Groups of organisms that share a suite of genetic and morphological attributes, and are reproductively isolated from other such groups
Species
Divergence of biological lineages and the emergence of reproductive isolation between lineages
Speciation
Biological species concept (BSC)
- reproductive isolation is key
- no gene flow between groups of organisms
- prezygotic and postzygotic barriers
Prezygotic barriers
Prevent fertilization between 2 species
Postzygotic barriers
Prevent hybrid zygotes from developing/reproducing
Live in different habitats
Habitat isolation
Breed at different times (day, year, or life)
Temporal isolation
Rituals that attract one mate to another disrupting gene flow
behavioral isolation
Reproductive “pieces” dont fit
Mechanical isolation
Sperm and egg are not compatible
Gametic Isolation
Hybrid development is incomplete and individual is frail
Reduced hybrid viability
Because of chromosomal differences, hybrid cannot breed
Reduced hybrid fertility
Hybrid is fertile, but cannot compete with full species
Hybrid breakdown
Morphological species concept
- species can be identified by body shape and other structural features
- (fossils, asexual organisms)
Lineage species concept
A species is one branch on the tree of life, each has a history that begins with a speciation event and ends either at extinction, or another speciation event
New species arise from 2 processes, depending on how gene flow is interrupted. (What are they?)
- allopatric speciation
- sympatric speciation
- physical barrier separates a population
- mutations arise in sub populations
- Natural selection, genetic drift, and/or sexual selection cause genetic differences
- Results in reproductive isolation creating 2 sister species
- (Founder events)
Allopatric speciation
- speciation events occurring when populations are in contact with each other
- polyploidy
- habitat differentiation
- sexual selection
Sympathy speciation
Polyploidy
- accident during meiosis, results in extra set of chromosomes
- more common in plants
- makes gametes that are incompatible with original species
Habitat differentiation
- genetic factors arise that allow some members of a population to exploit a resource which other cannot
- (disruptive selection)
Sexual selection
- mate force is driving factor in speciation
- mate choice is so drastic it leads to reproductive isolation
Ecological and behavioral factors influence speciation rates
- populations of species with a specialized diet may be more likely to diverge than those with generalized diets
- speciation rates are faster when animal pollinated, than when wind pollinated
- mechanisms of sexual selection result in high rates of speciation
- speciation rates are usually higher in groups with poor dispersal rates
The rapid proliferation of a large number of descendant species from a single ancestor species
Evolutionary radiation
When a rapid proliferation of species results in an array of species that live in a variety of environments
Adaptive radiation
