Ls 1 Lecture 3 - Evolution And Natural Selection

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evolution

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descent with modification

defined more narrowly as a change in the genetic composition of a population from generation to generation

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pattern of evolution

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revealed by data from a range of scientific disciplines
facts- observations about the natural world

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process of evolution

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mechanisms that produce the observed pattern of change

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Carolus Linnaeus

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developed the binomial system of naming organisms according to genus and species

did not resemblances among species to evolution, but creation pattern

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fossils

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remains or traces of organisms from the past

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strata

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superimposed layers of rock

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paleontology

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study of fossils

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Georges Cuvier

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paleontologist, thought extinctions occured a lot, opposed evolution, advocated catastrophism

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catastrophism

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principle that events in the past occurred suddenly and were caused by mechanisms different from those operating in the present

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James Hutton

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proposed that Earth's geologic features could be explained by gradual mechanisms still operating

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Lamarck's two principles

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use and disuse (idea that parts of the body that are used extensively become larger and stronger), while those that are not used deteriorate

inheritance of acquired characteristics (an organism could pass these modifications to its offspring)

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adaptations

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characteristics of organisms that enhance their survival and reproduction in specific environments

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natural selection

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a process in which individuals with certain inherited traits leave more offspring than individuals with other traits

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descent with modification

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Darwin's phrase that summarized his view of life

descendants of ancestral organism lived in various habitats over millions and of years, accumulated diverse modifications (adaptations) that fit them to specific ways of life

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artificial selection

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selecting and breeding individuals that posess desired traits (plants, pets)

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Darwin's 4 observations

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1. all species are capable of producing more offspring than their environment can support
2. owing to lack of food/ other resources, many of these offspring do not survive
3. members of a population often vary greatly in their traits
4. traits are inherited from parents to offspring

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Darwin's 2 inferences

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1. natural selection:
individuals who inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals
2. evolution: unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

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over time, natural selection can increase the match between ______ and their ________

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organisms
environment

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if a(n) _______ changes, natural selection may result in _______ to these new conditions, sometimes giving rise to a new ______ in the process

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if a(n) ENVIRONMENT changes, natural selection may result in ADAPTATION to these new conditions, sometimes giving rise to a new SPECIES in the process

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__________ do not evolve; _______ evolve over time

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individuals

populations

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natural selection can amplify or diminish only ______ traits

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heritable

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which traits are favored depends on the ____________

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environmental context

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Thoimas Malthus 1798

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economist who wrote "Essay on the Principle of Population"
poverty/famine inevitable
exponential growth appropriate only for initial colonization

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non-heritable variation

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due to environment
examples: himalayan rabbit, samese cat, hydrangea (coloration depends on pH of soil)

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heritable variation

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differences passed through genetic material

ex: facial horned lark

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"blending inheritance"

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Darwin's suggestion to the unsolved problem of how traits were passed down from parents to offspring

problem: decrease variation by blending

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mendel's hypotheses

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alternative versions of genes, alleles
for each character, organism inherits 2 genes
dominant vs. recessive
2 genes separate when gametes are produced (meiosis)

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definition of evolution

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hertiable change in a POPULATION through time

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modern synthesis of evolution

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continuous variation, more than 2 alleles

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microevolution

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change within a species
change in allele frequencies
short time scale, observable

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macroevolution

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formation of new species or higher taxonomic levels
long time scale
not observable

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convergence

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species from different genealogies resemble each other
analogous structures
>

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divergence

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differences develop over time
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example of divergence

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mammals --> whales

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example of convergence

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body shape for swimming

cacti and euphorbs

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evolution is not directed to any final ____ or ____

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goal or state (like flying/swimming)

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future versions of evolution is limited by

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history of structure
physical, chemical properties
change may involve tradeoffs