Ecology - Chapter 5
Peter and Rosemary Grant are known for their work on
Darwin's finches.
________ is the differential success of individuals in a population in response to environmental conditions.
Natural selection
Several years of heavy precipitation occur on the Galápagos Islands. What do you predict would happen to the beaks of Darwin's medium ground finches?
Offspring beak depth would increase.
(T/F) A trait cannot be subject to natural selection unless it is heritable.
TRUE
(T/F) Ecotypes are variants within a species that are adapted to local environmental conditions.
TRUE
(T/F) Gene flow is restricted between subspecies because of some extrinsic barrier, such as rivers or mountain ridges.
TRUE
(T/F) Genes are arranged in threadlike bodies called chromosomes.
TRUE
Under which of the following conditions would genetic drift exert the greatest influence?
a very small population
All of the DNA in a cell is collectively called the ________.
genome
A(n) ________ individual has the same alleles at the same locus on homologous chromosomes.
homozygous
The tongue length of an animal is controlled by two alternative alleles at a single locus, L (long) and l (short). If an individual has parents that are both homozygous dominant, it will be
homozygous dominant with a long tongue.
The simplest response an individual organism can make to a change in environmental conditions is to
move to a more suitable location.
What is the primary original source of genetic variation in a population?
mutation
The mechanism of evolution proposed by Charles Darwin in The Origin of Species is
natural selection.
The outward appearance of an organism for a given characteristic is called its ________.
phenotype
Identical twin raccoons are raised in different environments and yet behave very differently. This is an example of
the norm of reaction.
The fitness of an individual is measured by
the proportionate contribution it makes to future generations.
In a population with a q allele frequency of 0.6, what would the frequency of allele p be?
0.4
What is the allele frequency of q in a population with genotypic frequencies of P = 0.3, H = 0.4, and Q = 0.3?
0.5
Plants grown under a medium light condition would exhibit how much biomass?
20g
If a population has an allele frequency of 1.0, you would say that
B) genetic variation of that allele is low.
________ are heritable changes in a gene or chromosome.
Mutations
(T/F) The expression of most phenotypic traits is affected to varying degrees by the environment.
TRUE
(T/F) The position occupied by a gene on the chromosome is called the locus.
TRUE
Squirrels tend to have larger body sizes at higher latitudes. This could be an example of
a cline.
A(n) ________ is a measurable, gradual change over a geographic region in the average value of a trait.
cline
If the physical expression of a heterozygous individual is intermediate between those of the homozygotes, the alleles are ________.
codominant
The expression of different phenotypic traits for a given genotype under different environmental conditions is referred to as
developmental plasticity.
When genetic variation occurs among subpopulations of the same species, it is known as genetic ________.
differentiation
If birds with larger beaks are favored by the environment, it is likely that ________ selection will occur.
directional
The type of natural selection in which the mean value of a trait is shifted toward one extreme is called ________ selection.
directional
In tiger salamanders one phenotype is cannibalistic while another is not. Both are stable strategies. Which form of selection is best represented by this scenario?
disruptive
A(n) ________ is a population that has adapted to its unique local environmental conditions.
ecotype
The gene pool refers to all of the genetic information within a
population.
Define an adaptation and describe how it relates to natural selection.
In evolutionary theory, adaptation is the biological mechanism by which organisms adjust to new environments or to changes in their current environment. The idea of natural selection is that traits that can be passed down allow organisms to adapt to the environment better than other organisms of the same species.
According to the research of Beren Robinson, how would you expect stickleback species to differ between two lakes, one of which supports two species of stickleback and the other has a single species?
Marine stickleback populations live and breed strictly in the ocean. Sea-run stickleback fish are anadromous, meaning that they are born in fresh water, spend most of their lives in the ocean, Paxton Lake Benthic and Limnetic Threespine Sticklebacks are sympatric species derived from the Threespine Stickleback, but they have not been formally named. Limnetics primarily exploit plankton, and have traits that are considered adaptations to a zooplankton-consuming lifestyle.
(T/F) The selective agent is the environmental cause of fitness differences among organisms with different phenotypes.
TRUE
The alternate forms of a gene are called ________.
alleles
Individual beak size of individual finches of the Galápagos Islands
will greatly influence individual survival.
________ mating occurs when individuals choose mates nonrandomly with respect to some phenotypic trait.
Assortative
(T/F) An individual evolves during its lifetime.
FALSE
(T/F) Changes due to developmental plasticity are reversible.
FALSE
(T/F) Charles Darwin advocated a theory of evolution that involved individuals acquiring useful characteristics during their lifetimes.
FALSE
(T/F) Disruptive selection favors individuals possessing traits near the mean value of a population.
FALSE
(T/F) Inbreeding is usually beneficial to a population because it increases genetic diversity.
FALSE
(T/F) Most mutations are beneficial.
FALSE
(T/F) Variation within and among species would increase dramatically if the environment were homogeneous.
FALSE
T/F) Most traits are influenced by only one locus.
FALSE
Use an example to explain how and why the genotype and environment influence the phenotype of an organism.
Genes play an important part in influencing phenotype, but genes are not the only influence. Environmental conditions, such as temperature and availability of nutrients can affect phenotypes. For example, temperature affects coat color in Siamese cats.
Explain how the effects of mutation, genetic drift, and gene flow influence the genetic variation of a population.
Genetic drift thus removes genetic variation within demes but leads to differentiation among demes, completely through random changes in allele frequencies. ... In contrast, restricted gene flow promotes population divergence via selection and drift, which, if persistent, can lead to speciation.
________ is the mating of individuals in the population that are more closely related than expected by random chance.
Inbreeding
Which of the following represents acclimation?
Marine lionfish are able to tolerate freshwater in estuaries.
According to the Hardy-Weinberg principle, which of the following must be true for gene frequencies in a population to remain the same?
Mating is random.
Explain the difference between phenotypic plasticity and adaptation, and suggest how you would collect data that would distinguish between them.
Phenotypic plasticity can be distinguished from genetic differentiation which includes local adaptation (adaptive genetic changes) and maladaptive or non-adaptive genetic changes, depending on whether quantitative traits differences among populations in situ disappear by raising individual plants from these populations. Phenotypic plasticity can be defined as 'the ability of individual genotypes to produce different phenotypes when exposed to different environmental conditions' (Pigliucci et al. ... As with any organismal trait, the way in which an individual responds to environmental influences is subject to evolutionary change.
T/F) The characteristics maximize the fitness of an individual under one set of environmental conditions generally limit its fitness under a different set of conditions.
TRUE
Define a cline and a subspecies, and explain how they are affected by gene flow.
The term subspecies is typically used for geographically isolated populations of a species (e.g. by oceans or mountain ranges). ... There is another type of genetic structure when adaptation occurs along an environmental gradient within the range of a species. This is called a cline. Clines are often cited to be the result of two opposing drivers: selection and gene flow (also known as migration). Selection causes adaptation to the local environment, resulting in different genotypes or phenotypes being favoured in different environments. This diversifying force is countered by gene flow, which has a homogenising effect on populations and prevents speciation through causing genetic admixture and blurring any distinct genetic boundaries.
A gradual change in phenotype across an environmental gradient, such as white-tailed deer changing gradually in size from large in the north to small in the south, is referred to as
a cline.
A gene is
a stretch of DNA coding for a polypeptide chain (sequence of amino acids).
Bt corn is
a variety that possesses genes from a bacterium.
Reversible phenotypic changes in an individual organism in response to changing environmental conditions are referred to as ________.
acclimation
A(n) ________ is any heritable behavioral, morphological, or physiological trait of an organism that has evolved over a period of time by the process of natural selection.
adaptation
The specific traits of a particular organism enabling it to survive, grow, and reproduce within a given environment are called
adaptations.
The process by which one species gives rise to multiple species that exploit different features of the environment is called ________.
adaptive radiation
The Galápagos Islands are inhabited by 13 species of Darwin's finches that evolved from a single species. This is an example of
adaptive radiation.
The alternate forms of a gene are called
alleles.
Measurements of bill length in a population of seed-eating birds reveals two distinct groups: small-billed individuals feeding on soft-shelled seeds and large-billed individuals feeding on hard-shelled seeds. This bimodal distribution most likely resulted from
disruptive selection.
An allele that completely masks the effect of another allele is considered
dominant.
Which of the following characteristics is an example of a qualitative trait?
flower color
In the Hardy-Weinberg equation P + H + Q = 1, what does "Q" represent?
frequency of recessive homozygotes
An organism's structure and ________ reflect adaptations to its particular environment.
function
The movement of genes between populations is referred to as
gene flow.
The sum of genetic information (alleles) across all individuals in a population at any one time is called the ________.
gene pool
The sum of genetic information (alleles) across all individuals in the population is referred to as the ________.
gene pool
A transgenic organism is one that
has received genetic information from another organism.
The color of a flower is controlled by two alternative alleles at a single locus, R (red) and r (white). If an individual has the Rr alleles, it is considered to be
heterozygous with a red color.
The effect of positive assortative mating is to
increase the number of homozygotes in the population.
Phenotypic characteristics that have a continuous distribution are considered to be ________ traits.
quantitative
Traits that have a continuous distribution are known as
quantitative traits.
Researchers Rosemary and Peter Grant have discovered that beak size frequency of Galápagos Island medium ground finch populations varies with all the following, except
seed color.
A population of a species that is distinguishable from other populations by one or more characteristics is referred to as a(n) ________.
subspecies
Geographic isolates of a particular species that differ from other populations by one or more characteristics are considered to be
subspecies.
The phenotypic trait that selection acts upon directly is referred to as the ________ of selection.
target
