The Origin of Species Chapter 24 Biology – Campbell Reece

What is a species? Biological species concept: Biological species concept: Reproductive isolation Reproductive isolation

What is a species?

Prezygotic Barriers What are prezygotic barriers? What are prezygotic barriers? Habitat isolation Habitat isolation Behavioral isolation Behavioral isolation

Habitat and Behavioral Isolation

Prezygotic Barriers Temporal isolation Temporal isolation Mechanical isolation Mechanical isolation Gametic isolation Gametic isolation

Temporal, Mechanical & Gametic Isolation

Postzygotic Barriers What are postzygotic barriers? What are postzygotic barriers? Reduced hybrid viability Reduced hybrid viability Hybrid breakdown Hybrid breakdown

Reduced Hybrid Viability & Hybrid Breakdwon

Postzygotic Barriers Reduced Hybrid Fertility Reduced Hybrid Fertility

Reproductive Barriers

Modes of Speciation Allopatric speciation Allopatric speciation Sympatric speciation Sympatric speciation

Conditions for Allopatric Speciation More likely if the population is both small and isolated More likely if the population is both small and isolated Barrier has to be significant enough to not be crossable Barrier has to be significant enough to not be crossable They must become different enough that they can no longer interbreed They must become different enough that they can no longer interbreed

Adaptive Radiation What is it? What is it? Especially common on island chains such as the Galapagos and the Hawaiian Islands Especially common on island chains such as the Galapagos and the Hawaiian Islands

Sympatric Speciation in Plants When meiosis goes wrong… When meiosis goes wrong…

Sympatric Speciation in Animals Polyploid speciation in animals? Polyploid speciation in animals? Dependent on different resources Dependent on different resources Nonrandom mating Nonrandom mating

Punctuated Equilibrium vs. Gradualism

Microevolution vs. Macroevolution Microevolution Microevolution Macroevolution Macroevolution