Evidence for Evolution

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Evidence for

Evolution

Evidence for Evolution•Homology•Convergent evolution•Vestigial structures•Selective Breeding•Fossils•Embryology•DNA

Homology– Evidence of a Common Ancestor

• All of these evobots used the same red pieces that were present in their ancestor but not in earlier generations.

Vertebrate Limb Homology

Homology– Evidence of a

Common Ancestor

• We can see the steps between the reptile jaw and the human ear– they use what appear to be the same bones.

• When we see very similar parts in many living things, we gain evidence of their common ancestor and its characteristics.

• This is especially true when similar parts have different functions

Convergent Evolution

Divergent Evolution• Most evolution appears to be divergent– those closest to

the ancestral state are the most similar and organisms become more different as they evolve.

• This is not always the case. Sometimes, organisms come up with similar solutions to the same environmental problems.

Convergent EvolutionSimilar Structures for Similar Environments

• Most evolution is Divergent (species with similar traits have a common ancestor)

• According to Natural Selection, species evolve traits that help them survive in an environment.

• Sometimes, the requirements to survive in an environment are so strong that several VERY DIFFERENT SPECIES evolve traits that function in similar ways. This is convergent evolution.

Vestigial Structures

• Structures that are no longer useful, such as our appendix,, or the fingers on a whale are vestigial structures. They are evidence that these creatures evolved from other creatures that used these structures.

Other Flightless Birds with Wings

Kakapo(New Zealand)

Kiwi(New Zealand)

Cassowary(New Giunea)

Vestigial Human Characteristics

Spine Structure and tailbone

Body Hair and Goosebumps

Eyes in Blind, Cave-Dwelling Creatures

Selective Breeding• We humans have been selecting characteristics of pets and domesticated plants and animals for thousands of years. In many cases, we have dramatically changed how species look and behave.

• In some ways, animals do this too both through sexual selection and natural selection itself.

Selective Breeding or Artificial Selection

Selective Breeding in Agriculture

Cows are bred for beef or milk production (Video).

Corn has been selectively bred for 600 to 10000 years by people in North America.

Selective Breeding

Animals Do Selective Breeding too! Sexual Selection

Peacock Colors

Bowerbird Nests

In many animal species, females choose males that win competitions with other males. Alleles that help them win these competitions are then selected for.

Pollinators “select” flowers that are more appealing. Bees tend to select blue and purple flowers whereas humming birds prefer red.

Natural Selection as a form of Selective Breeding–

Just on Accident

Fishes “select” the angler fish with the most attractive lure--- by getting eaten by them!

Natural Selection as a form of Selective Breeding–

Just on Accident

Any prey species, inadvertently selects characteristics in a predator that allows the predator to catch and eat them.

Fossils

• There are fossils of many creatures that no longer exist today. They often show intermediate forms between species that exist today and their ancestors.

• We also see that fossils deeper in the earth only show simpler creatures with more advanced life forms closer to the surface.

Archeoptryx

Fossils

Whales in the Fossil Record

Whale Fossils– Migration of the Blowhole

Fossil Human Ancestors

Fossils

Embryology

•Embryos of some animals show traits that are not present in adults such as gills and tails in humans. These are evidence that these traits were found in our ancestors.

Embryology

Tail in Human Embryo

Hind Limb buds in Dolphin

DNA Similarities If you look at the DNA of living creatures

you can see the similarities. Many sections of DNA are don’t code foe

anything at all. These sections are similar to working or useful sections in other creatures.

Even in human DNA, you can see the broken parts of code that were important in an organism long ago

DNA Similarities

PseudoGenes Pseudogenes are sections

of chromosomes that resemble functioning genes in related creatures, but lack start codons (or promoters) and are never translate into proteins.

For example, genes for gills may be present in mammals, but in a non-functional, mutated, broken form.

Predictable Differences in DNA Humans and other chimps split from dogs

long before they spit from each other. We would expect to see more genetic

similarities between chimps and humans than either would have with dogs.

We would ALSO expect humans and chimps to show similar difference from chimps, and they do.

Evidence for Evolution•Homology•Convergent evolution•Vestigial structures•Selective Breeding•Old Earth •Embryology•Fossils•DNA

Evidence for Evolution

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