Advanced Biology: Unit One Introduction

Objectives:• Describe the steps of the scientific method.• Create an experiment using correct experimental design.• Distinguish between true observations and inferences.• Differentiate between a control group and an experimental group and between dependent and independent variables.

• Critique and analyze experimental design and data• Explain the procedure followed and the importance of a controlled experiment or a double-blind study.

• Identify the properties/characteristics of life• Distinguish between various types of reproduction• Describe the organization of life within a complex organism.• Explain how natural selection affects survival of a species.• Identify factors invalidating a study’s conclusions.

Vocabulary:hypothesis * observation * qualitative data * biology * quantitative data * control group * experimental group * dependent variable * independent variable * double blind * metabolism * homeostasis * tissues * organs * organ systems * autotroph * inference * heterotroph * adaptation

natural selection * evolution * operational definition * placebo/placebo effect * cells * convergent evolution * divergent evolution

Bio – “life” - logy “the study of”

Characteristics of life:1) All life is composed of one or more cells (the unit of life). More

complex organisms show organization of cells into tissues (“very thin” in French – so named by Bichat during the French Revolution). Tissues may be organized into organs ( a group of many tissues working toward a common function Ex: the heart contains nervous tissue, muscle tissue, vascular tissue, etc. in order to function as a pump in the circulatory (organ) system). Organs can be arranged into organ systems (Ex: circulatory system, digestive system, nervous system, etc.)

Cells to Tissues to Organs to Organ systems

2) Life requires energy for growth, repair, etc. Plants use the sun’s energy to photosynthesize. They are autotrophs (“self feeding”) or “producers”. Animals are heterotrophs (other feeders) or “consumers”. To extract energy from our food, we must metabolize it. Metabolism is the chemical reaction within cells that maintains life, using food to provide the necessary energy.

3) Living things maintain a relatively stable internal environment in spite of their external environment. The ability to keep conditions constant is called “homeostasis”. For example, cells maintain a relatively stable balance of Na+, K+, and Cl- ions. And, we maintain a relatively stable body temperature.

4) Organisms reproduce, grow, and develop.

* Reproduction may be asexual, such as a bacterium dividing through binary fission or a yeast “budding”. Conjugation PRIOR to asexual reproduction can allow genetic variability. Asexual cellular reproduction involves mitosis.

* Reproduction can be sexual, such as the production of egg and sperm through meiosis.

5) Organisms respond to their environment. This can be a simple stimulus/response like a plant bending toward the sun or a more complex response developing over time and generations. This is considered an adaptation.

Organisms that don’t adapt to their environment are less likely to survive. Organisms born with less desirable traits are also less likely to survive and reproduce. This is natural selection, also known as “survival of the fittest” (Darwin). Those organisms with the characteristics that best let them survive in their environment will thrive and reproduce. For example, those with coloration that blends with their environment (camouflage) are less likely to be seen by their predators/prey. Those without beneficial characteristics may not survive to reproduce so their genes will be lost. Remember, evolution does not occur in individuals, only in populations of species due to their genetic variability over time. This is evolution (the change in a species’ traits over time).

When organisms of different species living in similar environments begin looking more like each other (for example: polar bears, baby seals, and arctic hares all have white fur), it’s called convergent evolution. When organisms of the same species begin looking different from each other because they live in very different environments (Ex: tan desert hares with large ears for heat release versus white arctic hares with small ears for heat conservation), it’s called divergent evolution. Both forms of evolution are driven by natural selection. If a brown rabbit is born into a litter of artic hares, it’ll be seen by a predator and eaten, thereby removing its genes from the gene pool. If a brown rabbit is born into a litter in the desert, it blends into its environment and is more likely to survive, reproduce, and conserve its genes.

There are several ways to study living organisms:• Natural studies – pure observation of organisms in their environment• Controlled experiments• Double-blind studies

A controlled experiment is performed using the scientific method.The Scientific Method involves the following steps: 1) Problem statement - An explanation of what will be studied and

why.

2) Hypothesis - What you think the experiment will prove (an educated guess or prediction) and what background information/studies makes you believe this is the case.

3) Experimental design - This includes a very specific explanation of the steps to be followed. This must be clear enough that people not familiar with your experiment will be able to duplicate the experiment exactly. The control group (everything is kept standard) and experimental group(s) (1 variable) should be clearly identified. The independent variable (the variable being manipulated by the experimenter) in the experimental group(s) and the dependent variable (responding variable) being assessed must be clearly identified. Operational definitions (Ex: “Growth” means height) must be clear. The number of individuals studied, the amount of time they were studied or the number of trials completed by the individuals, and a clear identification of the individuals (Ex: Oak trees at three years of age. White, male Americans between the ages of 20 and 25. Etc.) is essential.

Control group – this is a group of individuals monitored during the experiment that receive “normal” treatment.

Experimental group – this is a group similar in composition (Ex: same age, species, and size of plants) to the control group, also given “normal” treatment EXCEPT for one variable (Ex: same amount of light, water, same soil, etc, BUT given 1 mg of vitamin D weekly.)

Independent variable - What the scientist changed from the “normal” condition. Ex: Growing plants under blue light waves only. Everything else is kept the same as in the control group.

Dependent variable – this is what the researcher EXPECTS to be affected by manipulating the independent variable. (Ex: I will measure plant growth under blue light because I think that light wave will increase growth.)

Operational definition – a specific explanation of terms or measurements (Ex: “Growth”, in this experiment means total biomass. For the purposes of this experiment, vitamin E refers to alpha-tocopherol only.) How measurements will be taken is also very important when reporting your experimental design.

4) Observation/Data Collection and Reporting – anything you can see, hear, taste, smell, or physically feel or measure is a true observation. It is important to avoid inferences. (Ex: “I heard yelling in the hall.” is an observation. Unless you actually saw it, adding, “There was a fight going on” is an inference, an assumption. This could be called “jumping to conclusions” and must be avoided.) Observations can be “qualitative” (non-numerical), such as “it turned blue” or “quantitative” (numerical), such as the item stood 3 inches tall, there were 5 episodes of . . ., etc. Qualitative data can sometimes be made numerical to help with comparisons between groups. Ex: “On a scale of 1 to 10, my pain was a 5.”

Tables, graphs, grids, and sample calculations should be used to report numerical data clearly and efficiently.

5) Analysis and Conclusion – This summarizes your data and states whether you feel this supports or refutes your hypothesis. Any unusual results should be addressed here (don’t ignore them). These should be explained along with any concerns about the experimental design, accuracy of data collection, equipment problems or limitations, etc.

Double-blind studies –a controlled experiment usually done when the experimental subjects are human and the experimental variable is a medication or vitamin. This is to eliminate the placebo effect. In this case, neither the test subject nor the person administering the medication/vitamin know whether they have the true product or the placebo. This prevents undue influence on the subjects by the provider of the pills and factors in a possible psychological effect.

Placebo effect – this is when people report feeling better due to treatment with an inert (non-medicinal) substance, i.e. the placebo.

It is important to use a critical eye when examining the conclusions given in other people’s experiments. Many inaccuracies or prejudices can be incorporated into a conclusion. This is especially true when the study is funded by a company that stands to benefit if the “right” conclusions are published.

Ex: A study done on the East Coast found that there was not a problem with “acidity” in the lakes. Yet, the pH levels were so low (acid) that fish could not live in the lakes. However, the conclusion was based on the operational definition defining a pH problem as existing only when the pH dropped lower (something like 4.5) than could sustain life. So, using their criteria for a “pH problem”, they could conclude there was no problem. Ex: A recent study concluded vitamin E did not help prevent blood components from sticking. Because the study defined Vitamin E as alpha-tocopherol, the conclusion was right. However, many of us consider Vitamin E to be a complex of 4 tocopherols and 4 tocotrienols with gamma-tocopherol being the agent that reduces stickiness.

Other factors that might invalidate a study’s conclusions:

Scientists often use inferences when forming their final conclusions. Since inferences are assumptions (based on their observations) they can be wrong.

Human error is always a possibility when performing experiments. A procedure can be performed incorrectly or the results could be misread.

Equipment can be faulty or not sensitive enough for certain measurements.

Cause/effect relationships must be scrutinized. Often, 2 things correlate, but one does not cause the other. Ex: In Europe, the stork population and human population grew at about the same rate over a period of 10 years. Although children used to be told that storks brought new babies to a home, the growth of the stork population certainly did not cause the growth of the human population. Both were probably related to a good environment for reproduction. So, be wary of cause/effect conclusions.

Studies must also contain adequate sample sizes. Conclusions cannot be accurately drawn when too few subjects are tested.

Studies must continue for long enough periods of time. The effects of many substances might not be seen for months or even years.

The age, pre-trial health, and sometimes sex of the subjects must be considered to draw valid conclusions.