Evolution and Behavior of

Species

Natural Selection

• Backbone of Darwin’s Theory of Evolution

• Drives evolution

• is the process by which organisms best adapted to their

environment survive and those less adapted are

eliminated.

• The nonrandom differential reproduction of genotypes

with selective forces in the environment.

Four components of natural selection :

• Variation

• Inheritance

• High rate of population growth.

• Differential survival and reproduction.

2 processes involved in Evolution

• Adaptation

– traits that confer an advantage to those individuals who leave

more offspring

• Speciation

– The smallest independently evolving unit.

SPECIATION

• Occurs when gene flow

within the common gene

pool is interrupted by an

isolating mechanisms.

Biological species concept

• defines a species as members of populations that actually

or potentially interbreed in nature, not according to

similarity of appearance.

Speciation

http://scienceblogs.com/evolvingthoughts/2007/03/11/basic-concepts-allopatry-and-s/

Sympatric Speciation

• Industrial Melanism

Main Features of Speciation

1. Reduced selection pressure

2. Isolation of subpopulation of the species so that

interbreeding with the main stock is prevented or at least

reduced.

3. The development of distinctive genotypes in

subpopulation as a result of some combination of

founder effect, drift and natural selections.

4. Reuniting of subspecies group with the parental stock but

without the resumption of interbreeding.

5. Intense competition between the two reunited groups so

that further divergence in the traits is hastened.

Domestication

Extinction

Causes of Extinction: Habitat Alteration

Hunting

Predator control

Mutation

Immigration

Individual Selection

Resource Prediction

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