Lecture 11
Biological Species Concept
Speciation: the process in which one species splits into 2 or more species
Microevolution: changes in allele frequency in a population
Macroevolution: Broad pattern of evolution above the species level
Species: a group of populations that are able to interbreed and produce viable fertile offspring. -Gene flow within a population holds members of the population together genetically
Reproductive Isolation: Barriers that prevent members of different species from interbreeding
1-Prezygotic Barriers:
Habitat Isolation: species live in different areas
Temporal Isolation: mating occurs at different seasons
Behavioral Isolation: members of a species practice mating rituals unique to their own species
Mechanical Isolation: morphological differences prevent transfer of gametes
Gamete Isolation: gametes fail to fuse due to biochemical differences
2-Postzygotic Barriers:
Reduced Hybrid fertility: Difference in chromosome number causes problems in meiosis
Reduced Hybrid viability: genes of parent species may have interactions that affect hybrid health
Hybrid breakdown: the first generation of offspring may be healthy and fertile but the second generation will be sterile or unhealthy Morphological Species Concept: Species characterized by body shape Ecological Species Concept: based on species ecological habitat Phylogenetic Species Concept: based on DNA and morphology How Does Speciation occur? * Allopatric Isolation: an ancestral species is divided into geographically isolated subpopulations * Sympatric Isolation: occurs within populations that live in the same geographic area -polyploidy: accident in cell division resulting in extra set pf chromosomes - habitat differentiation: a subpopulation may develop the ability to exploit a resource not used by the parent population - Mate choice: (based on color) How are Hybrids produced? When species with incomplete reproductive barriers mate