4.13 Quiz RETAKE

Match the following

• parasitism

• one species benefits while the other is unaffected

• mutualism

• both species benefit

• commensalism

• one species benefits while the other is harmed

What is a predator–prey cycle?

• A cycle where predators and prey coexist without affecting each other's population.

• A cycle describing the fluctuating population sizes of predator and prey species over time due to their interactions.

• A cycle where only the prey population changes while the predator population remains constant.

Answer explanation

The correct choice describes the predator–prey cycle as the fluctuating population sizes of predator and prey species over time, highlighting their interactions, which is essential for understanding ecosystem dynamics.

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In a predator–prey cycle, what happens when the prey population increases?

• The predator population remains the same.

• The predator population increases.

• The prey population decreases.

Answer explanation

When the prey population increases, there is more food available for predators, leading to an increase in the predator population as they can reproduce and thrive on the abundant prey.

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What does an energy pyramid represent in an ecosystem?

• The biomass at each trophic level

• The energy available at each trophic level

• The diversity of species at each trophic level

Answer explanation

An energy pyramid illustrates the energy available at each trophic level in an ecosystem, showing how energy decreases as it moves up from producers to top consumers.

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According to the 10 percent rule, if the 2nd trophic level has 1000 units of energy, how much energy is transferred to the 3rd trophic level?

• 1 unit

• 10 units

• 100 units

Answer explanation

According to the 10 percent rule, only 10% of energy is transferred to the next trophic level. Therefore, if the 2nd trophic level has 1000 units, the energy transferred to the 3rd trophic level is 100 units.

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What is the primary source of energy in most food chains?

• Sunlight

• Wind

• Water

Answer explanation

The primary source of energy in most food chains is sunlight. Plants, as producers, convert sunlight into energy through photosynthesis, forming the base of the food chain.

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Match each organism to its trophic level.

• primary consumer

• 
• secondary consumer

• 
• tertiary consumer

• 
• producer

• 

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In a food chain, energy is transferred from one trophic level to the next.

What happens to the energy that is not transferred?

• 
  It is converted into matter

• It is lost as heat

• It is stored indefinitely

Answer explanation

In a food chain, energy transfer is inefficient. The energy that is not transferred to the next trophic level is primarily lost as heat due to metabolic processes, making 'It is lost as heat' the correct answer.

negative feedback loop: a change in an ecosystem that trends back to the original state of the ecosystem

Which of the following examples best describes an example of a negative feedback loop?

• A rise in global temperatures causes ice to melt, leading to even higher temperatures.

• Increased pollution leads to algae blooms, which decrease oxygen levels and harm fish populations.

• An increase in rabbit population leads to more foxes, which then decreases the rabbit population.

Answer explanation

The correct choice describes a negative feedback loop where an increase in rabbit population leads to more foxes, which then reduces the rabbit population, helping to stabilize the ecosystem.

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A positive feedback loop is a process that makes changes in a system even bigger, often leading to increased effects and potentially destabilizing the ecosystem.

Which of the following statements best describes a positive feedback loop in a food web or a food chain?

• An increase in plant growth attracts more herbivores, which leads to a decrease in plant growth, eventually stabilizing the population.

• Algae blooms increase the amount of sunlight blocked from reaching underwater plants, which leads to further algae growth.

• A decrease in the number of plants leads to fewer herbivores, which helps plant populations recover.

Answer explanation

The correct choice describes how algae blooms block sunlight, promoting further algae growth, exemplifying a positive feedback loop that destabilizes the ecosystem.

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