Sexual Reproduction in Flowering Plants — BIOLOGY STD 12 Science — Question

“Bt toxin synthesized by some bacteria kills insects carrying protein, but not themselves.” Explain the statement with reasons.

What is medical termination of pregnancy and why is it needed.

Explain: amniocentesis

Define the following and give one example of each (a) False fruit, (b) True fruit, (c) Parthenocarpic fruit, (d) Polyembryony.

The cytological observations made in a number of insects led to the development of the concept of genetic/chromosomal basis of sex-determination mechanism. Honey bee is an interesting example to study the mechanism of sex - determination. Study the schematic cross between the male and the female honey bees given below and answer the questions that follow :

(a) Identify the cell divisions 'A' and 'B' that lead to gamete formation in female and male honey bees respectively.
(b) Name the process 'C' that leads to the development of male honey bee (drone).

What do you mean by in-situ and ex-situ conservation of wildlife?

Identify a, b, c and d in the following table:

S.No.	Name of the human disease	Name of the causal bacteria/virus	Specific organ or its part affected
1.	Typhoid	Salmonella typhi	a
2.	Common cold	b	c
3.	Pneumonia	Streptococcus pneumoniae	d

Name the cells, HIV (Human Immunodeficiency Virus)gains entry into after infecting the human body. Explain the events that occur in these cells.