Question

Earthworms are bisexual but still cross-fertilization is common in them. This is because

• A. Spermatozoa and ova mature at different times in the same earthworm.
• B. Spermatozoa of different earthworms are different.
• C. Ova from other earthworms may be larger.
• D. Sperm and ova from the same earthworm cannot fertilize.

Answer 1

Answer: (A)

Earthworms are bisexual, i.e., male and female reproductive organs are present in same organism. Bisexuality favours self fertilization but earthworms are cross fertilizing organisms. This is because the male reproductive organs mature earlier than the female parts, i.e., they are protandrous, which in turn makes them cross fertilizing organisms.