Impacts, Issues: What Am I Doing Here?

Lecture Outline

A.Current world events seem chaotic.

1.Humans spill oil that threatens aquatic life.

2.Diseases such as AIDS destroy lives.

3.Even the global temperatures seem to be unstable.

B.But past world events also have been destructive.

1.Bioterrorism was around in 1346 when soldiers hurled corpses of plague victims over walled cities.

2.In 1918, Spanish flu raced around the world, killing some 30 million people.

1.1Life's Levels of Organization

A.From Small to Smaller

1.Consider what can fit across the head of a pin: 375 red blood cells; 1,200,000 fat molecules
53, 908,355 hydrogen atoms.

2.Next imagine how many of these are in your body.

B.From Smaller to Vast

1.The molecules of life are: carbohydrates, lipids, proteins, DNA, and RNA.

2.The cell, composed of “biological molecules,” is the basic unit of life.

3.Multicelled organisms have increasingly complex levels of organization that result in tissues > organs > organ systems > organisms > populations > communities > ecosystems > biosphere.

1.2Overview of Life’s Unity

A.DNA, The Basis of Inheritance

1.Living and nonliving matter are composed of the same particles, operating according to laws governing energy—the capacity to make things happen, to do work.

a.Deoxyribonucleic acid, or DNA, is the special molecule that sets the living world apart from the nonliving by carrying the hereditary instructions for assembly of new organisms.

b.The flow is from DNA to RNA to protein.

2.Inheritance is the acquisition of traits through the transmission of DNA from parents to offspring.

a.Each organism arises through reproduction—the production of offspring by one or more parents.

b.DNA also guides development—the transformation of a new individual into a multicelled adult.

3.Each organism is part of a reproductive continuum that extends back through countless generations.

B.Energy, The Basis of Metabolism

1.Energy, the capacity to do work, moves through the universe in a series of transfers.

2.Metabolism is the cell’s capacity to:

a.obtain and convert energy from its surroundings, and

b.use energy for maintenance, growth, and reproduction.

3.Energy flows from the sun.

a.Plants (“producers”) trap this energy by photosynthesis.

b.Animals (“consumers”) feed on the stored energy in plants, using aerobic respiration.

c.Bacteria and fungi (“decomposers”) break down complex molecules of other organisms to simple raw materials suitable for recycling.

C.Energy and Life's Organization

1.The great one-way flow of energy into the world of life also flows out of it.

2.These events organize life in the biosphere.

D.Life’s Responsiveness to Change

1.Receptors and the stimuli they receive allow controlled responses to be made to heat and cold, harmful substances, and varying food supplies.

2.Homeostasis refers to a state in which the conditions of the “internal environment” are maintained within tolerable limits.

a.Increased sugar causes insulin release, which stimulates cells to take up sugar.

b.Decreased blood sugar causes another hormone to call on stored sugar reserves.

1.3If So Much Unity, Why So Many Species?

A.All organisms are made of the same materials and function according to the same laws of energy.

B.Yet there is much diversity, a fact that has led humans to develop classification schemes.

1.All organisms can be identified by a genus and species name; example: Scarus gibbus (humphead parrotfish).

2.Groupings from least inclusive to most inclusive are: genera > family > order > class > phylum > kingdom.

3.Three domains are presently recognized:

a.Archaea—the most ancient of bacteria, many anaerobic.

b.Bacteria—more recently evolved bacteria.

c.Eukarya—protists, fungi, plants, and animals.

4.Bacteria are prokaryotic (lacking a nucleus); all other groups are eukaryotic (having a true nucleus).

1.4An Evolutionary View of Diversity

A.Mutations are heritable changes in DNA.

1.Variations in hereditary instructions arise through mutations.

a.Many mutations are harmful.

b.Some may be harmless or even beneficial.

2.The environment tests the combination of patterns expressed in each organism and may prove the trait adaptive—increases survivability and reproduction.

B.Evolution is heritable change in a line of descent over time.

1.Charles Darwin reasoned that the practice of artificial selection used by pigeon breeders could serve as a model for his theory of natural selection; present-day overuse of antibiotics illustrates Darwin's model even more.

2.The key points of his theory are as follows:

a.Members vary in form and behavior; much of the variation is heritable.

b.Some varieties of heritable traits will improve survival and reproductive chances.

c.Those with improved chances will be more likely to reproduce and pass the adaptive traits on with greater frequency in future generations (natural selection).

1.5The Nature of Biological Inquiry

A.Observations, Hypotheses, and Tests

1.Biology is an ongoing record of discoveries arising from methodical inquiries into the natural world.

2.Explanations are sought using the following approach:

a.Ask a question.

b.Develop hypotheses (educated guesses) using all known information.

c.Make a prediction of what the outcome would be if the hypothesis is valid (deductive, “if-then” reasoning).

d.Test the predictions by experiments, models, and observations.

e.Repeat the tests for consistency.

f.Report objectively on the tests and conclusions.

B. About the Word “Theory”

1.A theory is a related set of hypotheses that form an explanation about some aspect of the natural world.

a.A theory has broader application than a hypothesis.

b.A theory is not “absolute truth”; scientists are “relatively” certain it is (or is not) correct.

2.The fact that an idea, or even a theory, might be subject to change is a strength of science, not a weakness.

1.6The Power of Experimental Tests

A.An Assumption of Cause and Effect

1.Experiments involve tests in which conditions are carefully controlled.

2.Control groups are used to identify side effects during a test that involves an experimental group.

3.The experimental group experiences all of the same conditions as the control group except for the variable being studied.

B.Example of an Experimental Design

1.A suburban Chicago theater was chosen as a “laboratory” to determine if the synthetic fat called Olestra caused gastroinstestinal cramps.

2.Both control and experimental groups were random samples of moviegoers who had no idea which fat-impregnated chips they were eating.

3.Later, the moviegoers were called at home to determine the extent of distress: 15.8 percent for Olestra, 17.6 percent for regular chips; no significant difference.

C.Example of a Field Experiment

1.Durrell Kapan confirmed Mullerian mimicry with an experiment in the forests of Ecuador.

2.He was able to show that birds that had “learned” to associate yellow markings with unpalatability of one species of butterfly would also avoid butterflies of another species with similar markings, even though they had not actually tasted them.

D.Bias in Reporting Results

1.Scientists prefer quantitative reports of experimental tests to guard against bias.

2.Changing one’s mind in the light of new evidence is a strength in science.

1.7The Limits of Science

A.Science is limited to questions that can be tested.

1.Subjective questions cannot be addressed.

2.All of human society must participate in moral, aesthetic, and other such judgments.

3.Science may be considered controversial when it offers explanations for an aspect of nature previously considered supernatural; for example, Copernicus correctly stated that the Earth circled the sun—a heresy in his day.

B.The external world, not internal conviction, must be the testing ground for science.