Bellwork

Spur

Imagine that you are traveling in Madagascar when you find the plant to the left. You see that the plant has an unusually large spur containing nectar in its tip. You remember learning in science class that some moths feed on nectar. Draw a picture of what you think a moth may look like that feeds on this plant.How might natural selection bring about the evolution of this orchid and the moth?

KEY CONCEPT Evolution occurs in patterns.

REMEMBER: Evolution through natural selection is not random.

• Natural selection can have direction.• The effects of natural selection add up over time.

The 3 patterns we’re going to discuss today are:

1. Coevolution2. Convergent Evolution3. Divergent Evolution

– We’ll also look at how these might be seen in the fossil record

Coevolution

• Sometimes organisms that are closely connected to one another by ecological interactions evolve together.

• An evolutionary change in one organism may also be followed by a corresponding change in another organism.

• The process by which two species evolve in response to changes in each other over time is called coevolution.

Co-evolution

Species A evolves an adaptation in response to

species B

Species B evolves in response to the adaptation

of species A

Coevolution

Coevolution can occur with species that help or compete with each other

The Star Orchid and the

Hawk Moth

• Mimicry occurs when one organism evolves to look like the other in order to benefit itself. The mimic benefits from the situation while the organism it mimics in unaffected.

Example: Orchid flowers that mimic female wasps

Mimicry is another example of coevolution

Convergent Evolution

• Convergent evolution describes evolution toward similar traits in unrelated species.

• When two species are similar in a particular characteristic, it’s only convergent evolution if their ancestors were not similar

Convergent Evolution

Divergent Evolution

• Divergent evolution describes evolution toward different traits in closely related species. Divergent evolution can lead to speciation.

kit fox

ancestor

red fox

Changes in the frequency of a gene in the gene pool initially leads to microevolution. Microevolution

refers to a small change in a population over a short amount of time.

Many small changes eventually lead to macroevolution. Macroevolution refers to the sum

total of many changes that transform organisms over a long period of time.

Macroevolution leads to speciation or the creation of a new species. When an evolving population can no longer interbreed with the original population, a new

species is formed.

Things to Consider:• Stasis - The organisms in the fossil record looks the

same from when they appear to when they disappear;

• Sudden appearance - When a species does not arise by gradually changing steadily from its ancestors; it appears all at once and fully formed.

• Sequential nature – Based on the layers of rock, we sequence organisms in the fossil record.

• What might cause stasis or sudden appearance?

So what about the fossil record…

WHICH PATTERN IS IT? coevolution convergent evolution divergent evolution

divergent evolution

The Galápagos finches evolved through natural selection from a common ancestor into a wide variety of different looking species with different kinds of beaks

http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T014608A.gif

WHICH PATTERN IS IT? coevolution convergent evolution divergent evolution

coevolution

Hummingbirds have a beak just the right length to reach the nectar in a cardinal flower and as they feed their foreheads bump into the pollen structure. Cardinal flowers are red which hummingbirds can see, but bees can’t, and their pollen structure is at just the right height forthe hummingbird to pick up pollen as it feeds.

WHICH PATTERN IS IT? coevolution convergent evolution divergent evolution

Convergent evolution

Whales, sharks, and penguins all have streamlined bodies and fins/flipper for moving in water even though they belong in different animal groups (mammals, fish, and birds)

WHICH PATTERN IS IT? coevolution convergent evolution divergent evolution

Adaptive radiation OR divergent evolution

Beaver in North America and capybara in South America are closely related species living in very differentenvironments that have evolved to look differentover time.

Beaver

NORTH AMERICA

Muskrat

CapybaraSOUTH AMERICA

Coypu

Beaver

Muskrat

Beaver andMuskrat

Coypu

BIOLOGY by Miller and Levine Pearson Publishing

WHICH PATTERN IS IT? coevolution convergent evolution divergent evolution

divergent evolution

The tortoises on the Galapagos islands share a common ancestor, but over time they have become adapted for obtaining food in different habitats on different islands by having different neck lengths