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Evolution

Evolution. Everything Evolves!!. Evolution – Important Definitions. Population: a group of organisms of the same species inhabiting a given area. Evolution: the change in the inherited traits (genes) of a population of organisms through successive generations (over a long period of time).

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Evolution

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  1. Evolution

  2. Everything Evolves!!

  3. Evolution – Important Definitions • Population: a group of organisms of the same species inhabiting a given area. • Evolution: the change in the inherited traits (genes) of a population of organisms through successive generations (over a long period of time). • When a population splits into smaller groups, these groups evolve independently and develop into new species. • Species: a group whose members can interbreed with each other.

  4. Thing to Remember as We Go • Populations evolve, not individuals. • Phenotypes are what are selected for or against. • Phenotypes (physical traits) reflect genotypes (allele combinations) • The environment selects for a phenotype. • Evolution is thoughtless • Selection pressures change when the environment changes

  5. Early Evolutionary Ideas • Jean Baptiste Lemarck – French Scientist • Law of Use or Disuse. • Believed that acquired traits were passed onto offspring. • Most famous for giraffe example • Believed that giraffes stretched their necks to reach higher leaves and as a result passed longer necks onto their offspring. • This theory not accepted – acquired traits are not heritable.

  6. Charles Darwin – Natural Selection • Charles Darwin – English Naturalist studied aboard the HMS Beagle • Most famous for his work studying finches (birds) of the Galapagos Islands • Developed the Theory of Natural Selection

  7. Darwin’s Observations • Finches on the islands closely resembled, but were not identical to, each other or organisms living in South America (mainland). • Therefore, the organisms must have changed somehow over time. • The finches looked similar, but had different beaks. • The different islands had different food sources, so they needed different beaks to eat the specific food on their island.

  8. Natural Selection • Darwin used these observations of finches to develop the idea of natural selection. • Natureselects for the “better” traits. • In natural selection certain individuals within a population may have behavioral or physical traits that are better suited to survival in the environment. • These individuals will reproduce more successfully based upon these traits. • The variations that were beneficial to the environment were “selected” and passed onto subsequent generations • Over time the population would show an increase in this beneficial characteristic and thus evolve (is now a new species)

  9. Darwin’s Theory Summarized • Evolution by Natural Selection • Genetic variation exists within a population. • These variations may be beneficial for survival. • Individuals with the beneficial variation (called an adaptation) have more babies than those without the trait. • Over time the new trait accumulates and the population changes (evolves).

  10. Other Factors in Natural Selection • 1. All populations have genetic variation (seen in the phenotype…look around you). • 2. The environment challenges reproduction – not all individuals will reproduce (not pass on their traits) for some selective reason. • 3. More offspring will be produced than can survive (creating competition for survival). • 4. Those who are the best will survive to pass on their genes. • Called “Survival of the Fittest.” ***Evolution through natural selection can lead to changes in biodiversity (the variety of plant and animal life in a particular habitat) through the increase or decrease of genetic diversity within a population.***

  11. Classic Example – Peppered Moth • Same species of moth – existed with two color variations • Light and dark • Variations are genetic and therefore can be passed on to offspring • Moths live in birch trees in England and are eaten by bird predators. • Birds will prey on the most visible moths (ones they can see the best).

  12. Peppered Moth • Prior to the industrial revolution light moths were very common because they were well camouflaged by hiding in the white birch trees. • The industrial revolution created a soot that coated trees, turning the trees black. • Which moths would be well camouflaged now? After Before

  13. Peppered Moth – Natural Selection How does this example show natural selection? • Over time the light moths were more susceptible to predation (eaten more). • The number of dark moths increased over time because they survived (weren’t eaten) and passed on their traits.

  14. Evidence for EvolutionHow we know that evolution really happens • 1. Fossils • 2. Comparative Anatomy • Homologous structures • Vestigial structures • 3. Molecular Biology/Biochemistry • DNA and Amino acids • 4. Embryology

  15. Fossil Evidence • Fossils: are the preserved remains or traces of dead animals, plants and other organisms from the past (formed in mud, sediment and rock). • The totality of fossils, both discovered and undiscovered, and their placement (layer) in fossil-containing rock formations is known as the fossil record. • Fossils show intermediate forms of an organism over time. • These intermediate forms show evolution of organism.

  16. Comparative Anatomy • Homologous Structures – anatomical structures have similar structure, but different functions. • Suggests common ancestry (evolved from a common ancestor, started as the same organism). • Structures evolved once and were modified based on environment.

  17. Comparative Anatomy • Vestigial Structures – anatomical structures that have evolved to be reduced in size and function (may have no function at all) • Suggests that these structures had a function in the past and then evolved to not be used. • Ex: Pelvic bones in whales, tailbone in humans, appendix

  18. Molecular Biology – DNA Comparison Comparing the DNA sequence of certain genes and the amino acid sequences of certain proteins can tell how closely related they are evolutionarily. Ex: DNA gene for cytochrome C molecule. Humans: TCCGCTATATCCGCT **use this as the base Chimpanzees TCCCATATATCCTCT 3 base differences Cheetahs: TCCGCCCTACCGCAG7 base differences Having 3 bases different in the DNA sequence for the gene means that chimpanzees are more closely related to humans than cheetahs which have 7 bases different from humans.

  19. Specific protein sequences are compared.The fewer the differences in amino acids the more closely related organisms are. Biochemistry - Amino Acid Comparison Species Amino Acid Differences from Human Hemoglobin Protein • Gorilla 1 • Rhesus monkey 8 • Mouse 27 • Chicken 45 • Frog 67 • Lamprey 125

  20. Embryology The study of the development of an embryo through stages from fertilization to the fetus stage. Similar developmental patterns of organisms suggest an evolutionary relationship (common ancestor). These are all organisms in stage 1 of development. Which one is the human?

  21. Embryology • This is stage 2 of development. • Which one is the human?

  22. Embryology • Now can you tell?

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