evolution preib evidence

7/28/2019 Evolution PreIB Evidence

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EVIDENCE, PLEASE


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1. Fossil Evidence

There is a lot of fossil evidence for evolution, but

the evidence is like a jigsaw puzzle with pieces

missing. But we can still see the overall picture.

Remember that a fossil is any evidence

of an organism that lived long ago.


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1. Fossil Evidence

There are several kinds of fossils:

preserved fossils, petrified fossils,molds, imprints, trace fossils and

whole preserved organisms. In

order to be preserved, most fossils

need to be buried in sedimentaryrock shortly after the organism

dies.


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1. Fossil Evidence

Imprint

Petrified tree

Mold


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1. Fossil Evidence

Preserv

ed Human

Ice Man

He died 5,300 years ago

Fossils provide evidence for evolution by

dating the fossils, and seeing organisms

change over the fossil record.


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1. Fossil Evidence

Fossils can be dated by two methods. The

first is simply comparing fossils in

sedimentary layers, called relative dating.The oldest fossils are those in the lowest

layers. Younger fossils are those near the

top.


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1. Fossil Evidence

Fossils can be dated by two methods. The

first is simply comparing fossils in

sedimentary layers, called relative dating.

The oldest fossils are those in the lowest

layers. Younger fossils are those near the top.

Relative dating can only compare ages, not to

accurately Provide an age for any fossil


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1. Fossil Evidence

Radioactive Dating can give the absoluteage of most fossils. By testing radioactive

isotopes, a precise age can be determined.

Radioactive materials decay at a steady rate (so

steady and reliable, in fact, that the most accurate

clocks in the world use radioactive materials).

Carbon -14 works well for organic matter.


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1. Fossil Evidence

Carbon can datecarbon compounds

up to 60,000 years

old; Potassium can

date rocks over

100,000 years old;Uranium-lead

dating can date

rocks over 3 billion

years old!

An example of howradioactive dating

works using

potassium-40


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The U.S. Standard

of time. Its time

reading can be

found at:

Cesium Fountain Clock

http://nist.time.gov/
http://nist.time.gov/http://nist.time.gov/


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2. Anatomical Evidence

Relationships can be shown bysimilarities in anatomy. For

example, all mammals have very

similar anatomiesskeletons,

internal organs, etc.

Well look at four aspects

of anatomy; homologous

structures analogous

structures vestigialstructures embryo

comparison.


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A. Homologous StructuresA homologous structure is a modified structure that

is seen among different groups of descendants similar structure but different functions.

A good example is the bone structure of

mammals as seen here.


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A. Homologous StructuresHomologous structures are believed to have a

common evolutionary origin (a common ancestor).Homologous structures developed from the same

embryonic tissuechanged as the tissue matured


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Pendactyl Limbs

similar structures

but differentfunction


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B. Analogous Structures

Structures that are similar in function, but differentin structure are analogous structures.

A good example is wings. The wings of birds and moths are

very different in structure, but serve a similar function.


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B. Analogous StructuresAnalogous structures are believed to show that

similar environmental pressures resulted in similarsolutions, through different means.


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B. Analogous StructuresAnalogous structures are believed to show that

similar environmental pressures resulted in similarsolutions, through different means.

Wings for Flight different structural composition

Birds hollow bones

Butterflies wings made of chitin

Bats non-hollow bones


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2. Anatomical Evidence

C. Vestigial Structures


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C. Vestigial Structures

Structures that have a reduced function or no functionin an organism are called vestigial structures.


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C. Vestigial StructuresVestigial structures are believed to be

structures that were used in an ancestor.


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Why have eye bulbs in blindsalamanders?


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Humans have a tailbone!


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D. Embryo Comparison

D. Embryo comparison show similarities between

the embryos of different organisms. The more

similar two organisms are, the more similar they

appear in the embryonic state and the longer it

takes to see the differences.


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D. Embryo ComparisonCan you tell which embryo is human?


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All vertebrate embryos have gill slits andtails

Strongly supports the idea of a common ancestor!


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3. Genetic Evidence

Best Evidence


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3. Genetic Evidence

Genetic comparisons also help us to see

evolutionary differences & similarities.

By looking at the nucleotide sequences in

DNA, scientists can determine relationships

among species and individuals.


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3. Genetic Evidence

For example, orangutans and gorillas aregenetically 96.3% identical.

In other words, 3.7% of their DNA accounts for all of

their differences.


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Chimps have 1 extra chromosomecompared to humans, but karyotype andsequence data show that human

chromosome 2 resulted from a fusion ofchimp chromosomes 2A and 2B

Strongly supports the idea of a commonancestor


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3. Genetic EvidenceGorillas and Chimpanzees are 97.7% identical.

Chimps and humans are 98.2% identical.


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3. Genetic Evidence

Genetic comparisons provide the strongest singlepiece of evidence for evolution. A high level of

identical DNA indicates a close common ancestor.

All all living organisms have DNA


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Myth Busters!

Myth: Humans Evolved from Monkeys.

Not possible.

Humans and monkeys exist today. One could

not have come from the other. Chimps are closerelatives, but not ancestors. Humans evolved

from a primate that no longer exists.

evolution preib evidence

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