What is Speciation?Speciation is the formation of new biological species, usually by the division of a single species into two or more genetically distinct one.

Four Types of Isolating MechanismsReproductive IsolationBehavioral IsolationTemporal IsolationGeographic Isolation

Reproductive IsolationReproductive Isolation is the

separation of a species or population so that they no longer interbreed and evolve into two separate species.

Members of a certain species share a common gene pool. Over time, genes are shared by interbreeding.

Over time, isolated gene pools diverge into separate species.

Behavioral IsolationBehavioral Isolation is a form of reproductive

isolation in which two populations develop differences in courtship rituals or other behaviors that prevent them from breeding.

Example: Eastern and Western MeadowlarkThe populations of the two subspecies

overlap in the midwest.

Behavioral IsolationMale birds sing a mating song that

females like, East and West have different songs. Females only respond to their subspecies song.

Temporal IsolationTemporal Isolation is a form of reproductive

isolation in which two or more species reproduce at two separate times.

Example: Northern Leopard Frog & North American Bullfrog

Mates in April Mates in July

Geographic IsolationGeographic Isolation is a form of

reproductive isolation in which two populations are separated by geographic barriers such as rivers, mountains or bodies of water, leading to the foundation of two separate subspecies.

Example: 10,000 years ago the Colorado River separated two squirrel populations.

Geographic Isolation Kaibab Squirrel Albert Squirrel

This resulted in a subspecies, but did not result in speciation because the two can still mate if brought together

ConvergenceConvergence occurs when species

evolve into a common phenotypic form due to a common need.

For example the diagram portrays a shark, ichthyosaurus, a penguin and a dolphin. These are fish, reptile. bird and mammal respectively . They all have a torpedo body shape, pectoral, caudal and dorsal fins. This is based on their common need to swim rapidly in an aquatic environment.

Divergent Evolution and Adaptive RadiationDivergence occurs when species

evolve in several directions away from a common ancestor. This happens usually to fill a vacant ecological niche. Also known as adaptive radiation.

Convergent or Divergent Evolution?

Convergent or Divergent Evolution?

What process is shown in diagram A? ExplainDivergent Evolution or Adaptive Radiation. It is because

one ancestral species has given rise to many new species

Why do the animals in diagram A look different from each other?

They have evolved to fit different niches.

What process is shown in diagram B? ExplainConvergent Evolution. It is because the three

organisms look similar but have been produced by separate evolutionary lines.

Why do the animals in Diagram B look similar to one another?They have evolved to fit similar niches.