Chapter 1

The Science of Biology

How do we determine whether something is living?

I. The Characteristics of Life

1.Cellular Organization (made of 1 or more cells)

2.Ordered Complexity (complex)

3.Sensitivity (responds to stimuli)

The Characteristics of Life (continued)

4. Growth, Development, and Reproduction

5. Energy Utilization (uses energy)

The Characteristics of Life (continued)

6. Homeostasis (balance between different systems)

7. Evolutionary Adaptation (those surviving have the best adaptations)

II. Hierarchy 1. Cellular Level

a.Atomb.Molecules – atoms bonded togetherc.Organelles – made of

macromoleculesd.Cells – organelles work together

i. Unicellular organisms ii. Multicellular organisms

II. Hierarchy (continued)

2. Organism Level

a. Tissues – cells working together

b. Organs

c. Organ system

II. Hierarchy (continued)

3. Population Levela. Population –

Organisms of the same species living together

b. Species – Organisms that can interbreed

c. Biological community – Populations of different species living together

II. Hierarchy (continued)

4. Ecosystem – Living and nonliving that interact in the same area

5. Biosphere – Any place on Earth that contains organisms

III. The Nature of Science (Scientific Method)

A.Science uses both deductive and inductive reasoning

1. Deductive reasoning a. Uses general ideas to lead to

a specific conclusion

b. Example:

Gravity causes objects to fall

This apple fell

Therefore gravity caused the apple to fall

2. Inductive Reasoning

a. Uses specific ideas to lead to a general conclusion

b. Example:

Hillary Clinton has hair

Barack Obama has hair

Therefore all politicians have hair.

Scientific Method

B. Hypothesis-driven science makes and tests predictions

1. Hypothesisa. An explanation for a group of

related observationsb. TESTABLE – can be proved

or disproved

Example: Observations• Soup exposed to the air spoiled — bacteria grew in

it. Containers of soup that had been boiled for one hour, and then were sealed, remained sterile. Boiling for only a few minutes was not enough to sterilize the soup. Louis Pasteur had previously demonstrated that the dust collected by drawing air through a cotton ball contained large numbers of bacteria, hence he knew that bacteria were present in the air and could be filtered out by using a cotton ball. He also knew that bacteria would settle out on the walls of a long, bent, glass tube as air was passed through it.

• Question: Is there indeed a “life force” present in air (or oxygen) that can cause bacteria to develop by spontaneous generation (from nonliving particles)?

• Germ Hypothesis: There is no such life force in air, and a container of sterilized broth will remain sterile, even if exposed to the air, as long as bacteria cannot enter the flask. Life comes only from preexisting life.

2. Experiment or Test – proves or disproves hypothesis

a. Variables (aka experimental variable, test experiment) changed in experiment

b. Control (aka control variable, control experiment) stays the same in experiment

• Test - Pasteur boiled broth in various-shaped flasks to sterilize it, then let it cool. As the broth and air in the containers cooled, fresh room air moved into the containers. None of the flasks were sealed — all were exposed to the outside air in one way or another.Control group — Some flasks opened straight up, so not only air, but any bacteria present in that air, could get into them.Variable or experimental group(s) — Pasteur used some flasks with long, S-shaped necks (swan-neck flasks) and closed others with cotton plugs. This allowed air to enter these flasks, but the long, swan neck or the cotton balls filtered out any bacteria present in that air. He subsequently broke the long necks off some of the swan-neck flasks.

3. Using predictions

a. If the experiment disproves the hypothesis, the hypothesis is rejected or modified

b. If the experiment supports the hypothesis, then more tests are carried out to see if the hypothesis is valid

c. If the hypothesis is valid, it should be able to correctly predict the outcome of these experiments

• Data: Broth in flasks with necks opening straight up spoiled (evidence: a bad odor and cloudiness in a previously clear broth, microscopic examination of the broth confirming the presence of bacteria), while broth in swan-neck flasks did not, even though fresh air could get it. Broth in flasks with cotton plugs did not spoil, even though air could get through the cotton. If the neck of a swan-neck flask was broken off short, allowing bacteria to enter, then the broth became contaminated.

• Conclusion(s): There is no such life force in air, and organisms do not arise by spontaneous generation in this manner. To quote Louis Pasteur, “Life is a germ, and a germ is Life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.”

C. The nature of scientific theories

1.Theory – a generally accepted principle supported by scientific evidence.

Example: Evolution

Charles DarwinAn Example of the Scientific Method

• Traveled around the world in the HMS Beagle.

Observations• Studied 14 species of finches that

varied slightly in appearance.

Observation: Malthus explains populations grow faster than their

food source.

Observation: Artificially bred pigeons creates great variation

Hypothesis – Natural Selection1. Finches are similar b/c they descended from a

common ancestor. They are different b/c the food available at each island varied.

2. Organisms produce more offspring than can survive. Those who do survive have a physical and behavioral advantage which they pass on to their offspring through genes.

3. Nature also produces variation within species.

Testing Natural Selection1. Fossil Record – intermediate species

2. Age of Earth – Radioactive decay reveals the age of Earth and organisms

3. Heredity - Genetics

4. Comparative Anatomy – homologous structures

5. Molecular Evidence – Similarities in DNA sequences

Strong evidence supports the hypothesis. Evolution is now a scientific theory.

IV. Unifying Themes in Biology

A. Cell Theory1. All organisms are made of cells.2. All cells come from preexisting cells.

B. The Molecular Basis of Inheritance Explains the Continuity of Life

1. DNA – set of instructions for organisms

2. Genes – passed down to offspring - heredity

C.Relationship between Structure and Function Underlies Living Systems 1. Form fits function

a. The aerodynamics of a birds wings allows it to fly

b. Elephant ears are large with great surface area to release heat.

D.Diversity of Life Arises by Evolutionary Change 1. 260,000 plants 2. 50,000 vertebrates 3. 750,000 insects

4. Widespread use of antibiotics has selected for antibiotic resistant bacteria

E.Evolutionary Conservation Explains the Unity of Living Systems 1. KPCOFGS

2. Compare DNA, proteins

King......Kingdom Philip....Phylum Could.....Class Only......Order Find......Family Good......Genus Students..Species

F. Cells are Information Processing Systems

1. Communication through the cell membrane

2. Homeostasis

G.Emergent Properties Arise from the Organization of Life

1. Total sum of all Parts

H.Science as a Process (Scientific Method)

1. Darwin’s Hypothesis to the Theory of Evolution

I. Energy Transfer1. Photosynthesis2. Respiration3. Food Web

J. Regulation (Homeostasis) 1. Body temperature is regulated by the

brain through feedback systems. 2. Predators regulate prey populations

K.Interdependence in Nature1. EXAMPLE: Trees interact with

soil (water and minerals), air (gas exchange), sunlight and animals (food)

2. Symbiosis

L.Science, Technology and Society

1.Good and Bad: live longer v environmental impact

2.Tools: Microscopes, X-rays