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April 25 Computer Lab. Use the powerpoint to take your notes! Play the games and fill in your paper! . Why is it called Natural selection?. Darwin saw how similar it was to artificial selection
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April 25 Computer Lab Use the powerpoint to take your notes! Play the games and fill in your paper!
Why is it called Natural selection? • Darwin saw how similar it was to artificial selection • Artificial Selection – humans “select” which individuals to reproduce (selective breeding) ex: different breeds of dogs
Natural selection – Most fit individuals reproduce the most successfully • Selection – results in a change in the inherited characteristics of a population
Natural Selection….. Original Population (bugs) Predator Those that survived reproduced, making them more fit There is a change in allele frequency over time = evolution Over time, what do you think might happen?
Descent with Modification • Darwin proposed that over long periods, natural selection produces organisms that look very different from their ancestors. • He believed that each living species descended, with changes, from other species.
Descent with modification implies common descent • Common Descent – all species (living and extinct) share a common ancestor and are distantly related to one another.
Evolution by Genetic Drift • In genetic terms, evolution is any change in the frequency of alleles in a population
Genetic drift – in small populations, individuals that carry a particular allele may produce more offspring randomly • (ex: natural disaster wipes out half of a population; survivors reproduce more)
#2. Random Genetic Drift • Genetic drift has the same result as natural selection (changes in characteristics and allele frequency) Original Population (bugs) AVALANCHE DESTROYS ½ the population randomly Those that survived reproduced, making them more fit There is a change in allele frequency over time = evolution Over time, what do you think might happen?
Evidence of Evolution 1. Paleontology • The study of fossils • Relative Dating: older rocks are further down • Absolute Dating: Uses radioactive isotopes and half-lives to tell age of rocks/fossils • Fossils allow us to “see” the changes in life over the different periods of time
2. Geographic Distribution of Species • Explains how similar organisms can be found over such long distances • Supports common ancestor (because when organisms share traits, they usually share a common ancestor) • Ex. Marsupials (kangaroos and opossums family)
3. Embryology • Study of the development of organisms • At the early stages of vertebrate development, all the embryos look alike. • Shows deep rooted relationships in organisms
4. Molecular Biology • Studies proteins (sequences of amino acids) in different organisms • The closer the amino acid sequences, the more likely it is the two species are closely related
5. Comparative Anatomy • Homologous Structures • Similar characteristics b/c of relatedness (i.e. common ancestor) • Same form but different function • Ex: dog’s leg, human’s arm, bird’s wing, and whale’s fin
Analogous Structures • Shows how unrelated organisms, under similar selective pressures, over time evolved similar (analogous) structures SEPARATELY • Ex: a bat’s wing and an insect’s wing are both used to fly, but have totally different structures
Vestigial Organs • Organs that are “leftover” from a common ancestor that have no use but are still in the genes and are “seen” • Ex. • Wings of flightless birds • Hind leg bones in whales • Human Tailbone • Appendix • Gill slits in Embryos