Exam 2: Evolution diversity, How new kinds of animals evolve

Lineages of animals

• a branch on phylogenetic tree

What happens to lineages over time

• stasis

• gradual change

• extinction

• diversification

Stasis

very little change over long periods of time

Gradual Change

body form over time; environment changed

Extinction

where everything goes

Diversification

many lineages

Variation in populations

• mutations

• recombination of existing alleles

• natural selection

• genetic drift

Population

group of similar interbreeding organisms in a particular area

A species

• group of populations with similar characteristics

• successfully interbreeding

  • gene flow

• reproductively isolated from other species

  • no gene flow

What biological processes are responsible for gene flow?

• process of alleles from one population and sharing them to another

• mating and migration

One species

• there is gene flow, interbreeding populations

• alleles shared throughout

• similar appearance behavior and ecological niches

• no reproductive isolation

two specoes

• no geneflow

• genetically distinctive

• differences in appearance, behavior and ecological niches

• reproductively isolated

reproductive isolating mechanisms

• pre-zygotic

• post-zygotic

Pre-zygotic

• habitat isolation

• temporal isolation

• behavioral barriers

• gametic barriers

habitat isolation

isolation by physical space

temporal isolation

breeding times are slightly different

behavioral isolation

different mating behaviors

mechanical barries

genitalia does not fit

gametic barriers

sperm can fertilize egg

Post-zygotic

• genetically incompatible programs

genetically incompatible programs

chromosome numbers dont match

Hybrids are infertile

• fist gen hybrids are fertile

• a gen or 2 offspring become weaker and potentially sterile

• Reproductive isolating mechanisms are evolving and becoming better at preventing it

Reproductive Isolating mechanisms are important?

prevent geneflow and aids in speciation