Question

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

Answer 1

Earthworm contains both male and female reproductive organs in the single organism, such organisms are called hermaphrodite. Though, earthworm is hermaphrodite but then also cross fertilisation is ensured in earthworms.

Hermaphrodite organisms have been evolved over the time and there can be different reasons for this like difficulty in finding mate, difference in the size of sexes or small genetically isolated species.

As far as complications of relation goes, reproduction itself is a complicated process where organisms propagate themselves in the best possible way be it a bisexual organism or unisexual organism. Both have their specific mechanisms.

Answer 2

Answer:

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.