IB DP Biology- D3.1 Reproduction- IB Style Questions For HL Paper 1A -FA 2025
▶️ Answer/Explanation
✅ Answer: (A) Structure Z is the anther, which is part of the stamen.
Question
Globozoospermia is a genetic condition that leads to male infertility due to the production of abnormal sperm. The diagram compares a normal sperm cell with one produced by a man with globozoospermia.
Why are sperm from males with this condition unable to fertilize eggs?
A. They lack enzymes to digest the follicle cells.
B. They have less genetic material.
C. They have no energy to swim through the oviducts.
D. They fail to reach the plasma membrane of the egg.
▶️Answer/Explanation
Answer: D. They fail to reach the plasma membrane of the egg.
Explanation:
Globozoospermia is a condition where sperm have round heads and lack an acrosome a structure that contains enzymes needed to digest the egg’s outer layers (like the follicle cells and zona pellucida). Without these enzymes, the sperm cannot penetrate the egg to fertilize it.
Let’s analyze the options:
A. Correct – They lack the acrosome, so they don’t have the enzymes to digest the follicle cells and reach the egg.
B. Incorrect – DNA content is normal; genetic material is not the issue.
C. Incorrect – Energy for movement may be normal; the main issue is penetration, not motility.
D. Incorrect – They fail to reach the egg membrane because they can’t digest the outer layers — this is a result, not the root cause.