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Chapter 11 Simple Inheritance and Meiosis
DRIVING QUESTION 1
1 How do the two alleles of the CFTR gene in a lung cell differ?
a
...

c
...

e
...

One is on chromosome 7 and one is on chromosome 3
...

all of the above
There is no difference because they are both the same gene
...

a
...
How many alleles of each gene are present?
Answer:

a
...

b
...

3 Consider a gamete
...
How many chromosomes are present?
b
...
A human gamete has 23 chromosomes
...
There is one allele of each gene present in a gamete
...

a
...
How many chromosomes are present in each of its haploid gametes?
Answer: a
...
16 chromosomes in each gamete

5 In diploid organisms, having two homologues of each chromosome can be beneficial if one allele of a gene encodes a
nonfunctional protein
...

Answer: If a haploid organism (with only one allele of each gene) has a nonfunctional allele as its only copy of an essential gene, it will not be
able to survive
...

Answer: As cystic fibrosis has an autosomal recessive inheritance pattern, Emily must have two recessive alleles and therefore inherited one
recessive allele from each parent
...

a
...

c
...

e
...

Assuming that meiosis occurs normally, which of the following represent eggs that she can produce?
a
...
a
c
...
AA
e
...
A or a
g
...

Maintaining this color distinction, now draw a possible version of chromosome 7 that could end up in a gamete
following meiotic division
...
4 and 11
...
The chromosomes are paired, making 41 pairs
...

Answer: If there are 82 chromosomes (41 pairs) in each somatic cell, when meiosis occurs each homologous pair of chromosomes will align,
recombine, and segregate during meiosis I
...


11 Describe at least two major differences between mitosis (discussed in Chapter 9) and meiosis
...
Neither of these events occurs during mitosis
...
Then, at meiosis II, sister chromatids would
separate, as in mitosis
...


DRIVING QUESTION 3
13 What is the genotype of a person with CF?
a
...

c
...

e
...
heterozygous
b
...
homozygous recessive
Answer: a
...
no CF; c
...
A carrier is
heterozygous, having one CF-associated (recessive) allele and one non-CF allele
...


16 Women can inherit alleles of a gene called BRCA1 that puts them at higher risk for breast cancer
...
Of the genotypes listed below, which carries the lowest genetic
risk of developing breast cancer?
a
...
Bb
c
...
BB and Bb carry less risk than bb
...
All carry equal risk
...
However, this
person does not have the disease phenotype
...


18 Assume that Emily (who has CF) decides to have children with a man who does not have CF and who has no family
history of CF
...

b
...

d
...

On the basis of the Punnett square results, what is the probability that they will have a child with CF?
On the basis of the Punnett square results, what is the probability that they will have a child who is a carrier for CF?

Answer:

a
...
From his family history, her partner is likely to be homozygous dominant (AA), so his
gametes will be A
...

A

A

a

Aa

Aa

a

Aa

Aa

c
...

d
...


19 You are a genetic counselor
...
You ask about other family
members
...
The student’s
father is 62 years old and does not have Huntington disease
...

a
...
The student has a half sister
...
Her father is 45 and does
not have Huntington disease
...
How does the half sister’s risk
compare to her brother’s (the student’s) risk? Could you give her a definitive answer about her risk? Why or why not?
Answer:

a
...
If the father is 62 and does not have Huntington
disease, it is most likely that he has not inherited a predisposition for it and is homozygous recessive (hh)
...

b
...
The risk of inheriting a dominant (H) allele from the mother is still 50%
...
Given the father’s age, it is too
soon to know (based on the progression of the disease) if he did indeed inherit a dominant allele from his father
...

20 From the discussion in this chapter, why might one person with a homozygous recessive CFTR genotype have a
somewhat different phenotype from another person who also has a homozygous recessive CFTR genotype?
Answer: While two people may have the same CFTR genotype, their genotypes at other alleles may differ
...


21 Phenylketonuria is considered to be an inborn error of metabolism
...
Testing of all newborns allows this
condition to be detected at birth
...
g
...
If two carriers of both cystic fibrosis and phenylketonuria were
to have a child, what is the probability that the child will have
a
...

c
...


both cystic fibrosis and phenylketonuria?
cystic fibrosis and be a carrier for phenylketonuria?
neither condition?
neither condition and not be a carrier for either?

Answer:

a
...
The probability of having
both is 1/4  1/4  1/16
b
...
The probability of having CF
and being a carrier for PKU is 1/4  2/4  2/16 1/8
c
...
The probability of not having PKU
and not having CF is 3/4  3/4  9/16
d
...
The probability of not having either condition and not being a carrier for either is 1/4  1/4  1/16

This question can also be worked out from a Punnett square (C and c  cystic fibrosis alleles, P and p  PKU alleles):
CP

Cp

cP

Cp

CP

CCPP

CcPp

CcPP

CcPp

Cp

CCPp

CCpp

CcPp

Ccpp

cP

CcPP

CcPp

ccPP

ccPp

Cp

CcPp

Ccpp

ccPp

ccpp

DRIVING QUESTION 4
22 Can cystic fibrosis be diagnosed prenatally by examining the fetal chromosomes (as shown in the inset in Infographic
11
...


23 Ivacaftor (trade name Kalydeco) is a drug designed to enhance the activity of the CFTR protein encoded by the G551D
allele
...
The drug has been
shown in laboratory studies to enhance the activity of this protein
...

a
...
Include who the
participants were, how participants were assigned to the experimental and the control group, and what treatment(s) were
given to participants in each group
...
Before treatment started, baseline measurements of lung function were obtained
...
This
measurement is known as the predicted FEV
...
The results are shown in the graph
...

• How soon did the experimental group experience an improvement in lung function as measured by predicted FEV?
• How long was the improvement sustained?
• By the end of the study, what was the absolute improvement of the experimental group relative to baseline?
c
...
Is ivacaftor likely to be a viable
treatment for patients whose CF is caused by this allele? Why or why not?

Data from Ramsey, B
...
, et al
...
Figure 1A
...


Answer:

a
...
They would have been randomly assigned to receive
either the drug or a placebo
...
This design reduces potential bias in the results
...
The experimental group showed distinct improvements in FEV relative to controls at day 15
...
At 48 months, the experimental group had an approximately 9% improvement in FEV, while
the control group had an approximate 2% reduction in FEV
...
As ivacaftor enhances the activity of proteins already in the membrane, it is not likely to be effective in patients with the
∆F508 allele because the protein has not made it to the membrane in these patients
...
The results revealed she has a G551D allele,
making her a candidate for ivacaftor
...
In this
case, the genetic test opened up a treatment option for a patient
...
g
...
If you were faced with the decision to take a genetic test, especially for a disease for which there
is no cure, would you take the test? Why or why not?
Answer: There are many possible opinions
...


MILESTONES IN BIOLOGY 4
1 You have a tall pea plant
...
What are its possible genotypes?
b
...

Answer:

a
...

b
...
If the tall plant is true
breeding (homozygous), then 100% of the offspring will be Tt (tall)
...

2 In crossing pea plants:
a
...
Will the offspring be true breeding? Explain your answer
...
If both parents are true breeding for both traits, then 100% of the offspring will be tall with purple flowers
...
In this case, all the offspring will be homozygous dominant (TTPP ) (as both their parents were homozygous dominant)
...

3 Half of the gametes of a heterozygous parent will carry the dominant allele, and half will carry the recessive allele
...
The two alleles will segregate from each other at meiosis I
...

a
...
What would such a violation suggest about the two genes?
Answer:

a
...

b
...


Chapter 12 Complex Inheritance
DRIVING QUESTION 1
1 Which of the following most influences the development of a female fetus?
a
...

c
...

e
...
This means that if a male inherits an X-linked recessive allele (from his
mother’s X chromosome), that is the only allele of that gene he has—there is no dominant allele on another X chromosome to mask the
recessive
...
If a female inherits an X-linked recessive allele on one of her two X chromosomes,
she will not develop the disease if her other X chromosome has the dominant allele to mask the recessive allele
...
Sons cannot inherit X-linked conditions from their fathers because sons inherit their father’s Y chromosome, not the X
...


4 Which of the following couples could have a boy with Duchenne muscular dystrophy (DMD)?
a
...

c
...

e
...
Use your answer to check your answer to
Question 1
...

b
...

d
...
female; b
...
male; d
...

a
...

b
...

Answer:

a
...
However, your son will inherit his Y
chromosome from his father (not your father)
...

b
...
Your son will inherit this same Y
chromosome from you
...

7 A wife is heterozygous for Duchenne muscular dystrophy alleles, and her husband does not have DMD
...
What percentage of their sons, and what percentage of their daughters, will have
a
...
an X-linked dominant form of rickets (a bone disease)?
Answer:

a
...
If the mother is a carrier and the father does not have the
disease, then none of the daughters will have Duchenne muscular dystrophy, and 50% of the sons will have the disease
...
As neither the mother nor the father has rickets, neither has an X-linked dominant allele of the rickets gene
...


DRIVING QUESTION 2
8 What aspects of height make it a polygenic trait?
Answer: Many genes contribute to height
...


9 Which of the following inheritance patterns includes an environmental contribution?
a
...

c
...

e
...
Multifactorial traits are those on which environment has an
influence
...
In codominance, heterozygotes display traits of both alleles present
...

Answer: If you are type A-positive, then you can donate to other A-positive people as well as to AB-positive people
...


13 If two women have identical alleles of the suspected more than 400 height-associated genes, why might one of those
women be 5 feet, 5 inches tall and the other 5 feet, 8 inches tall?
Answer: The environment can influence height
...
Similarly, if one of the women develops osteoporosis, she may lose height over time
...
10
...
If genes were the only contributor, then people with the shorter alleles would have higher rates of depression
regardless of stressful life experiences
...


15 Look at Infographic 12
...
At approximately how many stressful experiences does the homozygous short-allele
genotype begin to influence the depression phenotype?
Answer: It appears that three or more stressful experiences influence the depression phenotype
...
g
...


17 A serious car crash on a freeway has resulted in multiple injuries causing substantial blood loss in three members of
a family—a mother, a father and their 2-year-old daughter
...

a
...
What blood type should they use (consider both
ABO blood type and Rh factor)? Explain your answer
...
Both parents carry a blood donor card
...
From this information, what (if
any) additional blood types (beyond your answer to part a) can be given to either parent? Explain your answer
...
Does knowing the parents’ blood types give you enough information about the daughter’s possible blood type to use a
different blood type for her transfusion? Why or why not? (Hint: Consider possible blood types for the daughter and the
implications of, for example, using A-negative donor blood
...
Type O-negative is the universal donor, so this blood type should be used when no information is available about the blood
types of the recipients
...
As the mother is O-negative, she can receive only O-negative blood
...

c
...
However, we
don’t know if her father is heterozygous for the A allele (e
...
, AO) or homozygous (AA)
...
If he is a double heterozygote, then the daughter could be
O-negative
...
Because we don’t know the father’s genotype, it is not safe to use any blood type
other than O-negative
...
a human egg
b
...
a human zygote
Answer: a
...
23; c
...
However, cystic
fibrosis is caused by mutations that change the nucleotide sequence of the gene—these changes cannot be detected by simply looking at the
chromosomes
...

b
...

d
...

Answer: Most cases of trisomy 21 occur because of a nondisjunction during meiosis in egg development that results in an egg with 24
chromosomes, two of which are chromosome 21
...

Factor

Value

Consider known risks (e
...
, family history, mother’s
age)
...


Answer: Factors to consider include the age of the mother, abnormal prenatal tests, a previous child born with a genetic disorder or birth
defect, and the family history of both parents
...


23 The graph below shows the average (“mean”) age of women who had children with trisomy 21 (“Cases”), of those
who did not (“Controls”), and the average age of all women giving birth in the population studied
...

a
...
During which year was the average age of the cases closest to the average age of the controls? How close were the
average ages in this year?
c
...
Using the data points for each year over this 15-year period, calculate the overall average age of women having babies with
Down syndrome and the overall average age of women having babies who do not have Down syndrome
...
In general, women giving birth to children with Down syndrome are older than women giving birth to babies without Down
syndrome
...
In 1995, the average age of controls was just slightly less than 28, and the average age of the cases was approximately
29
...
This is a difference of a little more than 1
...

c
...
5
...
5 years
...
From the data shown, over the 15-year period the average age of women having babies with Down syndrome was
approximately 31
...
5
years
...
aureus be present in or on a person who has no evidence of an infection?
a
...
aureus is associated only with infections
b
...
yes, but only for very short periods of time (between touching a contaminated surface and washing the hands)
d
...
aureus is a common skin bacterium
e
...
aureus is a common bacterium found in the bloodstream
Answer: d

2 The term “MRSA” as it is used today refers to
a
...
aureus bacteria that are resistant to many antibiotics
...
a collection of skin and other infections caused by a type of bacteria
...
S
...

d
...
aureus bacteria that are normal residents of human skin in the vast majority of the human population
...
all bacteria that are resistant to antibiotics
...
aureus colonization and an S
...
Infections are associated with disease
...

b
...

d
...


on the surface of the skin
...

in the bloodstream
...

The presence of MRSA in any of those locations indicates a serious infection
...
How might this infection have been contracted?
Answer: The athlete could have been exposed by direct skin contact with another athlete who has MRSA or by coming into contac t with a
contaminated item (e
...
, towels, shared sports equipment), particularly if the contact occurs at sites where the skin is brok en, as by a scrape or
cut
...

Answer: Once the infection is confirmed as MRSA, it would be important not to treat with beta-lactam antibiotics, as MRSA strains are resistant
to beta-lactams in general (not just methicillin)
...
If the results of such tests are not available, then one or more
non–beta-lactam antibiotics should be tried first
...
Teammates and
relatives should be reminded to wash their hands frequently and not to share personal hygiene items such as towels or razors
...


DRIVING QUESTION 2
7 In the presence of penicillin:
a
...
aureus?
b
...
aureus?
Answer:

a
...
aureus will eventually burst (lyse) and die because of its weakened cell wall
...
A resistant strain of S
...

8 How do beta-lactam antibiotics kill sensitive bacteria?
a
...

c
...

e
...
)
Answer: Beta-lactam antibiotics interfere with the synthesis of peptidoglycan-containing cell walls
...
Eukaryotic cells therefore do not have
the structure that is the target of penicillin (and other beta-lactam antibiotics)
...
aureus bacterium acquires a new gene that allows it to resist the effects of beta-lactam antibiotics (that
is, the bacterium is now resistant)
...

b
...

d
...


synthesize beta-lactam antibiotics
digest beta-lactam antibiotics
produce a toxin
enhance colonization of human skin
enhance entry into the bloodstream

Answer: b

DRIVING QUESTION 3
11 What are the two major mechanisms by which bacterial populations generate genetic diversity?
a
...

c
...

e
...

b
...

d
...


the growth rate of the bacteria
how strong or weak the bacterial cell walls are
the relative fitness of different bacteria
the presence or absence of antibiotics in the environment
the temperature of the environment

Answer: d

13 What is the evolutionary meaning of the term “fitness”?
Answer: Fitness, in an evolutionary context, describes the ability of an individual to survive and reproduce in a given environment
...


14 The evolution of antibiotic resistance is an example of
a
...

c
...

e
...

diversifying selection
...

random selection
...


Answer: a

15 In humans, very-large-birth-weight babies and very tiny babies do not survive as well as midrange babies
...

b
...

d
...


directional selection
diversifying selection
stabilizing selection
random selection
steady selection

Answer: c

16 Binary fission is asexual
...
That parent passes on a copy of all of its genetic material to its off spring
...
The two daughter cells that are the products of binary fission could be genetically different if a
mutation occurred during replication of the parent genome before division
...


17 In what sense do bacteria “evolve faster” than other species?
Answer: Because bacteria divide very rapidly, they have a very short generation time
...
As there is a chance of one or more mutations to arise with every generation, there is a wealth of genetic
diversity for natural selection to act on
...
aureus cell gets into a wound on your foot
...
aureus divides by binary fission approximately once every
30 minutes
...
Thirty minutes after the initial infection, how many S
...
In 1 hour, how many S
...
In 12 hours, how many S
...
)
d
...
S
...
8  106 base pairs in its genome
...
0028 mutations will occur per cell in the population
...
aureus in the wound in your foot? What are the implications of this genetic diversity in
the context of treating a possible infection?
Answer:

a
...

b
...

c
...
224  16,777,216, the number of cells after 12 hours
...
At a rate of 0
...
0028  16,777,216) or approximately 46,976 mutations in the
population
...
With all those mutations, it is quite
possible that there are several (or more) cells in the population that have a mutation conferring resistance to antibiotics
...

19 If we take the fittest bacterium from one environment—one in which the antibiotic amoxicillin is abundant, for
example—and place it in an environment in which a different antibiotic is abundant, will it retain its high degree of
fitness?
a
...
yes; once a bacterium is resistant to one antibiotic it is resistant to all antibiotics
c
...
no; what is fit in one environment will never be fit in another environment
Answer: c

20 If a single bacterial cell that is sensitive to an antibiotic—for example, vancomycin—is placed in a growth medium
that contains vancomycin, it will die
...
If this population is placed into
vancomycin-containing growth medium, some bacteria will grow
...
If a single sensitive cell is allowed to divide in the absence of
vancomycin, the daughter cells in the population will begin to acquire mutations
...
When the entire population is transferred to vancomycin-containing medium, the sensitive cells will die, but the resistant cells will
continue to divide
...

a
...

b
...
Will individual snails mutate to change their color immediately? As the population evolves and adapts
to the new environment, what do you predict will happen to the phenotypes in your population of snails after several
generations in this new environment? How did this occur? Include the terms gametes, mutation, fitness, phenotype, and

environmental selective pressure in your answer
...
After a period of time, there would be snails that are shades of green and snails that are brown
...

b
...
The snails with the brown phenotype will be able to blend with the brown pebbles
...
Thus the proportion of
green snails will decrease in the population over time because of the different selective pressure exerted by the new
environment
...
By chance, some of these mutations will
change the color of the snail
...

Over time, the population will be composed of brown and yellow snails, which will have the highest fitness in this
environment
...
He
seems to be telling you that his doctor called in a prescription for an antibiotic for him to pick up at his pharmacy
...

a
...
What are the risks to your friend if he takes the antibiotic? (Think about what might happen if he should develop a wound
infection in the future
...
Your friend is a wrestler
...
Antibiotics are effective only against sensitive bacteria
...

b
...
In the
presence of the antibiotic, only bacteria that are resistant to the antibiotic will survive and grow
...
Because of the earlier
selection by antibiotics, those infecting bacteria are likely to be resistant to antibiotics, making the infection harder to treat
...
If he is a wrestler, then taking the antibiotics now may select for antibiotic resistant bacteria (as in part b)
...
If they have any scrapes
or abrasions, the resistant bacteria may enter their body and cause a resistant infection
...
She is feeling better and stops taking her
antibiotic before finishing the prescribed dose, telling you that she will save the remainder to take the next time she
becomes sick
...
Instead, the bacteria in the population at this point may be able to survive a certain concentration of antibiotic, having adapted to
the current amounts of antibiotic
...
Essentially, she is setting herself up for a
recurrence of the pneumonia—but this time with bacteria that can survive in the presence of the antibiotic
...
She is
thus setting herself up for a situation similar to the one in Question 22—normal bacteria are being selected for at least partial resistance to an
antibiotic, and these bacteria might be problematic in the future
...
This observation led him to consider
that the modern-day animals might be descendants of the ancient giant sloths
...
Darwin realized that individual organisms must
therefore compete for access to resources, and that any small variation that gave an individual an advantage would lead to its success over
others
...
Over time, these variations, or traits, would become more common in the population
...
As he himself was suffering
from malaria, Wallace realized that disease would eliminate the weakest members of a population, leaving the stronges t (the most fit)
individuals to survive and reproduce
...


4 What did the field experiences Darwin and Wallace had in observing the natural world at first hand, in addition to
communication with other scientists and careful consideration, add to their understanding of evolution that perhaps
reading and thinking alone couldn’t provide?
Answer: Both Darwin and Wallace made careful observations while on their voyages
...
His observation of the extinct sloth and smaller but similar modern sloths led him to consider how resemblances suggested
ancestral relationships
...
g
...
Without actually seeing these fossils, organisms, and events,
it is less likely that either scientist would have been able to develop his understanding of evolution
...
A population of 3,200 mice has 4,200 dominant G alleles and 2,200 recessive g alleles
...
2,200/6,400 gives an allele frequency of 0
...


2 The allele frequencies for a particular gene are given for three populations
...

Population A: 30% A1, 30% a1, and 40% a4
Population B: 25% A2, 25% A3, 25% a2, 25% a3
Population C: 20% A2, 20% A3, 30% a2, 30% a3
Answer: Population A has fewer alleles than the other populations, suggesting that it may be an isolated population
...
The E allele is represented
only in one, homozygous, individual:
Five individuals are D/A heterozygotes
...

Five individuals are A/B heterozygotes
...

Five individuals are C/C homozygotes
...

a
...

b
...
Now what are the allele frequencies of each of the five alleles in the
population?
Answer:

a
...
The allele frequencies are 10/52  0
...
38 A; 5/52  0
...
29 C; 2/52  0
...

b
...
16 D; 25/62  0
...
08 B; 15/62  0
...
11 E
...

4 Some populations, for example cheetahs, have gene pools with very few different alleles
...
If interbreeding with
distantly related species or populations is successful, then new alleles will be introduced into the population
...
Given this
situation, what selective pressures might the human population be currently facing or be expected to face in the near
future?
Answer: There are many possibilities
...
If city dwellers do not spend much time outside, there may be pressures
associated with low exposure to sunlight
...


DRIVING QUESTION 2
6 Which of the following statements apply to the founder effect?
a
...

c
...

e
...

It decreases genetic diversity
...

all of the above
b and c

Answer: e

7 Which of the following are examples of genetic drift?
a
...

c
...

e
...

b
...

d
...


an expansion of a population from a small group of founders
...

a reduction in the size of an original population followed by an expansion in size as the surviving members reproduce
...

an example of natural selection
...
A drunk driver plows
across the median strip, destroying most of the median strip and 90% of the ants
...

a
...
What type of event is this?

Answer:

a
...
The allele frequency for H is 1 (100% of the alleles are H)
...
As a random event affecting allele frequencies, this is an example of genetic drift—specifically, it has created a bottleneck
...
of Individuals

No
...
of Alleles, Gene
2

No
...
Population 1 is not only small, but has only one allele for one of the genes examined
...


11 In humans, founder effects may occur when a small group of founders immigrates to a new country, for example to
establish a religious community
...
If this population remains isolated from other
populations in the new country (e
...
, because of religious or cultural practices), there may not be much mixing with other populations in the
new country
...
Marrying within the group will maintain alleles already
present and will not introduce new alleles
...


13 The figure below shows a bar plot of moles from different parks in New York City
...
2, each vertical
bar represents genotypes from 18 genomic locations in one animal
...
From the data presented in the figure:
a
...
What factors could explain their
isolation, or lack thereof?
b
...
Populations B and C share the blue genotype, suggesting that they are possibly sharing alleles
...
These alleles are apparently not being shared with populations B and C
...
When populations are separated
geographically, they are less likely to share alleles than are populations with individuals that readily move between
populations
...
Population A has alleles not found in populations B and C
...


DRIVING QUESTION 3
14 Which of the following statements is/are true about a nonevolving population?
a
...

c
...

e
...

Genotype frequencies do not change over time
...

all of the above
a and b

Answer: e

15 A starting population of bacteria has two alleles of the TUB gene, T and t
...
8 and the frequency
of t is 0
...
The local environment undergoes an elevated temperature for many generations of bacterial reproduction
...
4 and the frequency of t is
0
...
Has evolution occurred? Explain your answer
...
The allele frequencies of the TUB gene have changed over many generations (in this case in response to a
change in the environmental conditions)
...
Over time, inbreeding reduces the frequency
of heterozygotes, and produces homozygotes that have two deleterious alleles
...
For example, it can be used to estimate the
frequency of carriers (heterozygotes) of rare recessive diseases in a population
...
(You may have
noticed on products that contain aspartame the statement “Phenylketonurics: contains phenylalanine,” a warning for
people with PKU that they should avoid consuming that product
...

a
...
Express their genotype in terms of Hardy–Weinberg (that is, would they be pp, pq, or qq?)
c
...
What is the frequency of the dominant allele?
e
...
S
...

Answer:

a
...
qq
c
...
Therefore, the frequency of the recessive allele (q) is the square
root of 1/15,000  0
...
The frequency of the dominant allele (p) is (1 – q)  (1 – 0
...
992
e
...
016 (1
...


DRIVING QUESTION 4
18 The biological species concept defines a species
a
...

c
...

e
...

on the basis of close genetic relationships
...

on the basis of the ability to mate and produce fertile offspring
...


Answer: d

19 How does geographic isolation contribute to speciation?
Answer: When populations are geographically isolated, they do not exchange alleles
...
As the number of different mutations accumulates in each
isolated population and the resulting phenotypes are acted on by natural selection, the two populations could diverge enough so that they
cannot successfully interbreed if they come into contact with one another
...
The shore on one
side of the lake is drier and has very different vegetation from that on the other side
...
How could you assess if they are still members of the
same species?
Answer: According to the biological species concept, if members of different populations can successfully reproduce (and prod uce fertile
offspring), then they are members of the same species
...


21 If geographically dispersed groups of a given species all converge at a common location during breeding season,
then return to their home sites to bear and rear their young, what might happen to the gene pools of the different
groups over time?
Answer: Even though each population may live in a separate region, the fact they converge during breeding season means that alleles will be
exchanged and shared throughout all the populations
...


22 More than 50% of the global human population now lives in urban areas, and it is predicted that 70% will live in urban
areas by 2050
...
Given this information, and what you have read in this chapter, write a compelling paragraph
on the need to conserve urban species and approaches to such conservation based on population genetics
...
Given the predicted shift of humans to urban settings, it is important that humans have the opportunity to interact with nature in urban
settings
...
Many wildlife species face challenges in urban settings
...
In order to maintain these populations in a healthy state, it is important to
allow distinct populations to exchange alleles of genes
...
Additionally, smaller green spaces such as rooftop or container gardens can provide opportunities for pollinators
...


23 The School of Ants is a citizen-scientist project to document the distribution and diversity of ants across the United
States
...
The Audubon Society uses the data collected by these volunteers to evaluate the health of bird
populations and make informed decisions about conservation
...
Carry out an Internet search to find a citizen-scientist project
that you find interesting
...

Answers will vary
...

b
...

d
...


a jellyfish
a worm
a wolf
an octopus (an organism that lacks a skeleton)
All of the above are equally likely to leave a fossil
...


3 You are examining a column of soil that contains vertebrate fossils from deeper to shallower layers
...

Answer: A fossil with four limbs and digits would be the fossil of an organism more recent than a “standard” fish
...


4 What can the fossil shown below tell us about the structure and lifestyle of the organism that left it? Describe your
observations
...
It has fins with rays, suggesting that this organism was aquatic and able to
swim
...
This may have been a predatory fish, as teeth appear to be present
...
You have found a fossil bed with many hard-shelled mollusks dating from the critical time,
but no fossil evidence to support your hypothesis about the sea cucumbers
...
Soft-bodied organisms
(such as sea cucumbers) do not fossilize well and so do not leave fossils in the fossil record
...
If similar oyster
fossils are found in European rock, in layers along with a novel type of barnacle fossil, what can be concluded about
the age of the barnacles? Explain your answer
...


7 Do an Internet search to find out about fossils discovered in your home state
...

Answers will vary
...

b
...

d
...


scales
teeth
a mobile neck
fins
none of the above

Answer: c

9 Tiktaalik fossils have both fishlike and tetrapod-like characteristics
...
What does this mean? Why are transitional
organisms significant in the history of life?
Answer: Transitional fossils are “intermediate” in that they are midpoints between two groups of organisms
...
Titkaalik represents the transition
between aquatic bony fishes and land-dwelling tetrapods
...
Speculate on the fossil appearance of its first true
tetrapod descendant—what features would distinguish it from Titkaalik? How old would you expect those fossils to
be relative to Titkaalik?
Answer: The first real tetrapod would likely have fully developed forelimbs and hind limbs, both of which would have jointed wrists and ankles
and could bear weight
...
These fossils woul d be younger (that
is, more recent) than the Titkaalik fossils, as true tetrapods would be the descendants of Titkaalik
...


DRIVING QUESTION 3
13 Compare and contrast the structure and function of an eagle wing with the structure and function of a human arm
...
All major bones are present in each and in the same
locations relative to other bones
...
Birds do not need to carry out this fine-scale manipulation, and their wings are specialized for
flying
...
What do these structures develop into in an adult
human? In an adult bony fish?
Answer: middle ear bones in humans; gills in adult bony fish

15 You have three sequences of a given gene from three different organisms
...
The
more differences there are, the less similar the sequences are
...
Ideally, you would compare a large number of genes before coming to a conclusion
...
Both humans and otters are dexterous with their hands, using them for a variety of important functions, so the continued presence of
five digits would have been selected for over evolutionary time
...


18 If, in humans, the DNA sequence TTTCTAGGAATA encodes the amino acid sequence phenylalanine–leucine–
glycine–isoleucine, what amino acid sequence will that same DNA sequence specify in bacteria?
Answer: As the genetic code is universal (with only a few exceptions), the same DNA sequence will encode the same amino acid sequence in
both humans and bacteria
...
Both produce protein X, but the yeast protein is slightly different from
the sea urchin protein
...
The fact that the amino acid sequences differ between sea urchin and yeast
means that the nucleotide sequence of gene X differs between sea urchins and yeast
...
The greater the number of nucleotide
differences, the longer it has been since the organisms split from their common ancestor, and the less closely they are related
...


20 The gene responsible for hairlessness in Mexican hairless dogs is called corneodesmosin (CDSN)
...
Look at the sequence of a portion of the CDSN gene from pairs of different species, given
below
...
From the variations in this sequence, which organism
appears to be most closely related to humans? Which organism appears to be least closely related to humans?
Species

Sequence

Homo sapiens (human)Canis lupus familiaris
(dog)

ACTCCGGCCCCTACATCCCCAGCTCCCAA
TTCTGGCTCCTACATTTCCAGCTCCCA

Homo sapiens (human)
Pan troglodytes (chimpanzee)

ACTCCGGCCCCTACATCCCCAGCTCCCA
ACTCCGGCCCCTACATCCCCAGCTCCCA

Homo sapiens (human)
Sus scrofa (pig)

ACTCCGGCCCCTACATCCCCAGCTCCCA
AGTCTGGCTCCTACATCTCCAGCTCCCA

Homo sapiens (human)
Macaca mulatta (rhesus monkey)

ACTCCGGCCCCTACATCCCCAGCTCCCA
ACTCTGGCCCCTACATCCCCAGCTCCCA

Answer: First pair, 5 differences; second pair, 0 differences; third pair, 4 differences; fourth pair, 1 difference
...


21 Fossils allow us to understand the evolution of many lineages of plants and animals
...
What if Tiktaalik (or an equally important transitional fossil) had been found by amateur
fossil hunters and sold to a private collector? Do you think there should be any regulation of fossil hunting to prevent
the loss of valuable scientific information from the public domain?
ANSWERS WILL VARY: Some considerations include the public sharing of important scientific data (much in the way the results of federally
funded research are available to the field); whether the fossils were found on public lands or private lands; and whether the removal of the
fossils caused harm to the site (or to the fossils themselves, if not properly stabilized when removed)
...


2 To date what you suspect to be the very earliest life on Earth, which isotope would you use: uranium-238, carbon-14,
or potassium-40? Explain your answer
...
5 billion years)
...


3 Place the following evolutionary milestones in order from earliest (1) to most recent (7), providing approximate dates
to support your answer
...
5 billion years ago); (3) the first
multicellular eukaryotes (~1
...

a
...
How much of the original uranium-238 is likely to be left today in that rock?
Answer:

a
...
5 billion years old
...
Approximately half of the original uranium-238 is left (after one half-life)
5 Diverse animal fossils are found dating from the Cambrian Period but not earlier
...
)
Answer: The ancestors of these organisms may have been primarily soft-bodied organisms that did not leave fossils
...


6 You are a paleontologist with a particular interest in early microbes
...
They claim that they used potassium-40 dating to date the fossil to 3
...
If the analysis is accurate, what percent of potassium-40 should remain in the specimen? If you used
uranium-238 dating to verify, what proportion of uranium-238 should remain in the specimen?
Answer: A 3
...
This means that approximately 12
...
The same 3
...
A little over 50% of
the original uranium-238 would remain
...
By radiometric dating, the
layer above these strata is determined to be about 290 million years old, and the layer beneath has been dated to
about 354 million years ago
...
The fossils are
clearly land-dwelling vertebrates
...

Answer: These land-dwelling vertebrates lived between 354 and 290 million years ago
...


8 You have carried out radiometric analysis on four igneous rocks uncovered at several sites you are exploring
...
2,

Rock A: 75% lead, 9 billion years old
Rock B: 50% lead, 4
...
25 billion

DRIVING QUESTION 2
9 If two organisms strongly resemble each other in their physical traits, can you necessarily conclude that they are
closely related? Explain your answer
...
While they may be closely related, they may also represent convergent evolution, in which unrelated groups of organisms share
common characteristics because of independent natural selection in similar environments
...
6
...
g
...
Over time,
through plate tectonics, the landmasses have moved farther apart to their present locations
...


11 A cactus called ocotillo (Fouquieria splendens), which grows in New Mexico, looks very much like Alluaudia procera,
a species of plant that grows in the deserts of Madagascar
...
Why then do they look so alike?
Answer: These two plant species may look alike because of convergent evolution; both have adapted to a desert climate
...


13 Both bats and insects fly, but bat wings have bones and insect wings do not
...

Answer: This is an example of convergent evolution
...


DRIVING QUESTION 3
14 Which of the following is not a domain of life?
a
...

c
...

e
...


Animalia
Eukarya
Bacteria
Archaea
Plantae
Neither a nor e is a domain of life
...

Domain
Species
Supergroup
Kingdom
Genus
Phylum
Answer: (1) domain; (2) supergroup; (3) kingdom; (4) phylum; (5) genus; (6) species

16 A phylogenetic tree represents
a
...

c
...

e
...

a grouping of organisms on the basis of cell type
...

a grouping of organisms on the basis of evolutionary history
...


Answer: d

17 Why was the classification of the kingdom Monera split into two domains? What are these two domains?
Answer: The kingdom Monera originally included all prokaryotic organisms
...
Today, these two groups are the domains Bacteria and
Archaea
...

b
...

d
...


1
2
3
4
Humans and corn do not share any ancestors
...
What groups of organisms are represented in
the statewide fossil record? What is the oldest fossil found in your state? What do the fossils in your state suggest
about the pattern(s) of evolution in your state?
Answers will vary
...

b
...

d
...


cell type
...

evolutionary history as assessed by genetic relatedness
...

degree of sophistication, that is, how evolutionarily advanced they are
...

Answer: The key difference is that eukaryotic cells contain membrane-enclosed organelles, particularly a nucleus, and prokaryotic cells do not
...

b
...

d
...


from a member of the domain Bacteria
...

from a member of the domain Eukarya
...


5 When first discovered, archaea were called “archaebacteria
...
” At the time of their discovery, archaea were found in “extreme” environments and
were thought to be ancient ancestors of bacteria, living in conditions that may have been similar to those on the early Earth
...


DRIVING QUESTION 2
6 The term prokaryotic refers to
a
...

c
...

e
...

a domain of life
...

a type of bacterium
...


Answer: a

7 If you were looking for a bacterium, where would expect to find one?
a
...

c
...

e
...

b
...

d
...


ability to grow at high temperatures
a nucleus
ability to grow at extremely acidic pH
a cell wall
ability to survive in a high-salt environment

Answer: b

9 If you are unable to culture archaea from an environmental sample, is it safe to conclude that there are no archaea
present? Why or why not?
Answer: No
...
Many archaea are very diffic ult to grow
(that is, culture) in the lab
...


10 Can you use cell structure to classify a cell as either bacterial or archaeal? Explain your answer
...
Both have prokaryotic cells, so the presence of a prokaryotic cell does not allow you to distinguish between bacteria and archaea
...
How is this beneficial to humans?
Answer: Photosynthesis provides organic molecules (particularly carbohydrates) that can be a source of food for the food chains and w ebs that
humans rely on
...


12 Halophilic archaea are able to prevent osmotic water loss from their cells, even in high-salt environments
...
If their internal solute
concentration is the same as that of the environment, there will be no net gain or loss of water from cells
...

Answer: No
...
Without their pili, the bacteria would not
succeed in establishing infections
...
For each feature, give a brief explanation of
why it is inhospitable for many organisms
...
High pressure—most organisms would be
crushed by the pressure at Lost City
...


15 If you were a prokaryotic organism and wanted to be successful at Lost City, what energy source must you be able to
use?
a
...

c
...

e
...


Answer: c

16 What is the significance of methane at Lost City? (Think about both the origin of life and the sustenance of early life
...
This means that the earliest
organisms at Lost City had at least two energy sources, H2 and methane
...


17 If methane were not produced abiotically at Lost City, what would be the implications for early life?
Answer: Many of the living organisms at Lost City rely on methane as their energy and carbon source
...
However, with hydrogen gas as an energy source and CO2 as a
carbon source, it is still possible for life to have formed at Lost City, but perhaps different organisms would be present
...

Answer: No
...


19 Do you think that the scientists studying Lost City should be concerned about introducing microbial contaminants
from their submersibles onto the towers of Lost City? How probable is this, given the conditions at Lost City and on
the surface? If such an event could happen, what would be the implications?
Answer: Because the conditions at Lost City are so extreme and harsh, it is unlikely that any microbes on the surfaces of the submersibles
could survive, much less thrive, in those conditions
...
On the other hand, microbes are diverse and
adaptable
...
The entire ecosystem of Lost City could be disrupted
...


20 Some of the chimneys at Lost City are actively venting
...
The exterior surfaces of the active chimneys are cooler (~7°C), contain oxygen,
and have a pH of ~8
...
Compared to the actively venting chimneys,
their interiors are much cooler (7°–20°C), lack oxygen, and have a pH of 8–10
...

From the properties of the organisms given in the table below, complete the table to indicate where in Lost City
each of these organisms is most likely to be found
...
5

8

Bacteria

Exterior of active
or inactive
chimneys

D

Anaerobic

90

Archaea

Interior of active
chimneys

E

Aerobic

7

Bacteria

Exterior of active
or inactive
chimneys

F

Anaerobic

85

Archaea

Interior of active
chimneys

Optimum pH

11

7
...

a
...
How do the challenges faced by Curiosity compare to those faced by Jason?
c
...
Both environments are, or contain, regions that are anoxic (that is, they lack oxygen)
...

b
...

c
...
On Mars, organisms would be anaerobic, and
would likely use simple molecules (e
...
, hydrogen, carbon dioxide, or methane) as their energy and carbon source
...
By studying organisms at Lost City,
scientists can learn more not only about the origins of life on Earth (knowledge relevant to every living organism on the planet), but also about
obtaining energy from novel sources
...
By
studying the community of organisms at Lost City, scientists may also learn more about how microbes live together, providing insight into how
a diversity of microbes lives in and on the human body, and how their interactions can lead to disease
...

b
...

d
...
unicellularity
Answer: d

2 What are the defining features of eukaryotes, members of the domain Eukarya?
Answer: Eukaryotes are defined by having cells with membrane-bound organelles, including a nucleus
...
Both have eukaryotic cells (with a nucleus and internal membrane-bound organelles)
...
Lake Michigan
b
...
a high alpine meadow in the Colorado Rockies
Answer:

a
...

b
...
Only some organisms have adaptations allowing them to survive in such conditions
...
The prairies of Kansas would likely have less diversity—the landscape is not very varied, and is dominated by grasslands
...

a
...
application of an insecticide
c
...
Herbicides kill plants (including trees) and would remove a huge number of species in the rain forest, as well as damage
the habitat for many other eukaryotes
...
Their
disappearance would have a huge impact on eukaryotic diversity
...
If fungi die,
decomposition will slow
...


6 A group of researchers designed an experiment to test the Janzen–Connell hypothesis, which they carried out in a
rain forest in Belize
...
If all the seeds germinate, the seedlings present should match the
diversity of species in the seeds
...
They identified and counted seedlings to determine diversity (number of
species) and abundance (number of seedlings) (* indicates a significant difference from control)
...
of species)
Abundance (no
...
7

3
...
2*

30

58*

35

Data from Bagchi, R
...
(2014) Pathogens and insect herbivores drive rainforest plant diversity and composition
...
1038/nature12911

a
...

b
...
Do insects or fungi have a greater impact on maintaining plant diversity (defined as number of species) in the rain forest?

Answer:

a
...
Insects appear to play a greater role than fungi in reducing the number of seeds that germinate into seedlings
...

c
...
There is a significant reduction in diversity
(number of species) after treatment with fungicide (relative to control) but not after removal of insects
...
As they do not have a vascular system to transport water
throughout their bodies, they live in damp environments
...


8 A major difference between a fern and a moss is
a
...

c
...

e
...

the presence of flowers
...

the presence of a vascular system
...


Answer: d

9 What is an advantage of having seeds? (Think about spreading to new locations and whether or not reproduction
relies on water
...
Seeds enable plants to survive temporarily harsh
conditions and, because they spread relatively easily, can introduce plants to new locations
...

Answer: An angiosperm; its seeds are enclosed in a fruit, which can be a tasty treat for a hungry animal
...

Plants are present in almost every landscape and are important in characterizing different habitats
...

a
...
Can fungi ingest their food?

c
...
Fungi are not photosynthetic; they are heterotrophs
...
They do not ingest their food
...
Fungi obtain nutrients and energy by secreting digestive enzymes onto their food source in the external environment
...

13 Which of the following meals include a fungus?
a
...

c
...

e
...
Why do you think fungi were grouped
with plants? What features distinguish them from plants?
Answer: Although both plants and fungi are eukaryotes, they are members of distinct groups
...
Fungi are distinguished from plants by having a
cell wall made up of chitin instead of cellulose and by being heterotrophs (they can’t carry out photosynthesis)
...
What type of body symmetry does a sand
dollar have?
a
...

c
...

e
...

b
...

d
...


They are all insects
...

They are all arthropods
...

They all have an exoskeleton
...

b
...

d
...

f
...

venom
flight
secondary metabolites
all of the above
a, b, and c

Answer: e

18 Which of the following is not a feature of all animals?
a
...

c
...

e
...
Why do we need to use so many different characteristics?
Consider the following five animals: cockroach, earthworm, honeybees, parrot, and slug; and the following three
characteristics: ability to fly, two-legged, exoskeleton
a
...
Would this grouping reflect their real taxonomic relationships?
c
...
Ability to fly: the cockroach, honeybees, and parrots, which can fly, would be grouped together, and the earthworm and slug
would be grouped together as nonflying
...
Exoskeleton: cockroaches and honeybees have an
exoskeleton; the other organisms do not and would be grouped together
...
The groupings in part a do not reflect accurate taxonomic relationships
...
Earthworms and slugs could be grouped together (in their own group) based on lack of legs or wings and lack of an
exoskeleton
...
Parrots and honeybees have wings and can fly (as do cockroaches)
...


DRIVING QUESTION 5
20 What do all members of the informal group known as protists have in common?
a
...

c
...

e
...

They all carry out photosynthesis
...

They are all decomposers
...
Some are photosynthetic and some are not, some are decomposers, some eat other organisms
...


22 Many protists have an organelle called the contractile vacuole that pumps out water that enters the cell by osmosis
...
)
Answer: In a freshwater environment, water tends to enter the cells of protists, increasing the internal pressure
...
If the contractile vacuole stopped working, the accumulated water might gener ate enough
pressure to burst the cell
...
Given the
tremendous biodiversity in the Amazon and medicines that have already been developed from natural sources in the
area, there are likely to be life-saving and lucrative medicines still to be discovered by bioprospecting rain forest
resources (bioprospecting is the search for natural resources that provide valuable products
...

a
...

b
...

c
...
You should consider preserving habitat; preserving biodiversity; the rights of indigenous peoples to land, resources, and
profits; and ensuring that resources are not depleted
...
Do some research to learn about one of these new national monuments
...
Where is it?
b
...
Are there any threats to the eukaryotic biodiversity present? Has the protected status of this national monument reduced
any of these threats?
Answers will vary depending on the monument investigated
...
How is Plasmodium falciparum dependent on the Anopheles mosquito?
b
...
)
Answer:

a
...

b
...

2 Historically, Phytophthora infestans was classified as a fungus and Pneumocystis carinii and Trypansoma brucei
were classified as protists
...

Answer: Phytophthora infestans has been reclassified as a Stramenopila, on the basis of molecular evidence
...
Trypansoma brucei is classified as a member of the Excavata supergroup
...

Answer: Pneumocystis carinii was formerly classified as an animal-like protist
...
This classification has allowed
the use of more appropriate drugs (antifungal drugs) to treat the pneumonia caused by this organism
...
For each of the substances listed below, state whether it is
directed against the mosquito or the parasite, and describe any current challenges to its use
...
artemisinin
b
...
quinine
Answer:

a
...
Resistance is emerging
...
DDT is directed against the mosquito
...

c
...
Resistance is emerging
...


Chapter 19 Human Evolution
DRIVING QUESTION 1
1 The ancestors of modern humans evolved in a high-UV environment
...
Their
skin color was likely dark
...

b
...

d
...


average annual temperature
average annual rainfall
levels of UV light
the vitamin D content of the typical diet
mitochondrial DNA inheritance

Answer: c

3 Jablonski and Chaplin hypothesized that darker skin is advantageous in
because darker skin

...

b
...

d
...


_ UV environments

high-; reduces vitamin D production
high-; protects folate from degradation
high-; increases the rate of folate synthesis
low-; allows more vitamin D to be produced
low-; allows more folate to be produced

Answer: b

4 If vitamin D production did not require exposure to UV, predict the skin color you might find in populations living at
the equator; in populations living in Greenland
...

Answer: Normally, folate is destroyed by exposure to UV, and dark skin protects folate from destruction in high-UV environments
...
In Greenland, levels of UV are low enough that folate is not destroyed, so skin is
light
...


5 Which of the following would help darker-skinned people who live in low-UV environments remain healthy?
a
...

c
...

e
...
g
...

People with dark skin likely have alleles associated with darker skin (e
...
, variants in the enzymes that produce melanin or in proteins that
determine the melanin-producing activity of melanocytes), and their ancestors likely originated in a high-UV environment near the equator
...
How
would the Jablonski–Chaplin hypothesis explain this observation?
a
...

c
...

e
...

Chimpanzees are not susceptible to skin cancer
...

Chimpanzees require much higher levels of vitamin D than humans do
...


Answer: c

8 Vitiligo is a disease in which melanocytes are destroyed, with resulting loss of pigmentation
...
If a dark-skinned person develops vitiligo and therefore lighter-colored skin, will his or her race change?
b
...
Biologically, people with vitiligo still have the same skin color genotype and the same ancestors as unaffected people in the
population
...
Their race has not changed
...
People with vitiligo may be perceived by others to be of a different race on the basis of their skin color
...


DRIVING QUESTION 2
9 Who is mtEve, and when did she live?
Answer: mtEve is a single female ancestor of all modern humans
...


10 The following three types of DNA can be used to trace evolutionary history
...

Type of DNA

Description

a

_ mtDNA

a
...
inherited by all children only from their father

c

_ Y-chromosome DNA

c
...
inherited by all children from both their mother and their father
e
...

b
...

d
...


Africans
Europeans
Asians
South Americans
Australians

Answer: a

12 Rank the levels of genetic diversity you would expect to find within the five populations listed in Question 11 from
highest to lowest
...

Answer: See Infographic 19
...
Africans have the highest level of genetic diversity
...
South Americans would be predicted to have the lowest levels of genetic diversity, on the basis of migration to
that region only 13,000 years ago
...
)
Answer: Although there were many women alive 200,000 years ago, the mitochondrial lineages of all but one ended, either because the others
or their descendants did not have children at all, or because at some point their only descendants were sons, who do not pass on their
mitochondrial DNA to the next generation
...
If ancient fossils had intact mitochondrial DNA that could be isolated and tested, we
would expect to find mitochondrial DNA from lineages that are no longer present in the human population
...
Her lighter-skinned husband
accuses her of infidelity
...
How reasonable is this, given the genetics of skin color? (Hint: The genetics of skin color are similar to the genetics of
height, shown in Infographic 12
...
)
b
...
Skin color is determined by many genes, each with at least two alleles
...
It is possible for a child to have darker skin than either of its parents, depending on which
combination of alleles it inherits
...
A
mother with medium skin tone could have a genotype of: Aa Bb cc Dd ee (three dominant alleles) and her lighter-skinned
husband could have a genotype of aa bb Cc dd Ee (two dominant alleles)
...

b
...
An mtDNA analysis would not be useful in a paternity test because the father does not contribute mtDNA to the child
...


DRIVING QUESTION 3
15 What percentage of DNA sequences do all humans share?
a
...

c
...

e
...

b
...

d
...


upright walking
the ability to control fire
social communication
tool use
a big brain

Answer: e

17 Place the following ancestors in order of earliest (1) to most recent (5)
...

Answer: The last common ancestor of gorillas and humans would be even more ancient than the last common ancestor of chimpanzees and
humans
...


19 Why would individual australopithicines who could make and use tools have had a selective advantage (that is,
higher fitness) over individuals who could not make or use tools?
Answer: Tool use is important for hunting and preparing food
...
Better nutrition would contribute to higher fitness, especially when food was not easily available
...
The ability to move around in trees was facilitated
by an opposable big toe that would help grip branches
...

Answer: If an opposable big toe conferred advantage on the ground, it would have been maintained by natural selection
...


21 Members of the genus Australopithecus walked upright, and their fossilized footprints show no evidence of an
opposable big toe
...
What foot structure and lifestyle might have been selected for if early hominid evolution occurred in a forested environment?
In a grasslands environment? Would you predict any differences because of the selective pressures in each environment?
Why or why not?
b
...
If early hominids had evolved in a forested environment, foot structure might still show evidence of an opposable big toe to
assist in tree climbing and moving along branches, particularly if tree climbing provided access to food
...
Instead, the foot, leg, and
pelvis would be adapted for walking and running
...
In a forested environment it would be helpful to have good vision in low-light conditions, a good sense of balance (for tree
climbing), upper body strength (for tree climbing), and perhaps height (to see over underbrush and saplings)
...
Speed (in running) would be an advantage (to avoid predators and chase prey)
...


22 An extensive study of a hominid fossil dating from approximately 2 million years ago was published in 2013
...
On the
basis of the features described, where would you place this fossil on the lineage between the chimpanzee–human
ancestor and modern humans—what genus is it likely a member of?
•
•
•
•
•
•
•

The shoulder structure and very long arms suggest the ability to climb and perhaps hang or swing
...

There is no opposable toe
...

The skeleton suggests that in walking on two feet the feet would roll inward with each step
...

The chest is not cylindrical but wider at the base and narrow at the shoulders, much like a triangle
...
The skeleton has a
mixture of features
...


23 The U
...
Census Bureau provides information on classifying race
(http://www
...
gov/topics/population/race/about
...
What races does the U
...
Census Bureau recognize?
What about people of mixed race? What about people who identify themselves as Hispanic? How easy is it for you to
identify yourself with respect to race given the racial categories on the U
...
Census?
Answers will vary
...
S
...


Chapter 20 Population Ecology
DRIVING QUESTION 1
1 What is the difference between a community and a population?
Answer: A population is a group of interbreeding organisms of the same species living in a particular geographic area
...
Populations represent a single species, communities represent multiple species
...

b
...

d
...


plant populations
...

predators in the population
...

all of the above

Answer: e

3 Palm trees can be found at oases in deserts
...


4 How would you explain to a 10-year-old what ecologists do?
Answer: Ecologists are biologists who study how organisms interact with their environments
...


5 Your local environmental group wants to determine the population size of squirrels in a nearby nature preserve
...
Instead, you can estimate the size of the population by counting all the squirrels found in a specific set of smaller square plots
...
As trees are not mobile, it may be
feasible to count all the trees in the preserve
...


6 An invasive plant species has been introduced into a particular region
...
What
kinds of impact might you predict on other species in the community? Explain your answer
...
If
some herbivores (e
...
, animals) cannot survive on the invasive plants, then their populations may decline
...
In contrast, if some insect herbivores favor the invasive plants, their
populations may increase, potentially creating a new food source for a bird or other population that eats insects
...

b
...

d
...


identical increases in both the birth rate and the death rate of a population
a decrease in the birth rate and an increase in the death rate of a population
an increase in the birth rate and a decrease in the death rate of a population
an increase in the birth rate and a larger increase in the death rate of a population
identical decreases in the birth rate and the death rate of the population

Answer: c

8 Which of the following statements describes an example of population growth?
a
...

c
...

e
...

Tropical fish have been found in waters more northerly than their usual habitat
...

The number of butterflies in a region has stayed the same from 1950 to 2010
...


10 The wolf population on Isle Royale was nine in 2014, three in 2015 and two in 2016
...
What must have happened to wolf birth and/or death rates between 2013 and 2016?
b
...
The birth rate must have decreased or the death rate must have increased or both
...
New wolves could travel to the island over the ice bridge, increasing the wolf population through immigration
...

11 Population Q has 100 members
...
Both are growing exponentially at a 5% annual
growth rate
...
Which population will add more individuals in 1 year? Explain your answer
...
After 5 years, what will be the size of each population?
c
...
Population R will add more members in a year
...

b
...
If the larger population (population R) reaches its carrying capacity after 3 years, it will stop growing
...


DRIVING QUESTION 3
12 The Mexican gray wolf has been reintroduced into parts of New Mexico and Arizona
...
Are these influences on the wolf population biotic or abiotic factors?
Answer: Shootings and traffic kills are directly related to human activities, and are thus biotic factors
...
The pond’s frog population dropped to 10% of its initial size
...


14 Which of the following is a density-dependent factor influencing population growth?
a
...

c
...

e
...

Answer: If the moose are dying primarily because of wolf predation, then one might reasonably expect the size of the wolf pop ulation to follow
the size of the moose population
...
The lack of food wi ll cause the wolf population to
decline, reducing the pressure on moose, and so on
...
In this case, with fewer moose on the island, the wolf population may have a much
stronger (and detrimental) impact on the moose population, to the point that the moose may not be able to recover
...
If a parasite were introduced to the lake—for example, by a
vacationing fisherman—would you expect it to have a greater impact on the population if the fish were at high density
or at low density? (Assume the parasite is passed from one fish to another through the water but can remain alive in
the water only for a very short period of time
...
Thus, its impact will be higher
at high population density
...
These factors will increase the probability that the parasite, and the illness it causes, will be transmitted to
a new host
...
Then predict the impact of each factor
on the moose population of Isle Royale
...

a
...

c
...

e
...
abiotic
...
Fewer prey are left for the wolves
...
biotic
...

c
...
A reduction in trees would starve the moose
...

d
...
Parvovirus can weaken or kill wolves
...

e
...
A deep winter snowfall may make it harder for moose to escape wolves
...
The wolves would experience a temporary increase in their population, but
there may not be enough moose to sustain this population
...
Predict the effect of this introduction
on
a
...

b
...

c
...

Answer:

a
...

b
...


c
...

19 Using the estimates provided below, graph the moose population size on Isle Royale since 2009
...


b
...
Because wolves hunt in
packs, their reduced numbers may make it harder to kill a moose for food
...
As the wolf population becomes increasingly
inbred, they may produce fewer and fewer (or no) viable offspring
...

a
...
If humans were to intervene, what kinds of strategies might help stabilize or increase the wolf population? Explain your
answer
...
Opinions will vary
...
Because there is evidence for inbreeding, introducing wolves from a distinct population may introduce new alleles to
compensate for the inbreeding
...
g
...

21 Use your knowledge of ecology to plan a home saltwater aquarium
...
Consider both biotic and abiotic factors and
the population densities of the organisms in your aquarium
...
Abiotic factors include temperature, salinity of the water, lighting, and size of the tank
...




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