e-Learning Session

1.1 How to Define Life

A. Living Things Are Organized

1. Organization of living systems begins with the cell; cells are made of molecules that contain atoms.
2. Cells combine to form a tissue (e.g., nervous tissue).
3. Different tissues combine to make up organs (e.g., the brain).
4. Organs work together as organ systems (e.g., the brain, spinal cord, etc.)
5. Multicellular organisms may have many organ systems.
6. A species in a particular area (e.g., gray squirrels, an oak forest) constitutes a population.
7. The populations inhabiting an area at the same time make up a community.
8. A community plus its physical environment constitutes an ecosystem.
9. Each level of organization has emergent properties beyond the sum of the parts.

B. Living Things Acquire Materials and Energy

1. Maintaining organization and carrying on life requires outside sources of energy.
2. Food provides nutrient molecules used as building blocks or for energy.
3. Energy is the capacity to do work; it takes work to maintain organization of the cell and organism.
4. Metabolism is all chemical reactions that occur in a cell.
5. Ultimate source of energy for nearly all life on earth is the sun through photosynthesis.
6. Organisms must remain homeostatic or keep themselves stable in temperature, moisture level, acidity, etc. by physiology and behavior.

C. Living Things Respond

1. Response often results in movements of plant or animal.
2. Ability to respond helps organism survive.
3. Responses to environment altogether constitute behavior of organism.

D. Living Things Reproduce and Develop

1. Reproduction is the ability of an organism to copy itself.
2. Bacteria, protozoa, etc. simply split into two.
3. Multicellular organisms may pair sperm with egg; resulting in an immature individual, which develops to become the adult.
4. Organisms develop as result of blueprint of instructions encoded in their genes.
5. Genes are made of long molecules of DNA that specify how the organism is ordered.

E. Living Things Have Adaptations

1. Adaptations are modifications that make an organism suited to its way of life.
2. Natural selection is process by which species become modified over time.
1. A species is a group of interbreeding individuals.
2. In natural selection, members may inherit a genetic change that makes them better suited to a particular environment.
3. Consequently, these members are more likely to produce more surviving offspring.
3. Descent with modification
1. All living things share the same basic characteristics: cells, DNA, etc.
2. This unity suggests all organisms descended from common ancestor -- the first cell.
3. Adaptations to different ways of life explain diversity of life-forms.

1.2. How the Biosphere is Organized

A. Populations

1. All ecosystems together make up the biosphere, the thin layer of life that encircles the earth.
2. Populations within a community interact among themselves and with the physical and chemical environments, forming a ecosystem.
3. Food relationships form a major part of interaction between populations.
4. Large ecosystem keeps cycling its raw materials (e.g., water and nitrogen)
5. In contrast, energy flows through an ecosystem and is eventually lost as heat.
6. A constant supply of solar energy is require for an ecosystem and for life to exist.

B. Tropical Rain Forest, a Terrestrial Ecosystem

1. Most complex ecosystem in the world; found at low altitudes near equator.
2. Require plentiful sun and rainfall all year long.
3. Broadleaf evergreen canopy intercepts most sunlight at different layers.
4. Most organisms live in canopy; includes tree sloths, monkeys, birds, butterflies, bats, etc.

C. The Human Population

1. Human populations tend to modify existing ecosystems for own purposes.
2. Fewer natural cycles are able to function adequately to sustain human populations.
3. For example, rain forests absorb carbon dioxide, keep temperatures lower, and lessen acid rain.
4. Preservation of biodiversity (variety of populations) is extremely important.

1.3. How Living Things Are Classified

A. Taxonomy and Scientific Names

1. Taxonomy is the discipline of identifying and classifying organisms.
2. Scientific name is binomial.
3. Scientific name of a species -- underlined or in italics -- contains two parts: first name is genus; second name is a specific epithet of organism.
4. Classification uses groups: species, genus, family, order, class, phylum/division, kingdom, and domain.

B. Five Kingdom and Three Domain Systems

1. Living things on the planet have commonly been categorized into five kingdoms:
1. Monera -- prokaryotic, unicellular organisms (archaebacteria and eubacteria);
2. Protista -- eukaryotic, unicellular, colonial, and simple multicellular organisms (protozoa, etc.);
3. Fungi -- eukaryotic, mostly multicellular, filamentous organisms that absorb their nutrients;
4. Plantae -- eukaryotic, multicellular, and photosynthetic organisms (plants);
5. Animalia -- eukaryotic, multicellular organisms (animals) that ingest their nutrients.
2. Biochemical evidence suggest kingdoms might be organized into three higher domains:
1. Archeae (ancient prokaryotes);
2. Bacteria (more derived prokaryotes);
3. Eukarya (eukaryotes, including the protists, fungi, plants and animals).

1.4. The Process of Science

A. Science is one way humans understand the natural world.

1. Science investigation is limited to questions that can be studied by direct or indirect observations.
2. An observable event is called a phenomenon.
3. Formulating a hypothesis involves inductive reasoning; (i.e., isolated facts are used to generalize about an observed phenomenon).
4. Science considers hypotheses that can be tested either in the laboratory or in a field setting.

B. A Field Investigation

1. Deductive reasoning begins with a general statement and infers a specific conclusion; it is often an "if...then" statement.
2. Controlled experiments have a control group that does not experience the tested variable; this eliminates the possibility results are due to nonidentifiable chance events.
3. Data are the results of experiments.
1. Data are careful counts or descriptions.
2. Careful records must be kept so other researchers can repeat the experiment.
4. By studying results, a researcher comes to a conclusion.
5. Results can falsify or show a hypothesis to be untrue; some think of science as what is left after alternative hypotheses have been rejected.
6. Science findings are reported in science journals so results are available to the research community.

C. A Laboratory Investigation

1. Some investigations are held in a laboratory where conditions can be kept constant.
1. A variable is a factor that can cause an observable change.
2. The experimental variable is the step that is deliberately manipulated.
3. A dependent variable is component of an experiment that changes due to the experimental variable.
4. Sweetener S discussion is example of a controlled experiment.

D. An Observational Investigation

1. Some investigations are based on observations rather than experimentation.
2. The science steps previously listed still apply.
3. Ultimate goal of science is to understand natural world in terms of theories; examples include Cell Theory, Biogenesis Theory, Theory of Evolution and Gene Theory.

E. The Scientific Method

1. Scientific method is a set of outlined procedures.
2. Actual science research may not follow this rigid outline and may involve chance (e.g., Alexander Fleming's discovery of penicillin).

F. Scientific Theories in Biology

1. Ultimate goal is to understand the natural world in scientific theories, conceptual schemes supported by a broad range of data.
2. Basic theories of biology are:
1. Cell theory: all organisms are made of cells.
2. Biogenesis theory: life only comes from life.
3. Evolution theory: living things have a common ancestor and are adapted.
4. Organisms contain coded information that determines their form and behavior.
3. The terms "law" and "principle" are also used for generally accepted theories.