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Copy of Evidence for Evolution
Transcript of Copy of Evidence for Evolution
Darwin's book provides lots of evidence for evolution.
The evidence comes from many areas of study.
5 of the most imporant sources of evidence include the
- fossil record
- developmental biology.
The Fossil Record
(similarity in structure)
All known fossils make up the fossil record.
Fossils are preserved remains left by an organism found in sedimentary rock.
Fossils can reveal a pattern of gradual change in organisms from past to present.
The study of the locations of living things.
Organisms living in similar environments tend to adapt in similar ways because environments shape evolution.
Comparisons of DNA or proteins can show hereditary relationships among organisms.
Genes, like the fossil record, show a pattern of gradual change over time.
The study of bodily structure.
Certain similarities in structure among species provide clues to evolutionary history.
For example, the forelimbs of all mammals consist of the same skeletal parts.
Human arms, cat forelegs, whale flippers, and bat wings all have the same combination of bones.
The functions of these forelimbs differ.
The study of the ways organisms develop from embryos.
Similar patterns of development are evidence of a common ancestor.
The evidence shows two important things:
1. Evolution occurs
2. Common ancestry
Younger rocks are layered ontop of older ones thus, the position of the fossils in the rock can reveal their relative age.
Fossil record is a chronological collection of life's remains in the rock layers, recorded during the passage of time
Fossil evidence suggests that ancient whales evolved evolved from ancestors with hind limbs.
Paleontologists - scientists who study fossils have found many ancestral life forms that link the past with the present.
- For example fossil evidence supports the hypothesis that whales (which have no hind limbs) evolved from land dwelling ancestors that had 4 limbs.
- The oldest fossil evidence of life consists of chemical traces in rocks from Greenlan that are 3.8 billion years old
Differences & similarties between organisms in different parts of the world were one of the main observations that Darwin saw on his voyage.
These observations suggested to Darwin that today's organisms evolved from ancestors.
Just as fossil record documents the history of species of the past, the geographic distribution of organisms serves as a clue to how modern species may have evolved.
Example - consider two islands with similar environments in different parts of the world. The species on the island have more similarities to species on the nearest mainland than they do to the species on the other island.
We learned in chapter 11 that your DNA sequence helps record an organism's ancestry.
- Siblings have very similar DNA and protein sequences are very similar.
- If you are unrelated then individuals of the same species show more differences.
If two species have genes and proteins with sequences that match closely, biologists can conclude that the sequences must have been inherited from a relatively recent common ancestor.
In contrast, the greater the number of differences in DNA between species, the less likely they share as close ancestor.
Comparison of the human and chimp DNA sequences for the gene that encodes the hormone leptin (which is involved in the metabolism of fats) reveals only five differences in 250 nucleotides
Data supports the hypothesis that humans are more closely related to primates than other vertebrates. There is only a 5% difference in the total DNA between these 2 species.
Such similar structures in species sharing a common ancestor are called Homologous Structures.
_Structures that originally functioned one way in ancestral species become modified as they take on new functions
Some structures have a major role in one species but are less important in another.
- Vestigial structures
are those structures that may have had an important meaning once upon a time but now serve no use.
Analogous Structures - similarities among unrelated species that results from convergent evolution.
- Structures function the same but they look different, different species. Happens due to the location
The similarities of these structures during development support the evidence that all vertebrates evolved from a common ancestor.