Reproductive Isolation in Evolution

Reproductive Barriers

• Hybrid inviability is the term used to describe the phenomenon where hybrid embryos die.
• Premating barriers, such as differences in behavior, habitat, or morphology, prevent mating or fertilization in different species before the formation of a zygote.

Hybrid Offspring

• Hybrid sterility or hybrid inviability is the term for the offspring of hybrids that are weak or infertile.

Postzygotic Reproductive Barriers

• Hybrid sterility or hybrid inviability prevents the development of fertile adults.

Plant Reproductive Barriers

• Structural isolation in plants prevents cross-pollination, ensuring that different species do not mate.

Gamete Incompatibility

• The male and female gametes of red and purple sea urchins fail to unite due to differences in their reproductive cells.

Failure of Hybrid Development

• When hybrid zygotes fail to develop or reach sexual maturity, it is known as hybrid inviability.

Structural Isolation

• The primary effect of structural differences in genitalia or flowers is to prevent copulation between different species.

Biological Species Concept

• A species is defined as a group of interbreeding populations that are reproductively isolated from other groups.
• Barriers to gene flow in the biological species concept prevent the exchange of genes between different species.

Prezygotic Reproductive Barriers

• One type of reproductive barrier is the prezygotic barrier, which prevents mating or fertilization in the biological species concept.
• An example of a prezygotic reproductive barrier is the difference in flowering times between two plant species, preventing them from cross-pollinating.