Question

Attempt either option (A) or (B):

(A) In flowering plants, the process of pollination leads to fertilization. (i) Explain with the help of a well-labelled diagram how the male germ cell from the pollen grain reaches the female germ cell located in the ovule. (ii) Differentiate between self-pollination and cross-pollination. (iii) Identify and name the parts 'R' and 'S' in the given diagram of a seed (where R points to plumule and S points to radicle/cotyledon).

OR

(B) (i) Name the special tissue inside the uterus that provides nutrition to the developing embryo. Describe its structure. State its two functions besides nutrition. (ii) Write any two sexually transmitted diseases in humans and their causative microbial agents.

Accepted Answer

Placenta supplies nutrition, oxygen, and removes waste. STDs: Syphilis/Gonorrhea (Bacteria) and AIDS/Genital Warts (Virus).. **Option (A):** (i) Pollen grain germinates on the stigma to grow a pollen tube down the style into the ovary/ovule where male gametes are released to fuse with the egg cell. (ii) **Self-pollination:** Transfer of pollen from anther to stigma of the same flower or same plant. **Cross-pollination:** Transfer of pollen from anther to stigma of a different plant of the same species. (iii) R = Plumule (future shoot), S = Radicle / Cotyledon. **Option (B):** (i) **Placenta:** A disc-like tissue embedded in the uterine wall containing villi on the embryo side and blood spaces on the mother side. *Functions besides nutrition:* Excretion (removal of nitrogenous wastes) and Respiration (exchange of $O_2$ and $CO_2$). (ii) **Bacterial STDs:** Gonorrhea (*Neisseria gonorrhoeae*), Syphilis (*Treponema pallidum*). **Viral STDs:** AIDS (HIV), Warts (HPV).

Plant Fertilization and Human Reproduction

Explanation

Practise this under board exam conditions