do you think these two organisms evolved from a common ancestor? ◦ what evidence would you need to...
TRANSCRIPT
Do you think these two organisms evolved from a common ancestor? ◦ What evidence would you need to convince
yourself?
Layers of rock contain fossils◦ Newer layers of rock cover older ones◦ Creates a timeline
Fossils can show a record of organisms that lived on Earth over a long period of time
• Many fossils link early extinct species with species living today
• Example: Tiktaalik- “missing” link between land and sea animals.
A transitional species: Tiktaalik
Like a fish complete with scales and gills
Flattened crocodile head with unusual fins
sturdy interior bones that would have allowed Tiktaalik to prop itself up in shallow water and use its limbs for support as most four-legged animals do.
Ancient reptile Thrinaxodon ancient mammal
Refers to structural similarities found between related organisms
Homologous structures – Limbs that perform different functions but are built from the same bones
Human Cat Whale Bat
Species that are only distantly related develop similar adaptations and resemble each other ◦ Because they live in similar environment and are
exposed to similar selective pressures
On pre-test: 59% got this wrong
Analogous structures – structures that resemble each other due to similar selective pressures and not to recent common ancestry
Remains of structures that were functional in ancestors◦ Eyes on a blind cave fish
Remains of structures that were important to the organisms’ ancestors but are not to the existing organisms
Whale Video◦ 9:15
On pre-test: 76% got this wrong!
Similarities in DNA and proteins
Amino acid sequences can be compared among various species for minor changes
The more similar the code, the closer related
yeast (Candida)
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40
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Types of Organisms
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Biochemical/Molecular Data
Branch points tell the number of amino acids that differ between human cytochrome c and
the organisms depicted
Percent Agreement between Beta Globin of Various Species
Species Human Chimp Gorilla Red fox DogPolar bear
Horse Rat Chicken
Human 100. 100. 99.3 91.1 89.7 89.7 83.6 81.5 69.2
Chimp 100. 100. 99.3 91.1 89.7 89.7 83.6 81.5 69.2
Gorilla 99.3 99.3 100. 91.8 90.4 90.4 82.9 80.8 68.5
Red fox 91.1 91.1 91.8 100. 98.6 95.2 80.8 80.1 72.6
Dog 89.7 89.7 90.4 98.6 100. 94.5 80.1 79.5 71.2
Polar bear
89.7 89.7 90.4 95.2 94.5 100. 80.8 82.9 71.9
Horse 83.6 83.6 82.9 80.8 80.1 80.8 100. 76.0 67.8
Rat 81.5 81.5 80.8 80.1 79.5 82.9 76.0 100. 65.8
Chicken 69.2 69.2 68.5 72.6 71.2 71.9 67.8 65.8 100.
Closely related organisms go through similar stages in embryological development
Organisms that appear different as adults may be very similar in embryonic stages = common ancestor
What do you think?
Of these four (in your packet), which do you think is the strongest evidence for evolution?