CBSE Guess > Papers > Question Papers > Class X > 2008 >Science > Science Theory

Q. 26. Illustrate the following with the help of suitable diagrams :
(i) Regeneration in Planaria (ii) Budding in Hydra

Ans. (i) Regeneration in Planaria : See Q.4 (S.A.T.), Chapter 8. [Page 86
(ii) Budding in Hydra : See Q.2 (iv), (L.A.T.), Chapter 8. [Page 90

Q. 27 (a)

(i) Name the parts labelled A and B in the neuron drawn above.
(ii) Which part acquires the information in the neuron?
(iii) Through which part does the information travel?
(iv) In what form does this information travel?
(v) Where is the impulse converted into a chemical signal for onward transmission?

(b) Name the hormone secreted by thyroid. What is its function? Why is the use of iodised salt advisable?

Ans. (a) (i) A → Dendrite, B → Axon
(ii) The information is acquired at the dendritic tip of a nerve cell.
(iii) The impulse travels from the dendrite to the cell body and then along the axon to its end.
(iv) Information travels in the form of an electrical impulse.
(v) At the end of the axon, the electrical impulse sets off some chemicals which cross the gap or synapse for onward transmission.

(b) Hormone secreted by thyroid is thyroxin. Thyroxin regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth. Iodised salt consists of Iodine. Iodine is essential for the synthesis of thyroxin. Incase Iodine is deficient in our diet there is a possibility that we might suffer from Goitre.

Or

(a) What are plant hormones? Give one example each of a plant hormone that

(i) promotes growth
(ii) inhibits growth

(b) Name the parts labelled A, B and C in the diagram given below. Write one function of each part.

Ans. (a) Plant hormones are the chemicals which are used for control and coordination in plants.
(i) Auxin
(ii) Abscisic Acid

(b) A → Pons. They take part in regulating respiration.
B → Medulla. It controls various involuntary actions such as heart beat, breathing, blood pressure and peristaltic movements of alimentary canal.
C → Cerebellum. It helps in maintaining posture and balance of the body. It also enables us to make precise and accurate movements.

Science 2008 Question Papers Class X
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