A. Exploring Life on its Many Levels
1. Levels of Biological Organization
a. Biological organization is based on a hierarchy of 12 structural levels, each building on the levels below.
1. Atoms: At the lowest level are atoms. (Fig. 2.5)
2. Molecules: Atoms are ordered into complex biological molecules. (Fig. 1.2)
3. Organelles: Many molecules are arranged into organelles. Organelles perform specific functions inside cells. (Fig. 10.6)
4. Cells: Organelles are the components of cells. (Fig. 7.8)
a. Cells are the basic units of life.
b. Some organisms consist of a single cell; others are multicellular aggregates of specialized cells.
5. Tissues: Similar cells are grouped into tissues. (Fig. 1.2)
6. Organs: Several tissues coordinate to form organs. (Fig. 1.2)
7. Organ systems: Several organs form an organ system. (Fig. 41.13)
8. Organism: Organ systems form an organism. (Fig. 1.2)
9. Population: Organisms belong to populations, localized groups of organisms belonging to the same species. (Fig. 52.2)
10. Species: A species is a group of organisms having the same anatomical characteristics and the ability to interbreed. (Fig. 24.2)
11. Biological community: Populations of several species in the same area comprise a biological community. (Fig. 53.0)
12. Ecosystem: These populations interact with their physical environment to form an ecosystem.
2. Properties of Living Organisms
a. Must have all 8 properties to be considered a living organism.
1. Order. (Fig. 1.3)
2. Reproduction by hereditary molecules (DNA)
3. Growth and development.
4. Energy utilization.
5. Response to stimuli.
6. Homeostasis-maintenance of internal environment (body temperature, etc).
7. Adaptation-characteristic that allows an organism to survive better in its environment.
8. Composed of one or more cells. (Fig. 1.11)
B. The Process of Science
1. Definition-the process of finding an explanation for a phenomenon by posing hypotheses and testing them
2. 6 steps of the scientific method
a. Observation: Make observations of a phenomenon
b. Question: Form a question about the observation(s)
c. Hypothesis: Construct a hypothesis (a possible answer to the question that accounts for all the observations)
d. Predictions: Generate predictions about the outcome of experiments or observations
e. Testing: Test the hypothesis (do experiments and/or collect data)
f. Conclusion: Decide whether to retain or reject the hypothesis
1. If the hypothesis is retained use it to generate more predictions and test them to further support the hypothesis.
2. If the hypothesis is rejected decide on a new one.
3. Example of the scientific method (flashlight that doesn't work)
a. Observation
b. Question
c. Hypothesis I
Hypothesis II
d. Prediction I
Prediction II
e. Testing
Experiment I
Experiment II
f. Decide whether to retain or reject each hypothesis
4. Points to remember
a. Observations are always in statement form.
b. It is best to keep observations small in number, simple in form and very precise.
c. The question(s) must directly and logically follow the observation(s).
d. Questions should always be in question form.
e. The hypothesis(es) must directly and logically follow the question(s).
f. The hypothesis is always in statement form.
g. The prediction(s) must directly and logically follow the hypothesis(es).
h. It is best to phrase predictions as if/then statements.
i. Not very many hypotheses are absolutely provable-most hypotheses in biology can be supported or refuted but not absolutely proved.
j. Experiments are repeated many times, usually by several investigators before a hypothesis is accepted by scientists.
k. Hypotheses that have been supported and accepted can later be rejected if new evidence is discovered.
5. What is a theory?
a. Definition for nonscientists-pure speculation which lacks evidence
b. Definition for scientists-a well established principle for which there is overwhelming supporting evidence
6. Using Controls in Experiments
a. What is a control?-An experiment in which the subjects are treated the same way as the experimental subjects except for the procedure or agent under test.
b. Example of why controls are necessary-test the effect of 3 plant nutrients on growth-What is the minimum number of plants you need?
7. What is a variable?-A factor that influences processes.
a. What is the process being studied in the plant nutrient experiment?
b. What factors (variables) can influence the process you are studying?
c. In an experiment you must keep all variables the same except the one being tested.
d. 3 types of variables
1. Independent variable-the proposed cause of something
2. Controlled variable-factor that is not being tested and that the experimenter tries to keep the same in all subjects
3. Dependent variable-condition or event that changes due to the independent variable