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Charles Darwin

• 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***

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

Artificial selection

When HUMANS modify domesticated plant and animal populations by choosing which individuals produce offspring

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*

Natural selelction

when NATURE selects which organisms have reproductive success based on fit to the environment

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

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

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

divergent evolution

organisms diverge from a common ancestor as they adapt to diverse environments

convergent evolution

organisms evolve similar characteristics as they adapt to similar environments

homologous structures

evidence of divergent evolution

analogous structures

evidence of convergent evolution

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

population

a group of individuals of the same species that live in the same area and can potentially interbreed

gene pool

all copies of every type of allele at every locus in all members of the population

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

calculate frequencies of alleles in a gene pool

frequency x3 = x3/x1+x2+x3

genetic drift

when chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next.

what makes a population more susceptible to genetic drift

when populations are smaller because they produce the bottlenecking effect and the founder effect

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

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

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

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

directional selection

selects for ONE extreme phenotype

stabilizing selection

selects for INTERMEDIATE phenotype

disruptive selection

selects for BOTH extreme phenotypes

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

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

5 prezygotic barriers

1. habitat isolation

2. temporal isolation

3. behavioral isolation

4. mechanical isolation

5. gametic isolation

habitat isolation

lack of opportunities to encounter each other

temporal isolation

breeding at different times or seasons

behavioral isolation

failure to send or receive appropriate signals

gametic isolation

broadcast sponsors, gametes only work with gametes from same species

3 postzygotic barriers

1. reduced hybrid viability

2. reduced hybrid fertility

3. hybrid breakdown

reduced hybrid viability

interaction of parental genes impairs the hybrid’s development or survival

reduced hybrid fertility

hybrids are vigorous but cannot produce viable offspring

hybrid breakdown

hybrids are viable and fertile, but their offspring are feeble or sterile

speciation

the process by which one species splits into 2 or more species

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

sympatric speciation

occurs when reproductive barriers form between subpopulations and there is no physical separation. can occur through sexual selection or habitat differentiation

punctuated evolutionary patterns

long periods of little apparent morphological change interrupted by relatively brief periods of sudden change

gradual evolutionary patterns

new species evolve gradually from the ancestral pattern

ecology

the scientific study of the interactions between organisms and the environment

biotic factors

all of the organisms in the area, the living components of the environment

abiotic factors

the environments nonliving components, the physical and chemical factors such as temperature, forms of energy available, water, and nutrients

the major abiotic factors (5)

temperature, precipitations, sunlight, wind, rocks/soil

Tropical forest

humid equator areas, lots of rainfall, 300+ species of trees, monkeys, birds, insects, snakes

savanna

warm, rainfall, grasses, poor soil so not a lot of trees, insects, mice, snakes, giraffes, zebras, antelope, lions, cheetahs, kangaroos

desert

HOT, low and unpredictable rainfall, water storing succulents/plants, birds, rodents, snakes, lizards, hawks

chaparral

ocean currents bring in cool air, rainy, shrubs, deer, birds, rodents, lizards, snakes

temperate grassland

cold, some rain, drought leads to fires, mostly treeless, shortgrass prairie, bison, pronghorn, wild horses, sheep, birds, small mammals

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

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

tundra

COLD, little to non precipitation, little light, frozen subsoil, no trees, dwarf shrubs, grasses, caribou, arctic fox, snowy owls, lemmings

community ecology

the study of how populations (of different species) interact with each other and the environment. the study of community interactions

interspecific competition

occurs when the niches of two populations overlap and both populations need a resource that is in short supply

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

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)

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

predation

one species (predator) kills and eats the other (prey) (EX: lions hunt and eat zebras)

herbivory

when animals only eat plants (EX: manatee only eats kelp)

Parasitism

one species (parasite) lives on or in another (host) (EX: ticks live on humans and other animals and feed on their blood)

commensalism

one species benefits and the other is unaffected (EX: cattle egret eat the bugs off the buffalo, but the buffalo get nothing

trophic structure

a pattern of feeding relationships consisting of several different levels

what are the different trophic levels in order

producer, primary consumer, secondary consumer, tertiary consumer, quaternary consumer

producers/autotrophs

make their own food using sunlight, water and carbon dioxide (plants)

consumers/heterotrophs

get their food by eating other organisms (animals)

carnivore

animal eater

herbivore

plant eater

omnivore

plant and animal eater

detrivore

consume organic wastes and dead animals

decomposer

bacteria and fungi that turn organic material into inorganic materials

ecosystem

consists of all the organisms in a community as well as the abiotic environment with which the organisms interact

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.

energy flow

the passage of energy through the components in an ecosystem. photosynthesis transfers sunlight energy into ecosystems

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

precipitaion

water falling from the atmosphere

evaporation

water becoming a gas

transpiration

water inside a plant becoming a gas

percolation

water moving down through soil

surface runoff

water moving on the ground to another location

groundwater

water stored between and in rocks

condensation

formation of clouds

what processes release carbon dioxide into the atmosphere in the carbon cycle

burning wood and fossil fuels, cellular respiration

what process removes carbon dioxide from the atmosphere in the carbon cycle

photosynthesis

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

respiration

living organisms breathing oxygen to release ATP

photosynthesis

plants use co2 to make sugar from sunlight

combustion

burning something

decay

something dying and breaking down

fossil fuels

something that was once alive (plants/animals) that is now fuel

waste

urine/feces

feeding/eating

taking in living things for energy

where is most of the nitrogen on earth located

the atmosphere and the soil. almost 80% of the atmosphere is nitrogen gas

what forms of nitrogen can be taken by living things

compounds such as nitrate, nitrite, ammonia, and ammonium

nitrogen-fixing

converts n2 to compounds of nitrogen that can be used by plants, nitrogen gas goes into soil

bacteria in nitrogen cycle

performs nitrogen-fixing, provide nitrogen to plants through their roots

nitrifying bacteria in nitrogen cycle

in soil, convert NH4+ to nitrate, which is more readily assimilated by plants

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

nitrification

the process by which ammonia and nitrite become nitrate by bacteria