127 lines
6.3 KiB
Plaintext
127 lines
6.3 KiB
Plaintext
A curious aspect of the theory of evolution is that everybody thinks he understands it. —Jacques Monod
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Jacques Monod: Biochemist, won Nobel Prize in 1965
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# Usual argumnt: Everything is so in place, how can it be random? It must be creationism.
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Evolution: The theory of evolution does not predict that species will constantly be evolving, or how fast they’ll change when they do.
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That depends on the evolutionary pressures they experience. Groups like whales and humans have evolved rapidly, while others, like the coelacanth “living fossil,” look almost identical to ancestors that lived hundreds of millions of years ago.
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Gradualism: It takes many generations for huge changes, the speed varies depending on the "natural selection" force, if it's strong, like when colonizing a new environment, it's fast, when animals are stable in their environment, it's slower, this force waxes and wanes (microbes can evolve fast because their generations are short, examples of evolution we can see)
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Speciation: 10M species alive, 250,000 Species as fossils, if no speciation, we would see only one highly-evolved specie
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- Evolution of groups that can't interbreed
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- Different Geographical environments, not attractive, different mating strategies
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- Because they can't interbreed, and most of the time, they live in different situations, they will evolve differently
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- Not dramatic at the time, not so much difference, as different as human children are from their parents
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- Not necessary
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- 99% of species go extinct
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- 1930, started to understand speciation
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- Example: language speakers
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- Isthmus of Panama: 7 species on each side, closest relative is on the other side
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Natural Selection:
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- Flawed: Indian Rhino has a single horn, while African rhinos have two, which is better, it doesn't always result in best
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- Built on what's already there: Turtles and flippers, can't add new limbs because of DNA
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- Not *accidental*, oldfield mice example
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- Mostly about reproduction, less survival
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- For good of individual, not species, lion male example
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Mechanism:
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- Genetic drift: random sampling -> biased towards one side
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- Biased mutation: Biased mutations on molecular level
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Theory:
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- More than just a speculation
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- Propositions used to explain facts about real-world
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- Testable, make verifiable predictions
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Fossils:
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- 10M species living today, 17M - 4B species estimated - 250,000 Fossil species - Make up only 0.1 to 1 percent of all species
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- Dating: 1945, radioactivie dating
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- Radioactive elements (radioisotopes) are incorporated into igneous (azarin) rocks, they decay to other elements at a constant rate
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How much was there at first? How much is there now? How long is the half-file? -> Determine age, 0.5% error
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Different radioisotopes: Uranium-238 (zircon), half-life 700M years. Carbon-14, half-life 5730 years (young rocks)
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They appear together, so can be cross-checked
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- Biological methods: Tides slow down earth's rotation, every 100,000years, the revolution of earth takes 2 more seconds
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After a long while, days are longer and years contain less days (circling sun is constant), Corals have daily and annual rings
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- Dates: 3.5B first photosynthetic bacteria, 2B years later, first Eukaryote, 1B years later, multicellular life
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- Sequence of species not random, in a complexity hierarchy
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Speciation in fossils:
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- Tetrapod: 365M, Tiktaalik 375M, Fish: 385M
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- in Fresh water, predicted between dates
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- Has neck, head flat like Salamandar, eyes and nostril on top, ribs for pumping air,
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- Gradualism, splitting of lineages, transitional form
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Vestiges:
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- Flightless birds: wings co-opted for other uses (show, running speed, swimming): not what they were made for
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- If food is available on ground, or no predators on land (like islands), no flight -> more energy to use for reproduction
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- Whales have pelvis bones that are not connected to anything
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- Mole rats have eyes covered by skin
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- Appendix's main use is for digesting cellulose, bigger in Koalas, Rabbits, Kangaroos, etc. Some people are born without one
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20% of people died because of it
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- Human tails are visible in embryo for 4 weeks, 14-22
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- Ears that can move, remains of our ancestral species
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- Lots of dead genes we don't use: smell, dolphins have 80% of their odor genes inactivated
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- Embryo goes through evolution-like stages
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Oceanic Islands:
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- Birds, insects and plants usually found in abundance
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- Galapagos: 30 islands, 28 species of similar birds native to the island, yet very diverse, finches
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- Yet lots of species _can_ do well on oceanic islands
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- (Aerial mammals such as bats can be found)
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- Species found on nearby land
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Artificial Selection:
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- Dog breeds, fruits
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- Bananas are infertile, yet we chose them
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Experimental Evolution:
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- Microbes, over 18 years, got used to feast and famine, grew 70% faster than the first generation, 9 genes changed - 40,000 generations
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Selection in the Wild:
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- Galapagos finches, after a draught, increased their beak size by 10% in one generation, because they couldn't eat small, soft seeds anymore
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Humans:
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- Not from Chimps, but closest relative: 1.5 different between protein sequences, not whole DNA, 80% difference, but small difference
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6% of genes in humans not found in chimps
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- There are transitional forms between humans and apes
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- We have significant DNS relativity
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Sahelanthropus tchadenesis:
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- Almost full skull, though broken down
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- Long cranium, small chimp-sized brain, flat face, small teeth, brow ridges
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- Probably could walk, from their foramen magnum
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Australopithecus afarensis (Lucy):
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- Definitely bipedal, from the structure of the femur
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- Smaller teeth, less rectangular
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- Arms longer than humans, shorter than chimps
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- Spent some time in trees
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- Head: apelike
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- Middle: mixture
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- Lower: human-like
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- Evolution of bipedalism first
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Homo Habilis:
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- Used tools such as stone hand axes for grazing and hunting birds
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Homo Erectus:
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- Use of fire: burned bones (animals on fire), fire-hardened clay at sites
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- Social: hunter gatherers
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- Successful, they were around for 1.5MY
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Neanderthals:
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- Mostly in europe
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- More robust body
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- Used to cold climate
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- Shorter legs, wide rib cage
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- Interbred with Homo Sapiens: Genetic evidence
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- Large brains, larger than homo sapiens probably
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First self-replicating molecule: 3.5B years ago
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