Question

1. What is reproductive isolation? Why is it important to speciation?

2. Define and give an example of the following reproductive isolating mechanisms. Pre-zygotic Mechanisms - isolate two populations without zygotes forming

Timing (Temporal isolation) –

Behavior (Behavioral isolation) –

Habitat (Ecological isolation) –

Physically Incompatible (Mechanical isolation) –

Post-zygotic Mechanisms – isolate two populations when zygotes form

            Hybrids fail to develop (Hybrid Inviability) –

            Hybrid Infertility –

3. How does geographic isolation lead to speciation and adaptive radiation? How do you know when two or more populations have become distinct species?

Answer 1

1. Any structural, functional or behavioral characteristic that act as a barrier for normal sexual reproduction between different species leads to reproductive isolation. This leads to genetic variability accumulation in the species. It is unique in evolution as it is not a individual character but a composite character as it is a combined property of a pair of species.

Reproductive isolation is important for speciation because it makes different species unable to interbreed and produce healthy , fertile offspring. It involves epistatic interaction between alleles, occuring in different species. Hybrid inviability is a result from genes that are normally viable in the members of own species but show lethality when interacting with alien genes in hybrids. Sexual isolation is caused when females evolved to prefer specific traits in males of same species encounter different traits in males of other species. This composite and epistatic nature of reproductive isolation confirms that speciation will show emergent genetic and phenotypic properties and mathematical theories of speciation. Speciation involves reproductive isolation of groups within the original population and accumulation of genetic differences between two groups.