Phenotype, Genotype and the Environment Unit 6 Phenotype, Genotype and the Environment

Definitions Regarding Evolution: A change in allele frequency(genes) over time. 1 What are the Main Definitions Regarding Evolution Descent with Modification: All life on earth descended from a common ancestor over millions of years. 2

3 Microevolution vs. Macroevolution: Microevolution: Shorter periods of time. Changes are within a species. Macroevolution: speciation (formation of new species) occurs.

Cladogram or phylogenetic tree: Illustrates descent with modification. 4

Natural selection: Those with advantageous traits Species: A group of organisms that interbreed. 5 Natural selection: Those with advantageous traits survive and reproduce. 6 Bell Curve: It is a graph of normal-distribution. In any normal population this would be the distribution of traits that you would expect 7 34% 14% 2%

Bell Curve for Height on A Football Team

Important Points About Evolution 1 Microevolution leads to macroevolution (descent with modification). Natural selection does not have a direction, scheme, or a grand plan. 2 Natural selection is the driving force behind evolution. 3

4 Selection occurs due to an organisms phenotype, not genotype. Why? The phenotype is exposed to the environment not the genotype. Color, size, strength, eye-sight, etc. The environment doesn’t “see” recessive alleles. They are hidden, but still passed on.

Stabilizing Selection: Favors the average and eliminates the extremes. The 3 Types of Natural Selection Babies that are too small are not strong enough, but if too large, complications in delivery.

Stabilizing Selection

2. Directional Selection. Favors one of the extreme variations of a trait.

3. Disruptive Selection: Favors both extreme variations of a trait.

Gene Flow - The loss or gain of alleles in a population due to the migration of fertile individuals or between gamete populations. When an organism moves from one area to another, it takes its alleles with it.

Founder Effect: A small group branches off or colonizes a new area. Population Bottleneck: A large population is dramatically reduced to a few individuals. . Genetic Drift = change in the gene pool that takes place as a result of chance