Ch 8 Review

Question 1

Explain what variation within a species means.
Explain how variations can arise in a sexually
reproducing species

Answer 1

• naturally occurring genetic differences among individuals of the same species

sexual reproduction (mutations is for asexual r)
-most of the variation is due to the scrambling
of existing alleles, including those that originated as mutations in earlier generations
-the processes of meiosis and fertilization shuffle the alleles and recombine them
-each offspring receives a new combination of alleles

Question 2

Explain what “allele frequency” means and
provide an example

Answer 2

Allele frequency refers to how common an allele is in a population
-e.g. in a pop. there are 14 red flower alleles and 6 white flower alleles, so the allele frequency for red is 70% (14/20) and for white is 30% (6/20)

Question 3

What is macroevolution? Give an example.

Answer 3

macroevolution encompasses more dramatic biological changes, many of which are evident in the fossil record
-these changes include the origin of different
species, the extinction of species, and the evolution of major new features of living things, such as wings or flowers

-e.g. humans, tetrapods, birds
-birds- through fossil records, scientists have long
believed that birds evolved from the theropod
dinosaur Archaeopteryx. It took tens of millions
of years for the exceedingly large theropods to
evolve into the much smaller, hollow-boned,
lightweight, feathered birds of today that can fly
long distances.

Question 4

What genotype for sickle cell disease is the
most beneficial for individuals living in regions
where malaria is common? Why?

Answer 4

heterozygous individuals with sickle cell disease are the most beneficial because Individuals with just one copy of the sickle-cell allele are resistant to the disease malaria

Question 5

The Hardy-Weinberg equilibrium applies only if five specific conditions of the population are met. Which of the following does not represent one of those conditions?

a) There must be no movement of individuals in or out of the population
b) There must be random mating
c) There must be no natural selection taking place
d) The population must be contained and small

Answer 5

The population must be contained and small

-The Hardy-Weinberg equilibrium includes no movement of individuals in or out of the population, random mating, no natural selection, no mutations, and a large population

Question 6

In the 1940s farmers in North America lost approximately 7% of their crops to pests. During the last decade, however, the percentage of crop loss has increased to nearly 13%, despite much more widespread pesticide use.
This example best describes

a) directional selection.
b) sexual selection.
c) the bottleneck effect.
d) genetic drift.

Answer 6

directional selection.

Directional selection occurs when individuals at one end of the phenotype range have a higher fitness. Pests that survive pesticide applications survive to reproduce and pass along their traits to their offspring. After several generations, directional selection has resulted in pests with a higher fitness.

Question 7

These wild horses show a range of different coat colours even though they belong to a single population.
These differences in coat colour largely result from:

-natural selection.
-sexual recombination.
-exposure to environmental chemicals.
-DNA replication errors.

Answer 7

sexual recombination.

-In organisms that reproduce sexually, the most important source of variation is sexual recombination of existing alleles during the production of gametes.

Question 8

This is a golden hamster, a popular pet. All golden hamsters alive today descended from a single mother and her litter of pups collected from the wild in Syria in 1930.

This best describes which kind of microevolution?

Answer 8

bottleneck effect

Question 9

At some point in their lives, female Hamadryas baboons, the individual on the left in this photo, leave their birth group and migrate to a different one. This behaviour helps to maintain the fitness of the species because it helps to preserve the species’ genetic diversity. This is an example of which kind of microevolution?

-Genetic drift
-The founder effect
-Sexual selection
-Gene flow

Answer 9

gene flow

Question 10

As polar bear habitat shrinks, polar bears will likely come into contact with other bear species such as the Kodiak brown bear in Alaska. There are confirmed examples of these two species reproducing with each other to create fertile offspring. These hybrid bears may become more common as a result of global warming. Which type of evolution is this?

-Convergent
-Habitat isolation
-None of the available choices describes this

     type of evolution
  	-Hybrid inviability

Answer 10

Correct Answer: None of the available choices describes this type of evolution

-Convergent evolution occurs when distantly-related species in different locations develop similar adaptations.
-Habitat isolation occurs when two groups do not interbreed based on a geographic isolation between the groups.
-Hybrid inviability occurs when different species reproduce, but the offspring are not healthy enough to reproduce themselves.

None of these terms describes the bear species in this question.

Question 11

Which statement about punctuated equilibrium is true?

a) Punctuated equilibrium is a theory that claims all major evolutionary changes occur only after catastrophic widespread extinction events remove potential competitors
b) Punctuated equilibrium is a theory that claims evolution can occur through rare rapid events of speciation
c) Punctuated equilibrium is a theory that claims once a certain amount of genetic variability accumulates in a species, that species must branch off into new species
d) Punctuated equilibrium is a theory that claims evolution of all species results from sudden short-lived violent environmental stress

Answer 11

Correct Answer: Punctuated equilibrium is a theory that claims evolution can occur through rare rapid events of speciation

-Gradualism, or the slow, gradual change in a species eventually bringing about speciation is not the only way new species can appear.

-Sudden, relatively quick evolutionary changes may also result in speciation. This is called punctuated equilibrium.

Question 12

The marine iguana is believed to have evolved from a land iguana, which arrived on the islands from South America perhaps on driftwood.
There is a species of land iguana with which the marine iguana will mate. The offspring can climb cacti like the land species and it can also forage for algae so they are a genetic success except that they are sterile.

Which kind of reproductive barrier between marine and land iguanas is this?

-Post-reproductive hybrid infertility
-Post-reproductive hybrid inviability
-Behavioural isolation
-Mechanical isolation

Answer 12

Correct Answer: Post-reproductive hybrid infertility

Although the two species can mate successfully, their offspring are infertile, and cannot reproduce themselves. This condition is called post-reproductive hybrid infertility.

Question 13

A seed-eating bird colonizes one island in a chain of islands (bottom bird in diagram below). Over many generations the seed eating bird colonizes five other nearby islands and each group evolves independently to exploit that island’s food resource.

Which descriptions fit this model of evolution?
I) Adaptive radiation
II) Convergent evolution
III) Divergent evolution
IV) Speciation

Answer 13

I, III and IV

Adaptive radiation, Divergent evolution and Speciation

Question 14

The Kagu is indigenous to a group of islands near Australia. It is almost flightless and it builds ground nests of sticks.

Why are there so many island species of birds such as the Kagu flightless?

Answer 14

There are no predators on many islands

Question 15

What is not an example of co-evolution?

a)The evolution of the hoverfly to look like a wasp so it can avoid being eaten

b)The evolution of the monarch caterpillar, which incorporates a plant toxin from its food to make itself poisonous

c)The evolution of poison and brightly coloured skin in the poison-arrow frog

d)The evolution of flowering plants and insects that pollinate them

Answer 15

Correct Answer: The evolution of poison and brightly coloured skin in the poison-arrow frog

Some species have life cycles interwoven so closely with other species that they may co-evolve. This refers to changes in one species causing changes in another. All of the examples given here illustrate co-evolution except the poison arrow frog, whose bright colours serve as a reminder to predators of the poisons found in members of the species.

Question 16

Over 65 million years ago, albatross-like penguin ancestors began losing the ability to fly and gaining the ability to swim and dive. Compare the morphology of the albatross with that of a penguin, shown here.

This transition took about 20 million years according to fossil records. Through what process did penguins evolve?

-Convergent evolution
-Mimicry
-Natural selection
-Co-evolution

Answer 16

Correct Answer: Natural selection

Albatross-like penguin ancestors underwent the process of natural selection to evolve into the flightless, diving penguins of modern times.

Question 17

A population that is in Hardy-Weinberg equilibrium is…
I) Cloned mice under laboratory conditions with randomized mating
II) Island wild horse population that is physically isolated from other horse populations
III) Population of goldfish that were discarded from a fish tank into a local estuary
IV) Population of wild Saskatoon bushes that is experiencing stabilizing selection

Answer 17

Correct Answer: I

The Hardy-Weinberg equilibrium is a special case that never occurs naturally, as populations found in nature are always under pressures to evolve. Cloned mice in a lab, under controlled breeding conditions, could perhaps be described as a population in Hardy-Weinberg equilibrium

Question 17

A population that is in Hardy-Weinberg equilibrium is…
I) Cloned mice under laboratory conditions with randomized mating
II) Island wild horse population that is physically isolated from other horse populations
III) Population of goldfish that were discarded from a fish tank into a local estuary
IV) Population of wild Saskatoon bushes that is experiencing stabilizing selection

Answer 17

Correct Answer: I

The Hardy-Weinberg equilibrium is a special case that never occurs naturally, as populations found in nature are always under pressures to evolve. Cloned mice in a lab, under controlled breeding conditions, could perhaps be described as a population in Hardy-Weinberg equilibrium

Question 18

The Hardy-Weinberg equilibrium concept is useful because

a)it describes the dynamics of healthy populations under average living conditions.

b)it provides a theoretical baseline from which gene pool changes can be measured.

c)it provides evidence that populations do not naturally evolve except in discrete and disruptive bursts of change.

d)it describes how populations behave when they are at the peak of genetic fitness.

Answer 18

Correct Answer: it provides a theoretical baseline from which gene pool changes can be measured.

The Hardy-Weinberg equilibrium is like a control that can be used to examine all other populations. It provides a theoretical baseline from which gene pool changes can be measured.

Question 19

Which statement about microevolution is false?

a)Microevolution occurs only when Hardy-Weinberg equilibrium is maintained

b)Microevolution is evolution on the smallest scale

c)Microevolution is a generation-to-generation change in allele frequency in a population

d) Microevolution may be driven by natural selection as well as sexual selection

Answer 19

Microevolution occurs only when Hardy-Weinberg equilibrium is maintained

-Microevolution is any disruption to the Hardy-Weinberg equilibrium. It is evolution on the smallest scale, occurring as a generation-to-generation change in allele frequency in a population. This may be due to a number of factors, including natural selection, sexual selection, artificial selection, genetic drift, and gene flow.

Question 20

In humans, babies of low birth weight lose heat quickly and get ill from infections easily. Babies of higher birth weights are sometimes difficult to deliver through the pelvis. These two extremes in birth weight are selected against. This example best illustrates which type of selection?

Answer 20

Stabilizing selection
When the centre of the phenotype range have a higher fitness than those at the low and high extremes of the range, stabilizing selection is said to be occurring.

Question 21

Which statement about genetic fitness is false?

a)Genotypes with higher genetic fitness tend to become more and more common in a population

b)Genetic fitness is the capability of an individual of a certain genotype to survive and reproduce

c)An individual’s genetic fitness is independent from the environment in which it exists

d)Diseases that kill individuals in old age have less impact on the genetic fitness of a population than diseases that kill infants or children

Answer 21

Correct Answer: An individual’s genetic fitness is independent of the environment in which it exists

Genetic fitness refers to the reproductive success of a certain genotype. Genetic fitness is reflected in the phenotypes exhibited, and therefore is dependent on the selective pressures of the environment in which it exists.

Question 22

_____ often occurs as a result of a population entering a new environment with unoccupied niches such as a newly formed lake or an isolated chain of islands. The colonizing population may diversify rapidly to take advantage of all possible niches.

Answer 22

adaptative radiation

Question 23

What key event is often required before adaptive radiation can occur?

Answer 23

geographic isolation

Question 24

A new fossil species may appear suddenly (in geological terms) in a layer of rock, and persist for thousands or millions of years without noticeable change. Then, it may disappear from the fossil record as suddenly as it appeared. Which model was developed to address these observations?

Answer 24

punctuated equilibrium

Question 25

The population of northern elephant seals off the coast of British Columbia is experiencing a genetic bottleneck because of over-hunting. Which statement about the bottleneck effect is true?

a)The bottleneck effect is a special and extreme case of stabilizing selection acting on a species

b)The bottleneck effect leads to a reduction in the number of individuals in a population

c)The bottleneck effect can reduce the overall number of alleles but not the variety of alleles in a population

d)The most negative impact on a population experiencing the bottleneck effect is reduction in the number of genes in that population

Answer 25

Correct Answer: The bottleneck effect leads to a reduction in the number of individuals in a population

If a population suddenly decreases in number, often as the result of a natural disaster or over-harvesting by humans, the bottleneck effect can occur. The number and the variety of genes are both greatly diminished. This has the effect of very extreme directional selection.

Question 26

Spines and thorns in plants perform the same protective function. However, a spine is a modified leaf, while a thorn is a modified stem
Spines and thorns are _____ and are an example of _____ evolution.

Answer 26

analogous, convergent

Question 27

Sexual selection vs. Artificial selection

Answer 27

Sexual selection is a special kind of natural selection in which mating preferences influence the traits of the organism

Artificial selection is a man-made selection of desirable traits in plants and animals, and the steps taken to enhance and perpetuate those traits in future generations

Question 28

Bottleneck effect

Answer 28

Decreases genetic variation in a population
-disasters such as earthquakes, floods, droughts, and fires may drastically reduce the size of a population, which also reduces the size of its gene
pool

Question 29

Founder Effect

Answer 29

The change in allele frequencies relates to the
genetic makeup of the founders of the colony
- few individuals colonize an isolated island, lake, or some other new habitat. The smaller the colony, the less its genetic makeup will represent the gene pool of the larger population from which the colonists came.

Question 30

What are the bottleneck and founder effects examples of?

Answer 30

genetic drift (change in the gene pool of a population due to chance)

Question 31

Give an example of a reproductive barrier that
prevents mating and a barrier that happens
after mating has occurred

Answer 31

prevents mating
-temporal isolation: different breeding seasons

barrier that happens after mating has occurred
-hybrid infertility: hybrid offspring mature into
adults, but are infertile.

Question 32

Under what conditions might adaptive
radiation occur?

Answer 32

-The founder effect, natural selection, and reproductive isolating mechanisms such as geographic, habitat, and behavioural isolation

Question 33

What is the difference between punctuated
equilibrium and gradualism?

Answer 33

gradualism: evolution of a species by gradual accumulation of small genetic changes over a long period of time

punctuated equilibrium: species often diverge
in spurts of relatively rapid evolutionary change + could lead to speciation

Question 34

How is mimicry an example of co-evolution?

Answer 34

Co-evolution is the process in which one species evolves in response to the evolutionary changes in another species

mimicry is an example of co-evolution because although, it’s a one-way influence, the mimic, (evolves to) resembles another species, the model, in order to gain survival advantage.

Question 35

Suppose taller people in a population are
selected for.
(a) What type of selection will occur?

Answer 35

Stabilizing selection because it occurs when individuals near the centre of the phenotype range are selected

Question 36

Explain how fossil organisms, asexually
reproducing species, and natural variation
within a species make it hard for scientists to
clearly define a species

Answer 36

biological species concept:
states that a species is a population or group of populations whose members have the ability to breed with one another in nature and produce fertile offspring

-fossil organisms are extinct and can’t breed
-asexually reproducing species don’t sexually reproduce
-natural variation within a species makes it hard to define the species because some species might look completely different due to an adaptation to an environmental pressure but might be the same exact species

Question 37

Within a few weeks of administering the drug
3TC to a patient, the HIV population in his
body consists entirely of 3TC-resistant viruses.
How can you explain these results?

Answer 37

directional selection=evolution of resistant viruses

-most survivors of the first drug treatments were viruses with genes that somehow enabled them to resist the drug attack
-other virus replications inherited the genes for drug resistance
-in each generation, the percentage of
drug-resistant individuals in the virus population increased
-the alleles that produce higher drug resistance increase in the population

Question 38

The myrtle warbler and the Audubon’s warbler
were once considered to be two distinct
species; but now, bird guides list them as
eastern and western forms of a single species,
the yellow-rumped warbler. What can explain
this new classification?

Answer 38

The two forms interbreed often in nature, and their offspring have good survival and reproduction

Question 39

Explain why speciation would more likely
occur on islands farther from a mainland, such
as the Galapagos islands, than an island close
to a mainland, such as P.E.I.

Answer 39

On an island far away from the mainland, there is greater geographic separation between the population on the island and the population on the mainland, so members of the different populations are less likely to interbreed, which would eventually lead to speciation.

Question 40

Two known species of violets grow in a field,
but there are also several unknown violets
growing there as well. These violets resemble
the two known species but appear to be new
species. Form a hypothesis to explain how the
new species may have evolved

Answer 40

-hybrids (two different species breeded= replication)

Question 41

The fossil record has helped us understand
evolutionary process. On the other hand, it
has its limitations. Describe two limitations
in using the fossil record to understand the
evolution of species.

Answer 41

-fails to show what are called “transitional forms,” generally the in-between stages as one type of creature evolved into another

-an organism had to be suddenly buried alive underground in order for the fossil to form. If an organism had already died before being buried, it would be partially decomposed