1. Mechanisms of Evolution
Natural Selection

2. Objectives
7C analyze and evaluate how natural selection produces change in populations, not individuals
7D analyze and evaluate how the elements of natural selection, including inherited variation, the potential of a population to produce more offspring than can survive, and a finite supply of environmental resources, result in differential reproductive success

3. In Question:
Answer the following “IN” question on your handout:
What is natural selection and what impact does it have on a population?

4. Natural Selection
Individuals that are better adapted to their environment survive, reproduce and pass on their genes.
Acts on populations of organisms, not individuals.

5. Darwin
Was a British Naturalist who traveled the globe on the HMS Beagle.
Gathered evidence to support his theory that populations evolved as a result of Natural Selection.
Published his findings in a book titled “On the Origin of Species”

6. Darwin’s Trip on the HMS Beagle

7. Darwin’s Finches

8. Darwin’s Finches Cont’d
Darwin’s Finches showed evidence of common ancestry. All finches shared a common ancestor from South America. As they migrated to different islands in the Galapagos, those that were best adapted for their environment survived and reproduced.
This shows ADAPTIVE RADIATION.

9. Galapagos Finches

10. Natural Selection A.K.A. “Survival of the Fittest”
Organisms with desirable phenotypes will survive and reproduce in their environment.

11. Natural Selection Acts on Populations, not individuals. Occurs because
Individuals within a population vary.
Some traits are better than others
Those traits are inheritable

12. Genetic Variation Variation of alleles among and within populations.
Ultimate source is Mutations! Not all mutations are bad or lethal!

13. Examples of Adaptations
Mimicry- resembling another organism
Camouflage- blending into your environment.

14. Mimicry
When one organism mimics another in terms of appearance or behavior.
Ex: Viceroy and Monarch and Coral and King Snakes

15. Camouflage
Organisms blend in with their environment to increase chances of survival

16. Elements of Natural Selection
Inherited Variation- Variations have to be coded for in the DNA so that they can be passed from parents to offspring.
Number of Offspring- more offspring equals an increase in odds for survival. This is typically seen in plants and insects.
Finite Amount of Resources- Limited resources such as space, water, food and mates can impact natural selection.
Differential Reproductive Success- Increased mating ensures genes will be passed down to offspring.

17. Complete “Out”…
EXPLAIN how natural selection works on populations and not individuals.
Be sure to use the terms: Natural Selection, Genetic Variation.
Also discuss how the elements of natural selection shape population.