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Evidences of EvolutionEvidences of Evolution
EvolutionEvolution
Genetic change in a Genetic change in a population over timepopulation over timeGenetic change in a Genetic change in a population over timepopulation over time
Charles DarwinOn his journey around the world, Darwin found evidence of gradual change (evolution).
Darwin cited evidences he found in fossil records, homologous structures, and geographic distribution.
Evidences of Evolution
Today most evidences for evolution are grouped into five main categories:
Fossil Record
Biochemical
Comparative Anatomy
Biogeography
Observable Events
Fossil Record
• Paleontology- the study of fossils
• Fossils – remains or traces of organisms that lived long ago
• Remains: ex. bones, teeth, or shells
• Traces: ex. burrows, footprints, or imprints
Most fossils are found in layeredsedimentary rock
Oldest fossils areon the lowest layer
Fossil Record
• The fossil record is incomplete– Some environments are less likely to cause
fossil formation– Bodies of some organisms decay faster than
others
• The fossils that have formed present strong evidence that evolution has taken place– Relative and radiometric dating
Fossil Record
Comparing fossils from different layersshows:
Life on Earth has changed
Increased number of life forms
Fossil Record
Biochemical Evidence• Universal Genetic Code
– Triplets of DNA nitrogen-base sequences that code for specific amino acids
The similarity of triplet DNA codes making-up amino acids shows:a probable common ancestor for all life on Earth
Biochemical Evidence• Amino Acid Sequencing
The amino acidsequence in aparticular protein iscompared betweenorganisms. Species that have fewdifferences are thought tohave shared a commonancestor more recently. Number of differences
from human hemoglobin
45
167
8
27
125
Species Difference
Gorilla 1
Rhesus Monkey 8
Mouse 27
Chicken 45
Frog 67
Lamprey 125
Amino Acid Difference in Hemoglobin
Compared with Human
Human hemoglobin has 146 amino acids
Amino Acid Sequencing is probably
the STRONGEST evidence for relationships
among organisms.
Biochemical Evidence
What organism belongs at
each branch?
• Cladogram: diagram that shows the evolutionary relationship among a group of organisms.
Species Difference
Gorilla 1
Monkey 8
Mouse 27
Chicken 45
Frog 67
Lamprey 125
Amino Acid Difference in Hemoglobin
Compared with Human
Number of Amino Acid Differences150
10050
040 2030 10
G
FE
DCBA
Common ancestor
Where would the common ancestor be?
Biochemical Evidence
Comparative Anatomy• Homologous structures- structures that share
a common ancestry; similar structures with different functions
TurtleAlligator
Bird
Mammal
Ancient lobe-finned fish Homologous structures show:an organism’s evolutionary pastand common ancestry
Comparative Anatomy
• Vestigial structures- structures that are present but diminished in size or function
Vestigial structures show:• an organism’s evolutionary
past• a common ancestor with
species that have similar structures that are still functioning
Examples: Human tailbone, snake pelvic bones and limb bones, and some cave-dwelling salamanders have eyes even though members of the species are completely blind.
Comparative Anatomy
• Embryology- embryos of different species may appear similar in early stages of development
Example: vertebrate development– Tail buds and
pharyngeal pouches
Comparative Anatomy
• Comparison of similarities in embryos can show:
relationships to a common ancestor
Biogeography• Geographic Distribution of Organisms
• Organisms living widely apart (even different continents) may be similar because they share a common ancestor
Beaver
Muskrat
Beaver andMuskrat
Coypu
Capybara
Coypu andCapybara
Observable Events• Observable events show that evolution is an ongoing
process• Some changes in species have been observed and
studied:
Peter & Rosemary Grant’s Study of Beak Size Shift in Darwin’s
Finches
H. Kettlewell’s Study of Peppered Moth Color
Shifts