A marine biologist designs an experiment to investigate how varying the salinity of seawat… — ACT

A marine biologist designs an experiment to investigate how varying the salinity of seawater affects the hatching rate of brine shrimp eggs. She places equal numbers of eggs into five separate tanks with different salt concentrations ( $10$ , $20$ , $30$ , $40$ , and $50\text{ ppt}$ ). All tanks are maintained at a constant temperature of $22^\circ\text{C}$ and receive $12\text{ hours}$ of light daily. After $48\text{ hours}$ , she records the percentage of hatched eggs in each tank. Match each experimental component on the left with its corresponding variable classification on the right.

Seawater salt concentrationIndependent variable
Percentage of hatched eggsDependent variable
Water temperature maintained at $22^\circ\text{C}$ Controlled variable

Answer

Seawater salt concentration matches with Independent variable; Percentage of hatched eggs matches with Dependent variable; Water temperature maintained at

22^\circ\text{C}

matches with Controlled variable.

The seawater salt concentration is the factor deliberately altered by the researcher across trials, so it is the independent variable. The percentage of hatched eggs is the metric observed and measured to quantify the effect, so it is the dependent variable. The water temperature of

22^\circ\text{C}

is kept identical in all test setups to ensure a fair test, making it a controlled variable.

Step-by-Step Solution

Identify the parameter that is systematically changed by the researcher across experimental conditions.

The salt concentration of seawater is deliberately varied from

10\text{ ppt}

50\text{ ppt}

, designating it as the independent variable.

The independent variable is the factor controlled or manipulated directly by the experimenter to test a hypothesis.

Identify the observed outcome or measurement recorded to assess the experiment's result.

The hatching percentage of brine shrimp eggs is measured after

48\text{ hours}

, designating it as the dependent variable.

The dependent variable represents the measured data that changes in response to the independent variable.

Identify environmental factors held constant across all test groups.

The water temperature is fixed at

22^\circ\text{C}

across all five tanks, designating it as a controlled variable.

Controlled variables are kept strictly uniform so they do not act as confounding factors during the experiment.

Key Concept

Classification of Independent, Dependent, and Controlled Variables in Experimental Design

Estimated Time:50s

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Step-by-Step Solution

Key Concept

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