NATURAL SCIENCE EXAM 1
QUESTIONS WITH CORRECT
SOLUTIONS
Explain how Darwin's research and observations of the natural world affected his ideas
about species. - ANSWER-Darwin's contemplations of the natural systems he observed
and the collections he accumulated during the surveying mission of the H.M.S Beagle
provided the evidence on which he based his hypothesis of descent with modification.
Describe the historical academic context of Darwin's publications. - ANSWER-Darwin
was influenced by Charles Lyell's writings about uniformitarianism and maintained a
collegial relationship with the geologist. Darwin delayed publication of his hypothesis of
natural selection to gather extensive supporting data, but when Alfred Russel Wallace
independently proposed the mechanism of natural selection, Lyell arranged for the
simultaneous presentation of both works. Wallace deferred primary intellectual
ownership to Darwin based on Darwin's more extensive development of the idea.
Describe Darwin's arguments for the theory of natural selection to explain descent with
modification. - ANSWER-Darwin's arguments for the mechanism of natural selection to
explain descent with modification are based on the observations that individuals in a
population vary in heritable traits and a population produces more offspring than can
survive. Darwin presented the logical inference that individuals with more adaptive traits
are more likely to survive and pass on those traits to offspring. Therefore, over
generations, adaptive traits accumulate in a population.
Generalize the effect of Darwin's ideas on science and society. - ANSWER-Darwin's
work has influenced generations of scientists, and his theory about how evolution
happens has been refined and supported and is now considered the unifying concept
for the life sciences. Even though Darwin's ideas were not popular with the Christian
church leaders at first, most mainstream religions now accept them. However,
controversies regarding the teaching of evolution are still raging in some regions of the
United States.
Alfred Russel Wallace (1823-1913) - ANSWER-Contemporary to Darwin; also
developed the hypothesis of natural selection and was a famed biogeographer.
biogeography - ANSWER-Study of the geographical distribution of species.
descent with modification - ANSWER-The outcome of natural selection: modifications
accumulated from generation to generation that can ultimately result in new species.
uniformitarianism - ANSWER-Theory that observable processes in the present have
always been taking place and can also explain activity in the past.
, Explain how a change in allele frequency is evolution. - ANSWER-According to modern
evolutionary theory, evolution occurs as a result of shifts in allele frequencies within a
population over time. Shifts in allele frequencies can result in significant changes in the
phenotypic traits of a population of organisms.
Describe different mechanisms by which allele frequencies can change, including
natural selection, genetic drift, and gene flow. - ANSWER-Natural selection involves the
preferential selection of alleles that confer the greatest fitness to individuals in a
population. Genetic drift is the random change in allele frequencies resulting from
chance events in a population. Gene flow is the change in allele frequencies arising
from the migration of individuals into and out of a population. Changes in allele
frequency in the same generation can lead to evolution in the next generation. However,
of these three mechanisms of evolution, only natural selection operates on adaptations
of populations to their environments.
Differentiate among stabilizing, disruptive, and directional selection. - ANSWER-Traits in
a population exist along a continuum, with most traits falling within a median range.
Stabilizing selection selects against individuals that express the extreme variants of a
trait and for individuals that express the median variants. Disruptive selection selects
against individuals that express the median variants of a trait and for individuals that
express the extreme variants. Directional selection selects against one extreme of a trait
and moves the average variation toward the other extreme.
allele - ANSWER-One version of a gene.
bottleneck effect - ANSWER-A form of genetic drift that occurs as a result of a rapid
decrease in the gene pool of a population; usually associated with a rapid decrease in
effective population size, that decreases genetic diversity and potentially decreases
population fitness because negative alleles may accumulate.
directional selection - ANSWER-A type of natural selection favors a trend toward one
extreme, shifting the population one direction or another.
disruptive selection - ANSWER-A type of natural selection in which selection is against
the common median trait, favoring the extreme variations.
founder effect - ANSWER-Type of genetic drift. A subsample of the original population
has different allele frequencies from the parent population.
gene flow - ANSWER-Mechanism of evolution involving the transfer of alleles between
populations
genetic drift - ANSWER-Chance events that cause changes in allele frequencies in a
population, such as the founder effect and bottleneck effect.
QUESTIONS WITH CORRECT
SOLUTIONS
Explain how Darwin's research and observations of the natural world affected his ideas
about species. - ANSWER-Darwin's contemplations of the natural systems he observed
and the collections he accumulated during the surveying mission of the H.M.S Beagle
provided the evidence on which he based his hypothesis of descent with modification.
Describe the historical academic context of Darwin's publications. - ANSWER-Darwin
was influenced by Charles Lyell's writings about uniformitarianism and maintained a
collegial relationship with the geologist. Darwin delayed publication of his hypothesis of
natural selection to gather extensive supporting data, but when Alfred Russel Wallace
independently proposed the mechanism of natural selection, Lyell arranged for the
simultaneous presentation of both works. Wallace deferred primary intellectual
ownership to Darwin based on Darwin's more extensive development of the idea.
Describe Darwin's arguments for the theory of natural selection to explain descent with
modification. - ANSWER-Darwin's arguments for the mechanism of natural selection to
explain descent with modification are based on the observations that individuals in a
population vary in heritable traits and a population produces more offspring than can
survive. Darwin presented the logical inference that individuals with more adaptive traits
are more likely to survive and pass on those traits to offspring. Therefore, over
generations, adaptive traits accumulate in a population.
Generalize the effect of Darwin's ideas on science and society. - ANSWER-Darwin's
work has influenced generations of scientists, and his theory about how evolution
happens has been refined and supported and is now considered the unifying concept
for the life sciences. Even though Darwin's ideas were not popular with the Christian
church leaders at first, most mainstream religions now accept them. However,
controversies regarding the teaching of evolution are still raging in some regions of the
United States.
Alfred Russel Wallace (1823-1913) - ANSWER-Contemporary to Darwin; also
developed the hypothesis of natural selection and was a famed biogeographer.
biogeography - ANSWER-Study of the geographical distribution of species.
descent with modification - ANSWER-The outcome of natural selection: modifications
accumulated from generation to generation that can ultimately result in new species.
uniformitarianism - ANSWER-Theory that observable processes in the present have
always been taking place and can also explain activity in the past.
, Explain how a change in allele frequency is evolution. - ANSWER-According to modern
evolutionary theory, evolution occurs as a result of shifts in allele frequencies within a
population over time. Shifts in allele frequencies can result in significant changes in the
phenotypic traits of a population of organisms.
Describe different mechanisms by which allele frequencies can change, including
natural selection, genetic drift, and gene flow. - ANSWER-Natural selection involves the
preferential selection of alleles that confer the greatest fitness to individuals in a
population. Genetic drift is the random change in allele frequencies resulting from
chance events in a population. Gene flow is the change in allele frequencies arising
from the migration of individuals into and out of a population. Changes in allele
frequency in the same generation can lead to evolution in the next generation. However,
of these three mechanisms of evolution, only natural selection operates on adaptations
of populations to their environments.
Differentiate among stabilizing, disruptive, and directional selection. - ANSWER-Traits in
a population exist along a continuum, with most traits falling within a median range.
Stabilizing selection selects against individuals that express the extreme variants of a
trait and for individuals that express the median variants. Disruptive selection selects
against individuals that express the median variants of a trait and for individuals that
express the extreme variants. Directional selection selects against one extreme of a trait
and moves the average variation toward the other extreme.
allele - ANSWER-One version of a gene.
bottleneck effect - ANSWER-A form of genetic drift that occurs as a result of a rapid
decrease in the gene pool of a population; usually associated with a rapid decrease in
effective population size, that decreases genetic diversity and potentially decreases
population fitness because negative alleles may accumulate.
directional selection - ANSWER-A type of natural selection favors a trend toward one
extreme, shifting the population one direction or another.
disruptive selection - ANSWER-A type of natural selection in which selection is against
the common median trait, favoring the extreme variations.
founder effect - ANSWER-Type of genetic drift. A subsample of the original population
has different allele frequencies from the parent population.
gene flow - ANSWER-Mechanism of evolution involving the transfer of alleles between
populations
genetic drift - ANSWER-Chance events that cause changes in allele frequencies in a
population, such as the founder effect and bottleneck effect.
