Archive for November, 2014

Biology X – Control and Coordination – Questions and Answers

November 24th, 2014

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?

 

Ans.

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.

Procedure:

1.
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

hydrotropism.

Precautions:

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?

Ans.

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.

Ans.

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?

Ans.

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.


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Biology X | How do Organisms Reproduce?

November 23rd, 2014

How do Organisms Reproduce?

Reproduction is the process by which living organism produce new individuals similar to themselves.

Reproduction ensured continuity of life on earth.

 

It involves continuation of characters from the parents to daughter cells by copying of DNA (deoxyribose Nucleic Acid) molecules present in the chromosomes of the cell.

 

The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs.

 

Therefore, a basic event in reproduction is the creation of a DNA copy. Cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell, and they will need to be separated from each other.

 

Copying of DNA is also not a foolproof exercise, even a minute changes bring about Variation in the blue print of the offsprings.

 

The useful variations are retained while the harmful one does not go beyond.

 

REPRODUCTION


Asexual Reproduction:

Asexual Reproduction is extremely useful as a mean of rapid multiplication. It is common in lower plants and animals.

Asexual reproduction can be divided in following parts:

  1. FISSION : When parent cell divides/split into two or more individuals.
    1. Binary Fission: when parent cell divides into two individuals it is termed as binary fission. e.g. Amoeba, Paramecium.

     


 

 

2. BUDDING : Some individual develops a small outgrowth from its body part known as bud, as the bud grows it detaches from the parent body and develops into a whole new individual.


 

Budding in yeast

 

  1. Spore Formation : Spores are small, bulb like structure develops at the top of the erect hyphae of the fungus plant. They a light weight and produce numerous spores at same time, released into the air and germinate, into new individuals after landing into food or soil.


Spore formation in Bread Mould

4. FRAGMENTATION : It is the accidental process when the broken pieces of an organism (fragments) grows into a complete organism. eg. fragmentation in spirogyra

 


Fragmentation in Spirogyra

 

 

 

 

5. REGENERATION : When the simple animals like Hydra, Planaria develop a new individual from their broken older part it is known as regeneration. It is carried out by specialised cells which grow large numbers of cells.


VEGETATIVE PROPAGATION :

A mode of reproduction in which part like the stem, root, leaves develop into new plant under favourable conditions.

e.g.
Sugarcane, roses, Bougain-villea, Chrysanthemum etc

Vegetative propagation are of following types:

  • Layering : The adventitious roots are produced in the branch of the stem before the plant is detached from the parent plant. The branch of stem is called a layer. This process is utilized in the propagation of plant and the phenomenon is called layering. Layering is used in the propagation of plants like Lemon, Guava, Hibiscus, Bougainvillea, Jasmine, Raspberry, Strawberry and many ornamental plants.
  • Grafting : In this method of reproduction, two plants of closely related varieties are joined together so that they leave as one plant.
  1. The portion of a plant that is grafted on the other plant is called scion, and the plant in which grafting is performed is called the stock.
  2. This method is applied to improve variety of fruits like mango, apple, peas, citrus and guava.


 

Benefits

1. Plants can bear flowers, fruits earlier than those produced from seeds.

2. Growing Banana, orange, rose, jasmine that have lost the capacity to produce seeds.

3. Genetical similarity is maintained in the plants.

eg. Sugarcane, rose, grapes by layering or grafting.

 

Assignment

  1. Which life process ensure that a plant or animal species will not disappear from the earth?                                        (1)

  2. Define Asexual reproduction?                            (1)

  3. Why is DNA copying an essential part of the reproduction?            (1)

  4. Can you consider cell division as a typr of reproduction in unicellular organism? Give one reason.                                    (1)

  5. What are the advantages of sexual reproduction over asexual reproduction?    (2)

  6. Why more complex organisms cannot give rise to new individuals through regeneration?                                    (2)

  7. How does reproduction help in providing stability to population of species?    (2)

  8. Why does bread mould grow profusely on a moist slice of bread rather than on dry slice of bread?                                    (2)

  9. (i) Which are the two main types of reproduction in lioving organisms?    (3)

    (ii) classify the following under these two types: Amoeba, frog, Earthworm. Yeast.

  10. Explain vegetative propagation with the help of two examples. List two advantages of vegetative propagation.                            (3)

  11. What is a sexual reproduction? How do potato and bryophyllum plants reproduce vegetatively?

  12. Write three differences between asexual and sexual reproduction.        (3)

  13. What are the various artificial methods of vegetative propagation in plants?    (5)

  14. Define asexual mode of reproduction. What are the different methods of asexual mode of reproduction? Define regeneration with the help of diagram.        (5)

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