Speciation Process Quiz

Speciation

• Speciation is the process by which a new species emerges from an existing one.

Reproductive Isolation

• Reproductive isolation ensures that different species do not interbreed, resulting in the production of offspring.
• It is a fundamental mechanism that maintains the integrity of species boundaries.

Isolation Mechanisms

• Pre-zygotic isolation mechanisms prevent mating or fertilization from taking place, whereas post-zygotic isolation mechanisms occur after fertilization, preventing the development of viable offspring.
• Ecological isolation is a type of pre-zygotic isolation that occurs when reproductive barriers arise due to differences in the environment, such as habitat, diet, or predation.

Allopatric Speciation

• The main purpose of allopatric speciation is to create new species through geographic isolation, resulting in reproductive barriers between populations.

Reproductive Barriers

• Distinct songs in Western and Eastern meadowlarks serve as a reproductive barrier, preventing interbreeding between the two species.
• Behavioral isolation occurs when potential mates meet but choose members of their own species due to failure to send or receive appropriate signals.
• Mechanical isolation occurs when copulation is attempted, but transfer of sperm does not take place due to physical incompatibility of reproductive parts.
• Gametic isolation occurs when there is molecular incompatibility of eggs and sperm or pollen and stigma.

Post-zygotic Barriers

• Zygotic mortality occurs when mating and fertilization are possible, but genetic differences result in the zygote being unable to develop properly.
• Hybrid inviability occurs when a hybrid individual develops but either dies before birth or, if born alive, cannot survive to maturity.
• Hybrid sterility occurs when a hybrid offspring remains healthy and viable but is sterile due to abnormal development of their gonads.

Temporal Isolation

• Temporal isolation occurs when individuals of different species do not mate because they are active at different times of day or in different seasons.

Examples of Isolation

• The Eastern Spotted Skunk breeding in late winter vs. in the fall is an example of temporal isolation.
• Sea urchins releasing their gametes into the water, with surface proteins preventing the gametes of different species from binding to each other, is an example of gametic isolation.
• F1 hybrids that are viable and fertile but have reduced fertility in further hybrid generations (F2 and backcrosses) is an example of a post-zygotic barrier.