BIO 2253 Midterm II Speciation Concepts

What is a species

evolutionary independent populations or groups of populations

Anagenesis

change in lineage over time

Cladogenesis

change and divergence over time

morphological species concept

evolutionarly independent groups are morphologically distinct
pros
- works with fossils

-easily applicable

cons

• sexual diorphism

• convergence

• subjective

Biological Species Concept

Evolutionary independent groups that are reproductively isolated

Pros

• directly aligns with the definition of a species

Cons

• asexual organisms

• hybrid species?

phylogenetic species concept

evolutionary independent groups form clades (monophyletic groups)

pros

• applicable to asexual organisms

• works for extinct and recently discovered species

cons

• splitting (polyatomies)

• horizontal gene transfer

Allopatruc speciation

begins in physical isolation

one species has two or more populations that are physically isolated

sympatric speciation

reduced gene flow between two groups of individuals despite being in the same place

divergence and reduction in gene flow occur simultaneously

Genetic isolation factors premating

• behavioral

• ecological

• mechanical

Genetic isolation post-mating

• copulatory behavior

• gametic isolation

Genetic isolation - pre-zygotic

intrinsic - development or fertility

extrinsic - don’t fit environment

secondary contact

reinforcement and hybridization

punctuated equilibrium model

stability marked by periods of divergence and rapid changes

Adaptive radiations

diversification within a single lineage resulting in many descendant species.

mass extinction

rapid extinction of a large number of diverse species are the world

>60 % of species lost within a million years

background extinction

average rate of extinction when no mass extinction is occuring

Permian extinction

largest mass extinction

96 % of all species lost

volcanic activity in siberian traps

Cretaceous Tertiary

astreiod impact in yucatan peninsula 66 millon years ago

massive impact

• global earthquake

• extreme hear and acid rain

• deccan traps