Speciation Flashcards
Speciation
One species splits in two species
Microevolution
Changes over time in allele freq in a population
Macroevolution
Broad pattern of evolution above species level
Species
Group of populations whose members have the potential to interpreted and produce viable, fertile offspringb
Gene flow
Transfer of alleles
Typically between different populations
Reproductive isolation
Impedes members of two species from interbreeding
BLOCK TO GENE FLOW
limit formation of hybrids
VITAL in formation of NEW SPECIES
Hybrids
Offspring that result from interspecific mating
Ex. Ligers triticale
Protozygotic barriers
Gametic isolation
Produced hybrid viability
Reduced hybrid fertility
Hybrid Breakdown
First generation may be viable and fertile but the next isnt
Prezygotic Barriers
Impeding members of different species from mating
Preventing completion of mating
Hindering fertilization if mating is completed
Biological Species Concept- Limitations
Fossils cant be evaluated
Asexual organisms
Distinct Species despite gene flow occurring (polar and grizzly)
Morphological Species Concept
Distinguished by body shape and features
(Works for fossils, asexual organisms)
Ecological Species concept
Species in ecological niche
How it interacts w biotic and abiotic members of environment
(Oak trees Species in different environments that still interbreed-still two species)
Allopatric speciation
Gene flow interruption when gene flow is geographically seperated
Geological or locational change
Sympatric Speciation
Speciation in two pop in the same geographically area
By way of:
Polyploidy
Sexual selection
Habitat differentiation
Polyploidy
Extra set of chromosomes
Autopolyploid
More than 2 sets of chromosomes but derived from same species
Allopolyploid
Sterile hybrid –> fertile hybrid
(Can breed with eachother but not parent species)
By way of: infertile hybrid propagating asexually (plants)
Habitat differentiation
Subspopulation exploits habitat not used by parent population
Sexial selection-sympatric speciation
Females prefer one features other another later 2 species form
Hybrid Zones
Memebers of Different Species with incomplete reproductive barriers mate and produce hybrids
Hybrid Zones Over Time
Reinforcement- becomes two species
Fusion- although they started to split they eventually fuse again (reproductive barriers decrease)
Stability-more hybrids are produced
Successful hybrid zones
Usually Hybrids survive and reproduce better than parent species
Unlikely case:
Despite being selected against the section for bombina is narrow enough that parent species keep going in to form hybrids
Punctuate equilibria
Periods of stasis punctuate by sudden change (fossils)
-speciation occurred rapidly
-if change is gradual then bio speciation is less obvious bc it doesn’t leave a fossil
How does speciation occur?
Not with a speciation clock
It only begins after gene flow between populations is interrupted and then populations become reproductively isolated
