Topic 1 Topic 8

Natural Selection

The process through which species adapt to their environment by favoring traits that enhance survival and reproduction.

Speciation

The evolutionary process by which one ancestral species diverges into two or more genetically distinct descendant species that are reproductively isolated.

Microevolution

Evolutionary changes at the population level, primarily through natural selection and genetic drift.

Macroevolution

Broad patterns of evolution occurring above the species level, such as mass extinctions and the origin of new groups.

Biological Species Concept (BSC)

Defines a species as a group of individuals that can interbreed and produce viable offspring, and are reproductively isolated from other species.

Morphological Species Concept

Identifies a species based on physical appearance or structural traits shared by members.

Ecological Species Concept

Defines a species by its role in the environment and its interactions with other organisms.

Phylogenetic Species Concept

Defines a species as the smallest group of individuals sharing a common ancestor as shown in a phylogenetic tree.

Reproductive Isolation

Biological factors or barriers that prevent two species from interbreeding and producing fertile offspring.

Prezygotic Barriers

Factors that prevent mating or fertilization between species.

Postzygotic Barriers

Factors that prevent hybrid zygotes from developing into viable, fertile adults.

Allopatric Speciation

Speciation that occurs when a population is geographically separated, leading to genetic divergence.

Sympatric Speciation

Speciation that occurs within the same geographic area, requiring reproductive isolation despite gene flow.

Hybridization

Interbreeding between different species that occurs when reproductive barriers are incomplete.

Polyploidy

A form of speciation that involves changes in the number of chromosome sets, often leading to reproductive isolation.

Sexual Selection

A process where individuals with certain inherited traits are more successful at attracting mates, leading to reproductive barriers.

Assortative Mating

A form of sexual selection where individuals preferentially mate with others who share specific traits.

Hybrid Zone

Regions where different species or divergent populations meet and mate, producing hybrids.

Reinforcement

The process by which natural selection strengthens reproductive barriers, reducing hybridization.