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What do you

notice?

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What do you notice?

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What do you noticed?

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What do you notice?

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______________________of Evidence for the Theory of

Evolution

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1.____________ Evidence of Evolution

• Fossils

• Rock fossils are created when three events occur– organism buried in sediment– calcium in bone or other hard

tissue mineralizes– surrounding sediment hardens to

form rock

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• Absolute dating:

• Relative dating:

• Isotopes, like U238, transform at precisely known rates into nonradioactive forms.

• The rate of decay is known as an isotope’s half-life

Fossil Evidence of Evolution

8Radioactive Decay

Fossil Evidence of Evolution

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Fossil

records

document

the course

of life through

time

Fossil Evidence of Evolution

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• Fossils

• The oldest known bird fossil is the

• It is intermediate between bird and dinosaur• Possesses some ancestral traits and some

traits of present day birds• Archaeopteryx was first found in 1859

Fossil Evidence of Evolution

11Fossil of Archaeopteryx

Fossil Evidence of Evolution

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Recent discoveries–Four-legged aquatic mammal

• Important link in the evolution of whales and dolphins from land-dwelling, hoofed ancestors

–Fossil snake with legs–Tiktaalik: a species that bridged the gap

between fish and the first amphibian–Oysters: small curved shells to large flat

shells

Fossil Evidence of Evolution

13Whale “missing links”

Fossil Evidence of Evolution

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Evolutionary change in body size and toe reduction of horses

Fossil Evidence of Evolution

HOMOLOGOUS STRUCTURE

• Similar features that originate in a shared ancestor (derive from same embryonic structure)

• Can result from modifications that change an original feature to 2 extremely different types (wing and arm)

Homologous structures

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Anatomical Evidence for Evolution• 2. Homologous structures:

• structures with common evolutionary origins (can be similar in structure, function, or both)

• The bones in the forelimb of mammals are homologous structures

• Different functions, same ancestor structure

17Homology of the bones of the forelimb of mammals

Anatomical Evidence for Evolution

ANALAGOUS FEATURE

• Serve identical functions and look similar• No anatomical/embryological similarity• Wing developed independently and

differently in more-recent ancestors of each animal

3. Analogous structures:

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• Vestigial structures:

Anatomical Evidence for Evolution

Vestigial structures of a whale: hind leg

bones!?

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Humans• Muscles for wiggling ears (similar muscles that

animals use to move ears to hear predators or prey)• Tail bones present in human and all vertebrate

embryos. In humans, the tail is reduced; most adults only have three to five tiny tail bones and, occasionally, a trace of a tail-extending muscle.

• Appendix Structure which presumably had a digestive function in some of our ancestors, like the cecum of some herbivores. In humans, it varies in length from 5–15 cm, and some people are born without one.

4. Vestigial Structures

Vestigial Structures cont.• Wisdom teeth There are two possible reasons why the

wisdom teeth have become vestigial. The first is that the human jaw has become smaller than its ancestors -and the wisdom teeth are trying to grow into a jaw that is much too small. The second reason may have to do with dental hygiene. A few thousand years ago, it might be common for an 18 year old man to have lost several, probably most, of his teeth, and the incoming wisdom teeth would prove useful. Now that humans brush their teeth twice a day, it's possible to keep one's teeth for a lifetime. The drawback is that the wisdom teeth still want to come in, and when they do, they usually need to be extracted to prevent any serious pain.

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Vestigial Structures cont.

Pythons • have tiny femurs (leg bone)Manatees• Fingernails on their finsBlind cave fish• Nonfunctional eyes

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• Strongest anatomical evidence supporting evolution comes from comparisons of how organisms develop.

• Early vertebrate embryos possess pharyngeal pouches (gill slits) that develop into:– In humans: glands and ducts– In fish: gills

Anatomical Evidence for Evolution

24Developmental similarities reflect descent from a

common ancestor

5. ________________ Evidence for Evolution

EMBRYOLOGY

6. • All • Two closely-related organisms will have similar DNA,

RNA, and protein (amino acid) sequences.• This also gives evidence of a common ancestor.

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Convergent Evolution• Biogeography: the study of the

geographic distribution of species–Some plants and animals have similar

appearance but are only distantly related• Convergent evolution: the independent

development of similar structures in organisms that are not directly related

• Convergent evolution is usually seen in animals and plants that live in similar environments

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• Marsupials and placentals–Marsupials: young are born in an

immature condition and held in a pouch until they develop

–Placentals: young are not born until they can safely survive in the external environment

Convergent Evolution

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Convergent Evolution

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Convergence among fast-swimming predators

Convergent Evolution