* traveled the world between 1831 and 1836 to the Galapagos Islands * he observed the diversity of habitats and organisms * developed the theory of evolution by natural selection to explain the diversity of life * related species share a common ancestor * species differ because the adapt to diff environments * species adapt to fit their environment through natural selection\*\*\*
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On the Origin of Species by Charles Darwin
2 Arguments:
1) through artificial selection (selective breeding) humans modify domesticated plant and animal populations by choosing which individuals produce offspring
2) through natural selection, nature selects which organisms have reproductive success based on fit to the environment
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Artificial selection
When HUMANS modify domesticated plant and animal populations by choosing which individuals produce offspring
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Darwin’s big idea: Natural Selection
1) Variation - variation exists in a population
2) Selection - organisms whose traits improve their chance of survival in the environment will produce more offspring
3) Response to selection - in the next generations, a greater proportion of the population will have the favorable traits. \*over generations, the population adapts to the environment\*
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Natural selelction
when NATURE selects which organisms have reproductive success based on fit to the environment
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4 lines of evidence that support the theory of evolution
1) direct observations of evolutionary change
2) homologous structures show diverse organisms are related
3) analogous structures show similar response to natural selection
4) historical record shows evidence of evolution
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how does homology infer common ancestry and support the theory of evolution
it causes species that share an ancestor to have characteristics that have an underlying similarity yet function differently. PENTADACTYL LIMB IN MAMMALS
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why do similar structures not always indicate common ancestry
convergent evolution can lead to analogous structures in organisms that are not closely related. SUGAR GLIDERS AND FLYING SQUIRRELS
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divergent evolution
organisms diverge from a common ancestor as they adapt to diverse environments
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convergent evolution
organisms evolve similar characteristics as they adapt to similar environments
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homologous structures
evidence of divergent evolution
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analogous structures
evidence of convergent evolution
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how do historical records provide evidence of evolution
fossil records show that living organisms evolve from extinct ancestors. biogeography shows that organisms that evolved in the same geographic area are more closely related
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population
a group of individuals of the same species that live in the same area and can potentially interbreed
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gene pool
all copies of every type of allele at every locus in all members of the population
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define evolution in terms of allele frequencies
a change in the prevalence of certain heritable traits in a population over a span of generations. scientists study the gene pool and its alleles and watch how the allele for the enzyme conferring resistance will increase in frequency and the other allele will decrease in frequency. when the relative frequencies of alleles in a population change like this over a number of generations, evolution is occurring on its smallest scale, called microevolution
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calculate frequencies of alleles in a gene pool
frequency x3 = x3/x1+x2+x3
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genetic drift
when chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next.
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what makes a population more susceptible to genetic drift
when populations are smaller because they produce the bottlenecking effect and the founder effect
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bottlenecking
occurs when the size of a population is greatly reduced due to an event or habitat loss. the surviving gene pool may have different allele frequencies and some alleles may be lost. can cause not all of the alleles to be present in the next generation. can decrease the populations range
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the founder effect
occurs when a small subpopulation breaks off from a parent population. the allele frequencies in founded populations differ from the parent population due to CHANCE. genetic drift causes the alleles frequencies to change due to chance in small populations
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how does gene flow impact genetic differentiation between populations
it occurs when individuals migrate from one population to another. it can alter the allele frequencies in both populations and it tends to reduce differences between populations
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which mechanism of evolutionary change consistently leads to adaptive evolution
natural selection bc it consistently favors some alleles over others, improving matches between organisms and their environment
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directional selection
selects for ONE extreme phenotype
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stabilizing selection
selects for INTERMEDIATE phenotype
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disruptive selection
selects for BOTH extreme phenotypes
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sexual selection
a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates
(EX: Manes on lions and bright colored birds
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biological species concept
definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring but do no produce viable, fertile offspring with members of other such groups
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5 prezygotic barriers
1) habitat isolation
2) temporal isolation
3) behavioral isolation
4) mechanical isolation
5) gametic isolation
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habitat isolation
lack of opportunities to encounter each other
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temporal isolation
breeding at different times or seasons
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behavioral isolation
failure to send or receive appropriate signals
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gametic isolation
broadcast sponsors, gametes only work with gametes from same species
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3 postzygotic barriers
1) reduced hybrid viability
2) reduced hybrid fertility
3) hybrid breakdown
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reduced hybrid viability
interaction of parental genes impairs the hybrid’s development or survival
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reduced hybrid fertility
hybrids are vigorous but cannot produce viable offspring
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hybrid breakdown
hybrids are viable and fertile, but their offspring are feeble or sterile
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speciation
the process by which one species splits into 2 or more species
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allopatric speciation
occurs when a population is separated by a physical barrier. subpopulations evolve differently over time. organisms will not reproduce together if they come back in contact
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sympatric speciation
occurs when reproductive barriers form between subpopulations and there is no physical separation. can occur through sexual selection or habitat differentiation
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punctuated evolutionary patterns
long periods of little apparent morphological change interrupted by relatively brief periods of sudden change
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gradual evolutionary patterns
new species evolve gradually from the ancestral pattern
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ecology
the scientific study of the interactions between organisms and the environment
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biotic factors
all of the organisms in the area, the living components of the environment
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abiotic factors
the environments nonliving components, the physical and chemical factors such as temperature, forms of energy available, water, and nutrients
cold, some rain, drought leads to fires, mostly treeless, shortgrass prairie, bison, pronghorn, wild horses, sheep, birds, small mammals
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temperate broadleaf forest
where we live, wide range of temp (hot summer, cold winter), high rainfall, deciduous trees (oak, hickory, birch, beech, maple), birds, rodents, black bears, bobocats, foxes, mountain lions
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northern coniferous forest
high elevations, long cold winters, short wet summers, most precipitation is snow, cone-bearing evergreen trees, moose, elk, hares, bears, wolves, grouse
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tundra
COLD, little to non precipitation, little light, frozen subsoil, no trees, dwarf shrubs, grasses, caribou, arctic fox, snowy owls, lemmings
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community ecology
the study of how populations (of different species) interact with each other and the environment. the study of community interactions
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interspecific competition
occurs when the niches of two populations overlap and both populations need a resource that is in short supply
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how does interspecific competition lead to resource partitioning
there isn’t enough resources for both species so one species needs to adapt to new similar resources
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competition
individuals of different species compete for a resource that limits growth and survival (ex: orange crowned warblers and virginia’s warblers compete for food in order to provide for their offspring)
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mutualism
both species benefit from the relationship (ex: when bees take nectar from flowers, they are getting food. but, they also spread the pollen from the flower, which allows the flower to reproduce
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predation
one species (predator) kills and eats the other (prey) (EX: lions hunt and eat zebras)
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herbivory
when animals only eat plants (EX: manatee only eats kelp)
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Parasitism
one species (parasite) lives on or in another (host) (EX: ticks live on humans and other animals and feed on their blood)
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commensalism
one species benefits and the other is unaffected (EX: cattle egret eat the bugs off the buffalo, but the buffalo get nothing
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trophic structure
a pattern of feeding relationships consisting of several different levels
make their own food using sunlight, water and carbon dioxide (plants)
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consumers/heterotrophs
get their food by eating other organisms (animals)
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carnivore
animal eater
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herbivore
plant eater
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omnivore
plant and animal eater
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detrivore
consume organic wastes and dead animals
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decomposer
bacteria and fungi that turn organic material into inorganic materials
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ecosystem
consists of all the organisms in a community as well as the abiotic environment with which the organisms interact
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how does the movement of energy and matter through ecosystems differ
energy is transferred into ecosystems and is converted into different forms of energy by the different organisms in the ecosystem. matter is transferred within the ecosystem. most ecosystems have a constant input of energy, but a limited supply of matter. so, matter is cycled between abiotic and biotic components within the ecosystem.
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energy flow
the passage of energy through the components in an ecosystem. photosynthesis transfers sunlight energy into ecosystems
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energy pyramid
shows the cumulative loss of energy with each transfer in a food chain. only about 5-20% of the energy from one level is moved to the next level, it isn’t efficient
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precipitaion
water falling from the atmosphere
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evaporation
water becoming a gas
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transpiration
water inside a plant becoming a gas
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percolation
water moving down through soil
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surface runoff
water moving on the ground to another location
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groundwater
water stored between and in rocks
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condensation
formation of clouds
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what processes release carbon dioxide into the atmosphere in the carbon cycle
burning wood and fossil fuels, cellular respiration
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what process removes carbon dioxide from the atmosphere in the carbon cycle
photosynthesis
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what is the relationship between photosynthesis and cellular respiration in the carbon cycle
photosynthesis returns the co2 that was released into the atmosphere from cellular respiration
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respiration
living organisms breathing oxygen to release ATP
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photosynthesis
plants use co2 to make sugar from sunlight
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combustion
burning something
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decay
something dying and breaking down
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fossil fuels
something that was once alive (plants/animals) that is now fuel
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waste
urine/feces
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feeding/eating
taking in living things for energy
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where is most of the nitrogen on earth located
the atmosphere and the soil. almost 80% of the atmosphere is nitrogen gas
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what forms of nitrogen can be taken by living things
compounds such as nitrate, nitrite, ammonia, and ammonium
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nitrogen-fixing
converts n2 to compounds of nitrogen that can be used by plants, nitrogen gas goes into soil
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bacteria in nitrogen cycle
performs nitrogen-fixing, provide nitrogen to plants through their roots
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nitrifying bacteria in nitrogen cycle
in soil, convert NH4+ to nitrate, which is more readily assimilated by plants
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denitrifying bacteria in nitrogen cycle
in soil, strip the oxygen atoms from no3-, releases n2 back into the atmosphere and depletes the soil reservoir of usable nitrogen
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nitrification
the process by which ammonia and nitrite become nitrate by bacteria