Chapter 1, Problem 17A

Summary Introduction

To differentiate:

Between the given terms

Introduction :

Biologists follow the same basic steps to do research and answer queries. These are called scientific methods. They conduct experiments, collect data, make hypothesis and gather evidences. After making a hypothesis, they have to test it. An experiment is a method to test a hypothesis.

Answer to Problem 17A

Independent variable- In a controlled experiment, two groups are tested and all conditions except one are kept same for both groups. The single condition that changes is called the independent variable.

Dependent variable- The condition caused by the change in independent variable is called dependent variable.

Explanation of Solution

Scientists gather information from various experiments. This information is called data. They then analyze the data and decide if the data supports the hypothesis. The experiments are conducted over and over again to gather more data. When a biologist conducts an experiment, he or she investigates a phenomenon in a controlled setting in order to testify a hypothesis. They form two groups to test the variable/ factor; a control group and an experimental group.

Independent variable- In a controlled experiment, only one condition is changed at a time. The condition that is tested is called the independent variable because it is the only change that affects the result of the experiment.

Dependent variable- While testing the independent variable, scientists observed a second condition that resulted due to change in independent variable. The condition caused by the change in independent variable is called dependent variable.

For example, in the experiment with kittiwakes, the supplemental feeding that was given is the independent variable. The change in the energy levels of kittiwakes as was measured in reproductive outcome is the dependent variable. Based on the results of the experiments, the scientists inferred that the kittiwakes would have more energy to lay eggs and chicks if they were given extra feeding during nesting time.