Page 55 - Biology - XII

Q5. The hanging cell mass in the embryonic development in mammals is seen in
(a) zygote stage (b) morula stage (c) blastula stage (d) gastrula stage

Q6. Implantation of ‘fertilised’ egg in interns is at
(a) zygote stage (b) blastula stage (c) morula stage (d) gastrula stage

Q7. Human blastocyst has
(a) 32 cells (b) 16 cells (c) 8 cells (d) No cells

Q8. Fertilisation of ovum in a human female takes place in
(a) uterus (b) ovary (c) ampulla of oviduct (d) none of these
Q9. The period of capacitation—Sperm activation in mammals is
(a) 2 hrs (b) 3 hrs (c) 5–6 hrs (d) 24 hrs

Answer key

1. (d), 2. (d), 3. (c), 4. (c), 5. (c), 6. (b), 7. (a), 8. (c), 9. (c)

Assertion-Reason Type Questions

These consist of two statements—Assertion (A) and Reason (R). Answer these questions by selecting
the appropriate option given below:

a. Both A and R are true and R is the correct explanation of A.
b. Both A and R are true, but R is not the correct explanation of A.
c. A is true, but R is false.
d. A is false, but R is true.

1. Assertion (A) : The embryo with 8 to 16 blastomeres is called a morula.
Reason (R) : The morula continuously divides to transform into trophoblast.
2. Assertion (A) : The fertilised egg contains 23 pairs of chromosomes.
Reason (R) : Zygote is formed by the fusion of egg and the sperm.

Answer key

1. (c), 2. (a)

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