Bio Chapt: 22 Orgins of New Species

What is a species?

group of populations whose members can interbreeding nature producing viable fertile offspring.

What is speciation?

One species splits into two

What is reproductive isolation?

The existence of biological factors (barriers) that impede two species from producing vaible, fertile offspring.

What are hybrids?

Offspring of crosses between two different species

What are the two classes of reproductive barriers?

• Pre-zygotic

• Post- Zygotic

Prezygotic barriers?

• Before fertilization, where they block fertilization from occuring

  • Impeding different species from attempting to mating

  • Preventing the successful completion of mating

  • Hindering fertilization

For prezygotic what are some examples of impediing different species from mating?

• habitat Isolation: Land vs Water snakes

• Behavioral isolation: Birds will only mate with blue feeted bird with a special dance

• Temporal Isolation: One skunk mates in the summer and one skunk mates in the winter

In prezygotic whats an example of preventing successful completion of mating?

Mechanical Isolation: Snals cant mate because shells are different directions

In prezygotic, whats an example of hindering fertilization if mating is successfuol?

• Gametic isolation: Sperm and Egg wont bind together

Post-zygotic barriers?

• Prevents the hybrid zygote from developing into a viable, fertile adult

  • Reduced Hybrid viability

  • Reduce hybrid fertility

  • Hybrid Breakdown

Whats an example of reduced hybrid viability?

Offsping fail to develop

Whats an example of reduced hybrid fertility?

Sterlile Mule

Whats an example of hybrid breakdown?

The second generation fails

What are the two ways to speciate?

• Allopatric Speciation

• Sympatric Speciation

Allopatric speciation

A population forms a new species while geographically isolated from its parents pop.

sympatric speciation

• A subset of a pop. forms a new species without geographic isolation

• Required reduced gene flow

• less common

Adaptive Radiation

• Allopatric

• Explosion of new species after colonized into a new area

What reduces gene flow?

• Habitat differentiation: genetic variation lets subpopulations exploit a habitat/resource

• Sexual selection: divergence of pop. due to mate choice

• Development of polyploidy: Due to a cell division error

Polyploidy

The presence of extra sets of chromosomes due to accidents during cell division