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BIG IDEA 4: INTERACTIONS
4.
While prokaryotes are considered to be strictly unicellular, most are capable of forming stable
aggregate communities. When such communities are encased in a stabilizing polymer matrix
("slime"), they may be called "biofilms." Which is a FALSE statement about prokaryotes? (4.4)
A) No membrane separates the DNA region called the nucleoid from the rest of the cell.
B) Only bacteria and archaea are prokaryotes.
C) The cell wall is usually made of cellulose.
D) Many prokaryotes exhibit “taxis” to move toward or away from a stimulus.
1.
The phospholipid bilayer is a universal component of all cell membranes. Its role is critical because
its structural components provide the barrier that marks the boundaries of a cell. The lipid bilayer is
typically about five nanometers thick and surrounds all cells, providing the cell membrane structure.
It only allows small, non polar, non charged particles to pass unimpeded. What property of the
phospholipids allows it to form a bilayer? [4.2]
A) The proteins are made of acidic R-groups while the lipids have a basic pH. The bilayer forms
to accommodate for the opposite charges.
B) The head of the phospholipid is hydrophilic while the fatty acid tail is hydrophobic. The
bilayer forms because the hydrophobic tails face the membrane interior to avoid water.
C) The unsaturated fatty acid kinks outward and prevents phospholipids from packing too closely
together, creating the need for two layers.
D) Different salts, such as choline, and amino acids in the head of each phospholipid create the
necessary asymmetrical distribution.
5.
Negative feedback is used to maintain homeostasis of many essential molecules. When insulin
levels are too low, people tend to feel fatigued. Because insulin is involved in fuel storage and
oxidation, low levels of insulin can have devastating effects on organs and tissues. Which is the
most likely explanation for the trend seen in the above graph from 30 minutes to 120 minutes? [4.8]
A) Insulin levels are decreasing because the insulin is releasing energy to regulate homeostasis.
B) Beta cells from the pancreas release insulin into the blood to convert glucose into glycogen in
the liver as a way to lower blood glucose levels.
C) The pancreas released low levels of glucagon, and thus, higher levels of insulin are needed to
substitute for glucagon and maintain hormonal homeostasis.
D) Insulin levels are decreasing in response to a decrease in blood glucose levels.
2.
Lysozyme (amino acid sequence above) is a protein involved in immunity. It catalyzes the
breakdown of peptidoglycan in bacterial cell walls. Lysozyme is found in tears, saliva, and mucus of
the digestive system. The amino acid side-chains glutamic acid 35 (Glu35) and aspartate 52 (Asp52)
have been found to be critical to the activity of this enzyme. Glutamic acid is acidic and polar.
What would happen if glutamic acid was mutated to the hydrophobic amino acid alanine? [4.3]
A) There would be altered DNA structure because of abnormal hydrogen bonding.
B) The backbone of the protein would be altered because of the hydrophobic properties of alanine.
C) R-group interactions would be altered because of the hydrophobic properties of alanine.
D) Nothing would change because the properties of amino acid side chains don’t affect the
protein.
6.
Neuronal signals are transmitted intracellularly by action potentials and intercellularly by
neurotransmitter release. Many psychoactive drugs alter neuron activity by acting on
neurotransmitters. Drugs like Prozac or Zoloft are selective serotonin reuptake inhibitors (SSRIs)
that block the neurotransmitters from being reabsorbed into the presynaptic terminal. What are the
biological system effects of this change at the synapse? [4.9]
A) Signal duration would be extended at the postsynaptic neuron.
B) More action potentials are fired because the presynaptic neuron believes no serotonin
neurotransmitters are being released.
C) The presynaptic neuron would be inactivated because serotonin is not being reused.
D) There would be no synaptic transmission.
3.
The surface of the rough endoplasmic reticulum (often abbreviated RER) is studded with proteinmanufacturing ribosomes giving it a "rough" appearance (hence its name). In addition to making
proteins, the ER serves as… (4.5-6)
A) the manufacturing, warehousing, sorting, and shipping center of the cell
B) the membrane factory of the cell, adding membrane proteins and phospholipids to its
own membrane
C) the control center for maintaining appropriate concentration of salts and other molecules
D) the main subcellular producer of microtubules and microfilaments
7.
Dopaminergic neurons exist in tracts passing from the midbrain to the frontal cerebral cortex. When
these nuerons release the dopamine neurotransmitter, people feel pleasure and have increased
attention. Drugs like Abilify and Clozaril are dopamine and norepinephrine antagonists. What
effect will an antagonist like Abilify and Clozaril have on a neural synapse? [4.9]
A) Because dopamine has been released and no effect has occured, the neuron will continue to
release dopamine until an effect occurs.
B) Dopamine is not released from the pre-synaptic neuron, eliminating dopamine signaling.
C) The drugs will bind to the receptor sites, preventing post-synaptic signal reception.
D) The antagonists prolong the signaling of dopamine.
The secondary production of an ecosystem is the amount of chemical energy in consumers’ food that is
converted to their own new biomass during a given time period. A caterpillar uses the energy it receives
from food for growth and cellular respiration, and the rest is waste products. To measure the efficiency of
animals’ energy usage, the following equation is used:
Production efficiency = Net 2° production/Assimilation of 1° production
Net secondary production is the total energy in biomass that was used for growth and reproduction.
Assimilation of primary production is the total energy consumed by the organism and used for growth,
reproduction, and respiration.
The snowshoe hare and Canada lynx are mammals commonly found in Canada. Their population rates
were recorded over a period of 80 years in the data shown below.
.
10. GRID-IN: What is the production efficiency of this caterpillar? (4.14)
8.
One predator of the snowshoe hare is the lynx. Lynxes are carnivorous animals while the hare is
omnivorous. Many lynxes and snowshoe hares are found in the boreal forests. The maximum
sustainable density of snowshoe hares in boreal forests is 1500 hare per km2. By looking at the
graph above, which of the following best explains the relationship between lynx and hare? [4.11]
A) The lynx population is dependent on the hare population. When more hare are present,
lynx reproduce more. With increasing lynx numbers, the hare population drops and soon
after the lynx population drops as well.
B) In a seasonal manner, lynx and hare die from extreme exposure to either heat or cold,
decreasing both populations. The resolution of the graph is not sufficient to determine whether
the summers or winters are the limiting time periods.
C) The hare population regularly exceeds carrying capacity (), but is brought back below  by
lynx predation.
D) These animals are becoming endangered to global warming and may become extinct if current
trends continue.
9.
If the Canada lynx population went extinct, which best describes what would happen to the
snowshoe hare population?
A) The snowshoe hare population would increase drastically due to a lack of predation.
B) The snowshoe hare population would decrease due to the increased likelihood of infectious
disease that comes with increased population density.
C) The snowshoe hare population would stay the same. The Canada lynx would have no affect on
the species.
D) The snowshoe hare population would increase due to the decreased competition over food.
11. Using the above information, what provides the best explanation of the definition of production
efficiency? (4.15)
A) The total amount of food energy consumed minus the energy passed on to waste products or
used for cellular respiration
B) The proportion of food energy consumed that is used for respiration
C) The proportion of food energy consumed that is not used in respiration and is not lost as waste.
D) The total amount of food energy consumed by the organism
12. The figure above shows two examples of a biomass pyramid, in which each level represents the total
dry weight of all the organisms. Most biomass pyramids are similar to the pyramid on the left, with
the primary producers forming the foundation of the pyramid and the tertiary consumers at the top.
However, biomass pyramids in some aquatic ecosystems are inverted (as shown to the right). Which
of the following is the best explanation for this inverted pyramid? (4.18)
A) The primary producers have a higher death rate than the primary consumers.
B) The primary producers have a short turnover time and can support a larger zooplankton
to phytoplankton ratio.
C) The primary producers have a lower trophic efficiency rate than the primary consumers.
D) The primary consumers have a higher reproductive and growth rate than the producers.
13. The figure above represents the energy flow between species in Estes Park, Colorado. When the
state suddenly opened the region to hunting in 2010, the parks biodiversity was dramatically
threatened. The region’s fox and bear populations experienced a radical decline due to overhunting.
As the fox disappears, its prey now has very few predators to keep their populations size in check.
This overhunting effects many of park’s predator-prey relationships. In the graphs below, the fox
population is represented in red, while the toad population is in green. Which graph best represents
what will logically happen to the toad population in Estes Park? [4.16]
14. In the image above, the distribution of acid precipitation in North America and Europe is shown.
Acid rain is formed when fossil fuels are burned and release sulfur and nitrogen oxides that react
with water in the atmosphere to form sulfuric and nitric acid. These acids will fall to Earth’s surface
eventually in the form of acid precipitation, with a pH lower than 5.6. Which of the following is a
result of acid precipitation? (4.21)
A) It leads to the depletion of the ozone layer.
B) It decreases the concentration of toxic heavy metals, like mercury and aluminum.
C) The deposition of acid precipitation in lakes leads to an increase in their buffering capacity.
D) The change in composition of the soil leads to the limitation of the growth of plants.
The following graph shows the population of the North American Moose and the Eastern Canadian Wolf
in Isle Royale National Park between 1955 and 1995. Both species are well adapted to their own
environments and are very successful at finding food, especially in the cold Michigan winters. These
winters can be brutally cold, sometimes with temperatures reaching -35°C. However, the thick coats of
both of the animals keep them warm throughout the winter.
15. Based on the graph, which is the most likely ecological relationship between the North American
Moose and the Eastern Canadian Wolf? [4.19]
A) Mutualism: both animals have different niches and together prevent the Canadian Lynx from
becoming too populous in the Isle Royale National Park and taking resources for the Moose
and Wolves.
B) Predation: the moose overpower the wolves and eat them for food.
C) Commensalism: the wolves prey on the moose and in return keep the moose population from
growing so large that they exhaust all the food in the area.
D) Predation: the wolves prey on the moose and depend on them for food.
16. In 1973, the moose population reached an all time high at 1423 moose. Immediately following this
peak, the population began to decline until about 1982. What was the most likely cause of this
decrease? [4.19, 4.13]
A) The female moose in the population contracted a disease that targeted their reproductive
system which reduced fertility rates among female moose.
B) Rising numbers of wolves caused the decrease by preying on the abundance of moose in
the area.
C) The moose population exceeded the region’s carrying capacity and numbers decreased based
on decreased food supply and habitat degradation.
D) This decrease is part of a natural cycle that repeats about every 20 years.
17. Based on the graph, what is the carrying capacity of the moose population in the Isle Royale
National Park? [ 4.11]
A) 1000
B) 1600
C) 2000
D) Carrying capacity cannot be deduced based on the graph
A common North American dwelling rodent, Zapus hudsonius (also known as the meadow jumping
mouse), is known for its ability to jump lengths up to 12 feet long. These mice can display a variety of fur
shades, most commonly black and white. Some known predators of these mice are hawks and eagles that
spot the mice from the sky. A population of mice living in a desert environment in New Mexico was
studied as they migrated to an area dominated by dark-colored volcanic rock. Below is a chart of the
recorded populations over a period of four years.
19. Toxic residue from a chemical plant leaches into a marine habitat near the Cape of Good Hope. One
of the chemicals is BTX, which inhibits receptors in the central nervous system of afflicted
organisms. The chemical is diluted upon entry into the water, and thus is not a direct harm to the
ecosystem, with the exception of the decimation of a population of krill which lives at the site of the
spill. As a result of the BTX spill, what is the most likely effect upon the marine ecosystem? [4.21]
A) The zooplankton population will increase in number.
B) The cod population will increase in number.
C) The penguin population will increase in number.
D) Nothing should change, since with fewer predators, the phytoplankton will thrive and support
the dependent populations.
20. Independent of the BTX spill, a large monsoon causes land runoff in the form of ammonia fertilizer,
precipitating a phytoplankton bloom. As a result of excess phytoplankton, what is the most likely
dynamic between the cod and leopard seal populations? [4.16]
A) Both the cod and leopard seal populations will increase indefinitely due to the perpetual
abundance of phytoplankton.
B) Both populations will decrease dramatically as a result of the phytoplankton consuming all
available aqueous nutrients.
C) The cod and leopard seal populations will increase simultaneously, but as the excess
phytoplankton are consumed, the cod and leopard seal populations will immediately decrease.
D) The cod population will increase, followed by a leopard seal population increase, but the
populations will eventually return to pre-monsoon levels.
18. Looking at the graph above, which of the following most accurately explains the data? (4.23)
A) Dark colored mice are less visible to predators thus their birth rate is much higher than the
white mice.
B) A group of white mice underwent genetic mutations that caused their fur to turn a darker color
and the population of the white mice went down
C) Dark colored mice are less visible to predators thus their death rate is much lower than
the white mice.
D) The white mice are less visible to predators therefore are less likely to be eaten and their death
rate is much lower than the dark colored mice.
21. On the Pacific Island Mikhayhu, the Eurasian hedgehog and the Mikhayhuian porcupine reproduce
during the same season. Hedgehogs follow porcupines to their nest and begin to build their nest next
to them. After giving birth the hedgehog carries its young into the porcupine’s nest. What best
explains why the porcupines defend the hedgehog infants? [4.18]
A) The porcupines are expressing altruistic behavior to increase the likelihood of infant survival.
B) The porcupine behaviors to protect their young are triggered by all organisms that resemble
their young.
C) Since both species share a common ancestor, this is an example of kin selection.
D) The hedgehogs roll into balls to appear like a rock inside the porcupine nest preventing the
porcupines from seeing them.
22. In the tundra region, shrubs must compete for limited soil nutrients, such as nitrogen, phosphorus,
potassium, and a host of other micronutrients. Birds of the ptarmigan family benefit from the
protection and mating opportunities presented among members of their own kind. Regarding shrubs
and ptarmigan birds, what types of dispersion patterns are most expected in the tundra? [4.19]
A) shrubs uniform, birds clumped
B) shrubs clumped, birds clumped
C) shrubs clumped, birds uniform
D) shrubs random, birds uniform
In 1988, a wildfire swept through Yellowstone National Park and damaged nearly 1.2 million acres of
coniferous forest, leaving almost nothing but bare soil. In the years following the disaster, life began to
repopulate the area. The graph below shows roughly how the destroyed area was repopulated over time.
26. Why, in the early stage of this process of succession, did the amount of mosses and grasses initially
dip when the perennials showed up? [4.20]
A) Wind blew the top soil is away, and took the grasses with it, because there were no large root
systems to keep the soil in place.
B) Being faster at horizontal growth, the perennials outcompete the mosses and grasses for surface
area for growth.
C) Being better able to grow vertically, perennials outcompete the mosses and grasses for
sunlight and soil nutrients.
D) The presence of perennials crowds the grasses and moss.
The volcano Tanotikihama is known for its violent and unpredictable, though rare, eruptions. The island
was characterized by its unique combination of climate zones which fostered 3 distinct types of forest:
coniferous, tropical, and deciduous forest. In June of 1983, the volcano erupted and destroyed everything
on the island.
23. Why do lichens appear earlier than grasses in primary succession? [4.20]
A) Lichen spores are extremely light, and are carried onto the island by wind, before heavier tree
or bush seeds.
B) Lichens can break down the hardened magma and transform it into rudimentary soil.
C) Unlike lichen, plants need a soil layer in order to grow.
D) Both B and C are correct.
24. Why do shrubs replace grasses? [4.20]
A) Shrubs’ roots can penetrate into the hardened magma further to access nutrient-rich soil.
B) The shrubs can grow taller than grasses to outcompete them for sunlight.
C) The roots of the shrub uproot the root system of the grasses.
D) The shrubs can grow taller than grasses to better access the raw elements of the air.
25. Will the island re-populate with all the same species of organisms as before? Why? [4.20]
A) Yes, the same species will be best evolved to take advantage of the environment of the island.
B) Yes, the same factors will be at play; for instance, the same winds and birds will bring the
same seeds for plants.
C) No, none of the organisms will be the same because they will be outcompeted by new
organisms from different locations.
D) No, only some of the organisms will be the same since repopulation will be somewhat
random, for instance, which seeds are brought in by birds and wind.
There are approximately 23,000 genes in the human genome, however, there are many more than 23,000
proteins in the human body. This is possible because of alternative splicing. The vast majority of human
genes include segments called exons that must be spliced together following transcription of the gene into
a pre-mRNA. Up to 76% of human genes express multiple mRNAs by alternative splicing.
27. Which of the following is the best example of how variation in molecular units provides cells with a
wider range of functions? [4.22]
A) The origin of the ”antifreeze” proteins of the AFP III gene in the Antarctic eelpout was
unclear however, its coding sequence was found to be very similar to the proteins of
different gene called SAS-B except with slight modifications.
B) Fruiting bodies are created by multicellular bacteria, sometimes using quorum sensing.
C) The recombination of bacteria by means of transformation.
D) Certain bacteria called, endospores, which cover themselves in protein layers in order to
essential “hibernate”.
28. DHF is an enzyme that assists in the production of TC3, an important protein for digestion in
hedgehogs. Although not necessary for the production of TC3, DHF increases the efficiency of TC3
production by fifty percent. However, when too much TC3 is present, the tissue of the digestive tract
produces the signaling molecule APN, which binds to the zeta cells of the pancreas to prevent
further DHF production. How could APN be stopping further production of DHF? [4.22]
A) APN binds to receptor proteins in the zeta cells’ membrane, activating a transduction
pathway that inhibits the production of DHF.
B) APN binds directly to the DHF, allosterically preventing it from binding to substrate.
C) APN releases a hormone to signal other cells to produce additional DHF.
D) APN takes up the additional space needed for more DHF production preventing the DHF
protein from creating more DHF
A)
B)
The graph above is a model of the allele frequencies of A (the dominant allele for a gene, a being the
recessive allele) in ten different populations of lizards over 100 generations, modeled on a program called
PopG. The lizards live on a desert island and have yellow-brown skin to camouflage themselves. The A
allele is for an antsy disposition while the a allele is for a relaxed disposition. The antsy lizards have a
slight survival advantage since they run more quickly at the hint of a predator. Their main predator is the
large-winged hawk.
29. Why have none of the populations lost the a allele completely even though its phenotype presents a
disadvantage? [4.23]
A) The heterozygous individuals retain the recessive allele within the population.
B) The simulation has not been run for enough generations; eventually the allele would die out.
C) The recessive phenotype does not represent enough of a disadvantage to disappear completely.
D) It is entirely by chance, if the simulation was run again the allele would be lost in some if not
all of the populations.
C)
D)
30. In generations after the ones shown on the graph, the hawks adapted to be able to better detect the
motion of the antsy lizards and now can catch them more easily. However, the relaxed lizards who
stay still are camouflaged enough that the hawks cannot detect them and those lizards escape to
reproduce. What would happen to the allele frequencies of A and a? [4.23, 4.24, 4.26]
A) The A allele would be less prominent in the population but not disappear completely.
B) The frequencies would remain the same.
C) The A allele would disappear completely given enough time.
D) The A allele would most likely mutate into something else.
31. The hispid hare Caprolagus hispidus, also called Assam rabbit is a leporid native to South Asia,
whose historic range extended along the southern foothills of the Himalayas. Today, the habitat of
hispid hares is highly fragmented with an area of occupancy of less than 500 km 2 (190 sq mi)
extending over an estimated area of 5,000 to 20,000 km2 (1,900 to 7,700 sq mi). Populations
experience a continuing decline in suitable habitat due to increasing agriculture, flood control, and
human development. Until now, there was no selection for either phenotype of the GRY coat color
gene and the two alleles (G and g) were of equal frequencies (0.5 each). However, due to a newly
introduced predator, the recessive phenotype is now disadvantageous. Which of the following most
accurately predicts the dominant allele frequency trends of the C. hispidus populations? [4.26]
Chaparall, characterized by mild winters and hot, dry summers, with temperatures that can reach 40 °C.
32. In the chaparral biome, there exists a certain hare population which contains approximately 528
individuals (as of June 2010) who, in order to cope with the heat and aridity of the region, have
developed either very large ears (~47% of the population), or normal sized ears but almost no fur
(~43%). There are some hares who have thick fur and normal sized ears, but they are few in number
(~10%). What is the best explanation for the difference in survival strategies evident in the
population? [4.25]
A) The hares acquire these differences in early childhood as a result of their environment.
B) The hares’ differences are a result of, and are perpetuated by, assortative mating habits.
C) The hare population must be composed of different species.
D) The hares have different genotypes manifested in these phenotypic adaptations.