The Nature of Science What is science?. Scientific Principles… Science seeks to explain the natural world and its explanations are tested using evidence.

The Nature of Science

What is science?

Scientific Principles…

Science seeks to explain the natural world and its explanations are tested using evidence from the natural world.

…Science can be a roundabout path to the truth.

…Science corrects itself.

…Science is conducted by humans.

Science requires…

Evidence Logical Thinking Creativity Skepticism Open-mindedness

Characteristics of Science

Conclusions tentative

Better information replaces existing info

May be biased, subjective

Explains natural, not supernatural

Characteristics of the Scientific Process

Founded on observations

Conclusions developed through reasoning

Tests subject to peer review and replication

The Process of Science

How does it work?

There is no such thing as "THE Scientific Method."

http://evolution.berkeley.edu/evolibrary/article/0_0_0/nature_05

A Scientific Method

Observation

Explanation

Test

AnalyzeCommunicate

Realistic Scientific Process

1. Observe2. Ask question3. Form hypothesis4. Test5. Repeat test6. Analyze results7. Form new hypothesis 8. Ask new question9. Test10. Analyze results11. Repeat test12. …

Goals of scientific process

Disprove hypotheses to weed out explanations

Find the best current explanation

There are two possible outcomes: If the result confirms the hypothesis, then you’ve made a measurement. If the result is contrary to the hypothesis, then you’ve made a discovery.

– Enrico Fermi

VARIABLES

DEPENDENT Outcome will depend on what you change.– What is being measured– Graphed on the y-axis

INDEPENDENT factors

that you consciously change– What is being manipulated– Graphed on x-axis

An experiment…

Beta-carotene supplements have been thought to protect against cancer. However, a study published in the Journal of the National Cancer Institute suggests this is false. The study was conducted with 39,000 women aged 45 and up. These women were randomly assigned to receive a beta-carotene supplement or a placebo, but they all followed the same diet and exercise routine. Their health was studied over their lifetime. Cancer rates for women taking the beta-carotene supplement did not differ systematically from the cancer rates of those women taking the placebo.

Can you determine?

Experimental group – women taking beta carotene

Control group – women taking placebo

Independent variable – supplement

Dependent variable – cancer rates

Control – Placebo

Constants– Over 45, diet, exercise routine

Hypothesis vs. Theory

Hypothesis – Testable explanation for an observation

Theory– A well tested explanation based on evidence,

experiments, hypotheses, observations, etc.

Writing a hypothesis (If…then, because)

If (independent variable) then (dependent variable), because (reason why the relationship exists).

Examples:– IF Family Guy is on, THEN I will accomplish less

homework, BECAUSE I will be distracted.

– IF a plant gets more sun, THEN the plant will grow more, BECAUSE more photosynthesis will occur and produce glucose for the plant to grow.

Example

Ms. Loch noticed that students who came in for extra help were scoring higher on tests than their classmates.

IF students come in for 1 hour/week of extra help, THEN they will score 10% higher on tests, BECAUSE they are getting questions answered and studying longer.

Putting It All Together

Sarah was interested in studying the effects of lack of sunlight on the height of plants. She took two identical trays and filled them with the same type of soil and planted the same type of seed in each. She then decided that she would keep one tray in a room that was completely dark and the other on the window ledge. She watered each with 50 mL of water a day.

Answers

Question– Does light affect the growth of plants?

Hypothesis– If a plant is placed in the dark, then it will not grow

as tall as plant in normal sunlight, because it will not be able to photosynthesize and grow.

Answers continued…

Independent Variable– Amount of light

Dependent Variable– Plant growth

Control– Plant on window ledge

Constants– Amount of water, type of soil, type of seed, trays