Rucete ✏ Biology In a Nutshell
1. What Is Reproductive Isolation?
Reproductive isolation prevents different species from interbreeding and producing fertile offspring.
It is a key mechanism for maintaining species boundaries and allowing speciation to occur.
2. Prezygotic Isolating Mechanisms
These barriers prevent fertilization before the formation of a zygote.
a) Habitat Isolation
- Species live in different habitats and do not encounter each other.
- Example: One species lives in water, another on land.
b) Temporal Isolation
- Species reproduce at different times (day, season, or year).
- Example: One plant blooms in spring, another in summer.
c) Behavioral Isolation
- Species have different courtship behaviors or mating calls.
- Example: Female insects ignore males of other species due to differences in mating rituals.
d) Mechanical Isolation
- Differences in reproductive anatomy prevent successful mating.
- Example: Flower structure only allows specific pollinators.
e) Gametic Isolation
- Sperm of one species cannot fertilize the eggs of another species.
- Example: Molecular incompatibilities prevent sperm binding.
3. Postzygotic Isolating Mechanisms
These barriers occur after fertilization, preventing viable, fertile offspring.
a) Hybrid Inviability
- Fertilized egg forms but fails to develop properly.
- Embryo dies early or fails to reach maturity.
b) Hybrid Sterility
- Hybrid offspring is sterile and cannot reproduce.
- Example: Mule (horse × donkey) is sterile.
c) Hybrid Breakdown
- First-generation hybrids are fertile, but their offspring are weak or infertile in subsequent generations.
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Biology in a nutshell