Question 1

Grain is eaten by cows,and cows are eaten by humans.If the ecological transfer efficiency between each trophic level is 10 percent,how much grain is required to produce 70 kg of human biomass?

Accepted Answer

Since the ecological transfer efficiency between each trophic level is 10%, only 10% of the energy from one trophic level is passed on to the next. Therefore, if 70 kg of human biomass is desired, 10 times that amount (700 kg) of cow biomass is required. Similarly, 10 times that amount of grain biomass (7,000 kg) is required to support the cow biomass needed to produce 70 kg of human biomass. Therefore, the correct answer is D, 7,000 kg.

Question 2

If gross primary productivity (GPP)is 120 units per day,and the respiration rate (R)of primary producers is 30 units per day,net primary productivity (NPP)is _______ units per day.[Note: Use the formula NPP = GPP - R.]

Accepted Answer

The formula for calculating NPP is NPP = GPP - R.

Given that GPP is 120 units per day and R is 30 units per day,

NPP = GPP - R

NPP = 120 - 30

NPP = 90 units per day.

Therefore, the correct answer is choice C.

Question 3

In a microbial community,autotrophs generate 1,000 calories per hour of GPP and 500 calories per hour of NPP.Primary consumers convert 60 calories per hour into their own biomass.What is the ecological efficiency in the link between autotrophs and primary consumers in this community?

Accepted Answer

The answer of In a microbial community,autotrophs generate 1,000 calories...

Question 4

Net primary productivity (NPP)of a community is approximately equivalent to

Accepted Answer

NPP is the amount of biomass (organic matter) produced by primary producers in a given area over a given period of time, minus the biomass that is used up in respiration by those same primary producers. Therefore, option C ("change in biomass of primary producers per unit time") is the correct choice.

Question 5

The notion of species diversity incorporates which factor(s)?

Accepted Answer

Species diversity incorporates both species richness (the number of different species present) and species evenness (how evenly distributed the individuals are among those different species).

Question 6

What is the most likely reason that the curve in the top graph mostly levels off between five and ten species?

Accepted Answer

As the community approaches its maximum productivity, given the resources available, the curve in the top graph levels off.

Question 7

Three plant communities have the species composition shown in the table below.Which community or communities have the highest species evenness?

Accepted Answer

The answer of Three plant communities have the species composition...

Question 8

Each species has a particular niche within a community.This niche is defined by which two sets of factors?

Accepted Answer

A species' niche is defined by both its physical and biological environment as well as its functional role within a community, which includes its interactions with other species and its impact on the ecosystem's processes. Net primary productivity may influence a species' distribution and abundance, but it is not one of the defining factors of its niche.

Question 9

The loss of a single species from a community will most often affect community function by affecting the community's

Accepted Answer

Trophic interactions are the interactions between different levels in a food chain, and the loss of a single species can disrupt the entire food chain, causing a ripple effect throughout the community. This disruption can include an increase in the population of the species that the extinct species preyed on, a decrease in the population of the species that the extinct species was a predator of, and changes in the overall diversity and composition of the community. This loss can ultimately lead to a decrease in the community's overall function.

Question 10

In the total of Earth's food webs,the sun represents

Accepted Answer

The sun is the major source of energy for all living organisms on Earth through the process of photosynthesis. It provides energy for the primary producers, which in turn are consumed by other organisms, creating a food chain/web.

Question 11

Three plant communities have the species compositions shown in the table below.Which community or communities have the highest species richness?

Accepted Answer

The answer of Three plant communities have the species compositions...

Question 12

The number of trophic levels in communities is limited by

Accepted Answer

As energy is lost between trophic levels, there is only a limited amount of energy available to be transferred to higher trophic levels. This limits the number of trophic levels that can exist in a community.

Question 13

A grassland is composed primarily of a single type of grass,with small amounts of three other grasses and several forbs.How will this species composition be likely to affect the function of this community?

Accepted Answer

Since the primary species in the grassland is a single type of grass, it is likely that this grass will dominate the community and define its function. The other grasses and forbs may have some effect, but it is likely to be secondary to the dominant grass species. Therefore, choice B - "The dominant grass will mostly define the function of the community" - is the best choice.

Question 14

A common way to measure community function is to measure

Accepted Answer

Flux, or flow rate of energy between community and environment, is the best way to measure community function because it takes into account the interactions between all species in the community and their environment. It provides an integrated measure of the functioning of the community as a whole, rather than just looking at individual species or individuals.

Question 15

Bumblebees live in nests in loose soil on the ground,in areas with little vegetation.However,they must be near vegetated areas,where they feed on and pollinate many flowering plants.This information describes the bumblebee's

Accepted Answer

The information provided describes the bumblebee's niche, which includes their habitat requirements (loose soil on the ground, near vegetated areas) and their role in pollinating many flowering plants.

Question 16

Use the following to answer questions :
Refer to the graphs below showing data from the studies of David Tilman and colleagues on the effect of species diversity on net primary productivity in prairie ecosystems. 
-Based on the data in the two graphs,how can the effects of species richness and number of functional groups (niches)on NPP best be described?

Accepted Answer

The data in the graphs show that an increase in the number of niches (functional groups) has a greater effect on increasing NPP than an increase in species richness alone. The highest NPP is seen when there are multiple functional groups present, even with a lower species richness. This suggests that the number of niches and the associated functional diversity are key factors in driving NPP in prairie ecosystems.

Question 17

Under stress,a community loses a number of species.When the stress is removed,the species composition recovers and then stabilizes.During this process,what will be the most likely effect on net primary productivity?

Accepted Answer

When stress is removed, species composition recovers, leading to an initial decrease in net primary productivity due to loss of species. As the ecosystem recovers, productivity increases and eventually stabilizes.

Question 18

Suppose that plants are able to convert 80 percent of the energy that they obtain into biomass,and that the ecological efficiency of primary consumers is 20 percent.For every calorie that is converted into primary consumer biomass,how much energy must be captured and converted into chemical energy?

Accepted Answer

To calculate the amount of energy that must be captured and converted into chemical energy, we need to work backwards from the 1 calorie of primary consumer biomass.

First, we need to determine how many calories of plant biomass are required to produce 1 calorie of primary consumer biomass. Since the ecological efficiency of primary consumers is 20%, we know that only 20% of the plant biomass that the primary consumer eats will be converted into primary consumer biomass. Therefore, 1 calorie of primary consumer biomass requires 5 calories of plant biomass (1/0.2 = 5).

Next, we need to determine how much energy must be captured and converted into chemical energy by plants to produce 5 calories of plant biomass. Since plants convert 80% of the energy they obtain into biomass, we know that to produce 5 calories of plant biomass, 6.25 calories of energy must be captured and converted into chemical energy (5/0.8 = 6.25).

Therefore, the answer is C) 6.25 calories.

Question 19

All of these factors reduce the efficiency of energy transfer between trophic levels except

Accepted Answer

Biomass stored as fat or starch does not reduce the efficiency of energy transfer between trophic levels, as it can still be consumed by organisms in higher trophic levels. In fact, it can even increase efficiency as it allows for energy storage and potentially larger consumers in higher trophic levels. The other options all reduce efficiency by either losing energy as heat, physically unable to be consumed, or lacking availability.

Question 20

Earth could support a larger human population if more people

Accepted Answer

Vegetarianism requires fewer resources compared to meat-based diets. Meat production requires a lot of water, land, and energy, along with contributing to deforestation, greenhouse gas emissions, and water pollution. Therefore, if more people shifted towards a vegetarian diet, we could support a larger human population without causing harm to the environment.

Quiz 44: Ecological Communities