1. Patterns in Evolution

2. Key concept : Evolution occurs in patterns
Evolution through natural selection is not random.
Natural selection can have direction.
The effects of natural selection add up over time.

3. Convergent Evolution Survival advantage to a particular environment.
Defined: Describes evolution toward similar traits in unrelated species.
Survival advantage to a particular environment.
Ex: Tuna (fish) and dolphins (mammals). They are an unrelated species living in a similar environment, the ocean.
Faced similar evolutionary pressures.

4. Kaibab Squirrel (Grand Canyon)
Divergent Evolution
Kaibab Squirrel (Grand Canyon)
ancestor
red fox
kit fox
Defined: Describes evolution toward different traits in closely related species.
Cause: Different environments

5. Coevolution
Defined: Two or more species evolve in response to changes in each other
Evolutionary paths become connected
Both species receive benefits from the other as a result of adaptations.
Ex: Plants and Insects
Plants: provide insects with nectar
Insect: transfers pollen from one plant to another

6. Coevolution Continued…
Coevolution can occur in competitive relationships, sometimes called an evolutionary arms race.
Example: Crab vs. Snail & Bacteria vs. Humans

7. Evolutionary Arms Race Continued… Antibiotic Resistance
Bad
Good
Antibiotics: chemicals designed to kill bacteria
Produced by other microorganisms to fight bacteria
Antibiotic Resistance: Bacteria are adapting to the use of antibiotics
Overuse & misuse speeds up the process
Importance: Bacteria infections are becoming harder to treat

8. Most bacteria killed
Strong Survive
Bacterial Resistance
Strong Reproduce

9. Species Can Become Extinct
Defined: The elimination of a species from Earth.
Mass Extinctions:
Cause: Catastrophic events
Ice Age, Meteorites
Destroys many species at global level
Very severe
Rare but much more intense
At least 5 mass extinctions in last 600 million years
Background Extinctions:
Cause: Local changes in environment
Forest fires, habitat destruction.
Affects a few species in a small area
Less severe.
Occur at roughly the same rate as speciation

10. How Fast Does Evolution Occur?
No exact time frame
Gradualism: slow & steady change of 1 species into another
Small changes continually build
Punctuated Equilibrium: Rapid periods of evolution
Due to sudden environment change
Ex: Mammal diversity exploded after dinosaur extinction
Examples of both models exist

11. Gradualism of the Horse

12. How Fast Does Evolution Occur?
To radiate = to s-p-r-e-a-d out
Adaptive radiation: A process of evolution where one species can split into a number of different species.
Ancestral species diversifies into many descendent species
Descendent species usually adapted to different (wide range of) environments