Question

Write short note on:
(i) Fertilization in human
(ii) Active and Passive Immunity

Hint:

Fertilization = sperm + ovum → zygote in fallopian tube. Active immunity = body makes antibodies, long-term. Passive = ready-made antibodies, short-term.

Answer 1

(i) Fertilization in human: \[\begin{array}{rl} \bullet & \text{Fertilization is the process of fusion of the male gamete (sperm) and the female gamete (ovum) to form a diploid zygote.} \\ \bullet & \text{It usually occurs in the ampulla of the fallopian tube.} \\ \bullet & \text{Steps:} \\ \bullet & \text{Capacitation: Sperm undergo physiological changes in the female tract to penetrate the ovum.} \\ \bullet & \text{Acrosomal reaction: Enzymes from the acrosome help the sperm penetrate zona pellucida of the ovum.} \\ \bullet & \text{Fusion: Plasma membranes of sperm and ovum fuse, and the sperm nucleus enters the cytoplasm.} \\ \bullet & \text{Cortical reaction: Prevents polyspermy (entry of additional sperms).} \\ \bullet & \text{Zygote formation: Male and female nuclei fuse to form the diploid zygote (2n = 46).} \\ \bullet & \text{Significance: Restores diploid chromosome number, determines sex of offspring, and initiates embryonic development.} \\ \end{array}\] (ii) Active and Passive Immunity: \[\begin{array}{rl} \bullet & \text{Active Immunity:} \\ \bullet & \text{Achieved when the body produces its own antibodies against antigens.} \\ \bullet & \text{Can be natural (after infection) or artificial (after vaccination).} \\ \bullet & \text{Provides long-lasting protection due to memory cells.} \\ \bullet & \text{Example: Immunity after polio vaccination.} \\ \end{array}\] \item Passive Immunity: \[\begin{array}{rl} \bullet & \text{Ready-made antibodies are introduced into the body.} \\ \bullet & \text{Provides immediate but short-term protection.} \\ \bullet & \text{Example: Anti-tetanus serum, mother-to-child antibodies via placenta or colostrum.} \\ \end{array}\] \end{itemize} Conclusion.
Active immunity is long-lasting and involves memory cells, whereas passive immunity provides immediate but temporary protection.