Question

Which of the following is an example of mechanical isolation?

Many insects have intricate "lock and key" mechanisms that prevent the male genitalia of one species from engaging with the female genitalia of a different species.

A sponge excretes eggs and sperm into the water, but only gametes from the same species will fertilize each other.

A mule, the offspring of a horse and a donkey, is sterile.

A female moth produces a pheromone to which male moths of another species are indifferent.

Answer 1

Example of mechanical isolation- A) Many insects have intricate "lock and key" mechanisms that prevent the male genitalia of one species from engaging with the female genitalia of a different species.

Postmating prezygotic barriers prevent contact between male and female gametes even though mating is attempted. Either the male is unable to deposit the sperm in the female genital tract or sperm are not viable inside female genital tract. Mechanical isolating barriers are examples of postmating prezygotic barriers.

Among animal species with internal fertilization, the structural differences of male and female copulatory organs may prevent copulation and deposition of sperm in female genital tract. The genitalia in insects are developed on "lock and key" principle and female genitalia are so exactly fitted to each other that even slight deviation in the structure renders copulation impossible and interspecific cross may cause injury to female.