Ecosystems

An experiment was conducted on the population growth of worms. Worms were added to two identical bins. The bins were both kept at 20°C, except for the month of January when bin 2 was kept at 30°C. Each week, 2.5 kg of food was added to bin 1. In bin 2, 2.5 kg of food was added each week in all months except April. In April, 3.5 kg of food was added per week. The results of the experiment are pictured. Which of the following probably accounted for the large drop in population in bin 2 from January to February?

• overpopulation

• lack of water

• overheating

• lack of food

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The food web shows the feeding relationships of six different populations in an aquatic ecosystem. Suppose overfishing by humans causes a drastic reduction in the herring population of this ecosystem. Which of the following populations will also be affected?

• zooplankton

• dolphin

• shark

• bluefish

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What would most likely happen in the ecosystem shown in the food web if the fox population significantly increased?

• The population of bees would increase.

• The population of mice would increase.

• The population of black bears would increase.

• The population of mice would decrease.

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The food chain shows the original feeding relationships of four different organisms in a rural environment. After a time, the rat population grew too large. To reduce the rat population, local farmers introduced cats, which are efficient predators of rats. The plan was successful, and the rat population began to decrease. Which of the following populations will most likely decline as a result of decreased food availability?

• the snake population only

• the snake, rat, and insect populations

• the insect population only

• the rat population only

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A species of seabird nests every year on the face of one wall of cliffs on one island. If these birds nest on the ground above the cliffs, they run a high risk of having their eggs eaten by predatory snakes. There are only about 5,000 suitable nesting sites in the cliffs and there are about 8,000 seabirds looking to nest. The only other option for these nesting seabirds, would be to nest in the rocks of a neighboring island. But if they do this, they run the risk of losing the flock, and missing out on breeding season. Which of these is placing a limitation on how large this population of seabirds can grow?

• the size of the cliff walls

• the distance to neighboring islands

• the number of snakes living on land

• all of these

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The food web shows the feeding relationships of six different populations in an ecosystem. Which populations compete with one another for food?

• mouse and spider

• sparrow and snake

• mouse and grasshopper

• snake and grasshopper

• spider and sparrow

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The food web shows the flow of energy through a terrestrial ecosystem. Which of the organisms shown in the food web is a predator of deer?

• rabbit

• plant

• fox

• owl

• chipmunk

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A dodder plant wraps itself around the stem of a clover plant, seriously damaging the clover. Small root-like structures from the dodder allow it to gain nutrients and water from the clover. Which type of relationship does this represent?

• mutualism

• commensalism

• competition

• parasitism

Rabbits and sheep both graze on shrubs, grasses, and other plants. The sharp rise in the population of rabbits in a region may result in a shortage of plants for sheep to graze upon. This relationship between sheep and rabbits is an example of _________.

• commensalism

• predation

• parasitism

• competition

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Which of the following relationships is symbiotic?

Select all that apply.

• A group of ants work together to build an underground nest.

• A bee pollinates a flower while feeding on the flower's nectar.

• A remora attaches to the body of a shark and feeds on scraps when the shark eats.

• A tick latches on to the body of a dog and feeds on the dog's blood.

• A male bluebird and a female bluebird provide care for their offspring.

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