Day 17 October 24th Chapter 8 Scribd

8/3/2019 Day 17 October 24th Chapter 8 Scribd

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Day 17 October 24th Chapter 8

400 million years between humans

and our fish ancestors


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What made humans different?

Moved from inland

Africa to the shores

Collected shellfish, ate

fish (DHA) Your brain is mostly

composed of fat!

Mammals haveplacenta

Mammals drink milk


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http://evolution.berkeley.edu/evolibrary/news/060201_zebrafish
http://evolution.berkeley.edu/evolibrary/news/060201_zebrafishhttp://evolution.berkeley.edu/evolibrary/news/060201_zebrafish


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Five primary lines of evidence:

1. The fossil record

2. Biogeography

3. Comparative anatomy and embryology

4. Molecular biology

5. Laboratory and field experiments


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8.17 The fossil record

documents the process ofnatural selection.

Although it has been central to much documentation of the

occurrence of evolution, it is a very incomplete record


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In Darwins

time, it was

assumed

that thedeeper

down in the

earth a

fossil wasfound, the

older it was.

Relative

Dating


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Happened in North America 55 million years ago

Many branches, not just a straight line


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First found in

northern Canadaand estimated at

375 million years

old, Tiktaalik

fossils appear torepresent a

transitional phase

between fish and

land animals.


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8-18. Geographic patterns of speciesdistributions reflect their evolutionary

histories.


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History Matters

Who arrived first?

Are numerous different habitats available?

In Hawaii, it appears that a finch-like descendant of the

honeycreepers arrived 4-5 million years ago and rapidlyevolved into a large number of diverse species.

The same process has occurred and continues to occur in

all locales, not just on islands.


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8.19 Comparative anatomy andembryology reveal common

evolutionary origins.


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Ernst Haeckel (1834-1919)


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Homologous Structures


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Similarities common ancestor

Differences adapted to environment

For example, look at the hands offour primates: tarsier, gibbon,chimpanzee, and human. Despite thesimilarities in their hands, thedifferences are what makes eachmost suitable for its way of life. The

tarsier leaps and clings, and has largefinger pads to help it do this. Thegibbon swings from the trees, so haslong, strong fingers for swinging. Thechimpanzee may be able tomanipulate very crude tools with itsstubby thumb, but the humans

thumb faces the forefinger, whichprovides dexterity for countlesspurposesfrom threading a needleto mountain climbingfrom carvingwood to buttoning a shirt.


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Vestigial Organs

A vestigial organ is a part of the body that serves no use. The

appendix is one example of a vestigial organ; wings on an ostrichare another. The human body has several vestigial organs,

including the tail bone, wisdom teeth and muscles in the ear.


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Vestigial Structures


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Convergent Evolution

Analogous structuresall developed fromdifferent original

structures.


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8.20 Molecular biology revealsthat common genetic sequences

link all life forms.The genetic code provides our fourthline of evidence that evolution occurs.


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DNA Similarities and Differences

Related vs. unrelated individuals

The more distantly you and anotherindividual are related, the more your DNAdiffers.


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Scientists ask the questionDoes

race exist?

The Human Genome Project

found all humans to have a

99.9 % similar geneticcontent and identity, but this

is challenged by a new more

detailed research suggesting

a higher genetic diversity,with further medical and

evolutionary implications.


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DNA Similaritybetween Two Species

Compare their DNA sequences forindividual genes.

In Rhesus monkeys, 138 amino acids outof 146 are the same as those found in

human hemoglobin.


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Recency of Common Ancestry

Estimates of evolutionaryrelatedness made from:

Comparative Anatomy

Embryology The Fossil Record

Molecular Clocks


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8.21 Laboratory and field experimentsenable us to watch evolution in progress.

A fifth line of evidence for the occurrence ofevolution comes from multigeneration

experiments and observations.


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Changes in the Frequencyof the Various Alleles


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Day 17 October 24th Chapter 8 Scribd

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