Unit 4: Ecosystem Dynamics

What is the primary source of energy for most ecosystems on Earth?

• The Moon

• The Sun

• The Earth's core

• Ocean currents

Answer explanation

The primary source of energy for most ecosystems on Earth is the Sun. It provides the light and heat necessary for photosynthesis, which is the foundation of food chains in ecosystems.

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What is the role of decomposers in the cycling of matter in an ecosystem?

• They produce energy for plants

• They break down dead organisms and recycle nutrients

• They consume primary producers

• They compete with herbivores for food

Answer explanation

Decomposers play a crucial role in ecosystems by breaking down dead organisms, which recycles nutrients back into the soil. This process enriches the environment, allowing plants to thrive and maintain the cycle of matter.

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Which of the following factors can affect the biodiversity of an ecosystem?

• Temperature changes

• Availability of water

• Human activities

• All of the above

Answer explanation

All of the listed factors—temperature changes, availability of water, and human activities—can significantly impact the biodiversity of an ecosystem, making 'All of the above' the correct choice.

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How does the introduction of a new predator affect the population dynamics of an ecosystem?

• It increases the prey population

• It decreases the prey population

• It has no effect on the ecosystem

• It increases the biodiversity

Answer explanation

The introduction of a new predator typically leads to increased predation on the prey species, resulting in a decrease in their population. This dynamic can disrupt the balance of the ecosystem.

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Which mathematical representation can be used to model the flow of energy in an ecosystem?

• Food web diagram

• Bar graph

• Line graph

• Pie chart

Answer explanation

A food web diagram effectively models the flow of energy in an ecosystem by illustrating the complex feeding relationships between organisms, showing how energy is transferred through various trophic levels.

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NGSS.HS-LS2-4

Evaluate the claim: "Ecosystems with high biodiversity are more stable than those with low biodiversity."

• True, because diverse ecosystems can better withstand environmental changes

• False, because biodiversity has no impact on ecosystem stability

• True, because biodiversity decreases competition

• False, because biodiversity increases competition

Answer explanation

True, because diverse ecosystems can better withstand environmental changes. High biodiversity allows for a variety of species that can adapt to changes, enhancing overall ecosystem stability.

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Which of the following is a factor that can limit the carrying capacity of an ecosystem?

• Unlimited food supply

• Limited water resources

• Abundant shelter

• High birth rates

Answer explanation

Limited water resources can restrict the growth and survival of organisms, thus limiting the carrying capacity of an ecosystem. In contrast, unlimited food supply, abundant shelter, and high birth rates do not inherently limit capacity.

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What is the role of producers in an ecosystem?

• To consume other organisms

• To convert solar energy into chemical energy

• To decompose organic matter

• To compete with herbivores

Answer explanation

Producers, such as plants, play a crucial role in ecosystems by converting solar energy into chemical energy through photosynthesis. This process forms the base of the food chain, supporting all other organisms.

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NGSS.HS-LS2-4

What is the goal of the 30 by 30 Initiative?

• To conserve 50% of US lands and waters by 2030

• To conserve 30% of US lands and waters by 2030

• To conserve 20% of US lands and waters by 2030

• To conserve 10% of US lands and waters by 2030

Answer explanation

The 30 by 30 Initiative aims to conserve 30% of US lands and waters by 2030, making it a crucial effort for environmental protection and biodiversity preservation.

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What term best describes this group of bison?

• Species

• Community

• Ecosystem

• Population

Answer explanation

The term 'Population' best describes this group of bison as it refers to a specific group of individuals of the same species living in a particular area. 'Community' and 'Ecosystem' involve multiple species and their interactions.

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