Biological Evolution by Natural Selection

Biology: Mr. McFadden

4-24-10Write the Red

Population a localized group of

individuals belonging to the same species

Wildebeest

What is a species? Biological species concept

(Mayr): a population or group of populations whose members have the potential to interbreed and produce viable, fertile offspring (genetic exchange is possible and that is genetically isolated from other populations)

Biological EvolutionWhat is needed:1. Genetic Variation: Differences that occur

in a population between individuals.3 Sources of Variation:

Mutations are changes in the DNA. A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations.

Gene flow is any movement of genes from one population to another.

Sex can introduce new gene combinations into a population during meiosis & fertilization.

Fig. 18-2a, p.285

Variation in Phenotype

Fig. 18-2b, p.285

Variation in Phenotype

Fig. 18-2c, p.285

Variation in Phenotype

Fig. 18-2d, p.285

Variation in Phenotype

Fig. 18-2e, p.285

Variation in Phenotype

Variation can exist in:•Form, Shape, or Color•Speed, Intelligence, or Strength•Behavior or senses•Beak Size!!!•The possibilities are endless…

Variation in Phenotype

2. Heritability: This variation can be passed to offspring.

3. Fitness: some individuals are better able to survive and pass their genes to their offspring when they reproduce.

4. Natural Selection: Individuals that survive and reproduce (highest fitness) are those with the genes that are best adapted to their environment (adaptation).

Selective Pressures:o Environmental Change

i. Temperature or Habitat Changeii. Earthquakes or Volcanoes

Selective Pressure Cont..

Predation

Selective Pressure Cont..Limited Resources

i. Food, Water, and/or Habitat

Review of Biological Evolution

1. Variation2. Heritability3. Fitness4. Natural Selection

Review: Selective Pressures

A pressure put on a species to survive such as an environmental change, predation, or limiting resources.

Go to the following website to complete the Planet Earth Evolution “Mini Lesson”

http://dsc.discovery.com/convergence/planet-earth/video-player/video-player.html

Your Task Today

Using your Notes and the Planet Earth Videos on Computers in the back, prepare a “mini-evolution” lesson to present to the class TODAY, with your video.

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