The following is the illustration of the sequence of ovarian eve

Subject

Biology

Class

CBSE Class 12

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 Multiple Choice QuestionsLong Answer Type

31.

Explain how does:

(a) a primary succession start on a bare rock and reach a climax community?

(b) the algal bloom eventually choke the water body in an industrial area?
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32.

The following is the illustration of the sequence of ovarian events (a to i) in a human female.



i) Identify the figure that illustrates ovulation and mention the stage of oogenesis it represents.

(ii) Name the ovarian hormone and the pituitary hormone that have caused the above mentioned event.

(iii) Explain the changes that occur in the uterus simultaneously in anticipation.

(iv) Write the difference between c and h.

(v) Draw a labeled sketch of the structure of a human ovum prior to fertilization.


(i) Figure 'f' illustrates ovulation. It represents the ovulatory stage of oogenesis.

(ii) The changes that cause ovulation are because of the change in level of the pituitary and ovarian hormones. The pituitary secrets two hormones called Follicle stimulating hormone (FSH) and Luteinizing hormone (LH). Estrogen is the ovarian hormone released during ovulation. The FSH and LH stimulate follicular development and secretion of estrogen from the primary follicles, the rapid secretion of LH induces graffian follicles to release and release ovum.

(iii) In anticipation of receiving the fertilised egg the primary follicles in the ovary grow to become graffian follicles and simultaneously the endometrium of the uterus regenerates and through proliferation and the blood supply is increased.

(iv) In the figure, (c) stage represents the secondary follicle and the (h) stage represents the degenerating corpus luteum.

Secondary follicle

Corpus luteum

1.It is found in the menstrual stage

1.It is found in the luteal stage.

2.It is Surrounded by layers of granulosa cells

2.Layers of granulosa cells are absent

3.Theca layer is present.

3.No theca layer is present


(v) Labeled diagram of the human ovum prior to fertilization.

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33.

How does the megaspore mother cell develop into 7-celled, 8 nucleate embryo sac in an angiosperm? Draw a labeled diagram of a mature embryo sac.

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34.

What is the inheritance pattern observed in the size of starch grains and seed shape of Pisum sativum? Workout the monohybrid cross showing the above traits. How does this pattern of inheritance deviate from that of Mendelian law of dominance?

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35.

State the aim and describe Messelson and Stahl experiment.

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