Question

pre- and postzygotic isolation
classify the following examples into either prezygotic or postzygotic reproductive isolation mechanisms.
a horse is crossed with a donkey. the resulting offspring is unable to reproduce with either horses or donkeys.
seeds from hybrid tomatoes are unable to produce more tomatoes.
eggs laid by female drosophila melanogaster that are fertilized by a male d. biarmipes fail to develop into larvae.
female gypsy moths produce pheromones that are not recognized by males of other moth species.
five species of flycatcher birds live in the same area but breed at different times of the year.
flowers of the black sage are pollinated by one insect and flowers of the white sage are pollinated by a different insect.
multiple species of coral release their gametes into the water but only those of the same species are able to successfully fuse.
postzygotic isolation
prezygotic isolation

Explanation:

To solve this, we first recall the definitions:

• Prezygotic Isolation: Mechanisms that prevent fertilization (gamete fusion) from occurring.
• Postzygotic Isolation: Mechanisms that act after fertilization (zygote is formed) to prevent viable, fertile offspring.

Classifying Each Example:

1. Postzygotic Isolation:

• A horse is crossed with a donkey...: Offspring (mule) is infertile (post - zygote issue, as fertilization occurred).
• Seeds from hybrid tomatoes...: Hybrid zygote forms, but offspring (seeds) can’t reproduce (post - zygote).
• Eggs laid by female Drosophila...: Fertilization occurs, but embryo fails to develop (post - zygote).

1. Prezygotic Isolation:

• Female gypsy moths...: Pheromone recognition prevents mating (no fertilization).
• Five species of flycatcher birds...: Different breeding times prevent mating (no fertilization).
• Flowers of black sage...: Different pollinators prevent pollen transfer (no fertilization).
• Multiple species of coral...: Only same - species gametes fuse (prevents cross - species fertilization).

Answer:

Postzygotic Isolation:

• A horse is crossed with a donkey. The resulting offspring is unable to reproduce with either horses or donkeys.
• Seeds from hybrid tomatoes are unable to produce more tomatoes.
• Eggs laid by female Drosophila melanogaster that are fertilized by a male D. biarmipes fail to develop into larvae.

Prezygotic Isolation:

• Female gypsy moths produce pheromones that are not recognized by males of other moth species.
• Five species of flycatcher birds live in the same area but breed at different times of the year.
• Flowers of the black sage are pollinated by one insect and flowers of the white sage are pollinated by a different insect.
• Multiple species of coral release their gametes into the water but only those of the same species are able to successfully fuse.