Origin of species

• What is a species?• Maintenance of

species.• Modes of speciation.• Rate of speciation.

Species & Species concepts• Biological Species:• A population or group

of populations whose have the ability to interbreed with one another in nature, producing viable offspring

• Evolutionary species: fossil record, morphology

Maintenance of species

• Reproductive isolating mechanisms

• Pre-zygotic• Post-zygotic

Pre-zygotic barriers

Post-zygotic barriers

Modes of speciation

Modes of speciation

• Allopatric speciation• Geographic isolation• Barriers:• Rivers, mountains,

Geographic isolation

Adaptive Radiation

Sympatric speciationAutopolyploid Allopolyploid

Rate of speciation