Natural Selection Flashcards
One cause of genetic drift is ___, in which a small group of individuals leaves its home population and establishes a new, isolated settlement.
the founder effect
Select all of the following that can lead to evolution in a population.
- mutation
- migration
- selection
A ____ is a change in an organism’s DNA sequence and is the raw material for evolution, because genes affect the phenotypes and evolution acts on phenotypes.
mutation
Reproductive success of an organism can also be referred to as
fitness
When a population size drops rapidly over a short period, causing a loss of many alleles that were present in the larger ancestral population, this is referred to as the ____ effect.
bottleneck
A change in allele frequencies hat occurs by chance and that tends to eliminate alleles in a population rather than increase diversity is called
genetic drift
A mutation can affect evolution in a species only if
subsequent generations inherit it
Rank the following from highest fitness at the top to lowest fitness at the bottom. (Assume that the numbers represent the entire lifetime of the mayfly mother.)
- A mayfly that lays 400 eggs and mothers 3 offspring that survive to reproductive age
- A mayfly that lays 800 eggs and mothers 2 offspring that survive to reproductive age
- A mayfly that lays 900 eggs and mothers 1 offspring that survive to reproductive age
- A mayfly that lays 1,000 eggs and mothers 0 offspring that survive to reproductive age
Select all the examples of nonrandom mating.
- mating only within a specific group
- choosing mates based on certain characteristics
- mate choice based on social position
When the intermediate phenotype of a trait is being selected for and the extreme phenotypes are being selected against, the population is probably undergoing
stabilizing selection
A difference in the appearance between males and females of a species is called
sexual dimorphism
Fitness depends on which of the following?
- number of successful reproductive efforts in lifetime
- proportion of offspring that survive to reproduce
- ability to survive long enough to successfully reproduce
Natural selection requires
genetic diversity
Select all the key properties of evolutionary adaptations
- they are heritable
- they can confer reproductive success
When two phenotypic extremes of a trait are being selectively favored, then a natural population is undergoing ____ selection.
disruptive
The ability of an organism to camouflage with its environment is an example of a(n)
adaptation
Selection for dark-winged moths in a population of moths with pigmentation that varies from light to dark is an example of ___ selection.
directional
Sexual selection is a special form of natural selection in which individuals vary in ability to
obtain mates
Rank the following turtles from lowest fitness at the top to highest fitness at the bottom.
- A turtle that dies at 100 years and fathers 0 surviving offspring
- A turtle that dies at 75 years and fathers 10 surviving offspring
- A turtle that dies at 50 years and fathers 20 surviving offspring
- A turtle that dies at 20 years and fathers 30 surviving offspring
Select all of the following that are examples of sexual selection.
- male to male combat during the mating season
- female birds choosing mates with the best nest-building skills
- males displaying showy plumage to females to get more opportunities to mate
Select all of the following that are examples of the bottleneck effect.
- North American bison
- greater prairie chickens
What is an example of the founder effect?
A few birds colonizing an isolated island
What causes the movement of alleles between populations?
Migration
Directional, disruptive, and stabilizing are all types of ____, in which certain phenotypes are favored over others.
natural selection
Select all of the effects of migration.
- introduce new alleles into a population
- decreased regional differences in genetic diversity
A chance change in a population’s allele frequencies, such as after a drastic reduction in population size, is the root of what force of evolution?
genetic drift
If a predator is more likely to prey upon fish that are brightest in color, then natural selection in this environment will favor
drabber fish
Select the true statement about mutation and natural selection.
Natural selection acts on existing mutation.
What is a mechanism by which harmful alleles can be maintained in a population even though homozygous recessive individuals have greatly reduced fitness?
heterozygotes have greater fitness
Select all of the following that can limit the actions of natural selection.
- an organism’s evolutionary history
- traits that affect survival but not reproduction
- disasters such as floods and volcanoes that eliminate allele combinations
Select all the reasons why males usually show the greatest effects of sexual selection.
- Females have high investment in reproduction
- Males mush compete for access to females
What genotype for the “sickle cell gene” causes mild symptoms of sickle cell disease but confers resistance to malaria?
heterozygous
The goal of natural selection is to produce perfect organisms.
False
Genetic drift has a greater effect on
small populations
The diagram illustrates change in a bacteria population due to the presence of an antibiotic over many generations. This is an example of
natural selection
If the environment changes, a trait that was adaptive may become nonadaptive or costly, demonstrating that
evolution continuously shapes populations
A population of snails is separated when an eight-lane highway is built. After 50 years, the two separate populations can no longer interbreed. This describes the process of
new species forming
The model that proposes that speciation occurs in brief bursts interrupted by long periods of little change is ____ equilibrium.
punctuated
Select all of the following that are prevented by postzygotic reproductive barriers.
- production of fertile offspring
- survival of offspring to maturity
Match the postzygotic reproductive barrier on the left with its example on the right.
- Hybrid inviability - Hybrid eucalyptus seeds do not germinate; seedlings die very early.
- Hybrid infertility - The offspring of a lion-tiger mating (liger) is infertile.
- Hybrid breakdown - Offspring of hybrid mosquitoes have abnormal genitalia.
If a zygote cannot form between two organisms, then a type of ____ reproductive barrier is present.
prezygotic
Organisms have changed over time; new species have appeared while other species have gone extinct. This is a description of ____.
macroevolution
The ____ model of speciation proposes that evolution proceeds in small, incremental changes over many generations.
gradualism
According to the biological species concept, a species is a population
whose members can interbreed and produce fertile offspring.
What type of reproductive isolating barrier occurs after the formation of a zygote and reduces the fitness of a hybrid?
postzygotic
Select all the examples of organisms from the fossil record that offer evidence of punctuated equilibrium.
- mammals
- bryozoans
- mollusks
Match the type of prezygotic reproductive barrier on the left with its example on the right.
- Habitat isolation - Herbivores ladybird beetles feed on different types of plants.
- Temporal isolation - Field crickets mature at different times.
- Behavioral isolation - Frog mating calls differ.
The formation of a new species is called
speciation
Select all of the reasons why the biological species concept is not a perfect definition of a species.
- It doesn’t apply to asexually reproducing organisms
- It only accounts for absolute reproductive isolation
- It is impossible to apply to extinct organisms known only from fossils
Select the two models of speciation.
- gradualism
- punctuated equilibrium
Match the name of the type of prezygotic reproductive barrier on the left with its description or an example on the right.
- Habitat isolation - populations live in different places
- Behavioral isolation - a variation in a courtship ritual
- Mechanical isolation - reproductive structures that do no fit together
- Gametic isolation - sperm that does not fertilize the egg
- Temporal isolation - active at different times of day
Select all the postzygotic reproductive barriers.
- hybrid infertility
- hybrid inviability
- hybrid breakdown
Over many hundreds of years, the definition of ____ has changed several times as scientists have refined ideas.
a species
The figure labeled A represents ____, and the figure labeled B represents ____.
gradualism; punctuated equilibrium
The speciation and extinction of the dinosaurs are examples of ____, and the increased frequency of a particular genotype that specifies a color patter in fish is an example of ____.
macroevolution; microevolution
When two populations no longer share the same gene pool, then ____ has occurred.
speciation
The accumulation of small changes in a population by microevolution can eventually lead to large-scale
macroevolution
Mechanisms of ____ prevent successful reproduction and include prezygotic barriers and postzygotic barriers.
reproductive isolation
Carolus Linnaeus classified species based upon ____ but not upon ____.
body structure; evolutionary relationships
Select all the criteria biologists can use to define species.
- reproductive isolation
- DNA sequence analysis
Select three ways that genetic divergence can occur between two separated populations.
- natural selection
- genetic drift
- mutation
Select the most accurate statement about gradualism and the fossil record.
For organisms such as diatoms that existed in large, connected populations, the fossil record shows a slow pace of gradual changes.
When might speciation occur rapidly? Select all that apply.
- After a key adaptation arises
- After a major environmental change wipes out many species
What type of organisms appear to have evolved by gradualism, as suggested by the fossil record?
microscopic protists
