Science Subtest Iii: Evolution

Front 1

________ is based on the survival of certain traits in a population through the course of time.

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natural selection

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"Survival of the fittest" refers to

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natural selection

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phenotype

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expressed trait, constantly exposed to environment
Example: long neck on giraffe

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explain why natural selection acts on the phenotype rather than the genotype of an organism

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the phenotype of an organism either help the organism to survive or in some way make its survival less likely. Based on an organisms phenotype, selection indirectly adapts a population to its environment by maintaining favorable genotypes in the gene pool

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what are the three modes of natural selection

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stabilizing selection
directional selection
diversifying selection

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favors the common phenotypes

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stabilizing selection

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shift the frequency of phenotypes in one direction

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directional selection

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favors individuals on both extremes of the phenotypic range

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diversifying selection

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why does diversity aid a population

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it provides possible improvements adn increases the chance of survival in changing conditions

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why do populations change

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because of the survival of a few who preferentially reproduce, not from the gradual change of all individuals in a population

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what two factors provide continued diversity

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spontaneous mutation and recessive alleles

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populations lacking in diversity are at risk for

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extinction

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biological diversity results from

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the adaptations of native or migrant predecessors to changing environments

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studies of fossil layers indicate that the diversity and complexity of species has ______ over time

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increased

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episodic speciation reveals that gaps in the fossil record may indicate that evolution proceeds _______, not in a strictly gradual way

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intermittently

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changes in lineages seen in the fossil record are often the result of

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episodic speciation events

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scientists defin a mass extinction event as

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a brief period where a large number of speicies become extinct

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How many mass extinction events have there been in earths history

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between 5 and 15

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what is evidence of a mass extinction

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disappearence of multiple species from the fossil record during a single time period

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what other factors can artficially erase species from the fossil record

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environmental changes

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the chance deviatoin in frequency of alleles (traits) resulting from teh randomness of zygote formation and selection is known as

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genetic drift

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the loss of traits associated with genetic drift in small populations can

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decrease genetic diversity

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the process of organisms developing similiar characteristics while evolving in different locations is known as

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convergent evolution

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organisms who undergo convergent evolution do NOTcome from

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common ancestors

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reduces biological deiversity by making distinct species more like each other

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convergent evolution

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the model of evolution that states the organismal forms diverge and species form rapidly over relatively short periods of time is known as

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punctuated equilibrium

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punctuated equilibrium affects the diversity of organisms in two ways:

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1. the diversity of organisms increases dramatically over periods of rapid change and speciatoin
2. the diversity of organisms remains nearly unchanged during the intervening periods

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the effects of selection on phenotypes is known as

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patterns of selection

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what are the four main patterns of selection

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stabilizing
disruptive
directional
balancing

Front 30

______ is the only pattern of selection that increases genetic diversity

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balancing selection

Front 31

name the three patterns of selection that all work to decrease diversity by totally elimnating unfavorable characteristics from the population

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stabilizing
disruptive
directional

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the selection against extreme values of a trait; selection for the average or intermediate values

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stabilizing

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the selection favoring individuals on both extremes of the distribution of a characteristic or trait

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disruptive

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the selection progessively favoring one extreme of a characteristic distribution

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directional

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the selection that maintains multiple alleles in a population, often by favoring heterozygote individuals

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balancing

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Evolution is defined as

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a change in genotype over time

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The Hardy-Weinberg theory of gene equilibrium is a

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mathmatical prediction to show shifting gene patterns

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List the five requirements that keep gene frequency stable and limit evolution accroding to the hardy-weinberg theory

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1. there is no mutation in the population
2. there are no selection pressures; one gene is not more desirable in the environment
3.there is no mating preference; mating is random
4. the populatin is isolated; there is no immigration or emigration
5. the population is large (mathematical probability is more correct with a large sample)

Front 39

If these five conditions are not met what can happen

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then gene frequency can shift, leading to evolution

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What is the formula used to determine if evolution is occuring

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1 = p^2 + 2pq + q^2

Front 41

in this formula, what is 1, p^2, 2pq, q^2

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1= the total population
p^2=number of AA individuals
2pq=number of Aa individuals
q^2=number of aa individuals

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why must you use the aa individuals to find that frequency first before AA and Aa

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because you cannot tell by looking if an individual is AA or Aa

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all the alleles at all gene loci in all individuals of a population is

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the gene pool

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when frequencies vary in the hardy-weinberg equilibrium the population is

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evolving

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when an organism is forced to adapt to a changed environment behavior is modified but ______ remains unchanged

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genotype

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an individual born into the changed environment may have a genotype that is

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favorable under the new conditions

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_______ demands that the individual with the favorable trait will be more likely to survive and reproduce

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survival of the fittest

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the offspring of the more fit individual will then carry forward the

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favorable genotype

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homology is

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any similiarity between characteristics due to shared ancestory

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example of homology

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the wings of a bat and the arms of a human: anatomical structures that perform the same function in different biological species and evolved from the same structure in some ancestor species

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example structures that are both homologous and analogous

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wings of a bat and wings of a robin: in evolution the bat and the robin have evolved through different lineages but they both had forelimbs that developed the same function so that the evolution became convergent with the structures analogous

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what are two causes of speciation

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reproductive and geographic isolation

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what is allopatry

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geographic isolation

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what are the effects of geographic isolation

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the survival of the fittest model may act upon a population causing the formation of a seperate species. when this occurs, even if reintroduced, the populations will have unsuccessful mating encounters

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_______ prevents two or more populations from exchanging genes

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reproductive isolation

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how does reproductive isolation occur

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by preventing fertilization or by the genesis of a degenerate of sterile hybrid (common mule can't reproduce)

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if ferilization does occur, what other barriors exist

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spontaneous abortion
for a hybrid that has been born it is probable that the hybrid will be sterile and produce no offspring

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hybrids that do produce offspring can

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produce sterile progeny

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groups are regarded as subspecies when

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interbreeding is mechanically possible but prevented by the geographical seperation of population

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provide an example of geographic isolation

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the african elephant has been regarded as a single species however evidence has found that there are dna differences between elephants in africa meaning the west african elephants are seperated from the savanna elephants

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The four stages that represent the transformation from nonliving materials to life are

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1. the nonliving (abiotic) synthesis of small monomers such as amino acids and nucleotides
2. these monomers combined to form polymers, such as proteins and nucleic acids
3. accumulation of these polymers into droplets called protobionts
4. the origin of heredity, with RNA as the first genetic material

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what is the role of prokaryotes in the theoretical origins of life on earth

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over time, some prokaryotic groups became multicellular because their small genome size limits the number of genes that control metabolic activities

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prokaryotes evolve to form

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complex bacterial communities where species benefit from each other

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the _______ theory states that the origin of eukaryotes states that eukaryotes arose from symbiotic groups of prokaryotic cells.

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endosymbiotic theory

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smaller prokaryotes lived within larger prokaryotic cells, eventually evolving into

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chloroplasts and mitochondria

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choroplasts are the descendant of

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photosynthetic prokaryotes

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mitochondria are likely the descendants of bacteria that were

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aerobic heterotrophs

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a sequence of endosymbiotic events is

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serial endosymbiosis

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branching diagram (cladogram) illustrating phylogeny

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p56 biology