24.1 The Biological Species Concept emphasizes Reproductive Isolation

1. 24.1 The Biological Species Concept emphasizes Reproductive Isolation

2. The Biological Species Concept • A species is a population or group of populations that can interbreed and produce FERTILE offspring, but cannot produce viable offspring with other groups. • Eastern meadowlark • western meadowlark

3. Reproductive Isolation • Biological species are defined in terms of reproductive compatibility. • When members of a species are isolated reproductively, the members of the now two separate populations cannot interbreed and produce fertile offspring. • Usually having some sort of barrier can on occasion lead to hybrids, many barriers can isolate an organism altogether. • Not all barriers are obvious.

4. Reproductive Barriers

5. Prezygotic/postzygotic Barriers Prezygotic Barriers Postzygotic barriers Various mishaps can prevent hybrids from being successful. • Block fertilization from occurring. Typically through geographic, temporal, or behavioral isolation.

6. Limitations to the Biological Species Concept • The Biological Species Concept is defined by the absence of gene flow (meaning hybrids typically are not a viable option). • Even though gene flow can occur between two organisms, other barriers can prevent a hybrid from forming (i.e. the grolar bear which is a combination of a grizzly and polar bear). • The Biological Species concept also doesn’t include asexually reproducing prokaryotes.

7. Other Species Concepts • Morphological Species Concept: categorizes a species based on its morphological characteristics. • Ecological Species Concept: Categorizes organisms based on their niche (role in the environment). • Phylogenetic Species Concept: categorizes a species as the smallest group of individuals that share a common ancestor. Compare morphology and molecular genetics.