Unit 4Concept: Evolutionary theory and natural

Selection

EQ: How do populations adapt to changing environmental Conditions?

Natural Selection• Individuals in a population vary in many ways.• Some individuals possess features that

enable them to survive better than individuals lacking those features.

• More offspring are produced than can generally survive.

• EQ: How do populations adapt to changing environmental Conditions?

Fitness

• The relative ability of an individual (or population) to survive, reproduce and propagate genes in an environment

• EQ: How do populations adap to changing environmental Conditions?

gene pool • is the complete set of unique alleles in a species

or population.• A large gene pool indicates extensive

genetic diversity, which is associated with robust populations that can survive bouts of intense selection. Meanwhile, low genetic diversity (see inbreeding and population bottlenecks) can cause reduced biological fitness and an increased chance of extinction, although as explained by genetic drift new genetic variants, that may cause an increase in the fitness of organisms, are more likely to fix in the population if it is rather small.

• EQ: How do populations adapt to changing environmental Conditions?

Immunity

• Immunity to disease that occurs as part of an individual's natural biologic makeup

• This includes local barriers to infection such as skin, stomach acid, mucous, the cough reflex, enzymes in tears and saliva and skin oils

• EQ: How do populations adapt to changing environmental Conditions?