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1. Many species of organisms presently inhabiting Earth are descendants of ancestral species that were different from the modern species.
2. Natural Selection was the mechanism for this evolutionary process. |
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| A population can change over generations if individuals that possess certain heritable traits leave more offspring than other individuals. |
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| An accumulation of inherited characteristics that enhance organisms' ability to survive and reproduce in specific environments. |
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A change over time in the genetic composition of a population
- descent with modification |
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(384-322 B.C.)
Species were fixed and unchanging through time.
Observed that life-forms existed on a scale of increasing complexity ("scala natura") |
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(1707-1778)
- Founder of taxonomy.
-no evolution
- Adopted nested classification system (grouped similar species into increasingly general categories)
- Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose. |
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the branch of biology concerned with naming and classifying organisms.
founded by Linnaeus |
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(1769-1832)
• Paleontologist
• Found different fossils in different strata and inferred extinction
• Believed boundaries between strata due to catastrophes
• Ironically, staunch opponent of evolution.
- Believed strata differences due to migration after catastrophe |
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Definition
- each boundary between strata (the layers in rock) represents a catastrophe (flood or drought) that destroyed many of the species living at that time
- periodic catastrophes were usually confined to local geographic regions, which were repopulated by species immigrating from other areas |
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| idea that profound change can take place through the cumulative effect of slow but continuous processes |
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(1726-1797)
Purposed that Earth's geologic features could be explained by graudal mechanisms currently operating in the world
- gradualism |
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(1797-1875)
- incorporated hutton's thinking into a more comprehensive theory
- the same geologic processes are operating today as in the past, and at the same rate
-gradualism |
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| Lamarck's Theory of Evolution |
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Definition
"Use and Disuse": parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate (ex: Giraffe's neck)
"Inheritance of Acquired Characteristics": an organism could pass these "acquired characteristics" off to their offspring
Transformism!
-recognized that evolutionary change explains the fossil record and organisms adapt to their environments
-failed to figure out why these changes occurred (improper change mechanisms) |
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| Descent with Modification |
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Definition
-summarized Darwin's take on life
-all organisms were related through descent from an ancestor that lived in the remote past
- as descendants o that ancestral organism spilled into various habitats over millions of years, they accumulated diverse modifications (adaptations) that fit them into specific ways of life |
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| 3 Inferences of Natural Selection |
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Definition
1. Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving each generation
2. Survival depends in part on inherited traits. Individuals whose inherited traits give them a high probability of surviving and reproducing in a given environment have higher fitness and are likely to leave more offspring that less fit individuals
3. The unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over generations |
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| Examples of Natural Selection in Action |
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1. Differential Predation and Guppy Populations
2. The evolution of drug-resistant HIV
3. the decrease in effectiveness of penicillin |
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| similar characteristics among related species descendent from common ancestors even though they may serve very different functions |
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Lecture: Similar anatomy of structures, regardless of function
Book: Variations on a structural theme that was present among a common ancestor
ex: arms, forelegs, flippers, and wings of different mammals |
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- DNA, RNA are conserved across all living organisms
• Same genes guide development in plants and animals
• The genetic code is universal |
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- Structures of marginal importance to the organism
- remnants of structures that served important functions in the organism's ancestors
- homologous structures!
ex: snakes have vestiges of the pelvis and leg bones of walking ancestors |
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Definition
- Structures that appear early in development are similar
- Embryo exhibits characteristics of the embryos of its
ancestors.
- many embryos possess gill slits and later exhibit a
tail (in human coccyx/tail bone). |
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Definition
definition: the geographic distribution of species
- was a key part in Darwin's theory of evolution because closely related species tend to be found in the same geographic region
- evidence of evolution |
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| - independently developed a theory of evolution almost identical to Darwin's |
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| Darwin's Five Observations |
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Definition
1. populations of all species would increase exponentially if all individuals that are born reproduced successfully
2. Populations tend to remain stable in size, except for seasonal fluctuations (despite #1)
3. Resources are limited
4. Members of a population vary extensively in their characteristics; no two individuals are exactly alike
5. Much of this variation is heritable |
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- the process initiated by humans that modifies other species over many generations by selecting and breeding individuals that possess desired traits
example: pets that do not resemble their wild ancestors |
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- Economist
- resources will outstrip populations
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- similarity by a shared way of life
- arise because of functional constraints
- NO common ancestry
example: hydrodynamic shape, flying wings |
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5 Pieces of Evidence for Evolution
(lecture) |
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Definition
1. Biogeography
2. The fossil record
3. comparative anatomy
4. Development (embryology)
5. The Molecular Record (biochemistry and molecular biology) |
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Term
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Definition
- Embryos exhibit characteristics of the embryos of its ancestors
- structures that appear early in development are similar
example: many embryos possess gill slits like a fish and later exhibit a tail |
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