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Which change in the environment would have a negative effect on the survival of a species in an ecosystem?

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Which of the following helps to produce urine in humans and other mammals?

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A certain disease of the spinal cord can be passed on from a dog to its offspring. This disease can result in the dog's muscles becoming weak, leading to paralysis. This is an example of

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Fourth graders are planning a roller-skate race. Which surface would be the best for this race?