evolution how gene pool change occurs. what exactly is a species? species: group of similar...

Evolution

How Gene Pool Change

Occurs

What exactly is a SPECIES?

•Species: Group of similar organisms that can breed and produce fertile offspring

•Example: Labrador and Pitt Bull

•Non-example: Horse and Donkey

The formation of a new species from a preexisting population is called: SPECIATION.

Changes in the gene pool can cause the population to evolve

Changes in the gene pool may be a result of many different causes

Causes of Change

Standard 8d• Students know reproductive or geographic isolation affects speciation.

Causes of Change1.Mutations in the genes (DNA) of

individuals causing new adaptations.

Are mutations always bad?

2.Reproductive Isolation: individuals unable to breed together: behavior or physical characteristics

Types of Reproductive Isolation

1. Geographic Isolation-population is split by some physical barrier: river, mountain, oceani.e. Albert & Kaibab squirrels of the Grand Canyon

2. Behavioral Isolation- two populations are capable of interbreeding but have different mating rituals or routines. i.e. eastern & western meadowlarks

3. Temporal Isolation- two or more species reproduce at different times.i.e. three types of rain forest orchids

Standard 8c•Students know the effects of genetic drift on the diversity of organisms in a population.

Sometimes the gene pool just changes……Genetic Drift is cause of evolution by random chance

No Natural Selection

Happens in small populations

2 types of Genetic Drift

1. Bottleneck Effect- a high percentage of a population is killed by a random act

reducing variation in the gene pool.2. Founder Effect- change in

allele frequencies as a result of the migration of a small

subgroup of a population