(b) The pollen tube of most seed plants acts as a passage way. It transports sperm cells from the pollen grain, from the stigma (in flowering plants) to the ovules at the base of the pistil.
(c) After fertilisation, the zygote divides several times to form an embryo within the ovule.
(i) The ovule develops a tough coat and is gradually converted into a seed.
(ii) The ovary grows rapidly and ripens to form a fruit.
OR
(a) Using condom for the penis during sex helps to prevent transmission of many of infections to some extent. The sexual act always has the potential to lead to pregnancy. Pregnancy will make major demands on the body and the mind of the woman, and if she is not ready for it, her health will be adversely affected. Therefore, many ways have been devised to avoid pregnancy. Condoms on the penis or similar coverings worn in the vagina can serve this purpose. Another category of contraceptives acts by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. These drugs commonly need to be taken orally as pills. However, since they change hormonal balances, they can cause side-effects too. Contraception to avoid pregnancy can be achieved by the use of condoms. Thus, use of condoms is beneficial for both the sexes involved in a sexual act.
(b) Oral contraceptives act by changing the hormonal balance of the body so that eggs are not released and fertilisation cannot occur. Thus, in this way they help in avoiding the pregnancies.
(c) Sex-selective abortion of female foetuses involves surgical removal of unwanted pregnancies with female foetus. These may be misused by people who do not want a particular child. For a healthy society, the female-male sex ratio must be maintained due to the reckless female foeticides, child sex ratio is declining at an alarming rate in some sections of our society, although prenatal sex determination has been prohibited by law in order to protect the abortion of the female foetus.