Natural Selection & Phenotype I will understand how natural selection acts on the phenotype rather the genotype of an organism. MT: Allele frequency

Review of Phenotype Phenotype = physical traits of an organism Expression of genotype Salamander's P'type: Orange, 4 limbs, 1 tail, 2 dark eyes, smooth, spots on posterior side

Review of Phenotype Describe this fox's phenotype? Describe this fox's fitness.

More practice... What is an adult penguin's phenotype? Does an adult penguin or a chick have better fitness? Defend your answer.

Phenotype & Natural Selection Compare box 1, 2, & 3. Which mouse is has a higher survival rate? Why?

Types of Natural Selection 1. Directional Selection 2. Stabilizing Selection 3. Disruptive Selection

1. Directional Selection Environment favors individuals with phenotype at one extreme Ex: 1. Giraffe neck Longer necks have better chance of surviving and reproducing so over time the whole species has a longer neck

1. Directional Selection Favors phenotype at one extreme Over time the whole population starts having the phenotype of one extreme

2. Stabilizing Selection Environment favors phenotype that is average (most common) Ex: human baby size at birth (7-9 lbs is best) Big babies have difficult time coming out. Small babies have difficult time surviving.

2. Stabilizing Selection Favors average phenotype Over time, majority of individuals are average

3. Disruptive Selection Environment favors phenotypes at both extremes Ex: Darwin's finches Some islands did not have the food needed for mid size beaks so small and large beaks were favored because they could find food

3. Disruptive Selection Favors phenotypes of both extremes Over time, can lead to speciation

Critical Question: How are natural selection and phenotype connected?

Answer: In nature, those who are best fit, have the best phenotype, thus have a higher chance of surviving and reproducing. So, natural selection directly acts on an organism's phenotype.

Planet Earth clip http://www.youtube.com/watch?v=A0E6geAq1k8 1.What was the phenotype of the wolf that was successful? 2. What type of selection (directional, stabilizing, or disruptive) most likely acted on the caribou's fur color?