Human Reproduction — BIOLOGY STD 12 Science — Question

Many secondary metabolites of plants have medicinal properties. It is their misuse that creates problems. Justify the statement with an example.

What is the use of aeration tank in the treatment of sewage?

When and where do chorionic villi appear in humans? State their functions.

Write the sex chromosomal complement of the following:

Explain the evolutionary theory of living form based on the observations of Charles Darwin.

List any three major categories of cancer. Explain briefly each category giving one example.

When does ovulation occur?

Ram saw a farmer spraying some chemicals on flowers. On asking farmer, he came to know that this act will lead to the formation of fruits without fertilisation. Ram thought that fruits developed in this way are not good to eat as chemicals are sprayed on it.
Next day, he asked his biology teacher about it, who explained him everything.

1. What chemicals were sprayed by the farmer?
2. Give difference between such a spray and usual pesticide spray?
3. What is parthenocarpy? Give its types.
4. What values are shown by Ram?

During a fire in an auditorium, a large number of assembled guests got burnt beyond recognition. Suggest and describe a modern technique that can help hand over the dead to their relatives.

Match Column I with Column II.

S. No.	Column I	S. No.	Column II
A.	Cleavage	1.	Outer layer of the blastocyst that attaches to the endometrium during implantation.
B.	Implantation	2.	Mitotic divisions of the zygote in quick succession.
C.	Inner cell mass	3.	Embedding of the blastocyst in the endometrium of uterus.
D.	Trophoblast	4.	Release of secondary oocyte from the ovary.
E.		5.	Group of cells attached to one end of trophoblast that differentiate into embryo proper.