Ecosystem Disruptions

How is this ecosystem MOST likely to be affected by a sudden decrease in the number of rats?

• The snake population will increase.

• There will be a decrease in the number of snakes, coyotes, and

  hawks.

• There will be an increase in the number of coyotes and hawks.

• There will be a decrease in the number of cacti and sagebrush

  plants.

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The first species to populate an area after a disturbance is called:

• A pioneer species

• A pilgrim species

• A founder species

• A primary species

Answer explanation

The correct answer is 'A pioneer species' because these organisms are the first to colonize disturbed areas, initiating ecological succession and paving the way for other species to follow.

How might a natural disaster, such as a forest fire, impact the energy transfer in a food web?

• It increases the number of predators

• It disrupts the availability of food sources

• It has no effect on the food web

• It increases the number of herbivores

Answer explanation

A forest fire disrupts the availability of food sources by destroying plants and habitats, which affects herbivores and subsequently the predators that rely on them, thus impacting the entire food web.

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DOK Level 2: Skill/Concept

Which of the following is an example of secondary succession?

• Lichen growing on a new lava flow

• Grass growing in a field after a fire

• Moss growing on a rock

• Algae growing in a pond

Answer explanation

Secondary succession occurs in areas where a disturbance has cleared an ecosystem but left the soil intact. Grass growing in a field after a fire exemplifies this, as it regrows after the fire, unlike primary succession which starts from bare rock.

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DOK Level 1: Recall

Which of the following is a consequence of reduced biodiversity in an ecosystem?

• Increased resilience to environmental changes

• Decreased stability and sustainability

• Enhanced food web complexity

• Improved ecosystem health

Answer explanation

Reduced biodiversity leads to decreased stability and sustainability in an ecosystem, as fewer species can result in less resilience to changes and disruptions, making the ecosystem more vulnerable.

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DOK Level 2: Skill/Concept

What is the effect of human intervention on the transfer of energy in food webs?

• It always increases energy transfer efficiency

• It can disrupt the natural flow of energy

• It has no impact on energy transfer

• It stabilizes the food web

Answer explanation

Human intervention can disrupt the natural flow of energy in food webs by altering habitats, introducing invasive species, or changing resource availability, which affects the interactions between organisms.

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DOK Level 2: Skill/Concept

In a real-life scenario, how might a decrease in a predator population affect an ecosystem?

• It would increase the prey population, potentially leading to overgrazing

• It would decrease the prey population, leading to starvation

• It would have no effect on the ecosystem

• It would increase biodiversity immediately

Answer explanation

A decrease in predator population allows prey to thrive, leading to population growth. This can result in overgrazing, as the increased number of herbivores consumes more vegetation than the ecosystem can sustain.

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DOK Level 2: Skill/Concept

What would happen if the primary consumers died out?

• the producers would grow and the secondary and tertiary consumers would die

• producers would die out

• consumers would grow

Answer explanation

If primary consumers die out, producers would thrive due to reduced competition for resources. However, secondary and tertiary consumers would face starvation without primary consumers, leading to their decline.

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What would happen to the bird if the green fish died out?

• the bird population would grow

• the bird population would die out

• the smaller fish will die out

Answer explanation

If the green fish died out, the birds that rely on them for food would struggle to survive, leading to a decline in the bird population. Thus, the correct answer is that the bird population would die out.

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Several owls live in a forest. The owls prey on mice. Hawks also prey on mice. Which might happen if several hawks move to the forest where the owls live?

• The number of owls will increase, and the number of hawks will decrease.

• The number of mice will increase, and the number of owls will decrease.

• The number of owls and hawks will increase.

• The number of owls and mice will decrease.

Answer explanation

If several hawks move to the forest, they will compete with owls for mice. This increased predation can lead to a decrease in both the number of owls and the number of mice, as both species rely on the same food source.

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