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natural selection
- individuals that have certain traits tend to produce more offspring than others do.
- darwin proposed that natural selection is part of evolution.
- evolution: a change in the inherited characteristics of a population from one generation to the next.
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theory of evolution by natural selection
- darwin's theory predicts that over time, the number of individuals that carry advantageous traits will increase in a population.
- 1 overproduction: every population is capable of producing more offspring than can possibly survive.
- 2 variation: variation exists within every population. Much of this variation is in the form of inherited traits.
- 3 selection: in a given environment, having a particular trait can make individuals more or less likely to survive & have successful offspring. So, some individuals leave more offspring than others do.
- 4 adaption: overtime, those traits that improve survival & reproduction will become more common.
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adaption
an inherited trait that is present in a population because the trait helps individuals survive & reproduce in a given environment
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darwin's theory in summary
explains evolution as a gradual process of adaption.
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what did Darwin present
a unifying explanation for data from multiple fields of science
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fossils
- traces of organisms that lived in the past.
- all fossils known to science make up a fossil record
- intermediate fossils must be found to make the record complete..
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biogeography
- the study of the locations of organisms around the world.
- geologists & biologists have found that the movement of landforms in earth's past help to explain patterns in the types & locations of both living & fossil organisms
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embryology
- the ancestry of organisms is also evident in the ways that multicellular organisms develop from embryos.
- interesting study because embryos undergo many physical & genetic changes as they develop into mature forms
- at some time during development all vertebrate embryos have a tail
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anatomy
- the bodily structure.
- another place to observe the results of evolution is inside the bodies of living things.
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homologous structures
characteristics that are similar in two or more species & that have been inherited from a common ancestor of those species.
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darwin as an important scientist
his work had three major strengths: evidence of evolution, a mechanisms for evolution, and the recognition that variation is important.
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strengths of darwin's ideas
- work is supported by & helps explain so much data
- presented a logical that testable mechanism that could account for the process of evolution.
- he changed the way scientists thought about the diversity of life.
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weaknesses of darwins ideas
- he knew very little about genetics
- inherited variation was crucial to dawin's theory of natural selection, yet his theory lacked a clear mechanism for inheritance.
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Modern synthesis of evolutionary theory
the unification of Darwin's theory & newer studies of fossil, anatomy, genetics, & more
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microevolution
evolution as a change in the genes of populations
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macroevolution
the appearance of new species over time
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speciation
- the link between microevolution & macroevolution.
- the formation of new species
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processes of microevolution
natural selection- can cause an increase or decrease in certain alleles in a population
migration movement between populations. can change the numbers & type of alleles in a population
mate choice
mutation can change alleles but its rare
genetic drift random effects of everyday life
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processes of macroevolution
convergent evolution if evolution is strongly directed by the environment then specie living in similar environments should evolve similar adaptations
coevolution species that live in close contact often have clear adaption to one another's existence
adaptive radiation spilt in lineages that produce new species
extinction die off
gradualism species evolve gradually
punctuated equilibrium change in environment create new species suddenly
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