ch 21 assignment questions
The idea that species are defined based on the ability to interbreed with each other and exchange genes is the basis of which species concept?
Biological species concept
if two reproductively isolated populations re-establish contact, _ will tend to increase differences between the populations, and _ will tend to decrease differences between the populations.
reinforcement; gene flow
What type of isolation occurs when members of one species are unable to successfully interbreed with members of another species?
reproductive
prevention of _ fusion acts as reproductive isolating mechanism because sperm from one species is unable to successfully fertilize the egg of another species.
gamete
Speciation is more likely in geographically isolated populations because which Of the following does not occur?
gene flow
in incompletely reproductively isolated populations, _ _ decreases genetic distinctiveness between the populations when hybrids are produced and reporduced with members of either population.
gene flow
when two incompletely isolated populations come together, _ _ immediately begins to occur between them.
gene flow
although speciation may occur in population that are geographically distant from one another, exchange of _ between the populations through processed such as migration or wind dispersal of pollen can cause the populations to remain integratedas the same _.
gene, species
What process can promote speciation through random changes between isolated populations?
genetic drift
in addition to natural selection, which of these can lead to speciation?
genetic drift
the idea that evolution occurs over time through the accumalation of small changes at a relatively steady pace is known as _.
gradualism
_ and _ _ are two ends of the continuum of the pace of evolutionary change.
gradualism, punctuated equilibrium
the _ view suggests that evolution proceeds at a relatively slow pace over time, whereas the _ _ view suggests that species experience long periods stasis alternating with bursts of evolution over short periods of time.
gradualism, punctuated equilibrium
What types of conditions may lead to adaptive radiation?
1 Formation of islands through volcanic activity and subsequent colonization 2 A species occurs in an environment with few other and many resources
Select events that likely led to mass extinctions in Earth's evolutionary history.
1 Global climate 2 Asteroid collisions
Select the two main types mechanisms based on when they act relative to the production of a zygote.
1 postzygotic isolating mechanisms 2 prezygotic isolating mechanisms
what is meant by the term allopatric
Occurring in geographically separated areas
True or false: Since the Cambrian period, biological diversity has greatly decreased around the glode.
false
The phenomenon that causes a single ancestral species to evolve into a wide array of descendant species with diverse habitats. forms. or behaviors that occurs often as a result of colonization Of a new area is known as
adaptive radiation
What evolutionary leads to the existence of groups of closely related species that have recently evolved from a common ancestor by adapting to different parts Of the environment?
adaptive radiation
What is the hypothesized process by which the great diversity of cichlid fish evolved in Lake Victoria?
adaptive radiation
the diversification of drosophila species in the originally vacant iches and frequently isolated habitat patches of the hawaiian islands is an example of
adaptive radiation
what process led to the diversification of alpine buttercups in New Zealand?
adaptive radiation
which is the best explanation for the evolution of the fourteen species of darwin finches?
adaptive radiation
as demonstrated strongly by biologist ernst mayr, _ populations are more likely to have eveolved differents leading to speciation due to the fact taht they are geographically seperated.
allopatric
speciation that occurs when populations are physically seperated from one another is _ speciation, whereas _ speciation occurs when populations co-occur.
allopatric, sympatric
Which form of isolation when differences in mating rituals. courtship songs, chemical and electric communication prevent members Of two different species from interbreeding?
behavioral
A female bird refuses to mate with a male bird of another species because he does not perform the correct courtship ritual. This is an example of which of the following?
behavioral isolation
the reproductive isolating mechanism that prevents interspecies hybridization because members of different species do not recognize each other's courtship rituals is _ _.
behavioral isolation
according to the _ species concept, species are distiguished by whether gene flow occurs between populations.
biological
the _ species concept defines a species as a group of individuals that is able to interbreed, producing viable and fertile offspring.
biological
the process by which natural selection produces a divergence in traits and resource use among sympatric speceis is called _ displacement.
character
the number of species worldwide is greater than it has ever been. Unfortunately, this number is currently _ due to _ activity.
decreasing, human
what organisms became extinct at the end of the Cretaceous period?
dinosaurs
sympatric speciation can result from which type of natural selection that produces two different phenotypes in a population
disruptive selection
genetic _ leads to random changes between populations that may result in reproductive isolation.
drift
Although the ranges Of the toads Bufo woodhouse/ and B. americanus overlap in areas, B. woodhouse/ breeds in streams whereas B. americonus breeds in rainwater puddles. Therefore, even though these two species can produce viable hybrids, they rarely do in nature due to
ecological isolation
the reproductive isolating mechanism taht occurs when the ranges of two species overlap, but they rarely come into contact with one another because they utilize different habitats is _ _.
ecological isolation
sympatric species generally do not _ because differences between the species would be homogenized.
exchange genes
in evolutionary time, sharp declines in species diversity are called mass _.
extinction
over evolutionary time, the rate of speciation has been greater than the rate of _.
extinctions
when two incompletely isolated populations come together, they may be able to produce fertile _ that cause gene flow between the populations.
hybrids
mechanisms that prevent genetic exchange between members of different species are termed reproductive _ mechanisms and often play a role in plant and animal speciation
isolating
gegraphic isolation can accelerate speciation because
it restricts gene flow
A trait that evolves within a species, allowing it to use resources or other of the environment that were previously inaccessible is known as a(n)
key innovation
The inability of different species to interbreed because of an incompatibility in reproductive Organs is known as
mechanical mechanism
according to the ecological species concept, species distinctions are maintained by Darwin's mechanism for evolution, knwown as _ _.
natural selection
which of the following processes can reinforce incomplete reproductive isolation of two species when interspecies hybrids are less fit than those taht are not hybrids?
natural selection
polyploidy is a major mechanism that has led to the emergence of many species of_.
plants
What mechanism can cause intermediate reproductive isolation and lead to sympatric speciation?
polyploidy
if an organism has three or more sets of chromosomes, it is known as _.
polyploidy
a catergory of reproductive isolating mechanisms called _ isolating mecahnisms block the development of a viable and fertile individual after fertilization has taken place.
postzygotic
in _ isolating mechanisms a hybrid zygote is formed, but it is unable to survive or reproduce due to developmental or genetic problems.
postzygotic
_ isolating mechanisms prevent the proper functioning of hybrids, and _ isolating mechanisms act to prevent the formation of hybrid zygotes.
postzygotic, prezygotic
the formation of an interspecies hybrid zygote is prevented by _ isolating mechanisms, whereas _ isolating mechanisms prevent the successful development of hybrid zygotes once they are formed
prezygotic, postzygotic
the idea that evolution proceeds with long periods of stasis alternating with relatively rapid periods of evolutionary change is known as _ _.
punctuated equilibrium
fourteen species of finches have evolved in the galapagos islands as an ancestral species underwnet adaptive _ to fill vacant ecological _ such as seed-feeding, tree-dwelling, and insect feeding.
radiation, niches
when natrual selection acts against hybrids and completes reproductive isolation, a process calle d_ has occured
reinforcement
when natural selection acts against hybrids and completes reproductive isolation, a process called _ has occured.
reinforcement
a long period of little or no evolutionary change in a species is known as _.
stasis
species that are _ species can occur in the same location and are phenotypically different.
sympatric
two species of oak tree occur in the same area but one thrives in the grassy lowlands whereas the other lives in scrubby, charparral habitats. These oak trees are _ species.
sympatric
What describes the Of ones species splitting into two species Without the species being geographically separated?
sympatric speciation
interspecies hybrids are usually not considered separate species because:
they are sterile
If two species that have evolved over time to completely reproductively isolated suddenly come into contact with one another,
they will remain distinct species
Prezygotic isolating mechanisms prevent the formation Of Which Of the following?
zygotes