Speciation

• Speciation: The evolutionary process by which new, distinct species are formed.
• Species: An interbreeding population that is reproductively isolated from other similar but morphologically distinguishable populations.

• Gene Pool: Each species represents a unique gene pool adjusted to its specific environment. Members can exchange genes with each other, but not with members of other species.
• Variation: There is a continuous variation among members of the same species, but a complete discontinuity of variation between different species.
• Populations: A species consists of numerous individual populations. Geographically closer populations share their gene pools more easily than widely separated populations.

Interrelations between individuals, populations and species:

• Formation: Because environmental forces vary by locality, observable differences arise between separated populations over time, dividing a species into races.
• Gene Flow: Distinction between races is not absolute. While races may differ in specific gene frequencies, these differences do not inhibit gene exchange. They still participate in the overall gene pool of the entire species.
• Example: Human beings have five main racial groups (Asian, African, European, American, and Pacific). Despite differing morphological characters and gene frequencies, all are members of the same species: Homo sapiens sapiens.

• Meaning: The inability of individuals from different populations to interbreed.
• Significance: It constitutes the most important, definitive boundary between different species.

In nature, a reproductive barrier prevents interbreeding between two species:

• Speciation is the evolutionary process responsible for the formation of new, distinct species.
• A species is defined as an interbreeding population that shares a specific gene pool and is reproductively isolated from other distinct populations.
• While members within a species exhibit continuous variation, there is a complete discontinuity of variation between different species.
• A species can be divided into geographical races with unique gene frequencies due to environmental differences, yet these races can still interbreed successfully.
• Reproductive isolation, which is the inability of individuals from different populations to interbreed, constitutes the most definitive boundary between different species.