UNIT ONE: Science and the Living Environment

A. Terms:

1. Observation: What is seen or measured.

2. Inference: A conclusion based on observation or evidence.

3. Hypothesis: A prediction based on available evidence. A good hypothesis states both cause and effect.

a. A correct hypothesis can be tested and falsified (proven incorrect) using an experiment.

b. The easiest way to write a correct hypothesis is as an “if-then”statement. (ex: If I give patients this pill, then they will not get sick.)

4. Theory: An explanation of natural events that is supported by strong evidence.

a. Theories tie together many scientific facts, hypotheses and laws.

b. Misconception: “Theories are things that are opinions, or are not

proven.” This is an incorrect use of the word “theory” in a scientific context.

A scientific theory is not a simple guess or conjecture, and is strongly supported by evidence.

B. Controlled Experiment: Compares the results of an experiment between two (or

more) groups.

1. Experimental group: Group being tested or receiving treatment.

2. Control group: “Normal” group. Should be identical to experimental group in

every way except one: it does not receive the new treatment.

3. Placebo: A sugar pill or other “fake” treatment given to the control group.

4. Independent Variable: Variable that is being tested (ex: new drug, new

fertilizer).

a. b. The “If” part of an “If-then” hypothesis.

The independent variable is always plotted on the X axis.

5. results.

Dependent Variable: Variable that is measured at the end of an experiment; the

a. b. The “then” part of an “If-then” hypothesis.

The dependent variable is always plotted on the Y axis.

D. Characteristics of a good experiment:

1. Can be repeated the same way and get the same results.

2. Have large sample size/many test subjects.

3. Are performed for longer periods of time.

4. Test only one independent variable. All other characteristics of the tested

groups should be the same.

5. Are peer reviewed – examined by several scientists to determine its accuracy.

6. Must test the hypothesis and show whether it is wrong or right.

7. Is objective – the experiment and conclusion are fair and unbiased. Fact and

opinion are not mixed.

8. The experiment follows established ethical and legal standards.

B. All living things must maintain homeostasis.

1. Homeostasis is a balanced state in an organism.

2. Dynamic equilibrium means that the body stays balanced by taking action

whenever the balance is disturbed (like sweating when the body is too hot).

3. To maintain homeostasis, organisms carry out the same basic life functions:

transport, nutrition, excretion, respiration, growth, synthesis, regulation and

synthesis. Know these terms!

4. Metabolism is the term used to describe all of these life processes.

5. Failure to maintain homeostasis will result in disease or death.

C. Transport:

1. Diffusion: movement of molecules from high concentrations to low

concentrations. Requires no energy (passive transport).

2. Active Transport requires the use of energy, usually moving molecules from a

low concentration to a high concentration (against the flow of diffusion).

3. Osmosis is the diffusion of water into or out of the cell. If water diffuses into the

cell, the cell swells (get larger) and may burst. If it loses water (being put in salt

water for example) it will shrivel up.I