Chapter 15 Flashcards
Speciation
process by which one species splits into two or more species
New species resulting from speciation share..
many characteristics because they descend from common ancestor
Speciation increases
diversity of life
Biological species concept
group of populations whose members have the potential to interbred in nature and produce fertile offspring
Biological species concept is useless for
defining prokaryotes
Biological species concept is problematic for defining
species of fossils
Morphological species concept
based on distinguishing physical traits
Morphological species concept can be applied to
fossils, asexualling and sexually reproducing organisms
Ecological species concept
defines species by its ecological role or niche
Ecological species concept focuses on
unique adaptions to a particular role in biological community
Phylogenetic species concept
defines species as the smallest group of individuals which share a common ancestor, each species forms 1 branch on tree of life
Phylogenetic species concept is problematic to..
determined amount of difference required separate species
Species interbreed resulting in
hybrids
Reproductive barriers
- prezygotic
- postzygotic
5 types of pre zygotic barriers
habitat isolation
- temporal isolation
- behavioural isolation
- mechanical isolation
- gametic isolation
Habitat isolation
two species live in same general are but not same kind of place
Temporal isolation
two species breed at different times
Behavioural isolation
there is little or no mate recognition between females and males of diff species
Mechanical isolation
female and male sex organs are not compatible
Gametic isolation
female and male games are not compatible
3 types of post zygotic barriers
- reduced hybrid viability
- reduced hybrid fertility
- hybrid breakdown
Reduced hybrid viability
most hybrid offspring do not survive
Reduced hybrid fertility
hybrid offspring are vigorous but sterile
Hybrid breakdown
first generation hybrids are viable and fertile but offspring of hybrids are sterile
Allopatric speciation
populations of the same species are geographically operated isolating their gene pools
Isolated population will no longer share changes in allele frequencies caused by
- natural selection
- genetic drift
- mutation
Gene flow between population is initially prevent by..
geographic barriers
Sympatric speciation
occurs when a new species arises within the same geographic area as parent species
Gene flow between population may be reduced by
- polyploidy
- habitat differentiation
- sexual selection
Most plants we grow for food are..
polyploids
Wheat species Have evolved for..
10,000 years
Allopatric speciation is the cause for..
most diversity on Earth
Adaptive radiation
evident in islands because far enough apart to permit evolution in isolating but close enough to allow occasional gene flow
Hybrid zones
regions in which members of different species mate producing hybrid offspring
3 possible outcomes of hybrid zones
- reinforcement
- fusion
- stability
Reinforcement
hybrid offspring are not fit, natural selection reinforces reproductive barriers
Fusion
reproductive barriers are not strong, speciation process reverses
Stability
hybrids continue to be produced but each species maintains its own integrity
Punctuated equilibria
long periods of little speciation interpreted by abrupt epodes of speciation
Time between speciation event averaged ___ ______ years and rarely took less than ______ years
6.5 million; 50,000
