Do Now: 5/8 (HW check – later, during video) Objective: Identify and describe the three types of natural selection: directional, stabilizing, and disruptive. Task: 1.What are the three conditions required for natural selection to occur?

Quick Review Natural selection is the evolutionary process by which favorable traits that are heritable become more common in successive generations of a population of reproducing organisms, and unfavorable traits that are heritable become less common.

3 conditions for Selection Natural selection for or against a specific trait can occur only if the following 3 conditions are met.

1. Variation

2. Differential Mortality Some phenotypes die more than others.

3. Heritability A trait must be heritable (genetic) to be selected for / against

Types of selection Depending on which phenotypes are successful in increasing survival and reproduction in a certain environment, different types of selection can occur.

Another Look at the 3 types of Selection

EvoTutor.org Computer simulations (models) of evolution are very powerful tools… let’s check one out!

Adaptation: The Result of Natural Selection Adaptation: the process by which a population of organisms becomes better suited to its habitat or niche as a result of natural selection Adaptation: a specific feature that makes an organism better suited to its habitat or niche. Example: Through the process of adaptation, horses developed the adaptation of flat teeth for grinding tough plants they eat.

Male fiddler crabs attract females by quickly waving their large front claw. If a claw is lost in a fight or accident, they quickly grow a hollow claw of equal length. Because the new claw is lighter, they can wave it faster. A male fiddler crab is shown below. The male fiddler crab’s new claw can be described as A.a clone B. a genotype C. an adaptation D. a dominant trait

Artificial Selection (Human-directed)

Exit ticket 1. What are the three conditions that must exist for selection to occur? 2. What type of selection did we see in the construction paper simulation yesterday? 3. Define: adaptation