Unit 5 Speciation

Exam 2 Study Guide

What is a species?

A group of actually or potentially interbreeding natural populations whose members can produce viable, fertile offspring

(They are reproductively isolated from other groups)

What are members in a species united by?

The potential to reproduce and exchange genes

What are some weaknesses for the biological species concept?

1. # of species to which this can be applied is limited

2. doesnt apply to species that reproduce asexually

3. many species are geographically isolated

What is a strengths for the biological species concept?

Explains a way by which speciation can occur → the evolution of reproductive isolation

What is speciation?

A lineage splitting event that leads to the formation of new + distinct species in the course of evolution

What is the key to speciation?

Reproductive isolation

What needs to happen for speciation to occur?

Enough genetic changes that lead to changes in traits that are important for reproduction

How does reproduction isolation effect species?

Different species may live in the same area but biological barriers of individuals prevents them from interbreeding +/or produce viable/fertile offspring

What are 2 barriers causing reproductive isolation?

Prezygotic and postzygotic barriers

Def of a prezygotic barrier

prevents the egg + sperm from uniting

Def of a postzygotic barrier

Prevents development, survival, or production of fertile offspring

What are factors preventing gametes joining? (prezygotic)

1. Habit iso

2. Temporal iso

3. Behavioral iso

4. Mechanical iso

5. Gametic iso

What is habit isolation?

2 species in the same habitat rarely encounter each other

What is temporal isolation?

2 species breed during different times of the day, year, or seasons

What is behavioral isolation?

courtship rituals that attract mates are unique to a species

What is mechanical isolation?

Mating attempted, but morphological diffs prevents completion (physically can’t reproduce)

What is gametic isolation?

incompatible gametes

What are 2 problems that can occur after gametes join? (postzygotic)

1. reduced hybrid viability

2. reduced hybrid fertility

What is reduced hybrid viability?

genes of diff species interact in ways that impair development or survival

What is reduced hybrid fertility?

Genes of diff species interact in ways that impair fertility of the hybrid

What are the 2 types of speciation?

1. allopatric

2. sympatric

What is allopatric speciation?

Population is divided geographically → gene flow gets interrupted + gene pool diverges

• evolutionary processes may alter allele frequencies

What is sympatric speciation?

new species forming w/o a geographic barrier → populations can live in the same area but may occupy different niches

• temporal iso can occur

What is a niche?

an organisms way of life