Biology X – Control and Coordination – Questions and Answers

Control and Coordination Class 10 Questions Answers

Control and Coordination is a very important topic in Biology of Class 10th CBSE. Here are NCERT Control and Coordination Questions and Answers given for Biology of Class 10th.

1.    What is the difference between a reflex action and walking?



Reflex Action Walking
  1. Reflex action is the sudden action in response to something in the environment
  1. Walking is the mechanism of electrical impulse which travels in the nerve cells & transmits to the concerning muscles with the result of that the muscles shrink and we start walking.
  1. It is controlled by the spinal cord.
  1. It is controlled by the brain.
  1. It occurs in a fraction of second

(iii) It occurs in responding by the brains through nerve cells so it takes time.


2.    What happens at the synapse between two neurons?

Ans.    In between two nerve cells or neurons the free tips dendrites come closer to the free ends of distal axon fibres. When the impulse travels the chemical compound is released which is filled in the gap between the synapse. The impulse travels through this compound into other neuron and after that this compound is drawn. Thus, the impulse is transmitted from one place or organ to another organ.

3.    Which part of the brain maintains posture and equilibrium of the body?

Ans.    Cerebellum a part of hind brain maintains the posture and equilibrium of the body.

4.    How do we detect the smell of an agarabatti (incense stick)?

Ans.    The cerebrum which is a part of the fore brain is responsible for the detection of smell of an agarbatti.

5.    What is the role of the brain in reflex action ?

Ans.    In reflex action we do something without thinking about it or without feeling in control of our reactions. The nerves of input are in the spinal cord on their way to the brain. Thus, the information through input nerves or sensory nerves go to the brain. The brain keeps the information of what the reflex action is doing.

The movement of the plant (shoot and root) due to the influence of sunlight is called phototropism. In this movement the cells of that part which are in direct contact of light shrink due to the transfer of wall from these cells to the cells of opposite side. Thus, the plant part bend towards sunlight. It is called positive phototropic. It does not have the effect of sensation by electrical-chemical means.

Fig: Reflex are in Human Body

6.    What are plant hormones ?

Ans.    Plant hormones are also known as phytohormones which are chemical substances produced in the cells Of root and shoot tips. These chemicals are responsible for controlling growth of the plant body. e.g. ethylene, cytokinin, etc.

7.    How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Ans.    In sensitive plants like Mimosa pitdica (Touch me not), there is electrical-chemical means to convey the information of touch from cell to cell. Plant cells change shape by changing the amount of water in them resulting in swelling or shriking.

This type of movements in sensitive plant is totally different from the movement of a shoot towards light in the following way.

The sensitive plant

The movement of the plant (shoot and root) due to the influence of sunlight is called phototropism. In this movement the cells of that part which are in direct contact of light shrink due to the transfer of wall from these cells to the cells of opposite side. Thus, the plant part bend towards sunlight. It is called positive phototropic. It does not have the effect of sensation by electrical-chemical means.

8.    Give an example of a plant hormone that promotes growth.

Ans.     Auxin

9.    How do auxins promote the growth of a tendril around a support?

Ans.    In weak plants like pea, the cells of the tip of the tendril produce auxins. The side part of the tendril which comes in contact with the support, transfers its auxins along with water towards opposite side due to which the cells elongate and turgid and the whole tendril bends, clinging to the support or around the support.

10.    Design an experiment to demonstrate hydrotropism.

Ans.    AIM: To demonstrate hydrotropism.

Material: A trough, soil water and germinating seeds or baby plants, perforated card board sheet equal to the diameter of trough.


Take a trough.

2. Fix the perforated card board sheet in the trough vertically.

3. Half fill one part of trough with soil and the other half or second part of the trough with water.

4. Now fix the germinating seed or baby plants in the soil.

5. Keep the whole apparatus in the sun in open place for few days.

Observations : After a few days, the following changes are observed.

1. The roots bend towards water.

2. The shoot part bends away from water.

Result: The experiment confirms that:

1. Water has positive effect on roots which is called positive hydrotropism.

2. Water has negative effect on shoot (stem and other aerial parts) which is called as negative



1.    Appartatus should be placed at open place in the sun so that plants may get all the necessary conditions.

2.    Perforations in the carboard sheet should neither be too big nor too small. Water should be diffused slowly.

11.    How does chemical coordination take place in animals?

Ans.     The chemical coordination in animals takes place by the hormones which are secreted by several endocrine glands. The hormones after secretion reaches into blood and after that through blood, it (hormone) reaches to the various parts of the body. Take an example of Adrenaline which is secreted by Adrenal gland and through blood it reaches to its target heart. As a result, the heart beats faster in order to supply more oxygen to the muscles and the target organs get more oxygen and satisfies its need of oxygen to work.

12.    Why is the use of iodised salt advisable ?

Ans.    Thyroid glands present in the neck region secrete thyroxin hormone. It is secreted in presence of iodine. So, iodised salt is advisable to every body.

13.    How does our body respond when adrenaline is secreted into the blood?

Ans.    Adrenaline hormone is secreted directly into the blood and carried to different parts of the body. It helps in the oxidation of carbohydrates, fats and proteins to produce energy. It goes to heart which increases the heart beats. Thus, the blood is pumped rapidly which supplies blood quickly to the target organ and thus organ gets large amount of energy and works.

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

Ans.    In case of some patients, the cells of pancreas do not produce insulin when sugar level in blood is high. In such a case, they are given insulin injections to decrease the sugar level in the blood.

Section B

1.    Which of the following is a plant hormone?

(a) Insulin     (b) Thyroxin     (c) Oestrogen     (d) Cytokinin

Ans.    (d) Cytokinin is a plant hormone which helps in cell division.

2.    The gap between two neurons is called a

(a) dendrite     (b) synapse     (c) axon         (d) impulse

Ans.    (b) In a human body, one neuron is connected with another via nerve endings and dendrites then a gap is created which is called synapse.

3.    The brain is responsible for

(a) thinking     (b) regulating the heart beat    (c) balancing the body     (d) all of the above

Ans.    (b) Brain controls thinking, regulating the heart beat and balances the body.

4.    What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Ans.    All information from our environment is detected by the specialised tips of some nerve cells. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So olfactory receptors will detect smell. If the receptor is not working properly, the environmental effects will be received by the receptors but the respond from the spinal cord and brain is not coming in due time to the effectors with the result of that the effector will be effected.

5.    Draw the structure of a neuron and explain its function.

Ans.    The dendrites of a neuron receive the environmental information from the receptor. This information travels in the whole body of neuron and then reaches to the synapse where the chemical compound is secreted out +o fill the gap of synapse when the information is passed out into the other neuron, the chemical compound is withdrawn. Thus, information reaches from the receptor to brain and spinal cord.

Structure of Neuron

6.    How does phototropism occur in plants ?

Ans.    The movement in plant due to light is known as phototropism. In this case, the plant parts move with effect of sunlight. The shoot-stem and the other parts related to it in the air show positive phototropism while the whole root system shows negative phototropism.

7.    Which signals will get disrupted in case of spinal cord injury?

Ans.    In case of spinal cord injury the reflex action will get disturbed due to which when we keep our palm on a flame, then we will not take our hand away from it because of defect in reflex action.

8.    How does chemical coordination occur in plants?

Ans.    Phytohormones are chemical compounds which are produced in the cells of the tips of main stem a branches. These hormones are diffused from the originating cells to the neighbouring cells through diffusion. They are responsible for cell elongation, cell multiplication, opening of flowers etc. Thus, chemical coordination occurs in plants.

9.    What is the need for a system of control and coordination in an organism?

Ans.    In multicellular organisms, all the activities concerning to any part of the body are controlled by spin cord and brain. All the cell of all the parts of the body are connected with them through nerves. There a thick network of nerves in the whole body. These nerves are of two types i.e. sensory nerves carry impulses from the receptor to brain and spinal cord and the response is carried to the effector through motor nerves. All these activities are possible by control and coordination. Brain and spinal cord control over the activities while nerves are the coordinating devices.

10.    How are involuntary actions and reflex actions different from each other?


Reflex actions

Involuntary actions

  1. It is controlled by spinal cord.

(i) It is controlled by brain

  1. It is very quick.

(ii) It takes some time.

  1. There is no need of thinking.

(iii) Brain takes the judgment and then respond accordingly.

  1. Response is given to the concerned organ just after receiving the stimulus.

(iv) There is need of thinking and not the environmental stimulus for response.

11.    Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.


Nervous Coordination

Homonal Coordination

  1. In this type there is a network of nerves which connects the cells of all the body organs to the central nervous system.

(i) In this type, there is no such system in the body.

  1. The coordination is controlled by brain and spinal cord.

(ii) There is no controlling organ for this coordination.

  1. There is no secretion of such type.

(iii) Hormones quantity affect the organ and the system.

  1. All type of functions are controlled by the nerves and the central nervous system.

(iv) Special hormone is responsible for particular function.

  1. There is no such effect of this system.

(v) Hormone’s quantity affect the organ and the system.

  1. The whole system is fixed at its own place in the body.

(vi) Endocrine glands are situated at various places in the body.

  1. The stimuli and the responses travel in the nerves.

(vii) Blood carries the hormones to the concerning body organs.

  1. The system functions according to the environmental stimuli.

(viii) The hormones have no effect of external environment.

12.    What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?


Movement in sensitive plants

Movements in les of human beings

  1. The leaves of sensitive plants are sensitive to touch.

(i) No special organs in leg for such action.

  1. They have electrical-chemical means to convey the information of touch.

(ii) The chemical meant to convey actions in this movement.

  1. There is no special tissue in plants for the conduction of information.

(iii) It is controlled by brain and spinal cord.

  1. The cells change their shape by changing the amount of water in them.

(iv) There is no effect of the amount of water on movement of muscles.


Biology X | Heredity and Evolution | EVOLUTION SHOULD NOT BE EQUATED WITH ‘PROGRESS’ and Human Evolution


In an exercise of tracing the family trees of species, we need to remember certain things. Firstly, there are multiple branches possible at each and every stage of this process. So it is not as if one species is eliminated to give rise to a new one. A new species has emerged. But that does not necessarily mean, like the beetle example we have been thinking about, that the old species will disappear. It will all depend on the environment. Also, it is not as if the newly generated species are in any way ‘better’ than the older one. It is just that natural selection and genetic drift have together led to the formation of a population that cannot reproduce with the original one. So, for example, it is not true that human beings have evolved from chimpanzees. Rather, both human beings and chimpanzees have a common ancestor a long time ago. That common ancestor is likely to have been neither human or chimpanzee. Also, the first step of separation from that ancestor is unlikely to have resulted in modern chimpanzees and human beings. Instead, the two resultant species have probably evolved in their own separate ways to give rise to the current forms.

In fact, there is no real ‘progress’ in the idea of evolution. Evolution is simply the generation of diversity and the shaping of the diversity by environmental selection. The only progressive trend in evolution seems to be that more and more complex body designs have emerged over time. However, again, it is not as if the older designs are inefficient! So many of the older and simpler designs still survive. In fact, one of the simplest life forms – bacteria – inhabit the most inhospitable habitats like hot springs, deep-sea thermal vents and the ice in Antarctica. In other words, human beings are not the pinnacle of evolution, but simply yet another species in the teeming spectrum of evolving life.

Human Evolution

The same tools for tracing evolutionary relationships – excavating, time-dating and studying fossils, as well as determining DNA sequences – have been used for studying human evolution. There is a great diversity of human forms and features across the planet. So much so that, for a long time, people used to talk about human ‘races’. Skin colour used to be the commonest way of identifying these socalled races. Some were called yellow, some black, white or brown. A major question debated for a long time was, have these apparent groups evolved differently? Over recent years, the evidence has become very clear. The answer is that there is no biological basis to the notion of human races. All humans are a single species.


Figure 9.14

Evolution — Ladder versus Tree

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