Natural Selection and Evolution Why two types of

Natural Selection and Evolution!

Why two types of clover? • • What advantages does the striped clover have? The plain? How does cyanide help/hurt these plants in different habitats?

Organisms have variation • • Same species (Trifolium repens), different characteristics Variation = differences among individuals of one species; different forms of same trait (ex: eye colors)

Variation helps organisms adapt • • Adaptation = inherited characteristic, increases an organism’s chance for survival Fitness = ability of an individual to survive and reproduce in its environment • Which clover is more “fit? ” Why?

Variation allows for Selection • • Humans and nature “choose” which organisms win and get to procreate Artificial selection = human select most useful variations, allow those to reproduce • • ex: race horses - what trait would be selected for? ex: broccoli and other veggie friends

The struggle for existence • • Resources are limited, so only some can survive Natural Selection = individuals better adapted to their environment survive, reproduce, and pass on their genes • • AKA “survival of the fittest” leads to change over time (EVOLUTION!)

Natural Selection Ex: Darwin’s Finches Beak size and shape vary - all descended from common ancestor but changed over time

Evolution by Natural Selection • Descent with modification = over time, natural selection produces organisms with differences from their ancestors • • Different food sources, habitats, body parts, behaviors Implies that living things are all related, have a common ancestor (common descent)

Common Descent - one ancestor in the past Phylogenetic tree - distance between organisms is directly related to differences in genes (short distance = few differences, long = many)