SC.7.L.17.1-3: Populations: Relationships, Food Webs, and Limiting Factors

Rhizobia are bacteria that live on the roots of some plants, such as legumes like pea plants. Rhizobia convert an element in the atmosphere into ammonia. Identify and explain the type of relationship this represents

• It is parasitism because the bacteria absorbs food from the pea plant

• It is commensalism because the bacteria and pea plant don't harm each other

• It is competition because the rhizobia and pea plant both need the limited amount of available nitrogen

• It is mutualism because the bacteria receives carbon from the pea plant, while the plant uses the ammonia to make amino acids

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Native bumblebees live in grasslands and consume pollen and nectar from flowers. The bumblebees carry pollen from one plant to another. The bees pollinate most but not all the flowers in their habitat. Amphibians and insects, such as dragonflies, eat bumblebees.

A local resident sets up honeybee hives in the habitat of the bumblebees. Honeybees are a nonnative species that eat the same food as the bumblebees. Food now becomes a limiting factor for the bumblebees.

How might the populations of flowers, bumblebees, and dragonflies change after the introduction of honeybees to the ecosystem?

• Flowers will increase, bumblebees will decrease, and dragonflies will decrease in population size.

• Flowers will decrease, bumblebees will decrease, and dragonflies will decrease in population size.

• Flowers will increase, bumblebees will increase, and dragonflies will increase in population size.

• Flowers will decrease, bumblebees will decrease, and dragonflies will increase in population size.

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A population of salamanders lives near a stream. A severe drought dries up the flow of the stream. What is this effect on the salamander population called?

• emigration

• limiting factor

• immigration

• biotic factor

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The Florida panther’s population was reduced to zero in Florida due to overhunting. Panthers were reintroduced to Florida in 1995 and small populations now live in the southern swamplands of the state. Wildlife scientists carefully watch to see how the populations change from year to year.

Which of the following events would decrease a population of panthers?

• Many white-tailed deer move in the panthers’ range.

• Water quality improves in the panthers’ habitat.

• Some panthers emigrate to another area far away.

• A mother panther gives birth to a litter of two offspring.

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All organisms take energy from their environment. Every organism needs this energy in order to grow and reproduce. How do producers get energy?

• They obtain energy by eating plants, bacteria, and algae.

• They extract chemical energy from decaying organic matter.

• They extract energy from the chemicals in soil, air, and water.

• They capture energy from sunlight and manufacture their own food.

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Some consumers, such as many flying insects, need large amounts of energy to grow and move from one place to another. How do consumers get energy to function?

• Consumers obtain all of their energy by eating other organisms.

• Consumers obtain some energy from other organisms and some from sunlight.

• Consumers obtain most of their energy by absorbing it from their environments.

• Consumers light energy from the sun and convert it into chemical energy stored in food.

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How do the decomposers in an ecosystem obtain energy?

• They use the energy of photosynthesis from living plants.

• They release stored chemical energy from compounds in dead organisms.

• They extract energy-rich compounds from living tissues of other organisms.

• They obtain energy directly from the air, soil, or water of their environments.

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What causes competition among organisms?

• One organism tries to prey on the other organism.

• Both organisms try to take on the form of the other.

• One organism tries to live on or in the other organism.

• Both organisms attempt to use the same limited resources.

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Aphids can infest and damage plants. Ladybugs eat these aphids. Ladybugs often live on such plants in order to be near their food source. Which answer describes the relationships in this example?

• parasitism, mutualism, and commensalism

• parasitism, predation, and mutualism

• parasitism, predation, and commensalism

• commensalism, mutualism, and predation

The rabbit in this food web would be considered a:

• Decomposer

• Producer

• Secondary Consumer

• Primary Consumer

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