SL Assignments

Chapter 1 - Invitation to Biology

Objectives

1.	List features that distinguish living organisms from nonliving matter.
2.	Describe the general pattern of energy flow through Earth’s life forms, and explain how Earth’s resources are used again and again (cycled).
3.	Explain what is meant by the term diversity, and speculate about what caused the great diversity of life forms on Earth.
4.	List as many steps of the scientific approach to understanding a problem as you can.
5.	Explain how people came to believe that the populations of organisms that inhabit Earth have changed through time.
6.	Understand as well as you can what limitations are imposed on science and scientists.

Lecture Outline

Impacts, Issues: What Am I Doing Here?

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.

1.1 Life'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.

1.2 Overview 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.

1.3 If 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).

1.4 An 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).

1.5 The 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.

1.6 The 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 OlestraÒ 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.

1.7 The 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.

Chapter 1 Summary
Section 1.1
Life shows many levels of organization. All things, living and nonliving, are made of atoms. The properties of life emerge in cells. An organism may be a single cell or multicelled. In most multicelled species, cells are organized as tissues, organs, and organ systems.
A population consists of individuals of the same species in a specified area. A community consists of all populations occupying the same area. An ecosystem is a community and its environment. The biosphere includes all regions of Earth's atmosphere, waters, and land where we find living organisms.
Section 1.2
Life shows unity. All organisms have DNA, which holds instructions for building proteins. They inherit the instructions from their parents and pass them on to offspring. By a process called metabolism, every cell uses energy and raw materials from the environment to grow and reproduce. Sunlight energy is captured by producers, who make their own food molecules from simple raw materials. Consumers survive by feeding on tissues, wastes, and remains of other organisms. All organisms sense changes in the surroundings and respond to them in controlled ways to maintain homeostasis.
Section 1.3
Life shows tremendous diversity. Many millions of species exist; many more lived in the past. Each is unique in some aspects of its body plan, function, and behavior. We group species that are related by descent from a common ancestor. A current classification system puts species in three domains: archaea, bacteria, and eukarya. The eukarya includes the protists, plants, fungi, and animals.
Section 1.4
Mutations change DNA and give rise to new variations of heritable traits. Natural selection occurs if a variation affects survival and reproduction. A population is evolving by natural selection when an adaptive form of a trait is becoming more common.
Section 1.5
Scientific methods are varied, but all are based on a logical approach to explaining nature. Scientists observe some aspect of nature, then develop a hypothesis about what might have caused it. They use the hypothesis to make predictions about what will happen if they carry out a test. A model helps scientists visualize processes that cannot be directly observed.
Scientists analyze test results, draw conclusions from them, and share this information with other scientists. A hypothesis that does not hold up under repeated testing is modified or discarded. A scientific theory is a long-standing hypothesis that explains a broad range of related phenomena and has been supported by many different tests.
Section 1.6
Science cannot answer all questions. It deals only with aspects of nature that lend themselves to systematic observation, hypotheses, predictions, and experiments.
Most aspects of nature are complex, an outcome of many interacting variables. A scientific experiment allows a scientist to change one variable at a time and observe what happens. Experiments are designed so experimental groups can be compared with a control group. Scientists share their results so others can check their conclusions.

Glossary
Chapter 1
animal	Multicelled, motile heterotroph that has embryonic stages and usually tissues, organs, and organ systems.
archaea	Evolutionarily distinct domain of prokaryotic organisms.
atom	Fundamental form of matter that has mass and takes up space, and cannot be broken apart by everyday means.
bacteria	The most widespread and diverse group of prokaryotic organisms.
biosphere	All regions of the Earth’s waters, crust, and atmosphere where organisms live.
cell	Smallest living unit, with a capacity to survive and reproduce on its own.
classification system	A way of organizing and retrieving information about species.
community	All species living and interacting in some habitat.
consumer	Heterotroph that obtains carbon and energy by feeding on other organisms.
control group	A group used as a standard for comparison with an experimental group.
deoxyribonucleic acid	See DNA.
DNA	Deoxyribonucleic acid. Carries the primary hereditary information for all living organisms and many viruses.
ecosystem	An array of species and their physical environment.
energy	Capacity to do work.
Eukarya	Domain of eukaryotic cells; all protists, plants, fungi, and animals.
experimental group	A group upon which an experiment is performed, and compared with a control group.
fungus	fungi; Eukaryotic heterotroph that obtains nutrients by extracellular digestion and absorption; notable for prolific spore formation.
homeostasis	Maintenance of physical and chemical aspects of the internal environment within ranges suitable for cell activities.
hypothesis	In science, a possible explanation of a phenomenon, one that has the potential to be proven false by experimental tests.
metabolism	All the controlled, enzyme-mediated chemical reactions by which cells acquire and use enrgy to synthesize, store, degrade and eliminate substances.
molecule	Two or more atoms of the same or different elements joined by chemical bonds.
mutation	Heritable change in DNA.
natural selection	Microevolutionary process; the outcome of differences in survival and reproduction among individuals that differ in the details of their heritable traits.
organ	Two or more tissues arrayed in a specific pattern and interacting in some task.
organ system	Two or more organs interacting chemically, physically, or both in a task.
plant	A multicelled photoautotroph with well-developed roots and shoots.
population	Group of individuals of the same species in a specified area.
prediction	Statement about what you expect to observe in nature.
producer	Autotroph; nourishes itself using sources of energy and carbon from the environment.
protist	One of the mainly single-celled species of eukaryotes traditionally grouped in the catch-all “kingdom Protista.” Currently being classified into groupings that reflect evolutionary relationships.
scientific theory	An explanation of the cause of a range of related phenomena; has been rigorously tested but is still open to revision.
species	One kind of organism. Of species that reproduce sexually, one or more groups of natural populations in which individuals interbreed and are reproductively isolated from other such groups.
test, scientific	A means to determine the accuracy of a prediction, as by conducting experiments, making observations, or developing models.
tissue	Of multicelled organisms, a group of cells and intercellular substances that function together in one or more specialized tasks.
variable	A specific aspect of an object or event that may differ over time and among individuals. In an experimental test, a single variable is directly manipulated in an attempt to support or disprove a prediction.