1. EVOLUTION MECHANISMS

2. NATURAL SELECTION
Environment favors the individuals that have the better adapted traits
Those that lack traits that help them survive will decrease in number
EX: peppered moths

3. DIVERGENT EVOLUTION
Several species evolve from a single ancestral species
Individuals migrate long distances over time and adapt to different environments
EX: horses; donkeys; zebra
EX: black bear; grizzley bear; polar bear

4. ADAPTIVE EVOLUTION
Several species evolve from a single ancestral species but within close proximity to each other
Become adapted to specific environmental conditions within similar habitats
EX: finches of Galapagos islands

5. CONVERGENT EVOLUTION
Unrelated species adapt similar features because they have adapted to similar environments
EX: sharks; fish; dolphins
Different ancestors
ANALGOUS STRUCTURES: fins for swimming in aquatic environment

7. COEVOLUTION

9. STABILIZING SELECTION
Individuals with average traits are favored over individuals with extreme traits
EX: clutch size in birds…birds that lay an “intermediate” amount of eggs have the highest survival rate…if mother bird lays too many eggs…some will starve…too few and lower number that will survive to reproduce themselves

10. DIRECTIONAL SELECTION
One extreme trait is favored
EX: wood peckers with longer beaks can reach deeper into tree bark & most likely to get enough food
EX: faster cheetah most likely to catch its prey

11. DISRUPTIVE SELECTION
Individuals at both extremes favored over the intermediate trait
EX: smallest spider & largest spider population increase over medium spiders…largest spiders too big for many birds to eat…smallest spiders harder to find/not worth the effort…but medium spiders just right!

12. Identify the type of selection…
1. DIRECTIONAL SELECTION
2. STABILIZING SELECTION
3. DISRUPTIVE SELECTION