Biology (Holt)

methods, and data analysis. The reviewers also check that the con-

clusions reached by the author are justified by the data obtained.

Publishing an investigation allows other scientists to use the infor-

mation for hypotheses they are forming. They can also repeat the

investigations and confirm the validity of the conclusions.

Analysis

1. Identify the dependent and
   independent variables in the
   experiment.


2. Identify the experimental
   groups in the experiment.
   3. Propose a liquid that could
   be used for a control group.
   4. Evaluate how the instructions
   could be changed to improve
   the design of the experiment.

5.Critical Thinking

Applying Information

Design an experiment that

students can perform to verify

the prediction that coffee will

increase heart rate in Daphnia.

Analyzing Experimental Design

Background

To study the effects of common substances on the heart rate of a

tiny aquatic organism known as Daphnia,students placed a

Daphniain a drop of water on a glass slide. The students then

added 1 or more drops of a test substance dissolved in water to

the slide, waited 10 seconds, then counted heart beats for 10

seconds. The students used a clean slide and a new Daphnia

each time. Their data table is shown below.

0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010

Magnification: 16

Daphnia

Heart Rate of Daphnia in Different Solutions

Substance tested Heart rate (beats per minute)

None (control) 58

Coffee 65

Ethanol 50

20 CHAPTER 1Biology and You

Summarize how scientists use observations,

hypotheses, predictions, and experiments in

scientific investigations. 3A

Differentiate independent variables from

dependent variables.

Define the word theoryin a scientific sense and

then in a more general sense.

Critical ThinkingEvaluating ResultsIs

Harte’s hypothesis the only possible hypothesis for

the decrease in the number of salamanders in the

Rocky Mountains? 3A

A researcher finds that 90

percent of salamanders hatch from eggs in water at

pH 7, 80 percent hatch at pH 6, 60 percent at pH 5,

and 40 percent at pH 4. What is the approximate

percentage that hatch at pH 5.5? 2C

A55 percent C70 percent

B61 percent D85 percent

TAKS Test PrepTAKS Test Prep

Section 3 Review