Producers and consumers are necessary for ecosystem function and for energy to pass through an ecosystem. What might happen in an aquatic system with excess producers relative to consumers?
Oxygen depletion would result in dieoff.
There would be no basal energy source.
Carbon cannot be sequestered.
There would be more undigestable animal parts.
36.
Energy is a fundamental component in an ecosystem and is contributed by the primary producers. Describe how light energy can, in turn, support the consumers of an ecosystem.
Light energy is converted by primary producers and primary consumers. Consumers belonging to higher trophic levels feed on them to gain energy.
Primary producers can only obtain energy from sunlight by photosynthesis and gain energy by feeding on them or other consumers which have consumed these producers.
Primary producers convert light energy by photosynthesis and consumers gain energy by feeding on them or other consumers which have consumed these producers.
Primary producers convert light energy through chemosynthesis and consumers gain energy by feeding on them or other consumers which have consumed these producers.
37.
In a microcosm experiment using fish tanks to mimic a lake environment, an increase in the number of stickleback species would increase the dissolved organic carbon particle size. How could this affect primary producers in the ecosystem?
enhance growth rate
increase abundance
decrease abundance
maintain growth rate
38.
Studies on stickleback fish revealed that the presence of two species of stickleback reduced the amount of algal blooms relative to the presence of one species of stickleback in a microcosm experiment. How does this occur?
This occurred as the presence of two species caused an increase in dissolved organic carbon molecule size, which blocked the penetration of light in water and prevented algal photosynthesis.
This occurred because two stickleback species consumed all the nutrients which prevented algae from being able to grow.
This occurred because dissolved organic carbon molecule size increased in the presence of one fish species which increased the amount of algal blooms.
This occurred as algae are consumed in more amounts in the presence of two stickleback species.
39.
This figure depicts energy exchange through trophic levels. Which level represents the primary producers?
A
B
C
D
40.
(credit: modification of work by Russell W. Markel and Jonathan B. Shurin/ESA Journals, under CC BY license)
Giant kelp forests are marine ecosystems with high biodiversity. Sea otters are a keystone species in giant kelp forests. The sea otters prey on sea urchins, which destroy kelp if left alone.
A research study explored the trophic level of black rockfish and copper rockfish, two types of fish that live in the kelp forests, in the presence and absence of otters. The graph shows their findings.
Make a claim based on the graph.
Otter presence affects the trophic level of copper rockfish but not the black rockfish.
Otter presence affects the trophic level of black rockfish but not the copper rockfish.
The trophic level of small copper fish is greatly affected by absence of otters.
The trophic level of large copper fish is greatly affected by absence of otters.
41.
The following is a food web for a meadow habitat that occupies 25.6 km2. The primary producers’ biomass is uniformly distributed throughout the habitat and totals 1,500 kg/km2. Developers have approved a project that will permanently reduce the primary producers’ biomass by 50 percent and remove all rabbits and deer. Which of the following is the most likely result at the completion of the project?
The biomass of coyotes will be 6 kg, and the biomass of hawks will be 0.5 kg.
The biomass of coyotes will be dramatically reduced.
The coyotes will switch prey preferences and outcompete the hawks.
There will be 50 percent fewer voles and 90 percent fewer hawks.
42.
This figure shows a food web of an ecosystem. What would happen to the food web if all of the species of the entire row B was wiped out by a natural disaster such as an oil spill? Why?
The producers may die out, causing the food web to collapse.
The food web would not be affected as the secondary and tertiary consumers would become primary and secondary consumers, respectively.
The tertiary consumers would die out due to lack of food and this could potentially lead to collapse of the entire food web.
The food web might suffer from loss of primary producers for a while which would then recover quickly, thus, reviving the ecosystem.
43.
Humans are very active in modifying ecosystems worldwide. If a new set of buildings on the edge of a forest block sunlight from reaching the majority of one part of the forest, what might happen to that part of the forest?
Herbivores would occur in high abundance.
Plants would occur in high abundance.
Everything would remain the same.
Herbivores would occur in low abundance.
44.
If you examined predator-prey relationships within an ecosystem and noticed that the removal of predators also resulted in the die-off of herbivores, what would you suspect occurred?
Removal of predators would directly lower the number of herbivores.
The lack of predators could mean that too much primary production occurred.
Herbivores from another region may have entered the ecosystem and consumed the primary producers, causing death of the original herbivores species.
Overeating by herbivores could have caused depletion of the primary producers, leaving the herbivores without enough food.
45.
Although producers are essential for energy to flow into an ecosystem, consumers also have important roles. What might happen in an aquatic system with excess consumers relative to producers?
Oxygen depletion would result in dieoff.
There would be an excess of the basal energy source.
Consumers would deplete the abundance of producers.
There would be more undigestable animal parts.
46.
The following is the equation for trophic level transfer efficiency: (production at present trophic level/production at past trophic level)×100. If primary producers produce 1600 kcal/m2, and primary consumers have 900 kcal/m2, what is the trophic level transfer efficiency?
50
200
800
1600
47.
There are four trophic levels in a food chain and the amount of energy at the trophic level of the primary producer is 33,000 kcal/m2. Which of the following represents the amount of energy of the tertiary consumer?
75 kcal/m2
500 kcal/m2
11,000 kcal/m2
33,000 kcal/m2
48.
Why does this figure show a higher value of gross productivity for the decomposers than the tertiary consumers?
Due to the difference in conversion efficiencies of decomposers and tertiary consumers.
Because large animals are tertiary consumers whereas small microorganisms are decomposers.
Because tertiary consumers only consume secondary consumers whereas decomposers consume dead components of each trophic level.
Because tertiary consumers only consume primary consumers whereas decomposers consume dead components of each trophic level.
49.
One of the key concerns about global climate change is excess amounts of carbon being released into the atmosphere. There are, however, some ways in which carbon can be sequestered from the atmosphere. Which of the following is a natural process that promotes carbon sequestration?
