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Bellwork. Imagine that you are traveling in Madagascar when you find the plant to the left . You see that the plant has an

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bellwork
Bellwork

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.

Spur

  • How might natural selection bring about the evolution of this orchid and the moth?
remember evolution through natural selection is not random
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
The 3 patterns we’re going to discuss today are:
  • Coevolution
  • Convergent Evolution
  • Divergent Evolution
    • We’ll also look at how these might be seen in the fossil record 
slide6

Co-evolution

  • 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.
slide7

Coevolution

Species A evolves an adaptation in response to species B

Species B evolves in response to the adaptation of species A

slide9

The Star Orchid

and the

Hawk Moth

mimicry is another example of coevolution
Mimicry is another example of coevolution
  • Mimicryoccurs 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

convergent evolution1
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
slide14

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

kit fox

red fox

ancestor

slide15

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.

t hings to consider

So what about the fossil record…

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?
slide19

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

WHICH PATTERN IS IT?

coevolutionconvergent 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

divergent evolution

slide20
WHICH PATTERN IS IT?

coevolutionconvergent evolution divergent evolution

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 for

the hummingbird to pick up pollen as it feeds.

coevolution

slide21
WHICH PATTERN IS IT?

coevolutionconvergent evolution divergent 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)

Convergent evolution

slide22

Beaver

Beaver

Muskrat

Beaver andMuskrat

Coypu

NORTH AMERICA

Muskrat

SOUTH AMERICA

Capybara

Coypu

WHICH PATTERN IS IT?

coevolutionconvergent evolution divergent evolution

Beaver in North America and capybara in South America are closely related species living in very different

environments that have evolved to look differentover time.

Adaptive radiation OR divergent evolution

BIOLOGY by Miller and Levine Pearson Publishing

slide23
WHICH PATTERN IS IT?

coevolutionconvergent 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

divergent evolution