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pg. 129-140


changes in populations, species, or group of species


the details of how populations of organisms change from generation to generation and how new species originate


describes patterns of changes in groups of related species over broad periods of geologic time
patterns determinate phylogeny


the evolutionary relationships among species and groups of species


theory of evolution had 3 important ideas
1. use/disuse
2. inheritance of acquired characteristics
3. natural transformation of species


-one of the 3 important ideas in Lamarck's theory of evolution
-described how body parts can develop with increased usage while unused parts weaken

inheritance of acquired characteristics

-one of the 3 important ideas in Lamarck's theory of evolution
described how body features acquired during the lifetime of an organism could be passed on to offspring

natural transformation of species

organisms produced offsprings with changes.
species didn't become extinct nor did they split and change into two or more species
each generation had a slightly diferent from toward some higher order of complexity

Evidence for Evolution

1. Paleontology
2. Biogeography
3. Embryology
4. Comparative Anatomy
5. Molecular Biology


provides fossils that reveal the prehistoric existence of extinct species


describes the distribution of species


reveals similar stages in development

Comparative anatomy

describes two kinds of structures: homologous and analogous

homologous structures

body parts that resemble each other in different species because of common ancestors

analogous structures

body parts that resemble one another in different species because they are adaptations to similar environments

molecular biology

examines the nucleotide and amino acid structures of DNA and proteins from different species

natural selection

differences in survival and reproduction among individuals in a population as a result of their interaction with the environment


ability to suvive or leave offspring

stabilizing selection

eliminates individuals with extreme or unusual traits
favors the middle

directional selection

favors traits that are at one extreme
traits at the opposite extreme are selected against

disruptive selection

occurs when environment favors extreme or unusual traits
doesn't favor the middle

sexual selection

differential mating of males and sometimes females in a population
female vs male

female choice

make a greater energy investment into producing offspring
can increase their fitness by increasing the quality of their offspring by choosing superior males

male competition

contribute little energy to the production of offspring
miximize the quantity of offspring produced

artificial selection

form of directional selection carried out by humans

sources of variation

1. mutations
2. sexual reproduction
3. diploidy
4. outbreeding
5. balanced polymorphism


provdes raw material for new variation

sexual reproduction

creates individuals with new combinatins of alleles
includes crossing over, independent assortment of homologoues, and random joining of gametes


presence of two copies of each chromosome in a cell


mating with unrelated partners

balanced polymorphism

maintenance of different phenotypes in a population
includes heterozygote advantage, hybrid vigor, and frequency dependent selection

heterozygote advantage

occurs when the heterozygous condition bears a greater selective advantage than either homozygous condition

ex: sickle cell carrier -- partial immunity to malaria

hybrid vigor

the superior quality of offspring resulting from crosses between two different inbred strains of plants

ex: corn hybrid produces larger ears of corn and is more disease resistant than either inbred species

frequency dependent selection

minority advantage
when the least common phenotypes have a selective advantage

causes of changes in allelic frewuencies

natural selection
gene flow
genetic drift
nonrandom mating

gene flow

describes the introduction or removal of alleles from the population when individuals leave or enter the population

genetic drift

random increaes of decrease of alleles
two kinds: founder effect and bottleneck

founder effect

occurs when allele frequencies in a group of migrating individuals are, by chance, not the same as that of their population of origin


occurs when the population undergoes a dramatic decrease in size
the small population becomes severely vulnerable to genetic drift

nonrandom mating

occurs when individuals choose mates based upon their particular traits
*inbreeding and sexual selection occurs


occurs when individuals mate with relatives


the formation of new species
can occur through:
1. allopatric
2. sympatric
3. adaptive radiation

allopatric speciation

when a population is divided by a geographic barrier so there's no interbreding
due to natural selection, if the geographic barrier was removed, there'd still be no mating between the two

sympatric speciation

formation of new species without geographic barriers
includes: balanced polymorphism, polylpoidy, and hybridization


the possesion of more than 2 set of chromosomes in diploid cells


when 2 distinctly different forms of a species mate and produce offspring

adaptive radtion

relatively rapid evolution of many species from a single ancestor
occurs when the ancestral species is introduced to an area where diverse geographic or ecological conditions are available for colonziaation

prezygotic isolating mechniasms

mechanisms that prevent fertilization
1. habitat isolation
2. temporal isolation
3. behavioral isolation
4. mechanical isolation
5. gametic isolation

habitat isolation

occurs when species do not encounter one another

temporal isolation

when species mate or flower at different times/seasons

behavioral isolation

when species do not recognize another species as a mating partner because they don't perform the correct rituals or give out the same signals, or relase the proper chemicals

mechnical isolation

occurs when male and female genitalia are structurally incompatible or when flower structures select for different pollinators

gametic isolation

occurs when male gametes do not survive in the environment of the female gamete or female gametes don't recognize the male gametes

postzygotic isolating mechanisms

prevents the formation of fertile offspring
1. hybrid inviability
2. hybrid sterility
3. hybrid breakdown

hybrid inviability

occurs when the zygote fails to develop peroperly and aborts ot dies

hybrid sterility

hybrids become functional adults, but are reproductively sterile

hybrid breakdown

occurs when hybrids produce ofspring that have reduced fertility/viability

Patters of evolution

1. divergent evolution
2. convergent evolution
3. parallel evolution
4. coevolution

divergent evolution

describes two or more species that originate from a common ancestor and become increasingly different over time
can happen because of allopatric/sympatric speciation or adaptive radiation

convergent evolution

describes two unrealted species that share similar traits
each species has developed these traits because they live in similar envrionments
*called analogous traits

parallel evolution

describes 2 related species or two related lineages that have made similar evolutionary changes after their divergence from a common ancestor


evolution of a species in response to new adaptations that appear in another species

ex: prey species gains an advantage, some variants in the predator population will be succesful in getting the prey despite the advantage. those that get the prey pass down the favorable trait to its offspring


descibes patterns of evolution for groups of species over extended periods of geologic time
includes phyletic gradualism and punctuated equilibrium

phyletic gradualism

evolution occurs by the gradual accumlation of small changes. individual speciation eventts or major changes in lineages occur over long periods of geologic time

punctuated equlibirum

evolution consists of geologically long periods with little or no evolution, then interrupted by geologically short periods of rapid evolution

chemical evolution

study of how life began

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