7th Grade Science Test on April 9, 2024

A farmer digs a small pond in a pasture. The farmer adds young individuals from two species of algae-eating fish to the pond and plants some reeds around the edges of the pond. The farmer wants the pond to be a sustainable ecosystem.

Which of the following would be most helpful in increasing the pond ecosystem's sustainability?

• Decreasing the number of plant species around the edges of the pond

• Introducing older fish of the same species into the population of algae-eating fish

• Having a greater diversity of living organisms in the pond

• Adding gravel between the water and where the reeds are planted

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Which ecosystem would be more likely to survive if a disease killed the grasses?

• The forest ecosystem, because most of the animals can eat other organisms

• The grassland ecosystem, because several predators compete for food

• The forest ecosystem, because it has three top predators

• The grassland ecosystem, because it has many herbivores

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Some student stake care of a vegetable garden. When it is time to plant in the spring, the students leave part of the garden empty in order to observe ecological succession.

Which of these will most likely occur first?

• Growth of weeds and grasses

• Growth of trees and shrubs

• Development of a stream

• Development of topsoil

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A plant with broad, flat leaves is BEST adapted for

• conserving heat in a tundra

• collecting water in a desert

• absorbing light in a rainforest

• avoiding insects in a prairie

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Students see crickets, ants, field mice and owls in a dry, grassy field, but they do not see any frogs. Which change would MOST likely allow frogs to live in the field?

• a disease that reduces the number of lions that live in the field

• a fire that burns away the tall grass that covers the field

• a flood that causes a new stream to run through the field

• a warm summer that increases the number of insects in the field

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Where are you most likely to find the greatest variety and numbers of animal life?

• in a pond, a few meters away from the water’s edge

• next to a paved surface

• close to a pond with rocks, water, and several types of plants

• on a newly mowed lawn by the bug zapper

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A good adaptation for living in a grassland would be

• the ability to hibernate

• the ability of plants to grow very high to reach the sunlight

• thick, insulating fur

• the ability of plants to regrow after prairie fires

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Increased biodiversity results in a more sustainable ecosystem because

• a greater number of plant species means that there is less barren land

• a greater variety of species present allows more organisms to adapt after changes occur

• the transition area between two ecosystems is narrower

• the greater number of plant species means the land will be prettier and greener

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If the grasses in each ecosystem are attacked or killed by a disease, which ecosystem will most likely survive?

• The prairie ecosystem, because fewer organisms eat grass

• The prairie ecosystem, because there are more bears

• The tundra ecosystem, because it has more snakes

• The tundra ecosystem, because there is a variety of producers

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The more diverse an ecosystem is

• the more threatened its populations are

• the more similar the species will be

• the more sustainable it is

• the fewer varieties of species are present

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