Biology Keystone Unit 8

Which sequence best orders ecological categories from the one with the fewest number of individuals to the one with the greatest number of individuals?

• ecosystem, population, community, biome

• population, community, ecosystem, biome

• biome, population, community, ecosystem

• community, biome, population, ecosystem

Answer explanation

Populations of different species interact in communities,

communities of organisms interact with abiotic factors in an ecosystem, and similar ecosystems in a large area make up a biome.

Energy pyramids describe food and energy relationships within an ecosystem. Which factor most likely limits the number of levels an energy pyramid can have?

• biomass of the top-level organisms

• predation by the top-level organisms

• energy loss between each level of organisms

• chemical energy being decomposed at each level of organisms

Answer explanation

The number of levels in an energy pyramid is limited by the amount of energy available for the next level of consumers.

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Orchids living in tropical rainforests often grow on the branches of trees to access sunlight. The trees are not affected by the orchids. Which term best classifies the relationship between the orchids and the trees?

• predation

• parasitism

• competition

• commensalism

Answer explanation

The orchids benefit from the trees without harming them.

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A student listed characteristics of a classroom aquarium ecosystem. Which characteristic is a biotic component of the aquarium ecosystem?

• The water temperature is 23°C.

• The pH of the water is usually between 6.5 and 6.8.

• The ammonia is controlled with a filter that uses two types of bacteria.

• The lighting is supplied by natural sunlight and a fluorescent light bulb.

Answer explanation

The bacteria in the filter are a biotic component of the

ecosystem.

Tadpoles grown in ponds with high densities of tadpoles have lower survival and growth rates than tadpoles grown in ponds with lower densities of tadpoles. Which interaction between tadpoles grown in high-tadpole-density ponds would most likely cause the decreased survival and growth rates?

• symbiosis

• mutualism

• competition

• commensalism

Answer explanation

Tadpoles in low-density ponds have less competition for resources.

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Which population description is most likely represented by the graph?

• A population of birds quickly increases but then becomes stable due to limiting factors in

  the environment.

• A population of mice slowly increases but then fluctuates seasonally as predators raise their

  young and limit prey populations.

• A population of fish quickly increases in the spring when there is plenty of food but then

  decreases quickly in the fall when food is limited.

• A population of wolves slowly increases because of limiting factors in the environment but

  then increases constantly when additional prey migrate into the environment.

Answer explanation

The trend line on the graph shows that the population increases slowly at first, then rapidly increases, and then levels off.

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Asian carp are an invasive species of fish. These large fish eat up to 40% of their body weight per day by feeding on phytoplankton. The carp also reproduce quickly. If these fish were to enter Lake Erie, how would the Presque Isle coastal ecosystem most likely be affected?

• Producers in the ecosystem would grow at a faster rate, and smaller fish such as yellow

  perch would thrive.

• The invasive fish would prey on mollusks such as mussels, but native fish species would

  quickly eat the invasive fish.

• Consumers in the higher trophic levels would suffer stress, but crustaceans such as amphipods would be unaffected.

• Most consumers in the ecosystem would face a shortage of food, and larger fish, such as walleye, would be unable to thrive.

Answer explanation

Asian carp would reduce the amount of phytoplankton available to primary consumers, causing secondary and tertiary consumers to

have fewer available food resources.

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Which set of ecological organization levels is most likely to contain the largest variety of species?

• multiple biomes in a biosphere

• multiple ecosystems in a biome

• multiple individuals in a population

• multiple populations in a community

Answer explanation

A biome is the most inclusive level of biological organization within a

biosphere and represents more variety than any other ecological level.

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Ash from a volcanic eruption decreases the amount of available solar energy for a region. Which statement describes how a decrease in available sunlight will most likely affect ecosystems of this region?

• Producer populations will decrease, causing a decrease in consumer populations.

• Producer populations will decrease, causing an increase in consumer populations.

• Decomposer populations will increase, causing a decrease in consumer populations.

• Decomposer populations will increase, causing an increase in consumer populations.

Answer explanation

Reduced sunlight will harm producers and consumers in the ecosystem.

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Strep throat is a common human illness often caused by the bacterium Streptococcus pyogenes. Which term best classifies the colonies of Streptococcus pyogenes in a person with strep throat?

• a population

• an organelle

• a community

• an ecosystem

Answer explanation

A population is composed of individuals of the same species (Streptococcus pyogenes bacteria colonies) within a habitat (a person’s throat).