropism? (d) hydrotropism? (e) thigmotropism?

Answer:

The stimulus in
(a) Phototropism: Light
(b) Geotropism: Gravity
(c) Chemotropism: Chemicals
(d) Hydrotropism: Water
(e) Thigmotropism: Touch

Question 10:

Give the scientific terms used to represent the following :
(a) Bending of a shoot towards light.
(b) Growing of roots towards the earth.
(c) Growth of a pollen tube towards ovule.
(d) Bending of roots towards water.
(e) Winding of tendril around a support.

Answer:

(a) Phototropism
(b) Geotropism
(c) Chemotropism
(d) Hydrotropism
(e) Thigmotropism

Question 11:

Give one example of the movement of a plant part which is caused by the loss of water (or migration of water).

Answer:

The folding of leaves in sensitive plants is an example of the movement of a plant parts. It is caused by loss of water (or migration of water).

Question 12:

Give one example each of a plant part :
(a) which is positively hydrotropic as well as positively geotropic.
(b) which is positively phototropic but negatively geotropic.

Answer:

(a) Roots are positively hydrotropic as well as positively geotropic.
(b) Shoots are positively phototropic but negatively geotropic.

Question 13:

Which of the following is a growth movement and which is not?
(a) folding up of leaves of sensitive plant on touching with hand.
(b) folding up of petals of dandelion flower when light fades.

Answer:

Neither of them are growth movements. They are nastic movements.
(a) This is a thigmonastic movement.
(b) This is a photonastic movement.

Question 14:

Name the plant part :
(a) which bends in the direction of gravity but away from light
(b) which bends towards light but away from the force of gravity

Answer:

(a) Roots bend in the direction of gravity but away from the light.
(b) Shoots bend towards the light but away from the force of gravity.

Question 15:

To which directional stimuli do :
(a) roots respond?
(b) shoots respond?

Answer:

(a) Roots of a plant respond to gravity.
(b) Shoots of a plant respond to light.

Question 16:

Fill in the following blanks :
(a) A plant's response to light is called ..........
(b) A plant's response to gravity is called ........
(c) Plant shoot grows upward in response to ........
(d) Plant roots grow downward in response to ........
(e) Tendrils wind around a support in response to .......
(f) Plant roots grow towards........ and in the direction of force of .........
(g) A root of a plant grows downward. This is known as ........
(h) ...... is the hormone that causes phototropism in plants
(i) The response of leaves to the sunlight is called ..........

Answer:

(a) A plant's response to light is called phototropism.
(b) A plant's response to gravity is called geotropism.
(c) Plant shoot grows upward in response to light.
(d) Plant roots grow downward in response to gravity.
(e) Tendrils wind around a support in response to touch.
(f) Plant roots grow downwards and in the direction of the force of gravity.
(g) The root of a plant grows downward. This is known as geotropism.
(h) Auxin is the hormone that causes phototropism in plants.
(i) The response of leaves to sunlight is called phototropism.

Question 17:

Plant parts show two types of movements, one dependent on growth and other independent of growth. Give one example of the movement in plant parts :
(a) which depends on growth
(b) which does not depend on growth

Answer:

(a) Phototropism depends on growth. It is the growth of plant stem in response to sunlight.
(b) Thigmonasty does not depend on growth. It is a non directional movement of plant part, such as leaves, in response to touch.

Question 18:

What is a plant hormone? Name four plant hormones. State one function of each.

Answer:

The chemicals that perform the function of control and coordination in plants are called plant hormones.
The four plant hormones and their functions are as follows:
1) Auxin: It promotes cell enlargement and cell differentiation in plants.
2) Gibberellins: It breaks the dormancy in seeds and buds.
3) Cytokinins: It promotes cell division in plants.
4) Abscisic acid: It promotes closing of stomata.

Question 19:

(a) What does a root do in response to gravity? What is this phenomenon known as?
(b) What does a stem (or shoot) do in response to light? What is this phenomenon known as?

Answer:

(a) The roots of a plant always grow downwards in response to gravity. This phenomenon is known as geotropism.
(b) The stem of a plant grows upwards in response to light. This phenomenon is known as phototropism.

Question 20:

(a) What does a stem (or shoot) do in response to gravity? What is this phenomenon known as?
(b) What does a root do in response to light? What is this phenomenon known as?

Answer:

(a) Stem always grows up and away from the pull of gravity. This phenomenon is known as negative geotropism.
(b) Root always grows downwards and away from light. This phenomenon is known as negative phototropism.

Question 21:

(a) What does a Mimosa pudica plant do in response to touch? What is this phenomenon known as?
(b) What happens to the dandelion flower (i) during daytime, and (ii) at night? What is this phenomenon known as?

Answer:

(a) Mimosa pudica folds its leaves and droops almost immediately in response to touch. This phenomenon is known as thigmonasty.
(b)
(i) A dandelion flower opens up during the day. (ii) It closes in the night.
This phenomenon is known as photonasty.

Question 22:

(a) What does a plant root do in response to water? What is this phenomenon known as?
(b) What happens to the moonflower (i) during daytime, and (ii) at night? What is this phenomenon known as?

Answer:

(a) A plant root always moves towards water. This phenomenon is known as positive hydrotropism.
(b) (i) Petals of a moonflower close during the day. (ii) They open during the night.
This phenomenon is known as photonasty.

Question 23:

What is a tendril? Name the two types of tendrils. What does a tendril do in response to the touch of a support? What is this phenomenon known as?

Answer:

Tendril is a thin thread-like growth on the stems or leaves of a climbing plant.
The two types of tendrils are stem tendrils and leaf tendrils.
Tendrils grow towards a support in response to their touch. This phenomenon is known as thigmotropism.

Question 24:

Name the five types of tropisms. How are tropic movements helpful to plants? Explain with an example.

Answer:

The five types of tropisms are phototropism, thigmotropism, geotropism, hydrotropism and chemotropism.
Tropic movements are helpful in the growth of plants.

Phototropism is an example of tropic movements. The stems of plants respond to sunlight by growing towards it. The plants also turn their leaves to face the sun. This enables their leaves to get as much sunlight as possible that is required for photosynthesis.

Question 25:

Define chemotropism. Give one example of chemotropism. State whether this example is of positive chemotropism or negative chemotropism.

Answer:

The growth of plant parts in response to chemical stimulus is known as chemotropism.
The growth of a pollen tube towards the ovule induced by a sugary stimulus is an example of chemotropism. This is an example of positive chemotropism as the pollen tube grows towards the stimulus.

Question 26:

Distinguish between tropic movements and nastic movements in plants. Give examples to illustrate your answer.

Answer:

Tropic movements	Nastic movements
These are directional movements of plants in response to stimulus.	These are non-directional movements of plants in response to stimulus.
Example: The upward growth of a plant stem in response to sunlight.	Example: The folding up of leaves in response to touch.

Question 27:

(a) What is meant by nastic movements in plants? Give one example of nastic movements in plants.
(b) What is the difference between photonasty and thigmonasty?

Answer:

(a) The non-directional movement of a plant part in response to an external stimulus is known as nastic movement . The folding up of leaves in sensitive plants in response to touch is an example of nastic movement.

(b)

Photonasty	Thigmonasty
It is the non-directional movement in plants in response to light.	It is the non-directional movement in plants in response to touch.

Question 28:

A potted plant is kept horizontally for a considerable time. The three positions of the parts A and B of the potted plant are shown in the following figures :

(a) Which figure shows the correct position taken by the parts A and B of the plant?
(b) What type of phenomenon is exhibited by the figure chosen in (a) above?

Answer:

(a) Figure 2 shows the correct position taken by the parts A and B of a plant.
(b) Geotropism is the phenomenon which is exhibited in this figure. Roots of a plant show positive geotropism, whereas stems show negative geotropism.

Question 29:

Name the plant hormones which are responsible for the following effects :
(a) falling of leaves
(b) opening of stomata
(c) bending of stem towards light
(d) closing of stomata

Answer:

(a) Abscisic acid
(b) Cytokinins
(c) Auxins
(d) Abscisic acid

Question 30:

Name the plant organs which are :
(a) positively phototropic
(b) positively geotropic
(c) negatively geotropic
(d) positively hydrotropic

Answer:

(a) Stem
(b) Roots
(c) Stem
(d) Roots

Question 31:

Why is the folding up of the leaves of a sensitive plant on touching with a finger not a tropism?

Answer:

The folding up of leaves in a sensitive plant on touching is not a tropism because it is a non-directional movement. Tropism is a directional movement where the direction of the movement of the plant part is towards the stimulus.

Question 32:

Why is the closing of a dandelion flower at dusk (when it gets dark) not a tropism?

Answer:

The closing of a dandelion flower at dusk is not a tropism because it is a non-directional movement in response to the intensity of light. On the contrary, tropic movement is the movement of plant parts towards the light. It does not depend upon the intensity of light.

Question 33:

(a) What is meant by 'tropisms' (or tropic movements)? Explain with an example.
(b) What are the different types of tropisms? Define each type of tropism. Write the name of stimulus in each case.
(c) How do tropisms differ from nasties (or nastic movements)?

Answer:

(a) The growth movement of plant parts in which the direction of the stimulus determines the direction of the response is known as tropisms.
Example: Phototropism, where the stems of plants grow upwards in response to sunlight.

(b) The different types of tropisms are:
(i) Phototropism: The movement of plant parts in response to light is known as phototropism. The stimulus is light.
(ii) Geotropism: The movement of plant parts in response to gravity is known as geotropism. The stimulus is gravity.
(iii) Hydrotropism: The movement of plant parts in response to water is known as hydrotropism. The stimulus is water.
(iv) Chemotropism: The movement of plant parts in response to chemicals is known as chemotropism. The stimulus is chemicals.
(v) Thigmotropism: The movement of plant parts in response to touch is known as thigmotropism. The stimulus is touch.

(c)

Tropism	Nasties
Tropisms are the directional movement of plant parts in response to an external stimulus.	Nasties are the non-directional movements of plant parts in response to an external stimulus.

Question 34:

(a) Define phototropism. Give one example of phototropism.
(b) How does phototropism occur in a plant stem (or shoot)? Explain with the help of labelled diagrams.
(c) What is meant by positive phototropism and negative phototropism? Give one example of each type.

Answer:

(a) The growth of plant parts in response to light is known as phototropism. An example of phototropism is the growth of plant stem in the upward direction in response to sunlight.

(b) The stems of plants grow towards sunlight showing positive phototropism.

(c) The movement of plant parts towards the light source is known as positive phototropism, whereas the movement of plant parts away from light is known as negative phototropism.
The stems of plants show positive phototropism as they grow upwards. The roots of plants show negative phototropism as they grow downwards into the soil.

Question 35:

(a) Define geotropism. Give one example of geotropism.
(b) What is meant by 'positive geotropism' and 'negative geotropism? Give one example of each type. Draw a labelled diagram to illustrate your answer indicating the plant part which shows positive geotropism and the plant part which shows negative geotropism.
(c) Name one plant part which exhibits positive thigmotropism.

Answer:

(a) The movement of plant parts in response to gravity is known as geotropism. The growth of plant roots is an example of geotropism.

(b) If the movement of the plant parts is towards the pull of gravity, it is known as positive geotropism; whereas if the movement of the plant parts is in the direction opposite to the pull of gravity, it is known as negative geotropism.
The movement of roots towards the soil is an example of positive geotropism, whereas the movement of plant stem away from the soil in the upward direction is an example of negative geotropism.

(c) Tendrils or climbing organs of a plant exhibit positive thigmotropism.

Question 36:

(a) How does control and coordination take place in plants? How does it differ from that in animals?
(b) Name five stimuli which act on plants. Name the type of tropism produced by each one of these stimuli.
(c) Define hydrotropism. Give one example of hydrotropism. State whether this example is of positive hydrotropism or negative hydrotropism. Illustrate your answer with the help of labelled diagram.

Answer:

(a) Control and coordination occur in plants with the help of hormones.
It differs from animals because animals have nervous system which is absent in plants.

(b) The five types of stimuli and the tropisms produced by each of them are:

Light produces phototropism
Water produces hydrotropism
Touch produces thigmotropism
Chemicals produce chemotropism
Gravity produces geotropism

(c) The movement of plant parts in response to water is known as hydrotropism.
An example of hydrotropism is the movement of plant roots towards water. It is a positive hydrotropism because the roots move towards the stimulus.

Question 37:

(a) What is meant by positive tropism and negative tropism? Explain with examples.
(b) Define thigmotropism. Give one example of thigmotropism.
(c) What is the difference between thigmotropism and thigmonasty? Name one plant which exhibits thigmotropism and one plant which exhibits thigmonasty. What behaviour (or responses) of these plants make you think that they exhibit thigmotropism and thigmonasty respectively?

Answer:

(a) If the movement of the response is towards the stimulus, it is known as positive tropism; whereas if the movement of the response is in the direction opposite to the stimulus, it is is known as negative tropism.
The movement of roots towards the pull of gravity is an example of positive geotropism, whereas the movement of plant stem in the direction opposite to the pull of gravity is an example of negative geotropism.

(b) The directional movement of plant parts in response to touch is known as thigmotropism. The movement of tendrils of climbing plants towards the things they happen to touch is an example of thigmotropism.

(c)

Thigmotropism	Thigmonasty
It is a directional movement of plant parts in response to touch.	It is a non-directional movement of plant parts in response to touch.
Example: Bitter gourd	Example: Mimosa pudica

Bitter gourd exhibits thigmotropism as its tendrils show directional movement towards the things they happen to touch.
On the other hand, Mimosa pudica exhibits thigmonasty as its leaflets show non-directional movement in response to touch.

Question 38:

Which of the following is not a plant hormone?
(a) auxin
(b) ascorbic acid
(c) cytokinin
(d) abscisic acid

Answer:

(b) ascorbic acid

Ascorbic acid is the chemical name of vitamin C and it is not a plant hormone.

Question 39:

One of the following plant hormones is responsible for the phenomenon of phototropism in plants. This is :
(a) gibberellin
(b) eltroxin
(c) cytokinin
(d) auxin

Answer:

(d) auxin

Auxin is responsible for the phenomenon of phototropism in plants.

Question 40:

The movement of a plant part in response to the force of attraction exerted by the earth is called :
(a) hydrotropism
(b) geotropism
(c) chemotropism
(d) phototropism

Answer:

(c) geotropism

The movement of plant parts in response to the force of gravity is called geotropism.

Question 41:

The movement of sunflower in accordance with the path of the sun is due to :
(a) photonasty
(b) phototropism
(c) hydrotropism
(d) chemotropism

Answer:

(a) photonasty

It is a non-directional movement of plant parts in response to light.

Question 42:

The plant part which exhibits negative geotropism is :
(a) root
(b) stem
(c) branch
(d) leaves

Answer:

(b) stem

Plant stem grows upward opposite to the force of gravity. Hence, it exhibits negative geotropism.

Question 43:

A big tree falls in a forest but its roots are still in contact with the soil.
The branches of this fallen tree grow straight up (vertically). This happens in response to
(a) water and light
(b) water and minerals
(c) gravity and water
(d) light and gravity

Answer:

(d) light and gravity

It is because a plant stem grows towards the light in the upward direction against the force of gravity.

Question 44:

Which of the following is not caused by a growth movement?
(a) bending of the shoot of a plant in response to light
(b) closing up of leaves of a sensitive plant on touching with an object
(c) climbing up of a plant on an object by using tendrils
(d) movement of the root of a plant towards a source of water

Answer:

(b) closing up of leaves of a sensitive plant on touching with an object

This is a non-directional movement of a plant in response to touch.

Question 45:

The root of a plant is :
(i) positively phototropic but negatively geotropic
(ii) positively geotropic but negatively phototropic
(iii) negatively phototropic but positively hydrotropic
(iv) negatively hydrotropic but positively phototropic
(a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv)

Answer:

(b) (ii) and (iii)

The root of a plant is positively geotropic, negatively phototropic and positively hydrotropic.

Question 46:

The main function of the plant hormone called abscisic acid is to :
(a) increase the length of cells
(b) promote cell division
(c) inhibit growth
(d) promote growth of stem and roots

Answer:

(c) inhibit growth

Abscisic acid mainly functions as a growth inhibitor.

Question 47:

The growth of tendrils in pea plants is due to the :
(a) effect of sunlight on the tendril cells facing the sun
(b) effect of gravity on the part of tendril hanging down towards the earth
(c) rapid cell division and elongation in tendril cells that are away from the support
(d) rapid cell division and elongation in tendril cells in contact with the support

Answer:

(d) rapid cell division and elongation in tendril cells in contact with the support

The growth of tendrils in pea plants is due to the rapid cell division and elongation in tendril cells in contact with the support.

Question 48:

Which of the following phytohormone is not associated with the promotion of growth in plants?
(a) auxin
(b) abscisic acid
(c) gibberellin
(d) cytokinin

Answer:

(b) Abscisic acid

Abscisic acid inhibits growth in plants.

Question 49:

The plant hormone which triggers the fall of mature leaves and fruits from the plant body is :
(a) auxin
(b) gibberellin
(c) abscisic acid
(d) cytokinin

Answer:

(c) abscisic acid

Abscisic acid causes abscission, i.e., falling of leaves and fruits from the plant body.

Question 50:

Which of the following terms denotes the movement of the root of a plant towards moisture in the soil?
(a) thigmotropism
(b) chemotropism
(c) hydrotropism
(d) geotropism

Answer:

(c) Hydrotropism

Hydro means water and tropism means movement. Thus, the movement of plant roots towards the moisture in the soil is called hydrotropism.

Question 51:

The growth of a pollen tube towards the ovule caused by a sugary substance as stimulus is an example of :
(a) phototropism
(b) chlorotropism
(c) gravitropism
(d) chemotropism

Answer:

(d) chemotropism

The growth of pollen tubes towards the ovule caused by a sugary substance is an example of chemotropism.

Question 52:

The bending of the shoot of a plant in response to light is called :
(a) geotropism
(b) phototropism
(c) thigmotropism
(d) photonasty

Answer:

(b) phototropism

Photo means light and tropism means movement. The bending of plant shoots in response to light is called phototropism.

Question 53:

The stimulus in the process of thigmotropism is :
(a) touch
(b) gravity
(c) light
(d) chemical

Answer:

(a) touch

The stimulus in thigmotropism is touch which causes movement.

Question 54:

A growing seedling is kept in a dark room. A burning candle is placed near it for a few days. The top part of seedling bends towards the burning candle. This is an example of :
(a) chemotropism
(b) hydrotropism
(c) phototropism
(d) geotropism

Answer:

(c) phototropism

The bending of the top part of the seedling towards the burning candle is an example of phototropism.

Question 55:

Which of the following acts as a stimulus in the process of hydrotropism?
(a) hydrocarbon
(b) hydrogen oxide
(c) hydrogen chloride
(d) hydrogen peroxide

Answer:

(b) Hydrogen oxide

Water or hydrogen oxide acts as a stimulus in the process of hydrotropism.

Question 56:

The growth movement of a plant part in response to the touch of an object is called :
(a) thigmonasty
(b) hydrotropism
(c) thigmotropism
(d) geotropism

Answer:

(c) thigmotropism

The growth movement of a plant part in response to the touch of an object is called thigmotropism.

Question 57:

The climbing organs of plants like tendrils grow towards any support which they happen to touch and wind around the support. This is an example of :
(a) chemotropism
(b) nastic movement
(c) thigmotropism
(d) geotropism

Answer:

(c) thigmotropism

This is an example of thigmotropism.

Question 58:

The rate of growth in roots is decreased by one of the following plant hormones. This plant hormone is :
(a) gibberellin
(b) auxin
(c) cytokinin
(d) ethene

Answer:

(b) auxin
Auxin decreases the growth rate of plant roots.

Question 59:

When the leaves of a Mimosa pudica plant are touched with a finger, they fold up quickly. This is an example of :
(a) chemotropism
(b) thigmonasty
(c) photonasty
(d) thigmotropism

Answer:

(b) thigmonasty

The leaves of a Mimosa pudica plant show response to touch. This response is non-directional and is categorised as a thigmonastic movement.

Question 60:

Dandelion flowers open the petals in bright light during the daytime but close the petals in dark at night. This response of dandelion flowers to light is called :
(a) phototropism
(b) thigmonasty
(c) chemotropism
(d) photonasty

Answer:

(d) photonasty
The response of dandelion flowers to light that involves the movement of the petals is an example of photonasty.

Question 61:

To which of the following directional stimulus roots of a plant do not respond?
(a) moisture
(b) candle light
(c) touch
(d) gravity

Answer:

(c) Touch

Roots do not respond to touch.

Question 62:

One of the following is not caused by the growth related movement of the concerned plant part. This is :
(a) phototropism
(b) photonasty
(c) thigmonasty
(d) thigmotropism

Answer:

(c) thigmonasty

The rolling up of plant leaves on touching is a thigmonastic movement and it is not related to growth.

Question 63:

The bending of the root of a plant away from a source of light is caused by a plant hormone called :
(a) cytokinin
(b) gibberellin
(c) abscisic acid
(d) auxin

Answer:

(d) auxin

The plant hormone auxin is responsible for negative phototropism in roots.

Question 64:

Most of the plant hormones promote plant growth. A plant hormone which inhibits growth is :
(a) abscisic acid
(b) ethene
(c) ascorbic acid
(d) cytokinin

Answer:

(a) abscisic acid

Abscisic acid inhibit plant growth.

Question 65:

The movement of a shoot towards light is :
(a) geotropism
(b) hydrotropism
(c) chemotropism
(d) phototropism

Answer:

(d) phototropism

The movement of plant shoots towards the light is an example of phototropism (photo = light; tropism = movement).

Question 66:

The bending of the stem of a plant towards a source of light is caused by the action of a phytohormone known as :
(a) abscisic acid
(b) auxin
(c) gibberellins
(d) cytokinin

Answer:

(b) auxin

Auxin causes phototropism, i.e., bending of plant stems towards the source of light.

Question 67:

Which of the following plant part exhibits negative phototropism?
(a) root
(b) branch
(c) leaves
(d) stem

Answer:

(a) Root

Roots bend away from the light source and show negative phototropism.

Question 68:

Which of the following are not tropisms?
(i) growing of pollen tube in response to a sugary substance
(ii) folding up of leaves of sensitive plant in response to touch
(iii) winding of tendril around a support in response to touch
(iv) opening up of the leaves of a daisy flower in response to light
(a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iv) (d) (ii) and (iv)

Answer:

(d) (ii) and (iv)

The folding up of leaves in sensitive plant as a response to touch and the opening up of leaves of a daisy flower in response to light are nastic movements.

Question 69:

The chemical substance P is made and secreted by the meristematic tissue at the tip of stem (or shoot) of a plant. The chemical substance P is responsible for a phenomenon Q in plants in which the stem bends towards a source of light. The same chemical substance P has an opposite effect on the root of a plant. It causes the root of a plant to bend away from the source of light in a process called R.
(a) What is the chemical substance P?
(b) State whether P prefers to remains in the sunlit side of a stem or in shade.
(c) What is the effect of substance P on the rate of growth of (i) a root, and (ii) a stem?
(d) What is the name of process (i) Q, and (ii) R?
(e) What is the general name of chemical substances like P? Name another substance which belongs to this class of chemical substances.

Answer:

(a) The chemical substance P is auxin.
(b) Auxin remains on the shaded side of the stem.
(c) Auxin increases the growth rate of shoots and decreases the growth rate of roots.
(d) Process Q is positive phototropism, whereas R is negative phototropism.
(e) The general name of chemical substances like auxin (P) is phytohormone. Cytokinins, gibberellins and abscisic acid are other examples of phytohormones.

Question 70:

A potted plant is growing in a transparent glass jar. In this plant, X and Y are the two growing parts having a lot of meristematic tissue. It is observed that the part X of this plant exhibits positive geotropism but negative phototropism. On the other hand, part Y of this plant exhibits negative geotropism but positive phototropism.
(a) Name the part X of plant.
(b) Name the part Y of plant.
(c) Which part of the plant, X or Y, will exhibit positive hydrotropism?
(d) Which part of the plant, X or Y, can have tendrils on it?
(e) Which phytohormone causes the part X to exhibit negative phototropism?

Answer:

(a) The part X is the root.
(b) The part Y is the shoot.
(c) The part X (root) will exhibit positive hydrotropism.
(d) The part Y (shoot) could have tendrils on it.
(e) The phytohormone, auxin causes the root to exhibit negative phototropism.

Question 71:

There are three plants A, B and C. The flowers of plant A open their petals in bright light during the day but close them when it gets dark at night. On the other hand, the flowers of plant B open their petals at night but close them during the day when there is bright light. The leaves of plant C fold up and droop when touched with fingers or any other solid object.
(a) Name the phenomenon shown by the flowers of (i) plant A, and (ii) plant B.
(b) Name one flower each which behaves like the flower of (i) plant A, and (ii) plant B.
(c) Name the phenomenon exhibited by the leaves of plant C.
(d) Name a plant whose leaves behave like those of plant C.
(e) Which plant/plants exhibit the phenomenon based on growth movements?

Answer:

(a) The phenomenon shown by the flowers of plants A and B is photonasty.
(b) A flower which behaves like the flower of (i) plant A is dandelion and (ii) plant B is moonflower.
(c) The leaves of plant C exhibit thigmonasty.
(d) A plant whose leaves behave like those of plant C is Mimosa pudica.
(e) The plants A and B exhibit the phenomenon based on growth movements.

Question 72:

While conducting experiments to study the effect of various stimuli on the plants, it was observed that the roots of a plant X grow and bend towards two stimuli A and B but bend away from a third stimulus C. The stem of the plant X, however, bends away from stimuli A and B but bends towards the stimulus C. The stimulus B is known to act on the roots due to too much weight of the earth. Keeping these points in mind, answer the following question :
(a) What could stimulus A be?
(b) Name the stimulus B.
(c) What could stimulus C be?
(d) The branches of a fallen tree in a forest grow straight up in response to two stimuli. What could be these two stimuli out of A, B and C? Also name these two stimuli.

Answer:

(a) The stimulus A is water.
(b) The stimulus B is gravity.
(c) The stimulus C is light.
(d) 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.

Question 73:

P and Q are two types of plants having weak stems which cannot stand upright on their own. The plants P and Q have organs R and S respectively which can grow towards any support which they happen to touch and wind around that support. It is observed that organ R originates from the leaves of the plant whereas organ S originates directly from the stem of the plant.
(a) What is (i) R, and (ii) S?
(b) What is the name of growth movement exhibited by the organs R and S?
(c) Name the stimulus involved in this case.
(d) State whether the behaviour of organs R and S is a tropic movement or a nastic movement.
(e) Name one plant like P and another plant like Q.

Answer:

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

Question 74:

The top part A of the flask-shaped reproductive organ X in the flower of a plant secrets a surgery substance into its lower part B which goes towards the bottom part C of the flask-shaped organ. When a tiny grain D coming from the top part E of another reproductive organ Y in the flower falls on part A, it grows a long tube F through the organ X in response to the sugary substance and reaches the bottom part C of flask-shaped organ to carry out fertilisation.
(a) What is (i) organ X, and (ii) organ Y, inside the flower?
(b) Name parts (i) A (ii) B, and (iii) C, of flask-shaped organ.
(c) Name (i) grain D, and (ii) part E of organ Y.
(d) Name the tube F.
(e) What is the phenomenon of growing a long tube in response to sugary substance in the process of fertilisation in a flower known as?

Answer:

(a) Organ X is carpel and organ Y is Stamen.

(b) (i) A - Stigma
(ii) B - Style
(iii) C - Ovary

(c) (i) Pollen grain
(ii) Anther
(iii) Pollen tube

(d) The tube F is pollen grain.

(e) This phenomenon is called chemotropism.

Question 75:

P, Q, R and S are four major types of phytohormones. P is a phytohormone which functions mainly as a growth inhibitor. It promotes the wilting and falling of leaves. Q, R and S are phytohormones which all promote growth of plants in various ways. Q is responsible for the phenomenon of phototropism in plants. R is involved mainly in shoot extensions. The phytohormone S helps in breaking the dormancy of seeds and buds. What are P, Q, R and S? Give one reason each for your choice.

Answer:

P is abscisic acid because it is antagonistic to growth and inhibits it.
Q is auxin because it causes bending of shoots towards the light.
R is gibberellins because it increases the cell division in a plant shoot and increases its length.
S is cytokinin because it breaks the dormancy of buds and seeds.

Question 76:

A potted plant having straight parts A and B was placed horizontally on its side as shown in figure (i). After a few days it was observed that the parts A and B of the plant acquire new positions as shown in Figure (ii).
(a) Name the phenomenon exhibited by the position of plant parts A and B in Figure (ii)
(b) Name the stimulus (other than sunlight) which causes plant part A to grow and bend upwards, and plant part B to bend downwards.

Answer:

(a) The phenomenon exhibited by the positions of plant part A is phototropism and plant part B is geotropism.
(b) The stimulus which causes plant part A to grow and bend upwards is light and part B to bend downwards is gravity.

Question 77:

When the leaves of a sensitive plant are touched with a finger, they fold up and when light fades at dusk, the petals of a dandelion flower close.
(a) State one way in which the above two processes are similar.
(b) State two ways in which the above two processes differ.

Answer:

(a) Both the processes are similar as the response is not determined by the direction of the stimulus. They are nastic movement.
(b) The first process of folding up of leaf is thigmonastic and the stimulus is touch. The second process of closing of petals is photonastic and the stimulus is light.

Question 1:

Name the two systems of control and coordination in higher animals.

Answer:

The two systems of control and coordination in higher animals are the nervous system and the endocrine system.

Question 2:

What are the two parts of the vertebrate nervous system?

Answer:

The two parts of the vertebrate nervous system are the central nervous system and the peripheral nervous system.

Question 3:

If we happen to touch a hot object unknowingly, we immediately pull back our hand. What is this type of action known as?

Answer:

After touching a hot object unknowingly, the hand is automatically pulled back at once. This type of action is known as a reflex action.

Question 4:

Name the three components of a neuron (or nerve cell).

Answer:

The three components of a neuron (or a nerve cell) are the cell body, the dendrites and the axon.

Question 5:

(a) What are the short fibres of a neuron known as?
(b) What is the long fibre of a neuron known as?

Answer:

(a) The short fibres of a neuron are known as the dendrites.
(b) The long fibre of a neuron is known as the axon.

Question 6:

Name the most important part of the human brain.

Answer:

The cerebrum (forebrain) is the most important part of the human brain.

Question 7:

Which part of the brain maintains posture and balance of the body?

Answer:

The cerebellum of the brain maintains posture and balance of the body.

Question 8:

State one function each of cerebellum and pons.

Answer:

The pons participate in regulating respiration. The cerebellum helps in maintaining balance and posture of the body.

Question 9:

Name one harmone secreted by the pituitary gland.

Answer:

Growth hormone in humans is secreted by the pituitary gland.

Question 10:

Where are hormones made in the human body?

Answer:

The hormones in the human body are made in specialised tissues called the endocrine glands.

Question 11:

What is the name of the system of glands which produces hormones?

Answer:

The system of glands that produces hormones is called the endocrine system or the hormonal system.

Question 12:

Which gland secretes the growth hormone?

Answer:

The pituitary gland secretes the growth hormone.

Question 13:

Name the hormones secreted by (a) testes, and (b) ovaries

Answer:

(a) The testes secrete testosterone.
(b) The ovaries secrete oestrogen and progesterone.

Question 14:

What are the scientific names for the following receptors in animals?
(a) receptors for light
(b) receptors for heat
(c) receptors for sound
(d) receptors for smell
(e) receptors for taste

Answer:

(a) Photoreceptor: receptors for light
(b) Thermoreceptor: receptors for heat
(c) Phonoreceptor: receptors for sound
(d) Olfactory receptors: receptors for smell
(e) Gustatory receptors: receptors for taste

Question 15:

Name the disease caused by the deficiency of insulin hormone in the body.

Answer:

Diabetes is caused by the deficiency of a hormone known as insulin.

Question 16:

Name the disease caused by the deficiency of thyroxine hormone in the body.

Answer:

Goitre is caused by the deficiency of thyroxine in the body.

Question 17:

Which halogen element is necessary for the making of thyroxine hormone by the thyroid gland?

Answer:

The thyroid gland requires iodine to make thyroxine hormone.

Question 18:

Why are some patients of diabetes treated by giving injections of insulin?

Answer:

Diabetes is caused by high sugar level in blood. Diabetic patients are treated by giving injections of insulin as it lowers the blood sugar level by controlling the metabolism of sugar.

Question 19:

What is the name of in-built 'arrangement' in our body which controls the timing and amount of hormones released by various endocrine glands in the body?

Answer:

Feedback mechanism is the in-built arrangement in our body that controls the timing and amount of hormones released by various endocrine glands.

Question 20:

Name one gland each :
(a) which acts only as an endocrine gland.
(b) which acts only as an exocrine gland.
(c) which acts both as an endocrine gland as well as an exocrine gland.

Answer:

(a) An endocrine gland is a ductless gland. For example, thyroid is an endocrine gland.
(b) An exocrine gland is a gland that has a duct. Example: salivary gland.
(c) Pancreas acts both as an endocrine gland and an exocrine gland.

Question 21:

What part does the diet play in helping us to have a healthy thyroid gland?

Answer:

Iodine is necessary in our diet for the proper functioning of the thyroid gland. Lack of iodine in our diet can cause a deficiency of thyroxine hormone.

Question 22:

If sugar is detected in the urine of a person, name the disease he is suffering from.

Answer:

Diabetes is characterised by large quantities of sugar in the urine of a person. Deficiency of insulin hormone causes diabetes.

Question 23:

Name two parts of the body which contain receptors of chemical stimuli.

Answer:

The nose and the tongue contain receptors of chemical stimuli.

Question 24:

Which part of the eye contains cells which are sensitive to light?

Answer:

The retina of an eye contains light-sensitive cells.

Question 25:

What are the two main communications systems in an animal's body?

Answer:

The nervous system and the endocrine system are the two main communication systems in an animal body.

Question 26:

Which one term in each of the following includes the other three?
(a) thyroid, ductless gland, thymus, pituitary, ovary
(b) adrenalin, insulin, hormone, thyroxine, estrogen

Answer:

(a) Thyroid, pituitary, thymus and ovary are types of ductless glands.
(b) Adrenalin, insulin, thyroxine and estrogen are types of hormones.

Question 27:

Which parts of the body form the central nervous system?

Answer:

The central nervous system consists of the brain and the spinal cord.

Question 28:

Give three examples of reflex actions.

Answer:

Coughing, yawning and blinking of eyes are examples of reflex actions.

Question 29:

Why do you need iodine in your diet?

Answer:

Iodine is needed in our diet because it helps the thyroid gland in making thyroxine hormone.

Question 30:

State whether coughing is a voluntary action or reflex action.

Answer:

Reflex actions are those actions which we do without thinking to protect ourselves. Coughing is a reflex action as it clears our windpipe.

Question 31:

Fill in the following blanks with suitable words :
(a) The two examples of effectors are .........and ...........
(b) Our.............system allows us to react to our surroundings. Information from receptors passes along...........neurons to our brain. Our brain sends impulses along..........neurons to our muscles.
(c) A neuron which carries an impulse to the brain is called a ........... neuron.
(d) The neuron which carries a message for action to a muscle or gland is known as a......... neuron.

Answer:

(a) The two examples of effectors are muscles and glands.
(b) Our nervous system allows us to react to our surroundings. Information from receptors passes along the sensory neurons to our brain. Our brain sends impulses along the motor neurons to our muscles.
(c) A neuron which carries an impulse to the brain is called a sensory neuron.
(d) A neuron that carries a message for action to a muscle or a gland is known as a motor neuron.

Question 32:

(a) What are the various sense organs in our body?
(b) What is meant by receptors and effectors? Give two examples of each.

Answer:

(a) There are five sense organs in our body. They are the eyes, the ears, the nose, the tongue and the skin.

(b) A receptor is a cell present in the sense organs that is sensitive to specific stimuli.
Example: The eyes have light receptors which can detect light and the ears have sound receptors which can detect sound.

An effector is a part of body which can respond to a stimulus according to the instructions given from the nervous system.
Example: Muscles and glands of the human body.

Question 33:

(a) What is spinal cord? What is its main function?
(b) Give the functions of medulla.

Answer:

(a) The spinal cord is a part of the central nervous system. It is a cylindrical structure enclosed by a bony cage called the vertebral column. It is responsible for spinal reflex actions and the conduction of nerve impulses to and from the brain.
(b) The medulla controls various involuntary actions such as the heart beat, breathing, blood pressure and peristaltic movements of the alimentary canal.

Question 34:

(a) Name the three types of nerves which constitute the peripheral nervous system.
(b) What is the difference between a reflex action and walking?
(c) How do we detect the smell of an incense stick (agarbatti)?

Answer:

(a) The three types of nerves which make up the peripheral nervous system are the spinal nerves, the cranial nerves and the visceral nerves.

(b)

Reflex action	Walking
A reflex action is an involuntary action that is a rapid and automatic response to stimuli.	Walking is a voluntary action that requires our thinking and is in our control.

(c) When the smell of the incense stick reaches our nose, the olfactory receptors present in our nose detect it and send this information to our brain in the form of electrical signals. The brain interprets this information as the smell of incense stick where it has been already stored.

Question 35:

(a) What substances are made by endocrine glands?
(b) What is the function of receptors and effectors in our body?

Answer:

(a) The endocrine glands secrete chemical substances called hormones.
(b) Receptors receive stimuli from the surrounding environment and send the messages conveyed by them to the spinal cord and the brain as electrical impulses through the sensory nerves. On the other hand, effectors respond to stimuli according to the instructions sent from the nervous system.

Question 36:

(a) Name the hormones secreted by the following endocrine glands :
(i) Thyroid gland
(ii) Parathyroid glands
(iii) Pancreas
(iv) Adrenal glands
(b) Write the functions of testosterone and oestrogen hormones.

Answer:

(a)
(i) Thyroxine
(ii) Parathormone
(iii) Insulin
(iv) Adrenaline

(b) The functions of testosterone hormone is to control the development of male sex organs and male characters such as deepening of voice, moustache, beard and other body hair.
The functions of oestrogen hormone is to control the development of female sex organs and female characters such as feminine voice and soft skin.

Question 37:

(a) Write the names of the regions in hindbrain. Give one function of each region.
(b) Name the function of cerebrum.

Answer:

(a) The hindbrain has three regions: the pons, the cerebellum and the medulla.
The pons take part in regulating the respiration.
The cerebellum helps in maintaining posture and balance of the body.
The medulla controls various involuntary actions such as the heart beat, breathing, blood pressure and peristaltic movements of the alimentary canal.
(b) The cerebrum is the logical part of the brain. It is the site of our faculties such as learning, reasoning, intelligence, personality and memory. All of our thoughts, sensations, actions and movements are controlled by the cerebrum.

Question 38:

(a) The human brain can be broadly divided into three regions. Name these three regions.
(b) What is cranium? What is its function?

Answer:

(a) The human brain can be broadly divided into three regions: the forebrain, the midbrain and the hindbrain.
(b) The cranium is a bony box in the skull which protects the brain.

Question 39:

(a) How does chemical coordination take place in human beings?
(b) Why is the use of iodised salt advisable?

Answer:

(a) Chemical coordination takes place through hormones in human beings. Hormones instruct the brain when to pace up or slow down a particular function.
(b) Iodised salt contains iodine which is essential for making thyroxine by the thyroid gland.

Question 40:

What is the function of insulin hormone? What type of patients are given insulin injections?

Answer:

The function of insulin hormone is to lower the blood sugar level. Insulin controls the metabolism of sugar. Deficiency of insulin causes diabetes. Diabetic patients are treated by giving injections of insulin.

Question 41:

Compare the nervous system and endocrine system (hormonal system) for control and coordination in humans.

Answer:

Nervous system	Endocrine system
Made of neurons.	Made of secretory cells called glands.
Messages are transmitted in the form of electric impulses.	Messages are transmitted in the form of chemicals called hormones.
Messages are transmitted along nerve fibres.	Messages are transmitted through the bloodstream.

Question 42:

State the functions of the following hormones :
(a) Thyroxine
(b) Adrenaline
(c) Growth hormone

Answer:

(a) The function of thyroxine hormone is to control the rate of metabolism of carbohydrates, fats and proteins in the body.
(b) The function of adrenaline hormone is to regulate heart beat, breathing rate, blood pressure and carbohydrate metabolism.
(c) The function of growth hormone is to control the development of bones and muscles.

Question 43:

Write the names of all the major endocrine glands present in the human body. Which of these glands also function as exocrine glands?

Answer:

The major endocrine glands present in the human body are the pineal gland, hypothalamus gland, pituitary gland, thyroid gland, parathyroid glands, thymus, pancreas, adrenal glands, testes in males and ovaries in females.

The pancreas, testes and ovary also function as exocrine glands.

Question 44:

Match the hormones given in column I with their functions given in column II :

Hormones	Functions
(i) Thyroxine	(a) Causes breasts to develop in females
(ii) Adrenaline	(b) Causes the male to start producing sperms
(iii) Insulin	(c) Prepares the body for an emergency
(iv) Estrogen	(d) Controls the metabolic rate
(v) Testosterone	(e) Regulates the amount of sugar in blood

Answer:

(i) Thyroxine (d) Controls the metabolic rate
(ii) Adrenaline (c) Prepares the body for an emergency
(iii) Insulin (e) Regulates the amount of sugar in blood
(iv) Estrogen (a) Causes breasts to develop in females
(v) Testosterone (b) Causes the males to start producing sperms

Question 45:

A person walks across a room in barefeet and puts his foot on a drawing pin lying on the floor. He lets out a cry. Explain what happens in his nervous system in bringing about this response.

Answer:

It is an example of a reflex action. The stimulus in this example is pain which is felt by the foot on touching the drawing pin. This pain is sensed by a receptor in the foot. The receptor triggers an impulse to a sensory neuron which transmits the message to the spinal cord. Here, the impulse is passed on to a relay neuron which, in turn, passes it to a motor neuron. The motor neuron passes the impulse to a muscle in the foot. The muscle, then, contracts and pulls the foot away from the drawing pin.

Question 46:

In what ways are puberty and adolescence result of the activity of some glands in the human body?

Answer:

Puberty and adolescence are results of the activities of testosterone in males and oestrogen in females. In males during puberty, testosterone secretion is increased resulting in the development of male sex organs and male characters such as deeper voice, moustache, beard and more body hair.
Similarly, in females, oestrogen secretion is increased at the time of puberty resulting in the development of female sex organs and female characters such as feminine voice, soft skin and mammary glands.

Question 47:

List three ways in which neurons are similar to other cells.

Answer:

Neurons are similar to other cells in the following manners:

(a) Both consist of cytoplasm
(b) Both contain nuclei
(c) Both are bounded by cell membranes

Question 48:

Explain the difference between each of the following pairs of terms :
(a) receptor and effector
(b) cerebrum and cerebellum

Answer:

(a)

Receptor	Effector
A receptor is a cell (or a group of cells) present in a sense organ which is sensitive to a particular types of stimuli such as light, sound, smell, taste, heat and pressure.	An effector is a part of the body which can respond to a stimulus according to the instructions sent from the nervous system.
Eyes have light receptors; ears have sound receptors, etc.	Muscles and glands are examples of effectors.

(b)

Cerebrum	Cerebellum
The cerebrum is a part of the forebrain.	The cerebellum is a part of the hindbrain.
It is the site of our faculties such as learning, reasoning, intelligence, personality and memory.	It helps in maintaining posture and balance of the body. It also enables us to make precise and accurate movements.

Question 49:

What is the difference between a voluntary and an involuntary action? Which kind of action is digestion? Explain your choice.

Answer:

Voluntary action	Involuntary action
A voluntary action is under the control of one's will.	An involuntary action is not under the control of one's will.

Digestion is an involuntary action as it occurs inside our body without our conscious choice.

Question 50:

What does CNS stand for? Which part of CNS : (a) consists of two cerebral hemispheres, and (b) has spinal nerves attached to it?

Answer:

CNS stands for Central Nervous System.
(a) The cerebrum consists of two cerebral hemispheres.
(b) The spinal cord has spinal nerves attached to it.

Question 51:

Which hormone :
(a) prepares the body for action?
(b) controls the amount of glucose in blood?
(c) gives boys a deep voice?
(d) gives girls soft skin?

Answer:

(a) Adrenaline prepares the body for action.
(b) Insulin controls the amount of glucose in blood.
(c) Testosterone gives boys a deep voice.
(d) Oestrogen gives girls soft skin.

Question 52:

When you smell a favourite food your mouth begins to water (that is, you secrete saliva). Write down what the following are examples of :
(a) the smell of the food
(b) the cells in your nasal passages which perceive the smell
(c) the gland which is stimulated to secrete saliva.

Answer:

(a) The smell of food is a stimulus.
(b) Olfactory receptors present in our nasal passage perceive the smell.
(c) Salivary gland (effector) is stimulated to secrete saliva.

Question 53:

(a) Name the structural and functional unit of the nervous system.
(b) Draw a flow chart to show the classification of nervous system into various parts.
(c) What is autonomic nervous system? What is its function?
(d) What is voluntary nervous system? Explain the working of voluntary nervous system with an example.

Answer:

(a) A neuron is the structural and functional unit of the nervous system.

(b) Classification of the nervous system into various parts:

(c) Autonomic nervous system is the part of nervous system that controls and regulates the functions of internal organs of the body by its own.
Its main function is to control and regulate involuntary body functions like heartbeat, blood flow, breathing and digestion.

(d) Voluntary nervous system is the part of the nervous system that is responsible for carrying motor and sensory information both to and from the central nervous system (CNS). It is associated with voluntary control of body movements through the actions of skeletal muscles. It is also responsible for sensing external stimuli, which helps the body to remain in touch with its surroundings.
For example, when the skin is penetrated by a sharp object like a pin, the pain is detected by the pain receptor. The nerve impulses are generated in the sensory nerves and conducted to the brain. The brain sends instructions to the skeletal muscles (effector muscle) through the motor nerves to remove the pin. Then the muscle acts accordingly and removes the pin.

Question 54:

(a) What is a reflex action? Explain with the help of an example.
(b) Define reflex arc. Give the flow chart of a spinal reflex arc.
(c) How are involuntary actions and reflex actions different from each other?

Answer:

(a) Reflex action is a rapid and automatic response to a stimulus. It is not under the voluntary control of the brain. For example, if we unknowingly touch a hot plate, we immediately move our hand away from it.
(b) The path travelled by an impulse during a reflex action is called a reflex arc.

Spinal reflex arc:

(c)

Involuntary actions	Reflex actions
These are normal involuntary actions of internal or external organs of the body.	These are sudden involuntary responses to external stimuli.

Question 55:

(a) What is the function of our nervous system?
(b) What are the main organs of the human nervous system? Draw a labelled diagram to show the main organs of the human nervous system.
(c) How does the human nervous system work? Explain.

Answer:

(a) The function of the nervous system is to coordinate the activities of our body. The nervous system helps all the other systems of our body to work together.
(b) The main organs of the human nervous system are the brain, the spinal cord and the nerves.

Human nervous system:

(c) When the sense organs such as eyes, ears, nose, tongue or skin are affected in our body, they send message to the brain in the form of electrical impulses through the sensory neurons. The brain analyses this message and decides the action to be taken. The brain, then, sends out instructions to the muscles of the concerned body part through the motor neurons. The concerned body part, then, acts according to the instructions sent by the brain.

Question 56:

(a) What is a neuron? Draw a labelled diagram of a neuron.
(b) What is a synapse? What happens at the synapse between two neurons? How are the messages carried across a synapse? Explain with the help of a labelled diagram.

Answer:

(a) A neuron is a structural and functional unit of the nervous system. A neuron or nerve cell has three components: the cell body, the dendrites and the axon.

Diagram of a neuron:

(b) Synapses are microscopic gaps present in between pairs of adjacent neurons over which nerve impulses pass from one neuron to the next.

A nerve impulse, on reaching the terminal end of an axon, releases chemicals called neurotransmitters at its tip. These chemicals cross the synapse and start the impulse in the next neuron or to an effector organ.

A receptor in a sense organ is in touch with the dendrites of the sensory neuron. When a stimulus acts on the receptor, a chemical reaction is initiated that produces an electrical impulse in the receptor. This impulse travels from the dendrites of the sensory neuron (say A) to its cell body and, then, along its axon. At the end of the axon of the sensory neuron A, the electrical impulse releases chemical substances called neurotransmitters into the synapse which cross the synapse and start a similar electrical impulse in the dendrites of the next neuron (say B). From the dendrites, this electrical impulse is carried to the cell body and, then, to the axon of the second neuron.

Question 57:

(a) Name two systems which taken together perform the functions of control and coordination in human beings.
(b) What does the central nervous system in humans consist of? What is the job of the central nervous system?
(c) Give the various functions of brain.

Answer:

(a) The nervous system and the endocrine system together perform the functions of control and coordination in human beings.

(b) The central nervous system consists of the brain and the spinal cord. It is responsible for the coordination and control of the activities of the nervous system. It directs incoming messages to the motor neurons which are connected to the part of the body that will respond to a stimulus.

(c) The various functions of the brain are as follows:
(i) It receives information-carrying nerve impulses from all the sensory organs of the body.
(ii) It responds to the impulses brought in by the sensory organs by sending instructions to the muscles and glands making them function accordingly.
(iii) It correlates the various stimuli from different sense organs and produces the most appropriate and intelligent responses.

Question 58:

(a) Write the names of five endocrine glands found in the human body. Name the hormones secreted by each gland.
(b) How do hormones reach the organs they control?
(c) Name the gland which controls the secretion of hormones from the pituitary.
(d) How does our body respond when adrenaline is secreted in large amounts into the blood?
(e) Name the disease which occurs in adults due to the deficiency of iodine in the diet. What is the main symptom of this disease?

Answer:

(a) The five endocrine glands found in the human body are:

Pituitary gland which secretes growth hormone.
Thyroid gland which secretes thyroxine hormone.
Parathyroid gland which secretes parathormone.
Pancreas which secretes insulin.
Adrenal glands which secrete adrenaline.

(b) Hormones reach the target organ through the blood and act on it.

(c) Hypothalamus regulates the secretion of hormones from the pituitary gland.

(d) An increase in the amount of adrenaline in our body increases our heart beat, breathing rate, blood flow into the muscles and causes the liver to put more stored glucose in our blood. All these actions of adrenaline produces a lot of energy in our body very quickly and enable us to take quick action.

(e) Iodine deficiency in our diet causes goitre. The main symptom of goitre is swelling of the thyroid gland which is present in the neck.

Question 59:

A cell (or group of cells) in a sense organ which is sensitive to a particular type of stimulus is called :
(a) interceptor
(b) effector
(c) receptor
(d) acceptor

Answer:

(c) receptor

A receptor is a cell (or a group of cells) which is present in a sense organ and is sensitive to a particular type of stimulus such as light, sound, smell, taste, heat or pressure.

Question 60:

Which of the following cannot be considered a receptor?
(a) ear
(b) nose
(c) muscle
(d) eye

Answer:

(c) muscle
Sense organs contain receptors. The ear, nose and eye are sense organs, a muscle is not.

Question 61:

One of the following acts as an endocrine gland as well as an exocrine gland. This one is :
(a) salivary gland
(b) pancreas
(c) pituitary
(d) parathyroid

Answer:

(b) pancreas
The pancreas acts as an exocrine as well as an endocrine gland. The salivary, pituitary and parathyroid glands are endocrine glands.

Question 62:

Which of the following helps in maintaining posture and balance of the human body?
(a) cerebellum
(b) cerebrum
(c) medulla
(d) pons

Answer:

(a) Cerebellum
The cerebellum is a part of the hindbrain which helps in maintaining posture and balance of the body.

Question 63:

The number of pairs of nerves which arises from the spinal cord is :
(a) 21
(b) 31
(c) 41
(d) 51

Answer:

(b) 31
As many as 31 pairs of nerves arise from the spinal cord.

Question 64:

Cerbellum, medulla and pons are the parts of :
(a) mid-brain
(b) hind-brain
(c) forebrain
(d) spinal cord

Answer:

(b) hindbrain
The hindbrain consists of three centres called the pons, the cerebellum and the medulla.
The forebrain consists mainly of the cerebrum.
The midbrain does not have any further divisions.
The spinal cord is a cylindrical structure.

Question 65:

Which of the following are cerebral reflexes?
(i) a person pulls away his hand on touching a hot object
(ii) a person spits out immediately when a fly enters his mouth while talking
(iii) A person walking bare foot lifts his foot at once on stepping on to a nail
(iv) A person's pupil contracts at once in the presence of bright light
(a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (ii) and (iv)

Answer:

(d) (ii) and (iv)
Cerebral reflexes are those reflex actions which involve the brain. They occur in the organs present in the head as these organs are directly connected to the brain.

Question 66:

Iodine is necessary for the synthesis of which of the following hormone?
(a) adrenaline
(b) auxin
(c) thyroxine
(d) insulin

Answer:

(c) Thyroxine

Iodine is required for the synthesis of thyroxine hormone by the thyroid gland.

Question 67:

Which of the following is a mis-matched pair?
(a) adrenaline : pituitary gland
(b) estrogen : ovary
(c) pancreas : insulin
(d) progesterone : ovary

Answer:

(a) adrenaline : pituitary gland

Adrenaline is secreted by the adrenal glands which are located on top of the kidneys.

Question 68:

One of the following is an incorrect statement about insulin. This is :
(a) it is produced in pancreas
(b) it regulates growth and development of the body
(c) it regulates blood glucose level in the blood
(d) its deficiency in the body will cause diabetes

Answer:

(b) it regulates growth and development of the body

Insulin is produced in the pancreas. It regulates blood sugar level and its deficiency causes diabetes. The growth and development of the body is regulated by the growth hormone.

Question 69:

The spinal cord orginates from :
(a) cerebrum
(b) cerebellum
(c) medulla
(d) pons

Answer:

(c) medulla

The spinal cord is a tubular structure connected to the medulla oblongata of the brain.

Question 70:

The involuntary actions in the body are controlled by :
(a) medulla in forebrain
(b)medulla in hindbrain
(c) medulla in spinal cord
(d) medulla in midbrain

Answer:

(b) medulla in the hindbrain

The medulla controls various involuntary actions such as heart beat, breathing, blood pressure and peristaltic movement in the body.

Question 71:

Which of the following is not an involuntary action?
(a) vomiting
(b) chewing
(c) heart beat
(d) salivation

Answer:

(b) chewing
Chewing is a voluntary action, while actions like vomiting, heart beat and salivation are involuntary.

Question 72:

Which of the following hormone prepares our body for action in emergency situations?
(a) testosterone
(b) growth hormone
(c) adrenaline
(d) insulin

Answer:

(c) adrenaline

Adrenaline released from the adrenal gland prepares our body for action in emergency situations. Hence, it is called emergency hormone, i.e., hormone of fight or flight.

Question 73:

One of the following controls the peristaltic movements of alimentary canal. This one is :
(a) cerebrum
(b) cerebellum
(c) pons
(d) medulla

Answer:

(d) medulla

The medulla controls the involuntary actions like the peristaltic movements of the alimentary canal.

Question 74:

The hormone which is associated with male puberty is called :
(a) oestrogen
(b) adrenaline
(c) testosterone
(d) progesterone

Answer:

(c) testosterone

Testosterone is the male sex hormone which is associated with male puberty.

Question 75:

Which of the following endocrine gland does not occur as a pair in the human body?
(a) adrenal
(b) pituitary
(c) testis
(d) ovary

Answer:

(b) Pituitary

The pituitary gland does not occur in pairs, while the adrenal gland, testis (in male) and ovary (in female) do.

Question 76:

The junction between two adjacent neurons is called :
(a) nerve junction
(b) sensory junction
(c) synapse
(d) neuro-muscular joint

Answer:

(c) synapse

A synapse is a functional junction between the axon of a neuron and the dendrites of the next neuron. It is separated by a small gap known as the synaptic cleft.

Question 77:

The life processes in humans are controlled and regulated by :
(a) reproductive and endocrine systems
(b) respiratory and nervous systems
(c) endocrine and digestive systems
(d) nervous and endocrine systems

Answer:

(d) nervous and endocrine systems

The life processes in humans are controlled and regulated by the endocrine and the digestive system. They work together to communicate, integrate and coordinate the functions of various organs and other systems of the body.

Question 78:

A doctor advised a person to take injection of insulin because :
(a) his blood pressure was high
(b) his heart beat was high
(c) his blood sugar was high
(d) his thyroxine level in blood was high

Answer:

(c) his blood sugar was high.

Insulin controls the blood sugar level. Hence, the doctor advised him to take an injection of insulin to bring his sugar level to normal.

Question 79:

All the voluntary actions of our body are controlled by :
(a) cerebrum
(b) cerebellum
(c) pons
(d) medulla

Answer:

(a) cerebrum

All the voluntary actions of our body are controlled by the cerebrum. The cerebrum is the largest and the most prominent part of the brain.

Question 80:

One of the following statements is not true about thyroxine. This is :
(a) Thyroid gland requires iron to synthesise thyroxine
(b) It regulates carbohydrate, protein and fat metabolism
(c) Iodine is essential for the synthesis of thyroxine
(d) Thyroid gland can enlarge due to lack of thyroxine

Answer:

(a) thyroid gland requires iron to synthesise thyroxine.
Statement (a) is incorrect. Iodine is required for the synthesis of thyroxine hormone by the thyroid gland.

Question 81:

Which of the following does not act as an endocrine gland as well as an exocrine gland?
(a) testis
(b) ovary
(c) pituitary
(d) pancreas

Answer:

(c) Pituitary

The pituitary gland is an endocrine gland, while the ovary, testis and pancreas are heterocrine glands. Those glands which are partly exocrine (with duct) and partly endocrine (without duct) are known as heterocrine glands. Here, the exocrine part releases secretion into the duct, while the endocrine part releases hormones into blood.

Question 82:

The part of brain which controls the involuntary action such as heart beat, breathing, blood pressure, etc. is :
(a) pons
(b) medulla
(c) cerebrum
(d) cerebellum

Answer:

(b) medulla

The medulla controls various involuntary actions such as the heart beat, breathing, blood pressure and the peristaltic movement in the body.

Question 83:

Dwarfism results due to :
(a) excessive secretion of thyroxine hormone
(b) excessive secretion of growth hormone
(c) less secretion of adrenaline hormone
(d) less secretion of growth hormone

Answer:

(d) less secretion of growth hormone

Dwarfism is characterised by retarded physical growth and a normal brain. It is caused due to the hypo-secretion of growth hormone.

Question 84:

The dramatic changes in body features associated with puberty are mainly because of the secretions of :
(a) estrogen from testes and testosterone from ovary
(b) estrogen from adrenal gland and testosterone from pituitary gland
(c) testosterone from testes and estrogen from ovary
(d) testosterone from thyroid gland and estrogen from pituitary gland

Answer:

(c) testosterone from the testes and estrogen from the ovary

The dramatic changes in the body features associated with puberty are mainly due to the secretion of testosterone from the testes (in male) and estrogen from the ovary (in female).

Question 85:

Which of the following statements is correct about receptors?
(a) gustatory receptors detect taste while olfactory receptors detect smell
(b) both gustatory and olfactory receptors detect smell
(c) auditory receptors detect smell and olfactory receptors detect taste
(d) olfactory receptors detect taste and gustatory receptors detect smell

Answer:

(a) gustatory receptors detect taste, while olfactory receptors detect smell

Gustatory receptors detect taste; olfactory receptors detect smell; while auditory receptors detect sound.

Question 86:

The part of brain which takes part in regulating respiration in the human body is :
(a) medulla
(b) pons
(c) cerebellum
(d) cerebrum

Answer:

(b) the pons
The pons take part in the regulation of respiration in the human body.

Question 87:

Electrical impulse travels in a neuron from :
(a) dendrite → axon → axon end → cell body
(b) cell body → dendrite → axon → axon end
(c) dendrite → cell body → axon → axon end
(d) axon end → axon → cell body → dendrite

Answer:

(c) dendrite → cell body → axon → axon end

In a neuron, the electrical impulse travels from the dendrites to the cell body and from the cell body to the axon and, then, to the axon end.

Question 88:

In a synapse, chemical signal is transmitted from :
(a) axon to cell body of the same neuron
(b) cell body to axon end of the same neuron
(c) dendrite end of one neuron to axon end of adjacent neuron
(d) axon end of one neuron to dendrite end of adjacent neuron

Answer:

(d) axon end of one neuron to the dendrite end of the adjacent neuron.

In a synapse, a chemical signal is transmitted from the axon end of one neuron to the dendrite end of the adjacent neuron.

Question 89:

In a neuron, the conversion of electrical signal to a chemical signal occurs at/in :
(a) dendrite end
(b) cell body
(c) axon end
(d) myelin sheath

Answer:

(c) axon end

The conversion of an electrical signal to a chemical signal occurs at the axon terminal.

Question 90:

One of the following gives the correct sequence of the components in a reflex arc. This is :
(a) Receptors → Muscle → Sensory neuron → Motor neuron → Spinal cord
(b) Receptors → Motor neuron → Spinal cord → Sensory neuron → Muscle
(c) Receptors → Spinal cord → Sensory neuron → Motor neuron → Muscle
(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

Answer:

(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

The pathway taken by a nerve impulse in a reflex action is called reflex arc.
The correct sequence of the components in a reflex arc is given below:

Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

Question 91:

Which of the following statements are true?
(i) sudden action in response to something in the environment is called reflex action
(ii) sensory neurons carry electrical signals from spinal cord to muscles in a reflex action
(iii) motor neurons carry signals from receptors to spinal cord in a reflex action
(iv) the pathway of transmitting signals from a receptor to a muscle is a reflex action
(a) (i) and (ii)
(b) (i) and (iii)
(c) (i) and (iv)
(d) (i), (ii) and (iii)

Answer:

(c) (i) and (iv)

Statements (i) and (iv) are correct, while statements (ii) and (iii) are not. Sensory neurons carry signals from the receptors to the brain or the spinal cord, while motor neurons carry signals from the brain or the spinal cord to the effector organs like muscles and glands.

Question 92:

The gustatory receptors of our body are in one of the following organs. This organ is :
(a) ear
(b) nose
(c) tongue
(d) skin

Answer:

(c) tongue

The gustatory receptors which detect taste are present in the tongue.

Question 93:

The olfactory receptors in humans are located in :
(a) eyes
(b) tongue
(c) ears
(d) nose

Answer:

(d) nose

The olfactory receptors which detect smell are located in the nose.

Question 94:

The contraction of pupil of the eye in the presence of bright light is an example of :
(a) Voluntary reflex
(b) Spinal reflex
(c) Cerebral reflex
(d) Adrenal reflex

Answer:

(c) cerebral reflex

The contraction of the pupil of the eye in the presence of a bright light is an example of cerebral reflex. A reflex action that involves the brain is called cerebral reflex. It is found in the organs present in the head that are directly connected to the brain.

Question 95:

The faulty functioning of an endocrine gland can make a person very short or very tall. This gland is :
(a) thyroid
(b) pineal
(c) adrenal
(d) pituitary

Answer:

(d) pituitary

The pituitary gland secretes a hormone known as growth hormone which controls the growth of the human body. Deficiency of growth hormone can make the person very short, while excess of this hormone can make a person very tall.

Question 96:

The underactive endocrine gland which causes goitre is :
(a) pancreas
(b) thyroid
(c) adrenal
(d) pituitary

Answer:

(b) thyroid

Under-secretion of thyroxine hormone from the thyroid gland can lead to goitre.

Question 97:

The endocrine gland whose malfunctioning causes diabetes disease is :
(a) pituitary
(b) pineal
(c) parathyroid
(d) pancreas

Answer:

(d) pancreas

The pancreas secretes a hormone called insulin. Insulin lowers the blood sugar level. Deficiency of insulin can lead to a disease called diabetes.

Question 98:

The use of iodised salt is recommended to prevent :
(a) diabetes
(b) gonorrhoea
(c) dysentery
(d) goitre

Answer:

(d) goitre

It is advised to use iodised salt to prevent goitre. It is because the thyroid gland requires iodine to synthesise thyroxine hormone. Deficiency of iodine in the body can lead to the under-secretion of thyroxine hormone which, in turn, can lead to goitre.

Question 99:

Which of the following are often called glands of emergency?
(a) thyroid
(b) pituitary
(c) adrenal
(d) pancreas

Answer:

(c) adrenal

The adrenal glands are often called glands of emergency. It secretes adrenaline hormone which prepares the body for action.

Question 100:

P is a cell (or group of cells) in the human body which is sensitive to a particular type of stimulus and conveys the messages to CNS through nerves Q. On the other hand, R is a part of the human body which can respond to a stimulus according to the instructions sent from the CNS through nerves S.
(a) What is P? Name five organs which contain cells (or group of cells) like P.
(b) Name the nerves Q.
(c) What is R? Give two examples of R.
(d) Name nerves S.
(e) How do messages travel through the nerves Q and S?

Answer:

(a) P is a receptor. The five organs which contain receptors are: eyes, ears, nose, tongue and skin.

(b) Q represents sensory nerves. Sensory nerves bring impulses from sensory organs to the CNS.

(c) 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.

(d) S represents motor nerves. Motor nerves carry impulse from the CNS to the effector organs like the muscles or glands.

(e) Messages travel in the form of electrical impulses or nerve impulses through sensory nerves (Q) and motor nerves (S).

Question 101:

The human body contains a large number of cells A which are very long and branched, and look like electric wires. The longest branch of this cell is B whereas there are many small branches C. Any two A cells do not join to one another completely in the human body. There is a microscopic gap D between every pair of adjacent A cells through which electric impulses can pass by the release of a chemical substance.
(a) What are cells A?
(b) What is the name of (i) branch B, and (ii) branches C?
(c) What is the microscopic gap D known as?
(d) What is the function of cells like A in the human body?
(e) The cells A are of three types. name the three types.

Answer:

(a) A represents neurons. Neurons are the largest cells in the human body, which look like electric wires.
(b)
(i) B represents the axon.
(ii) C represents the dendrites.
(c) 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.
(d) A neuron transmits messages to and from the central nervous system. It is the structural and functional unit of the nervous system.
(e) The three types of neurons are sensory neurons, motor neurons and relay neurons.

Question 102:

When we touch a hot plate unknowingly, then this heat is sensed by a receptor P present in our fingers. The receptor triggers and impulse in neuron Q which transmits the message to an organ R which is a part of the central nervous system. Here the impulse is passed on to a neuron S which in turn passes it to a yet another neuron T. The neuron T passes the impulse to a tissue U in our arm. The tissue U then contracts and pulls our hand away from the hot plate.
(a) What is the name of (i) receptor P (ii) neuron Q, and (iii) organ R?
(b) What is (i) neuron S, and (ii) neuron T?
(c) Name the tissue U.
(d) What name is given to the phenomenon in which hand is pulled away quickly from the hot plate?
(e) Name the effector in this whole process.

Answer:

(a) (i) P is a thermoreceptor.
(ii) Q is a sensory neuron.
(iii) R is the spinal cord.

(b) (i) S is a relay neuron. The impulse from the spinal cord is passed on to a relay neuron.
(ii) T is a motor neuron. From the relay neuron, the impulse is passed on to a motor neuron.

(c) U is a muscle.

(d) Reflex action is the phenomenon in which the hand is pulled away quickly from a hot plate. It is performed automatically by an individual.

(e) The effector organ is the muscle of the arm.

Question 103:

The gland X which is located just below the brain in the human head secretes a chemical substance Y which controls the development of ones and muscles in the body of a person. Secretion of too little of substance Y as well as the secretion of too much of substance Y by the gland X leads to abnormal development of the body of a person.
(a) Name the gland X.
(b) What is the chemical substance Y?
(c) What happens if too little of substance Y is secreted?
(d) What happens if too much of substance Y is secreted?
(e) Name the system of glands in the human body of which gland X is a part.

Answer:

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

Question 104:

A and B are the two systems of control and coordination in the human body. The messages in system A are transmitted in the form of chemical substances C which travel comparatively slowly through the blood stream. The substances C are made in tissues D present in the head and trunk of human body. The messages in system B are transmitted very quickly in the form of electrical impulses through fibres E. The effect of messages transmitted by system B usually lasts for a much shorter time as compared to those transmitted by system A.
(a) Name the system A. What does system A consist of?
(b) Name the chemical substance C.
(c) What is tissue D? Name any five such tissues in the human body.
(d) Name the system B. What does system B consist of?
(e) Name the fibres E.
(f) State whether system A controls the working of system B or system B controls the working of system A.

Answer:

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

Question 105:

A cylindrical structure P in our body begins in continuation with medulla and extends downwards. It is enclosed in a bony cage Q and surrounded by membranes R. As many as x pairs of nerves arise from the structure P. The structure P is involved in the reflex actions of our body and conduction of nerve impulses to and from another organ S of our body with which it forms CNS.
(a) Name the structure P.
(b) Name (i) bony cage Q, and (ii) membranes R.
(c) How much is x?
(d) Name the organs S.
(e) What are the reflexes involving structure P only known as?

Answer:

(a) The structure P is the spinal cord. It is a cylindrical structure that begins in continuation with the medulla and extends downwards.
(b) (i) The bony cage Q is the vertebral column. The spinal cord is enclosed by the vertebral column.
(ii) R represents the meninges. The spinal cord is surrounded by membranes called the meninges.
(c) x represent the number of pairs of spinal nerves. They are 31 in number.
(d) S is the brain. The central nervous system consists of the brain and the spinal cord.
(e) The reflex actions involving the spinal cord (P) are known as spinal reflexes.

Question 106:

The pancreas is made up of two parts A and B. The part A secretes insulin whereas part B secretes pancreatic juice.
(a) Which part is functioning as an endocrine gland? Why?
(b) What is insulin and what effect does it have in the body?
(c) Name the disease which can be treated by giving insulin injections.
(d) What does pancreatic juice contain? Where does pancreatic juice go?
(e) Name the life process in which pancreatic juice is made use of.

Answer:

(a) 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.

(b) Insulin is a hormone which is secreted by the pancreas. It controls the blood sugar level.

(c) Deficiency of insulin in the body can lead to diabetes. Diabetes can be treated by giving injections of insulin.

(d) 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.

(e) Digestion is the process where the enzymes present in the pancreatic juice are used to break down the food.

Question 107:

The gland A is attached to the wind pipe in the human body. The gland A makes and secretes a hormone B which controls the metabolism of carbohydrates, fats and proteins in the body. The non-metal element C is necessary for the formation of hormone B. The deficiency of C in the diet can cause a deficiency of hormone B in the body leading to a disease D in which the neck of a person appears to be swollen. People are advised to use salt E in cooking food so as to avoid disease D.
(a) Name (i) gland A, and (ii) hormone B.
(b) What is the element C?
(c) Name one type of food which can provide sufficient C in the diet of a person.
(d) Name (i) disease D, and (ii) salt E.

Answer:

(a) (i) A represents the thyroid gland. It is attached to the wind pipe in the human body.
(ii) B represents thyroxine. It regulates the metabolism of carbohydrates, fats and proteins in the body.
(b) The non-metal element C is iodine. It is essential for the synthesis of thyroxine hormone by the thyroid gland.
(c) Sea foods like fish provide sufficient amount of iodine in the diet of a person.
(d) (i) D represents the disease called goitre. It is characterised by abnormal enlargement of the thyroid gland in the neck.
(ii) E represents iodised salt. It is advised to use iodine in cooking food in order to prevent goitre.

Question 108:

A piece of thread was tied tightly around an animal's pancreatic duct. The animal subsequently had difficulty in digesting food but did not get diabetes. Explain.

Answer:

When a piece of thread is tightly tied around an animal’s pancreatic duct, the pancreatic juice containing digestive enzymes will not be able to reach the small intestine. The pancreatic juice contains enzymes which help in the digestion of food. In its absence (due to the blockage of the pancreatic duct), the animal would have difficulty in digesting certain food substances.

However, the pancreas being an endocrine gland releases insulin directly into the blood. Since, the main function of insulin is to maintain the blood sugar level in the body, the animal will not suffer from diabetes.

Question 109:

Which is the target organ of both adrenaline and insulin?
(a) heart
(b) kidney
(c) liver
(d) pancreas

Answer:

(c) liver

The liver is the target organ for both adrenaline and insulin. Target organs and target cells are specific organs and cells upon which hormones act and produce their effects.

Question 110:

A gland W is located just below the stomach in the human body. The gland W secretes a hormone X. The deficiency of hormone X in the body causes a disease Y in which the blood sugar level of a person rises too much. The person having high blood sugar is called Z.
(a) Name (i) gland W, and (ii) hormone X.
(b) What is the function of hormone X?
(c) Name (i) disease Y, and (ii) person Z.
(d) What advice would you like to give to a person who is suffering from disease Y due to faulty life-style?

Answer:

(a) (i) W represents the pancreas. It is located just below the stomach in the human body.
(ii) X represents insulin, which is secreted by the pancreas.
(b) The function of insulin (X) is to maintain the sugar level in blood.
(c) (i) Y represents diabetes, which is a disease caused by increased blood sugar level.
(ii) The person Z is known to be diabetic.
(d) 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.

Question 111:

There are two similar glands P which are located on the top of two similar organs Q in the human body. The gland P are often called glands of emergency and they secrete a hormone R into the blood stream. The hormone R is secreted in large amounts when a person is frightened. It brings about temporary changes in the body which allow a lot of substance S from the liver to go into blood so as to provide a lot of energy in a very short time. This helps the person concerned to fight back or run away from the frightening situation.

What are P, Q, R and S?

Answer:

P refers to the adrenal glands.
Q refers to the pair of kidneys on which the adrenal gland rest.
R refers to the hormone adrenaline produced by the adrenal glands.
S refers to glucose which is released from the liver to provide energy.

Question 112:

The two glands A and B which occur in pairs, are present in the endocrine system of humans. The pair of gland A is found only in females whereas the pair of gland B occurs only in males. The glands A make and secrete two hormones C and D whereas glands B make and secrete only one hormone E. In addition to hormones, glands A make gametes F whereas glands B make gametes G.
(a) What are glands A?
(b) What are hormones C and D?
(c) What are glands B? Name the hormone E.
(d) What are gametes (i) F and (ii) G?
(e) Which event in the life of males and females is associated with the secretion of the hormones C, D and E?

Answer:

(a) Glands A refer to ovaries.
(b) C and D refer to the hormones oestrogen and progesterone.
(c) Glands B refer to testes and the hormone which they produce is called testosterone.
(d) Gametes F - ovaries
Gametes G - sperm
(e) When males and females reach puberty, the secretions of hormones like oestrogen, progesterone and testosterone begin.

Question 113:

The organ A which is located inside the skull of our body is protected by a bony box B and it is surrounded by three membranes C. The space between the membranes is filled with a liquid D which protects the organ A from mechanical shocks. The organ A in combination with another organ E makes up the central nervous system.
(a) What is organ A?
(b) What are (i) B, (ii) C and (iii) D?
(c) Name the organ E.
(d) While walking barefoot, if we happen to step on a sharp piece of stone, we immediately lift our foot up. Which of the two organs: A or E, is directly involved in this action?
(e) If we step out from a darkened room into bright sunshine, we close our eyes for a moment. Which of the two organs, A or E, is directly involved in this action?

Answer:

(a) Organ A is brain.
(b) (i) B - Cranium
(ii) C - Meninges
(iv) D - Cerebro spinal fluids
(c) Organ E is spinal cord
(d) It is the organ E which is involved in this type of reaction and organ E refers to spinal cord.
(e) It is the organ A (brain) which is involved in this reaction.

Question 114:

Write down the following in the correct order for a simple reflex arc:
(a) impulse travels in the motor fibre
(b) impulse travels in the sensory fibre
(c) effector organ stimulated
(d) impulse crosses the synapse

Answer:

The correct order for a simple reflex arc is -
(b) impulse travels in the sensory fibre
(d) impulse crosses the synapse
(a) impulse travels in the motor fibre
(c) effector organ stimulated

Question 115:

Explain why the tongue may be considered to be both a receptor and an effector organ.

Answer:

Receptors are sensory structures (organs/ tissues/ cells) that detect changes in the environment, which are called stimuli, and turn them into electrical impulses to be transferred to the brain. The tongue has taste buds which can detect chemicals in food and identify taste. Hence, it is considered as receptor.

Effector is an organ that responds to stimulus. The tongue is a muscular organ that can respond to a stimulus. Hence, it is also considered as an effector organ.

Lakhmir Singh Manjit Kaur Biology 2020 2021 for Class 10 Science Chapter 2 - Control And Coordination

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