Question

Hybrid inviability (postzygotic reproductive barriers)

Answer 1

Hybrid inviability is a postzygotic barrier where a hybrid embryo cannot survive, due to genetic incompatibilities. Hybrid sterility is where a hybrid cannot produce offspring. Both are mechanisms of reproductive isolation that prevent gene flow and aid in speciation.

Step-by-step explanation:

Hybrid Inviability and Postzygotic Reproductive Barriers

Reproductive isolation is an essential concept in evolutionary biology, contributing to the formation of new species. Scientists categorize reproductive barriers into prezygotic barriers and postzygotic barriers. Prezygotic barriers prevent fertilization and thus, zygote formation. Conversely, postzygotic barriers come into play after a zygote has formed.

Hybrid inviability is a type of postzygotic barrier where hybrid embryos are not viable and do not survive to birth or die shortly thereafter. This can occur due to genetic incompatibilities between the differing parent species. Hybrid inviability is different from hybrid sterility, where the hybrid organism can grow to adulthood but is unable to produce viable offspring, as seen in mules (the sterile offspring of a female horse and a male donkey).

These barriers contribute to reproductive isolation, ensuring that there is no gene flow between the two distinct species and thus reinforcing speciation. Natural selection can also impact this process by favoring the reproduction of individuals with genetic traits that are favorable in the given environmental context.

Answer 2

Hybrid inviability is a postzygotic reproductive barrier where hybrids fail to develop properly and die before birth. Hybrid sterility is another postzygotic barrier where hybrids grow to maturity but cannot reproduce. Both serve as mechanisms to prevent successful interbreeding and maintain species differences.

Step-by-step explanation:

Reproductive isolation mechanisms divide into two categories: prezygotic barriers and postzygotic barriers. A prezygotic barrier prevents fertilization and the formation of a zygote. In contrast, a postzygotic barrier takes effect after a zygote has been formed. One form of postzygotic barrier is hybrid inviability, where hybrids fail to develop properly and do not survive past embryonic stages. Essentially, these hybrids are not viable, hence the term 'hybrid inviability'.

There is also the scenario where hybrid viability is not an issue, but the resulting organism is infertile, known as hybrid sterility. For example, a mule is the sterile offspring of a female horse and a male donkey. The inability for hybrids to reproduce prevents gene flow between the two parent species, reinforcing speciation. The essence of postzygotic barriers is that they serve as an evolutionary mechanism to maintain species differences by preventing successful interbreeding.

Complete question is as follows :

Explain what is Hybrid inviability (postzygotic reproductive barriers)?