Pinky's science fair project in junior high focused on an observation that the crickets outside her window chirped less frequently when the temperature was colder.

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Explanation:

The complete question: Pinky's science fair project in junior high focused on an observation that the crickets outside her window chirped less frequently when the temperature was colder. Consider if data was collected consisting of the average number of cricket chirps  at different temperatures in her backyard. What's the independent variable?

The independent variable would be the temperature.

Independent variables are variables that produce effects on another variable while remaining unaffected themselves. They can be manipulated in the course of a research in order to measure the kind of effects they exert on other variables - the dependent variables to be specific. The dependent variables are the actual variables needed to test the hypothesis of a research.

In this case, a variation in temperature was observed to have an effect on the chirping frequency of crickets. Hence, the independent variable would be the temperature.  

answer: accepted answer: aquatic animals use the oxygen dissolved in water to carry out respiration. since the amount of dissolved oxygen in water is low as compared to the amount of oxygen in the air, therefore the rate of breathing in aquatic animals is much faster than it is in terrestrial animals.

explanation: