Question 1

After developing a yeast infection in the urinary tract,and taking an antibiotic,the yeast infection declines in numbers of cells while the microbes that normally are present reestablish themselves.The reason for the decline of the yeast infection is explained by

Accepted Answer

The competitive exclusion principle describes how two species competing for the same limited resources cannot coexist in the same environment if one species has even a slight advantage over the other. In this case, after taking the antibiotic, the normal microbes are able to outcompete the yeast for resources, leading to a decline in the number of yeast cells.

Question 2

You go on a canoe trip to the Boundary Waters Canoe Area (BWCA) in northern Minnesota. This ecosystem is cold most of the year and receives plenty of rainfall. It has many lakes that are full of walleye pike. You know that walleye like to eat minnows. In turn, the minnows feed on scuds (zooplankton), which eat algae (phytoplankton).
-Zooplankton are which of the following?

Accepted Answer

Zooplankton are organisms that primarily feed on phytoplankton, making them primary consumers. They are not decomposers, producers, nor higher-level consumers such as secondary or tertiary consumers.

Question 3

Prior to 1972,a pesticide called DDT was used widely in the United States,but was found to pose risks to human health and wildlife.The concentration of the nonpolar pesticide DDT would have been highest in which of the following,when still in use?

Accepted Answer

Seagulls are higher up in the food chain than the other options listed, and would accumulate the highest concentration of DDT due to biomagnification.

Question 4

Why are top-level predators like lions and eagles so rare in a community?

Accepted Answer

Energy transfers from one trophic level to the next is inefficient, with only about 10% of the energy being passed on. As a result, the amount of energy available to support top-level predators is limited, which in turn limits their numbers.

Question 5

The interaction between panic grass and its endophyte fungus that allow them to grow at 65°C together,but not independently is an example of

Accepted Answer

Mutualism is an interaction in which both the species benefit from each other. Panic grass and its endophyte fungus have a mutualistic relationship as the fungus provides the grass with thermal tolerance, and the grass provides the fungus with nutrients and a host to grow on. Without this mutualistic relationship, neither species could survive at 65°C, making it a necessary and mandatory partnership.

Question 6

The virus in this study

Accepted Answer

The answer of The virus in this study
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Question 7

Mycorrhizal fungi obtain food from plants in exchange for water and nutrients.This is an example of

Accepted Answer

The described relationship between mycorrhizal fungi and plants is an example of mutualism, as both species benefit from the interaction: the fungi obtain nutrients from the plant, and in exchange they provide the plant with water and minerals that they absorb from the soil.

Question 8

You go on a canoe trip to the Boundary Waters Canoe Area (BWCA) in northern Minnesota. This ecosystem is cold most of the year and receives plenty of rainfall. It has many lakes that are full of walleye pike. You know that walleye like to eat minnows. In turn, the minnows feed on scuds (zooplankton), which eat algae (phytoplankton).
-Mercury released from coal burning power plants would be at the highest concentration in

Accepted Answer

Mercury accumulates up the food chain in a process called biomagnification, meaning that top predators, such as eagles eating the walleye, would have the highest concentration of mercury.

Question 9

If there are 10,000 calories of net primary productivity in a field,how much on average will be available to a secondary consumer?

Accepted Answer

In an ecological energy pyramid, only about 10% of the energy from one trophic level is passed on to the next level. Therefore, if there are 10,000 calories at the level of primary producers, primary consumers (herbivores) would on average receive about 1,000 calories (10% of 10,000). Secondary consumers, in turn, would receive about 10% of that, which is 100 calories.

Question 10

Some scientists predict that as atmospheric carbon dioxide levels increase,the pH of the oceans will drop,threatening coral and organisms with shells.What is the best explanation for this hypothesis?

Accepted Answer

Carbon dioxide dissolves in water to form carbonic acid, which lowers the pH of the ocean water. As the pH decreases, it becomes more acidic, which can affect the ability of organisms such as corals and shellfish to build their shells and skeletons.

Question 11

An insect that resembles leaves is using _____ to avoid predation.

Accepted Answer

Camouflage is a strategy used by an organism to blend in with its surroundings and avoid detection by predators. An insect that resembles leaves is using camouflage to avoid predation. Mimicry involves an organism evolving to resemble a different species for various purposes such as scaring off predators or attracting prey. Warning coloration is when an organism has bright or bold colors to signal to predators that it is toxic or dangerous. Mutualism is a type of interaction between two different species where both benefit. Chemical defense involves an organism using toxic chemicals or substances to deter predators.

Question 12

How was the virus detected?

Accepted Answer

Detection of double-stranded RNA is a characteristic feature of many types of viruses. This is because double-stranded RNA is not normally found in mammalian cells, and its presence is therefore indicative of viral infection.

Question 13

Mistletoe is a plant that grows in the branches of trees.Its roots penetrate the bark of the tree,allowing it to obtain water and nutrients.The tree is harmed,and can even die as a result of this interaction.This is an example of

Accepted Answer

This is an example of parasitism, as the mistletoe benefits from the tree by obtaining water and nutrients, while the tree is harmed and can even die as a result of this interaction.

Question 14

Some scientists predict that as atmospheric carbon dioxide levels increase,plant growth will also increase.What is the best explanation for this hypothesis?

Accepted Answer

During photosynthesis, plants use carbon dioxide from the atmosphere and convert it into glucose for growth. Therefore, an increase in atmospheric carbon dioxide levels would potentially lead to an increase in plant growth due to the availability of more carbon dioxide for photosynthesis.

Question 15

You go on a canoe trip to the Boundary Waters Canoe Area (BWCA) in northern Minnesota. This ecosystem is cold most of the year and receives plenty of rainfall. It has many lakes that are full of walleye pike. You know that walleye like to eat minnows. In turn, the minnows feed on scuds (zooplankton), which eat algae (phytoplankton).
-Walleye pike tend to live in deep waters and feed at night.Northern pike live in shallower waters and feed all day.Which of the following best explains these differences?

Accepted Answer

Walleye pike and northern pike exhibit differences in their niche and habitat utilization, resulting in competition for resources. Walleye have adapted to living in deep waters where they are less likely to compete with northern pike for prey resources during the day. Instead, they have evolved to feed at night when their competitors are less active. Meanwhile, northern pike have adapted to living in shallower waters, where they hunt throughout the day and have access to a wider variety of prey than walleye. This demonstrates how competition can drive adaptation and lead to niche differentiation.

Question 16

An insect that resembles the face of a snake is using ___ to avoid predation.

Accepted Answer

Mimicry is the adaptation where an organism evolves to resemble another species to gain an advantage, such as avoiding predation. In this case, an insect resembling the face of a snake is an example of Batesian mimicry, where a harmless species evolves to mimic the warning signals of a harmful species to deter predators.

Question 17

Eutrophication can be caused by excess accumulation of which of the following in a body of water?

Accepted Answer

Eutrophication is caused by excessive accumulation of nutrients in a body of water, particularly nitrogen and phosphorus, which leads to an overgrowth of algae and other aquatic plants. Carbon is not typically a limiting nutrient for aquatic plant growth.

Question 18

Lichens live on the side of trees,getting better access to the sun,with no apparent harm to the tree.This is an example of

Accepted Answer

This is an example of commensalism, as the lichens benefit from the tree by getting better access to sunlight without causing any harm to the tree.

Question 19

If there are 10,000 calories of net primary productivity in a field,how much on average will be available to a primary consumer?

Accepted Answer

According to the 10% rule, only 10% of the energy from one trophic level is available to the next trophic level. Therefore, a primary consumer can only access 10% of the 10,000 calories of net primary productivity, which equals 1,000 calories.

Question 20

Nitrogen-fixing bacteria in the roots of soybeans help provide a source of nitrogen to the plants and,in exchange obtain food from the plants.Which reaction can these bacteria catalyze?

Accepted Answer

Nitrogen-fixing bacteria in soybean roots can catalyze the conversion of nitrogen gas (N2) to ammonium (NH4+), which can be utilized by the soybean plant for growth. This process is called nitrogen fixation and is possible due to the presence of enzyme nitrogenase in these bacteria. Option A and C are not correct as nitrogen-fixing bacteria cannot convert nitrate to nitrogen gas. Option D is also incorrect as the conversion of nitrate to ammonium is not a process catalyzed by nitrogen-fixing bacteria. Option E is incorrect as ammonium cannot be converted to nitrate in this context.

Quiz 38: Communities and Ecosystems