Transcript Answer Key – LO 1.2

Answer Key – LO 1.2
Which of the following is NOT a way in which natural selection affects the
distribution of phenotypes?
A) Directional selection
B) Chance events
C) Stabilizing selection
D) Disruptive selection
Directional selection is most common wen a population’s environment changes or
when members of a population migrate to a new habitat with different
environmental conditions than their former one. Stabilizing selection acts against
extreme phenotypes and favors intermediates variants. Disruptive selection occurs
when environmental conditions favor individuals on both extremes of a phenotypic
range over intermediate phenotypes. An example of directional selection is that
black bears in Europe increase with size during the colder weather, only to
decrease during the warmer weather. An example of stabilizing selection is the
birth weights of most human babies lie in the range of 3-4 kg; babies who are
much smaller or larger suffer higher rates of mortality. An example of disruptive
selections is black- bellied seed cracker finches have two different beak sizes for
cracking different types of seeds.
ANSWER KEY- LO 1.3
All members of an isolated village were genotyped for a particular RFLP. Of the 1000 individuals, 200 were homozygous for the
presence of the restriction site, 700 were heterozygous, and 100 were homozygous for its absence. What is the frequency of
the "restriction site present" allele, p?
A)
B)
C)
D)
E)
0.45
B) 0.9
C) 0.2
D) 0.55
E) None of the above
(A) How can the Hardy-Weinberg principle of genetic equilibrium be used to determine whether this population is evolving?
(B) Identify a particular environmental change and describe how it might alter allelic frequencies in This population. Explain which
condition of the Hardy-Weinberg principle would not be met.
The Hardy-Weinberg principle can be used to determine if the population is evolving by a ratio. If the ratio of the dominant
genotype to the recessive is 3:1 the population can be looked at as evolving. There are several environmental changes that
could alter allelic frequencies in a population, thus causing certain conditions of the Hardy-Weinberg principal not to be met.
An example of an environmental change would be the population decreasing in size due to a natural disaster. This would
disrupt the Hardy-Weinberg condition of the population being large. Environmental changes can also cause mutation which
would disrupt the Hardy-Weinberg condition. If the population changed due to Bottleneck or founder’s effect, then the
population would become small and allele frequencies would change causing the principal not to be met.
L.O. 1.4 M.C. Question: From left to right in the picture shown, what 3 types of selection
are shown?
A) stabilizing, diversifying, directional
Directional selection is when on of the
B) directional, diversifying, stabilizing
extreme cases is chosen, so the graph goes to
C) diversifying, directional, stabilizing
one side. Stabilizing is when the middle trait is
D) directional, stabilizing, diversifying
shown, so the graph stays in the middle and
gets slimmer. Diversifying selection is when
both the extreme cases are chosen, so the
middle of the graph drops and the two sides
raise up.
Learning Log/FRQ-style Question:
Identify and describe each type of
selection and provide an example of
each.
Directional selection is when one of the extremes is chosen, such as when a typically
beige type of snail has offspring that are dark brown due to the rocks they live on
changing from a lighter color to a dark brown. Stabilizing selection is when the middle
trait is chosen, and this could result in the beige snails having almost all beige offspring
due to all the rocks in their environment being beige. Diversifying selection is when both
the extremes are chosen, so the snails would be either white or dark brown, and that
could be caused by the rocks being brown with big white spots on them.
Answer Key - LO 1.5
M.C. Question: A large assemblage of land snails is subdivided into two populations (A and B) by a river that effectively isolates the
populations for an indefinitely long period. From an evolutionary standpoint, which of the following is the LEAST likely to occur in the two
populations?
A) Populations A and B will eventually differ in their ecological requirements.
B) Population A may ultimately breed at a different time of the year that population B does.
C) Population A may undergo instantaneous speculation by the doubling of its chromosome numbers (polyploidy).
D) Under laboratory conditions, cross-fertilization between members of the two populations may be successful even after a long period of
geographical separation.
E) The two populations may become morphologically very dissimilar.
Learning Log/FRQ-style Question: Suppose a population of mice live on the side of a volcanically active mountain. The population of mice
has a dominant gene for white fur, and a recessive gene for black fur. At the moment the mice are hunted at the same rate; what would the
population look like ten months after a volcanic eruption? Why? What kind of selection is this? Draw and label a graph depicting the two
populations. Label the original population and the population after natural selection.
Example of a given diagram (labels included) :
The recessive gene of black fur would be naturally
favored because these mice better fit their new
environment. The new, dark, habitat created by the
volcanic eruption will hide the mice from predators
and white mice populations with decline. This is
know as disruptive selection; the environmental
factors changed and favored one phenotype over
another.
ANSWER KEY LO 1.6
M.C. Question: Supposed in a large colony of
isolated beetles, where the allelic frequencies
used to be equal a few generations ago, the
frequency of the recessive allele was now
nearly double that of the dominant allele, and
the frequency is still increasing. Which of the
following is most likely true concerning the
scenario stated above?
A) It follows the Hardy-Weinberg equation
because the population is large enough to
counteract the climbing recessive allelic
frequency.
B) Genetic drift is occurring in the population.
C) Something recently has changed in their
environmental surroundings that has caused
natural selection to favor the recessive allele
over the dominant allele.
D) The beetles with the dominant allele will
emigrated out of the colony.
a)Discuss the difference between the founder effect and the
bottleneck effect and b) describe how natural selection is more
“predictable” than genetic drift
a) The bottle neck effect is when you have
destruction of the environment that
results in a few of the population
remaining to repopulate, and they may
not be representative of the original
population. The founder effects has
similar effects, except that instead of an
environmental disaster, it results from a
portion of the original population settling
in a different area.
b) Natural selection is more predictable
because the environment weeds out those
who are not as best fitted (reproduction of
the fittest). Genetic drift, however,
happens completely by chance.
L.O. 1.7 Which of the following would not cause genetic drift in a population?
a) Immigrants from Asia coming to a town on the west coast of the US
b) Mating in a population of butterflies is dependent on the most colorful wings
c) A population squirrels is very large with several traits for tail shape
d) A drought occurs that allows only plants with water conservation techniques to survive
e) A mutation occurs in a population of rabbits which causes more padded feet for crossing snow
FRQ-Style Question: Name three factors involved in achieving Hardy Weinberg equilibrium and explain how
it may impact genetic drift. Describe how these influences on genetic drift may lead to evolution in a
population.
A factor which may disrupt equilibrium is the occurrence of selection for a specific trait in the
population. If one trait is favored by the environment, then it will alter the gene pool as this will
impact the potential for reproduction and thus the frequency of the alleles which shall lead to drift
in future generations. The equilibrium may also be hampered by the occurrence of gene flow within
the population. The movement of organisms in and out of the population would alter the allelic
frequency and may lead to further drift in later generations. Another influence on equilibrium is the
requirement of maintaining a large population to prevent genetic drift. This is due to the fact that a
larger gene pool would minimize any alteration to the gene pool and will provide greater stability
for future generations. These instances of genetic drift would cause alterations to the gene pool of a
population and act as a mechanism of evolution. Evolution occurs through drift as the population
begins to express a certain trait more frequently, and speciation may occur for the population
expressing this gene leading to a new step of evolution for the population.
Answer Key – LO 1.8
M.C. Question: A scientist studying birds on two adjacent islands discovers that the Bingle Bird, which has a short and
strong beak, on the Island of Seuss and the Hephalump Bird, which has a long and narrow beak, on Winnie Island have a
common ancestor, but can no longer reproduce together. Which of the following predictions correctly explains this
phenomena by using a theory that incorporates the Bottleneck Effect and the Founder Effect?
A) A drought on the Island of Seuss caused only the birds with short and strong beaks that could open hard seeds to be
able to survive on the island, while the birds with long and narrow beaks had to find another habitat where they
could feed on flowers. The extended separation of the birds led to the development of two different species.
B) A tsunami destroyed Winnie Island, killing many birds and forcing several of the ancestral birds to move to the
Island of Seuss. By chance, the alleles for a short and strong beak were represented more on the Island of Seuss
and the alleles for a long and narrow beak were represented more on Winnie Island. Eventually, the separated
populations became too genetically different to reproduce.
C) Winnie Island has many plants with long flowers from which it is easier to obtain nectar if a bird has a long and
narrow beak. The food source on the Island of Seuss is mostly hard seeds that are easily opened with a short and
strong beak. The once homogenous population went through natural selection to create two new populations that
were better suited for the food sources.
D) Foreign predators were introduced on the Island of Seuss and Winnie Island. The predators of the Island of Seuss
preferred to eat birds with long and narrow beaks while the predators on Winnie Island ate birds with short and
strong beaks. The abundant predators caused their respective prey to become extinct, creating a population of short
and strong beaked birds on the Island of Seuss and a population of long and narrow beaks on Winnie Island.
FRQ: Darwin’s research on finches in the Galapagos Islands led to his theory of evolution and its mechanism, natural
selection. Describe TWO mechanisms of genetic drift and explain how each can result in a new species.
Migration can be one mechanism of genetic drift. Members of a species can become isolated from the population due to
geography, and the new colonizing population represents alleles in different ratios than represented in the original
population. This causes genetic drift and can eventually result in populations that are so genetically different that
they can no longer reproduce. Another mechanism of genetic drift is the bottleneck effect. When a natural disaster
like a tsunami or a forest fire occurs, random members of a populations are killed. The surviving individuals
represent alleles in different frequencies than they were in the original population. The population can have such
different alleles that the gene pool shifts entirely and a new species evolves.
L.O. 1.9 M.C. Question: Analysis of forelimb anatomy of human, bats, and whales shows that humans and
bats, and whales shows that humans and bats have fairly similar skeletal structures, while whales have
diverged considerably in the shapes and proportions of their bones. However, analysis of several genes in
the species suggests that all three diverged from a common ancestor at about the same time. Which of the
following is the best explanation for these data?
a. Humans and bats evolved by natural selection, and whales evolved by Lamarckian mechanisms?
b. Evolution of human and bat forelimbs was adaptive, but not for whales.
c. Natural selection in an aquatic environment resulted in significant changes
to whale forelimb anatomy.
d. Genes mutate more rapidly in whales than in humans or bats.
e. Whales are not properly defined as mammals.
Describe the modern theory of evolution and show how it is supported by evidence from two of the
following areas: population genetics, molecular biology, and comparative anatomy and embryology.
In modern terms, evolution is a change over time in the genetic
composition of a population. In molecular biology, comparisons of
nucleic acid sequences are often used. If the species are very closely
related, the sequences likely differ at only one or a few locations. In
contrast, comparable nucleic acid sequences in distantly related
species usually have different bases at many sites and may even have
different lengths. The arms, forelegs, flippers, and wings of different
mammals are homologous structures that represent variations on a
structural theme that was present in their common ancestor. One kind
Of homologous structure is vestigial organs, structures of marginal, if
Any, importance to the organism. Vestigial organs are remnants of
Structures that served important functions in the organism’s ancestor.
Answer Key: LO 1.10
MC Question: All of the following pairs of structures are homologous structures except which?
A)
B)
C)
D)
The wings of a bat and the wings of a butterfly
The arm of a human and the leg of panther
The hooves of a camel and the hooves of a sheep
The scales on the foot of a chicken and the scales on a lizard
Learning Log/ Free Response Question:
A paleontologist on an expedition in Hong Kong finds the remains and fossils of an extinct
species of supposed city dwelling rodent. The scientist expects to find organisms of common
ancestry in an area close to New York city. Explain why the scientists prediction is either
valid or invalid and describe the scientific evidence that supports your reasoning.
The paleontologist’s prediction is invalid; the extinct species of rodent would most
likely share common ancestry with other rodent species in the surrounding area. Based
on evidence supported by biogeography, closely related species tend to be located in the
same geographic region, whereas the same ecological niches in distant regions are
occupied by very different species even though they may be similar looking.
ANSWER KEY– LO 1.11
M.C. Question: Which of the following is not a scientific argument for the theory evolution.
A) Chimpanzees and Humans share 98% of their DNA.
B) Fossils of species with both lungs and gills have been found in Nunavut.
C) Africans and Asians have similar physical features.
D) Species in different parts of the globe with similar environments share many behaviours/ physical
features.
Learning Log/FRQ-style Question: How can homologous structures and biochemistry be used to explain the changes
of organisms over time? Use specific examples.
The evolution of organism overtime is an effect of changes in habitat, changes in food, geographical isolation, etc.
In convergent evolution, genetically unrelated species share a set of common traits. For example, sharks and
dolphins both have flippers, yet they belong to a different biological class. This is due to their shared food source
and habitat. Similarly, similar genetic makeup serves in divergent evolution to show how two genetically close
species can have different features. For example, the finches of the Galapagos all have different beaks because of
their different food sources and habitats (they were isolated geographically from each other- a natural hindrance
to reproduction/ genetic variation). However, their strikingly similar DNA shows that they share a common
ancestor.
ANSWER KEY-LO 1.12
M.C Question: If Darwin had been aware of genes, and of their typical mode of transmission to
subsequent generations, with which statement would most likely have been in agreement?
A)
Somehow if natural selection can change one gene’s frequency in a population over the
course of generations then, given enough time and enough genes, natural selection may
cause sufficient genetic change to produce new species from old ones
B)
If an individual somatic cell genes change during its entire lifetime, supposedly making it more
fit, then it will be able to pass these genes on to its offspring.
C)
If an individual’s acquires new genes by engulfing, or somehow being infected by, another
organism, then a new genetic species will possibly be the result.
D)
A single mutant gene in a single gamete will, if perpetuated, will produce a new species within
just two generations.
Of all mutations that occur, why do only a small fraction become widespread in a gene
pool?
Most mutations occur in somatic cells that do not produce gametes and so are lost when the
organism dies. Of mutations that do not occur in cell lines that produce gametes, many do
not have a phenotypic effect on which natural selection can act. Others have a harmful
effect and are thus unlikely to spread in a population from generation because they decrease
the reproductive success of their barriers
Answer Key- L.O. 1.13
There are 100 students in a class. Ninety-six did well in the course whereas four blew it totally and received a grade of F. In the highly
unlikely event that these traits are genetic rather than environmental, if these traits involve dominant and recessive alleles, and if the
four (4%) represent the frequency of the homozygous recessive condition, calculate the frequency of the recessive allele.
a.) 40%
b.) 4%
c.) 20%
d.) 2%
*We know that the 4% represent the homozygous recessive condition, therefore, we know that q 2 = 0.04 (which is 4%) and
√0.04 = .2 (q) .2 = 20%
A large population of Biology teachers have 396 red-sided individuals and 557 tan-sided individuals. Red is completely recessive.
Calculate the following:
a.) The allele frequencies of each allele.
b.) The expected genotype frequencies.
c.) The number of heterozygous individuals you would predict.
d.) The expected phenotype frequencies.
a.) First, calculate the total number of people: 396+557= 953. Recessive (q 2 )=all red.
396 ÷ 953 = 0.416 (q2 ) √0.416 = 0.645 recessive p-q=1 1 – 0.645 = 0.355 dominant
b.) AA= p2 (0.355)2 = 0.126
Aa= 2pq = 2(0.355)(0.645) = 0.458
2
2
aa = q = (0.645) = 0.416
c.) 0.458 (Aa calculated in part b) × 953 (total population) = 436 teachers
d.) A phenotype= 0.126 + 0.458 = 0.584
a phenotype= 0.416 (calculated in part b)
Answer Key- LO 1.14
Learning Log/FRQ-style Question: Among the varied forms of life on
earth, many organisms share common life processes despite
other enormous functional and taxonomical differences.
M.C. Question: Which of the following
characteristics is not exclusive to eukaryotic
life?
A) cell wall composed of either chitin or
Identify and describe two processes shared across multiple
kingdoms, examine their differences between kingdoms while
cellulose
listing at least two of the taxonomical kingdoms that share
B) flagella or other external structures used in
them.
locomotion
C) cytoskeleton of microtubules, microfilaments,Light dependent reactions of photosynthesis are instrumental in
and/or intermediate filaments
the conversion of environmental sunlight, water, and carbon
dioxide into sugars that can be hydrolized for energy. In
D) presence of the Golgi apparatus
plants, such reactions occur in the thylakoid membrane within
E) genetic material wrapped into chromosomes
the membrane-bound chloroplast, but in photosynthetic
bacteria light dependent reactions take place in the plasma
membrane of the cell.
Sexual reproduction is the method developed by eukaryotes to
introduce genetic diversity into populations by combining the
genetic materials of partnered organisms into unique
offspring. Although performed in some capacity in animals,
plants, and fungi, sexual reproduction has many variations. In
animals, the process typically occurs when two diploid
organisms combine their respective haploid gametes to create
a new, genetically unique, diploid organism. In plants and
fungi, however, this can occur differently such as in the case of
self-fertilization, the sexual generation of an organism using
only the sex organs of a single parent. Additionally, plants,
fungi, and animals often exhibit varying life cycles with
prominent example such as mosses existing as haploid
organisms even when fully mature.
Answer Key- LO 1.15
Based on your knowledge of membrane bound organelles, which of the following
statements is true?
A) Plants are more closely related to protists than fungi
B) Bacteria developed before protists
C) The earliest cells were eukaryotic
D) Animals were the last kingdom to evolve
You are an evolutionary biologist comparing the genetic codes of a species of animal
and a species of plant. Using conserved core biological processes or features in your
answer, explain why the two species’ genetic codes are so similar.
Even though the two species are dissimilar on the macroscopic level, they are both
eukaryotes, and therefore share all of the structures common to eukaryotes, such as
a cytoskeleton and a nuclear envelope. Animal and plant cells also use similar
processes to function, like hormonal signaling and sexual reproduction. These
structures and functions account for a large portion of any given organism’s genetic
code, and therefore any two organisms who share these traits can be expected to
have much of the same DNA.
Answer Key- LO 1.16
Which of the following would be most useful for constructing a phylogenetic tree for several
fish species?
A.
B.
C.
D.
E.
Several analogous characteristics shared by all the fishes
A single homologous characteristic shared by all the fishes
The total degree of morphological similarity among various fish species
Several characteristics thought to have evolved after different fishes diverged from
one another
A single characteristic that is different in all the fishes
Darwin is considered the “father of evolutionary biology.” One of his contributions to the field
of evolutionary biology is branching evolution, which implies the common descent of all species.
Discuss one example of supporting evidence.
One explanation of common ancestry is homology, which is similarity in characteristics
resulting from a shared ancestry. This could be embryological, structural, molecular, or
processes. For example, vestigial organs are remnants of structures that served important
functions in the organisms ancestors.
ANSWER KEY 1.17
What can be inferred from a species that is on a clade above a specific characteristic?
A) The species does not possess this characteristic.
B) The characteristic was lost through natural selection and no longer possessed by the species.
C) The species has evolved so that it possesses that characteristic.
D) An ancestor of the species possessed this characteristic.
A group of scientists predict that two types of birds evolved from one common ancestor. One species of bird
was found in Alaska while the other was discovered in the northeast region of Russia. What visual diagram
could be used to display the relationship between the two species in relation to their ancestor? The two
birds look almost identical, but one type on bird can fly while the other cannot, and when face postzygotic
barriers when scientists attempt to mate them together. Between which two classification groups does this
suggest divergence occurred? What does this suggest about each bird species’ binomial?
A phylogenetic tree could be used to display the divergence that occurred between the two species of a
common ancestor. Because species that appear to be closely related are grouped into the same genus,
these two birds have most likely evolved from the same genus into different species. This suggest that the
first part of their binomials are the same because they belong to the same genus group, but that they
have two different specific epithets.
Answer Key- LO 1.18
MC Answer
The underlying premise of cladistics and phylogeny is that
A. Taxa that share many homologous traits are more closely related than species that share few.
B. The more recently that taxa have branched from a common ancestor the less similar should they be in
morphology and in their DNA sequences
C. Taxa that share many derived traits are likely to be most closely related.
D. A and C only
Learning Log/FRQ Answer
The more recently a species diverged the more closely related they are as they still share genetic material and
the organisms will look more similar and share more DNA. If the species underwent speciation longer ago, the
branches are further apart and they are more distantly related as share less genetic material as organisms
have evolved over time. The more branches a phylogenetic tree has the more speciation has occurred and the
less branches it has, the less speciation has occurred and the more similar the organisms are to the other
organisms that share that branch.
ANSWER KEY- LO 1.19
M.C. Question: Which of the following would be a
constructive reason for creating a phylogenetic tree for
leopards?
A) Several analogous characteristics shared with similar
animals
B) A single characteristic is shared with several animals
C)Several characteristics predicted to have evolved
from other species over the years
D) A single characteristic shared with all leopards.
Learning Log/FRQ Question: Hierarchical classification is
reflected in the continuous branching of phylogenetic
trees. Species that appear to be closely related are put in
the same group. Name TWO ways phylogeny can be
traced. Draw and label THREE of the hierarchical
classifications in the correct order.
Hierarchical classification involves similar species being
placed in certain groups. The bottom three categories are
domain also known as Eukarya, Kingdom also known as
animalia, and phylum also known as chordata. Domain
being the first classification, and the other two following
behind. Phylogeny can be traced by relative dating and
absolute dating. Relative dating is based on the layer of
fossil found. Either it is older or younger. Absolute
dating is also known as radiometric dating that involves
isotopes. It uses the decay of radioactive isotopes to
determine the age of the rocks or fossils.
ANSWER KEY- LO 1.20
M.C. Question: Which situation below would ENCOURAGE speciation?
A) A large population of animals.
B) Population exhibits zero net mutation.
C) Animals mate randomly.
D) A small population of animals.
Explanation: The smaller a population is, the easier it is for it to be subject to genetic drift. This may
been seen in phenomena such as the bottleneck effect or the founder effect.
FRQ: To the left is a hypothetical graph following the populations of dingoes and thylacines (a striped
wolf much like the dingo) on the Australian mainland. Given what you know about extinction, give
TWO reasons why the thylacine might have gone extinct. Also give TWO reasons why over 4,000
years, the dingo and thylacine might have become two different species descendant from wild dogs
while together on mainland Australia.
The thylacine might have gone extinct due to loss of food
source. If the dingoes were larger and had more muscular
jaws, they could have easily stolen food from thylacines or
outhunted them. They might have also been more adapted to
the environment with their camouflaged light-colored coats,
making it harder to hunt them than the thylacines. Two
reasons they may have sympatrically speciated are sexual
selection of similar partners or natural selection that favored
dogs with characteristics on extreme ends of the spectrum.
plain coat
striped coat
discouraged
ANSWER KEY – LO 1.21
What is a leading cause of extinction among species?
A) Competition
B) Natural Selection
C) Habitat loss
A type of modern evidence of speciation is
D) Increasing disease
molecular biology or blasting DNA
sequences to make comparisons amongst
One of Darwin’s key pieces of evidence in
species. This new type of data looks
proving his theory of evolution was fossils.
directly at the chromosomes to give a
Compare and contrast modern evidence
molecular ‘proof’ of a common ancestor.
of speciation with the fundamental
Fossils were an original piece of proof as
observation of fossils. Why were fossils
it was visual and made a rebuttal to the
originally so significant in comparison to
proposed theory very difficult. Fossils in
other types of evidence and why do they
modern times now work as a backbone,
still hold merit?
so to speak, providing more support and
evidence for the theory of evolution. It
provides evidence of homologous
structures between different species
which can then be blasted for molecular
comparison.
Answer Key – LO 1.22
An orange tiger is heterozygous for the white fur and orange fur gene,
it mates with another tiger with the exact same genotype in the snowy
mountains of Nepal. After multiple matings between tigers of the same
genotype occur in the same area, the majority of offspring seem to be
white. This is due to an adaptation for camouflage purposes, what kind of natural selection is this?
A) Stabilizing selection
B) Directional selection
C) Disruptive selection
D) Super selection
For each type of natural selection (directional, disruptive and stabilizing),
list an example, and define the type of natural selection. Give an advantages
and disadvantage of one of the types of natural selection.
Directional selection is when a population’s trait distribution shifts to another extreme.
An example of this could be when a bird with a narrow beak mates with a bird with a wide beak,
but the population needs a narrow beak to survive in the habitat. The beak distribution
would shift to the narrow beak to help aid survival. Disruptive selection is when the two extreme
phenotypes are mainly seen in a population, mostly homozygous dominant or recessive.
Stabilizing selection is when the extreme phenotypes of a population are rarely seen, the
opposite of disruptive selection. An advantage of stabilizing selection is that the unfavored
genotypes could be selected against, such as an albino offspring. A disadvantage of
stabilizing selection would be a decrease of the population diversity.
Which of the following does not tend to promote speciation?
A) founder effect
B) reproductive isolation
C) natural selection
D) gene flow
Describe a method of speciation that can lead to the development of separate species from one
common specie? Give an example.
One method of speciation is allopatric speciation (geographic isolation). This occurs
when a population of one species becomes physically separated by some geographic barrier. Some
geographic barriers could be a mountain range, river, ocean, lake, etc. Once the species are separated
they start to adapt to their new environments. The long the species are apart the more they change
causing two new species to form. An example of this are the Galapagos turtles.
L.O. 1.23
Answers- L.O. 1.24
M.C. Question: More epic and manly manes on lions have evolved to be so magnificent due to the fact that
lady-lions love the scruffy, neck-scarf mane. The process by which these lion’s manes have evolved is best
described as
A. Genetic drift that changes the frequencies of the alleles for mane manliness
B. Natural selection for sexual reproduction that maintains variations in the genes that influence sexy manes.
C. Intersexual selection for traits, such as long flowing manes, that help males attract mates.
D. Intrasexual selection for traits, such as long flowing manes, that help males win contests for access to
females.
E. Directional selection for traits, such as long flowing manes, that improve males’ ability catch food and stun
onlookers.
Suppose a population of 1000 unicorns experience a bottle neck where 50% of the population is wiped out.
The original population was 55% red, 35% pink and 10% white; homo. Dominant, heterozygous, and
homo. Recessive, respectively. What would likely be the most common phenotype? Least common? Why?
What would likely happen to the white unicorn phenotype?
The likely outcome of this bottle neck effect on this population of majestic creatures would be a shortage of
the infamous white unicorn. Obviously the new populations would approximately reach 275 red unicorns,
175 pink unicorns, and only about 50 white unicorns. Red would still maintain the majority of the new
population while white would likely hold the smallest representation, meaning red would be the most
common phenotype while white was the least common phenotype. This is because a bottle neck effect
that kills every other unicorn, assuming color has no effect on death selection, would be equally
distributed across the population. If the white unicorn population where reduced to such low numbers
they could have a chance of becoming extinct due to the fact that white is the recessive gene in this
scenario.
Answer Key- L.O. 1.26
Analysis of forelimb anatomy of humans, bats, and whales shows that humans and bats have fairly
similar skeletal structures, while whales have diverged considerably in the shapes and proportions
of their bones. However, analysis of several genes in these species suggests that all three diverged
from and common ancestor at about the same time. Which of the following is the best explanation
of these data?
a. Humans and bats evolved by natural selection, and whales evolved by Lamarckian mechanisms.
b. Evolution of human and bat forelimbs was adaptive, but not for whales.
c. Natural selection in an aquatic environment resulted in significant changes to whale forelimb
anatomy.
d. Genes mutate more rapidly than in humans or bats.
e. Whales are not properly defined as mammals.
Using your knowledge of evolution, describe how the following concepts relate to Darwin’s theory of
evolution by natural selection:
• Over reproduction of populations: more offspring than strictly necessary, some of which won’t
survive.
• Limited resources: 2 or more organisms are in need of the same limited resource and are forced
to compete for it. The stronger/ more equipped of the two will survive.
• Heritable variation: This is the differences among individuals in morphology, behavior, and
reproductive performance that have a genetic basis.
Species have the potential to produce more offspring than survive (over reproduction), leading to a
struggle for resources, which are limited. Populations exhibit a range of heritable variations,
some of which confer advantages to their bearers that make them more likely to leave more
offspring than less well-suited individuals. Over time this natural selection can result in a greater
portion of favorable traits in a population (evolutionary adaptation).
ANSWER KEY – LO 1.27
The most compelling evidence that RNA evolved before DNA is…
A) RNA is copied by ribozymes, which evolved before DNA Polymerase.
B) RNA’s single stranded coding allows it to assume different shapes to interact and adapt better.
C) DNA was too complex for such primitive cells.
D) RNA uses nucleotides that evolved before those in DNA.
Using the picture to the right, Explain why Miller and Urey might have used certain features in their
experiment and what they represent in Earth as it was billions of years ago.
Every part of Miller and Urey’s experiment
simulated something in the primitive Earth. The
water with a flame under it would have represented
the ocean being heated by the earth. This water
would have evaporated. The spark emitted by the
electrodes represents lightning, which scrambled
atoms to bind in different ways. The gases used in
the experiment are the same as what the primitive
Earth’s atmosphere would have had. The cooling
and condensing of the water simulates rain.
ANSWER KEY– LO 1.28
M.C. Question: Scientists agree that the first molecules on earth were:
1.
2.
3.
4.
A) Proteins
B) Nucleic acids
C) RNA
D) None of the above
Explain the Primordial (Organic) Soup theory. Does
this process involve reduction or oxidation, and why?
Primordial Soup is the collection of Amino Acids and
organic molecules that were used to make other
compounds. The elements were all mixed together in
the primitive earth, inspiring the soup analogy. This is a
reduction reaction because electrons are added.
(Drawings could be added to help demonstrate
student’s knowledge of the subject.)
L.O. 1.29 Miller and Urey created and performed an experiment using the Primordial Soup theory. Their
experiment proved that this theory was a possibility for the origin of life. According to their experiment,
which statement is false?
A) Life could start through chemical reactions
B) Organic compounds are capable of being made
through extreme conditions
C) Used known gases on primitive earth
D) It was done using a closed environment like primitive
earth
Compare and contrast the early Earth vs. Earth today, be specific about the environment and conditions
that existed.
Early Earth’s atmosphere did not consist of oxygen and today’s atmosphere does. Early
Earth experienced heavy amounts of UV radiation and although UV radiation is becoming a
problem for us today, we do not experience
the same amount of UV radiation as early
Earth did. Early Earth did not initially contain
any life forms, but over time life forms have
evolved and have reached very complex
levels today. The primeval sea consisted of
only the basic monomers and today our
oceans contain great life forms.
Answer Key- LO 1.30
Multiple Choice: RNA is most likely the first genetic material on Earth because __________.
A. RNA is structurally simpler than DNA.
B. RNA has simpler reproduction.
C. RNA is able to assume a variety of 3D shapes mandated by nucleotide sequences.
D. All of the above.
Explanation: All these characteristics of RNA contribute to the hypothesis RNA was the first genetic material. The simplicity of
RNA is easier for the simple organisms of the time to.
Free Response Discuss the elements and conditions of early Earth and how the combination contributes to the creation of early
life. reproduce. Describe the most widely accepted theory for the early evolution of life. Remember to discuss protbionts, genetic
materials, and scientific experiments in the explanation
Early Earth consisted of high levels of CO2, methane, ammonia, hydrogen, and hydrogen sulfide. The combination of these
elements with the violent lightening storms and thick atmosphere with water vapor gave way to the creation of life. As Earth
cooled, the water vapor condensed into oceans, and much of the hydrogen escaped to space. Early oceans were a solution of
organic molecules from which life arose. The Miller- Urey experiment found the simulation of early Earth produced a variety of
amino acids found in organisms today along with other compounds. Protobionts are also a part of the early evolution of life.
Protobionts exhibit some of the properties associated with life, like simple reproduction and metabolism, as well as the
maintenance of an internal chemical environment different from their surroundings. Laboratory experiments demonstrate
protobionts could form spontaneously from abiotically produced organic compounds and with a membrane or membrane-like
structure. Protobionts likely had RNA. The simplicity of RNA allowed protbionts to carry limited amount of genetic information.
The most successful protobionts would increase in number, because they could effectively exploit their resources and pass their
abilities to future generations. The RNA likely gave way to the DNA world and future generation of life on Earth.
2
ANSWER KEY- LO 1.32
Which of the following is the likely source of energy for the synthesis of the small organic molecules that
presumably predated the first forms of life on Earth?
A.) Fermentation by bacteria
B.)Photosynthesis by microscopic algae
C.) Lightning from constant storms D.) Shifts in ocean currents
Some scientists believe that in order for ecosystems to maintain a balanced or steady state, biodiversity must
be conserved. Using both classical Darwinian thought and the modern synthesis of evolutionary theory, answer
the following question as it relates to biodiversity.
Insects are the most diverse group of organisms on Earth. Give some possible explanations for why this
diversity exists.
The most diverse group of organisms by far is the Class Insecta. Their diversity is explained by a combination
of certain morphological advantages and ecological associations. First of all, insects evolved wings that
allowed them to escape predation and take advantage of several new ecological niches. Insects are closely
associated with flowering plants and their fast radiation is closely linked to the radiation of the angiosperms
as they colonized a changing land climate. Insects also have short generations, allowing them to produce
many offspring in short periods of time. These factors combined in traits that conferred selective advantages
and provided insects with higher fitness. Also, the higher rate of reproduction and gamete production
allowed more chances for viable mutations to occur. Since mutations are the ultimate source of genetic
variation, the greater the rate of mainting a mutation, the higher the rate of accruing variation.