Topic 8 Flashcards
Microevolution and Mechanism
Evolution at the population level with changes in allele frequency in a population over time.
Occurs through natural selection and genetic drift
Macroevolution and Mechanism
Broad patterns of evolutionary change above the species level occurring on geological time scales and includes the origins of novel traits (ex: wings), and the origin of new groups.
Macroevolution is the cumulative result of small changes from microevolution, new genetic variation, and mass extinctions
Biological Species Concept (BSC)
A species is a group of individuals that can interbred, produce viable offspring, and are reproductively isolated from other species
Limitations of the BSC
Not applicable to fossils or asexual organisms.
Forgets about gene flow between species and hybridization
Morphological Species Concept
identifies a species based on their physical appearance or structural traits.
Includes sexual and asexual organisms, but relies on subjective criteria
Ecological Species Concept
defines a species by its role in the environment or ecological niche and how the species interacts with other organisms
Phylogenetic Species Concept
defines a species as the smallest group of individuals that share a common ancestor based on evolutionary history
Prezygotic Barriers and examples
Reproductive pariers that bloc fertilization from occuring by impeding different species from attempting to mate, preventing the successful complete of mating, and preventing fertilization if mating is successful.
Ex) habitat, temporal, behaviour, mechanical, or gametic isolation.
Postzygotic barriers
Reproductive barriers that prevent a hybrid zygote from developing into a viable fertile adult including reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown.
Reduced hybrid viability
A postzygotic barrier where genes of the different parent species may interact to impair the hybrid’s development or survival
Hybrid breakdown
Postyzygotic barrier where some 1st-generation hybrids are vigorous and fertile, but when these hybrids mate with one another or with either parent species, offspring of subsequent generations are feeble or sterile.
Polyploids
Sympatric speciation where organisms with a different number of chromosome sets than their parent forms and can only interbreed with individuals of the same ploidy.
Arises from hybridizations and chromosomal error during meiosis.
Allopolyploids
A species with multiple sets of chromosomes derived from the hybridization of different species. They have double the number of chromosome sets than the parent species
Autopolyploid
An individual with more than two chromosome sets, derived from one species. Can arise spontaneously by genome doubling or by fusion of 2n gametes
Hybridization zones
Where the ranges of two species overlap, allowed for hybridization to occur between species with incomplete reproductive barriers
