Biology Chapter 1

Biological Species Concept

Species are groups of actual, or potentially, interbreeding natural populations that are reproductively isolated from other such populations.

Ernst Mayr

Proposed the biological species concept in the early 1940s, building on ideas from Charles Darwin.

Gene Pool

The range of genes and all their alleles present in a population.

Relation of Biological Species Concept to Gene Pools

Each species represents an isolated gene pool where individuals can interbreed and produce viable offspring under natural conditions.

Limitations of Biological Species Concept

1. Fossils cannot determine interbreeding or new species; 2. Proof of mating is hard to observe; 3. Hybrids complicate classification.

Hybrid

An organism resulting from the interbreeding of two different species.

Challenges in Classifying Hybrids

Hybrids occupy restricted zones, may not survive well, and blur species boundaries, complicating identification.

Example of Hybrid

Polar–grizzly bear hybrid, also known as a 'grolar bear,' found in Arctic regions.

Morphological Species Concept

A definition of species based on physical characteristics.

Phylogenetic Species Concept

A definition of species based on the smallest group of individuals with a common ancestor, often determined using genetic analysis.

Biological Species Concept and Fossils

Fails with fossils as they don’t show mating behavior, offspring fertility, or reproductive isolation.

Hybridization and Species Definitions

Hybrids in overlapping zones indicate genetic compatibility, complicating the definition of separate species.

Most Widely Used Species Concept

The biological species concept.