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bio exam review


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2 major points in "the origin of species"
1. evidence that many organisms are descendants of ancestral species
2 major points in "the origins of species"
2. mechanism for evolutionary process = natural selection, evolutionary adaptation is result of evolutionary adaptation
why are fossils important to darwinian evolution?
they are remains/traces of organisms from past, deeper/older the strata, the more dissimilar fossils are from current life, show extinctions
where are fossils found?
sedimentary rock strata, each stratum has fossils that rep. species from that period of earth's history
paleontology? developed by?
Georges Cuvier study of fossils
each boundary between strata represents a catastrophe, only major catastrophes can change the basic formation of the earth
change takes place through the cumulative effect of slow but continuous processes
charles lyell mechanisms of change are constant over time, change result of slow continuous processes
2 major aspects of Lamarcks theory of evolution
species evolved through 1. use/disuse of body parts 2. inheritance of acquired characteristics
"descent with modification"
evolution, all organisms are related through descent from an ancestor that lived in the remote past
4 observations of natural selection and adaption
1. members of a pop very greatly in their traits 2. traits are inherited from parents to offspring 3. all species are capable of producing more offspring than the environment can support 4. owing to lack of food/resources, many of these offspring dont survive
2 inferences of natural selection and adaption
1. individuals whose inherited traits give them a higher prob of surviving and adapting leave more offspring 2. unequal ability of individuals to survive and reproduce will lead to an accumulation of favorable traits over generations
examples of Darwinian natural selection
1. predation and coloration in guppies 2. evolution of drug resistant HIV
smallest unit of evolution
a population
a localized group of individuals capable of interbreeding and producing fertile offspring
gene pool
total combination of genes in a population at any one time
hardy-weinberg theorem
describes a population in which there there random mating and where allele frequencies dont change-describes a population that is not evolving
hardy-weinberg equation
p^2+2pq+q^2=1 p^2=dominant 2pq=heterozygous q^2=recessive p=freq of dominant allele q=freq of recessive allele
3 major factors that can alter allele frequencies
1. natural selection 2. genetic drift 3. gene flow
natural selection and alleles
differential reproductive success
genetic drift
allele frequency fluctuate unpredictably from 1 generation to the next
bottleneck effect
sudden reduction in a population size due to a change in the environment
founder effect
occurs when a few individuals become isolated from a larger population
gene flow
movement of alleles among populations
discrete characteristics
can be classified on an either-or basis
quantitative characteristics
vary along a continuum within a population
individuals that differ in DISCRETE characters
phenotypic polymorphism
a population in which 2 or more distinct morphs for a character are readily noticeable
genotypic polymorphism
the heritable components of characters that occur in a population
3 modes of natural selection
1. directional=favors individuals at 1 end of phenotypic range 2. disruptive=favors individuals at both extremes of phenotypic range 3. stabilizing=favors intermediate and acts out against the extreme
3 mechanisms preserving genetic variation
1. diploidy 2. balancing selection (heterozygote advantage and frequency-dependent selection) 3. neutral variation
maintains genetic variation in "hidden" recessive alleles which are propagated in heterozygous individuals. rarer the allele, greater the protection
balancing selection
natural selection maintains stable frequencies of 2+ phenotypic forms in a pop... balanced polymorphism heterozygote advantage frequency-dependent selection
neutral variation
genetic variation appears to confer no selective advantage/disadvantage
sexual selection
natural selection for mating success
heterozygote advantage
when heterozygotes have a higher fitness then both homozygotes ex=sickle cell anemia
frequency-dependent selection
fitness of phenotype declines if it becomes too common in the pop, selection can favor whichever phenotype is less common
sexual dimorphism
marked differences between the sexes in secondary sexual characteristics-size
intra-sexual selection
competition among individuals of 1 sex (males) for mates of the opposite sex
inter-sexual selection
mate choice, when individuals of 1 sex (females) are choosy in selecting mate-male showiness
process by which 1 species splits into 2+ more species
adaptions that evolve within a pop, confined to 1 gene pool
change above species level, broad pattern of evolution over a long time span
biological species concept
a species is a group of pops whose members have the potential to interbreed in nature and produce viable, fertile offspring
reproductive isolation
biological factors that prevent members of 2 species from producing viable, fertile offspring
prezygotic barriers
impede mating between species or hinder fertilization of ova -habitat isolation -temporal isolation -behavioral isolation -mechanical isolation -gametic isolation
postzygotic barriers
prevent hybrid zygote from developing into a viable, fertile adult -reduced hybrid viability -reduced hybrid fertility -hybrid breakdown
allopatric speciation
when a pop is divided geographically, separate pops may evolve independently through mutation, gene flow, and genetic drift
sympatric speciation
takes place in geographically overlapping pops through chromosomal changes (polyploid) and nonrandom mating (sexual selection and habitat differentiation)
individual with more than 2 chromosome sets derived from a single species, gametes are diploid and offspring is tetraploid
species with multiple sets of chromosomes derived from different species
example of sympatric speciation
cichlid fish, color differentiation
4.6 bya?
earth is formed
3.9-3.8 bya?
atmosphere is formed?
3.5 bya?
prokaryotes appear
2.1-2.7 bya?
eukaryotes appear, oxygen revolution
2.1 bya?
oldest eukaryote fossils
1.2-1.5 bya?
early multicellular eukaryotes=small algae
600 mya?
large, complex multicellular organisms appear, oxygen levels rise
4 stages in origin of life
1. abiotic synthesis of small organic molecules (nucleotides and amino acids) 2. macromolecules (proteins and nucleic acids) 3. protobionts 4. self-replicating molecules allowing for continuity of life
serial endosymbiosis
mitochrondia and plastids were formally small prokaryotes living within larger host cells
cambrian explosion
explosion of diversity, first 20 million years of cambrian period, animals with hard plates and exoskeletons
continental drift
process by which earths continents move slowly over underlying hot mantle
2 mass extinctions
1. permian, ~250 mya, separates paleozoic and mesozoic, caused by volcanoes 2. cretaceous, ~65 mya, separates mesozoic and cenozoic, caused by meteorite, dinos died
evolutionary history of a species or group of related species
taxonomy and creator
created by carolus linnaeus, ordered division of organisms into categories based on a set of phenotypic characteristics used to assess similarities/differences, includes binomial nomenclature and hierarchal classification
how can phylogeny and classification be linked?
systematists depict evolutionary relationships in branching phylogenetic trees, look at morphologies, genes, and biochemistry
monophyletic clade
ancestor species and all of its descendants
paraphyletic grouping
ancestor species and some but not all descendants
polyphyletic grouping
consists of various species that lack a common ancestor
shared ancestral features
homologous structure that predates the branching of a particular clade from other members of that clade
shared derived feature
an evolutionary novelty unique to a particular clade
a species/group of species that is closely related to the ingroup
the various species under study
outgroup comparison
differentiate between shared derived and shared ancestral characteristics, based on assumption that homologies present in both outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor
relationship between homoplasies and convergent evolution?
convergent evolution occurs when environmental pressures and natural selection produce similar/analogous adaptions in organisms from different evolutionary lineages
orthologous genes
found in a single copy in the genome and are homologous between species, can only diverge after speciation, nucleotide substitutions are proportional to the time since they last shared a common ancestor
paralogous genes
result from gene duplication so are found in more than 1 copy of genome, can diverge within the clade that carries them and often evolve new functions, nucleotide substitutions are proportional to the time since the genes duplicated

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