Q 1. What is meant by trisomic condition? (1 mark)
Ans1. Trisomy is the presence of an extra chromosome i.e., so that a particular chromosome is present in three copies.

Q 2. State the presence or absence of sinus venous in a fish and a mammal. (1 mark)
Ans2. Fish and mammals do not have sinus venosus because a sufficiently high blood pressure cannot be maintained in the open spaces.

Q 3. Which type of cartilage is present between vertebrae to allow limited movement? (1 mark)
Ans3. White fibrocartilage

Q 4. Name any two breeds of wild rock pigeon that have been developed through artificial selection. (1 mark)
Ans4. (i) Pouter, and
(ii) Jacobin.

Q 5. Which chromosomes are called autosomes? (1 mark)
Ans5. Autosome is any chromosome other than a sex chromosome. In humans they are 22 pairs.

Q 6. When is a tumour referred to as malignant? (1 mark)
Ans6. A tumour is called malignant, if it has the capacity to undergo metastasis.

Q 7. What are the two factors that contribute for the dissociation of oxyhaemoglobin in the arterial blood to release molecular oxygen in an active tissue? (1 mark)
Ans7. PO2 in the tissues lower than arterial blood, and PCO2 in the tissues higher than arterial blood.

Q 8. Which one of the following is fatal unless oral rehydration therapy is administered :
(i) Whooping cough (ii) Cholera (iii) Tetanus (1 mark)

Ans8. Cholera

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