BIOL 100

Chapter One

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1.1 How Does Science Impact theEveryday World?

• Science plays an increasingly important role inthe everyday lives of Americans.– Technology– Medicine/Healthcare– Food production– Water resources

Role of Science

• The average American has at best an unevenknowledge of science.

– 80% know about plate tectonics

BUT

– 25% think the sun goes around the Earth!

Understanding Science

Figure 1.3

Early humans did not coexist with dinosaurs.

Antibiotics kill bacteria but not viruses.

The father’s gene determines the sex of a child.

The Earth goes around the sun.

The oxygen we breathe comes from plants.

48%

51%

65%

75%

79%

87%

Percent of Americans who understand that:

Continents are moving on the Earth’s surface.

Understanding Science

1.2 What is Science?

• Science is a body of knowledge, but only looksto find “what is there”…

• Based upon:• observation

– objectivity

• repeatability

What is Science?

• Repeated objective observations mayeventually lead to a theory

• Theory -– A general set of principles, supported by evidence

(observations), that explains some aspect of nature.– Very different from a “theory” outside of science.

• conjecture

What is Science?

Two Approaches to Science

• Discovery Science

• Hypothesis Driven Science

– most scientists use a combination of both types

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Discovery Science

• Observations (verifiable) and measurements• No experimentation• Can lead to important conclusions by using

inductive reasoning– Very specific observations in large numbers

generalized outward to a specific conclusion• Example: 10,000 organisms observed found to

be made of cells.– Therefore - All organisms are made of cells

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Hypothesis-Driven Science• Observations lead to questions which leads to

a hypothesis which leads to experimentation• What is a hypothesis?

– An explanation on trial– Must be testable

• Does this organism require oxygen? - testable• Does canned food make a dog happy? - not testable• Must be definable

• Use deductive reasoning– If A = B and B = C then A = C

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Hypothesis and Prediction

• a scientific “prediction” based on priorknowledge

• a type of “if …. then” statement that istestable and only has ONE factor or variable

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Design the Experiment

• hardest part of the experiment• many factors will affect your experiment,

these are called variables• independent variable is what you change• dependent variable is what you measure• in a controlled experiment, it is “assumed”

that you have accounted for as many of thevariables as possible

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Collect the Data

• defining your dependent variable is the mostimportant step– Again, is it testable?

• you may have to refine your technique– Organized trial and error

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Evaluate

• Correlation versus causation• Very rarely will a “good” scientist say that

results are causation.• We never prove a hypothesis true!

– Hypotheses are only falsifiable– Again, repeatability

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• An example of hypothesis testing is LouisPasteur’s experiment regarding thespontaneous generation of life– Prior to this experiment, many believed life could

arise from nothing…• Maggots appear to “spontaneously generate” on meat

left exposed

Example

ExampleWhen you start w ith a sterileflask of sterile meat broth. . .

Observation

Question: What is the source of the liv ing material?

Pasteur’s experiments:

Conclusion: No growth appears in the broth unless dust is admitted from outside. Reject “spontaneous generation” hypothesis.

Hypothesis:

. . . a grow th of new liv ing materialgenerally appears in the broth.

The liv ing material is deriv ed from nonliv ingmaterial (spontaneous generation).

sterile flask

Particletrap

sterilebroth

dust trappedin neck of flask

remov e trap

no growth

growth

growth

tip flask to mix trappeddust into broth

Hypothesis 1 Hypothesis 2

The liv ing material is deriv ed fromliv ing material outside of the flask.

growth ofnew materialin broth

sterile flask

sterile broth

Scientific method at work: Pasteur tests “spontaneous generation”

• Never! (officially anyway)– Only falsifiable

• Every assertion regarding the natural world issubject to challenge and revision.– Hence, repeatability

• As hypotheses are independently repeated,they are either “supported” or “unsupported”– Only after many repetitions with the same result

will a hypothesis become a theory• Always and forever subject to further testing or

knowledge

When is a Theory Proven?

1.3 The Nature ofBiology

• Biology is the study of life– Bio = life– ology = study of

• So, What defines life?

The Nature of Biology

Life is defined by a group of eight characteristics possessedby living things.– 1. Assimilate energy.– 2. Respond to their environment.– 3. Maintain a relatively constant internal environment.– 4. Reproduce.– 5. Possess an inherited information base, encoded

in DNA, that allows them to function.– 6. Are composed of one or more cells.– 7. Are evolved from other living things.– 8. Are highly organized compared to inanimate objects.

The Nature of Biology

Organization of Life

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• Life is organized in a hierarchical manner, inincreasing complexity:

AtomsMoleculesOrganelles

CellsTissuesOrgans

Organ systemsOrganismsPopulations

CommunitiesEcosystemsBiosphere

Organization of Life

atom(hydrogen)

Molecule(water)

organelle(nucleus)

cell(neuron)

tissue(nervous tissue)

organ(brain)

organ system(nervous system)

organism(sea lion)

population(colony)

community(giant kelp

forest)

ecosystem(southern California

coast)

biosphere(Earth)

Levels of Organization

• Atoms– Made in stars– Most consist of protons, neutrons and electrons

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• Molecules– Made up of atoms

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Levels of Organization

• Cells– Smallest unit of life– A membrane bound unit of living matter

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Levels of Organization

• Tissues– Groups of similar cells that work together– 4 Main Types (CMEN)

• Connective, Muscle, Epithelial, Nervous

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Levels of Organization

• Organs– Different tissues working together in a

coordinated manner.

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Levels of Organization

• Organ Systems– Individual organs working together– Digestive, excretory, nervous, etc.

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Levels of Organization

• Organism– All organ systems working together– The individual

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Levels of Organization

• Population– Individuals of a species that interact

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Levels of Organization

• Community– All the organisms of different species (biotic)

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Levels of Organization

• Ecosystem– Includes biotic and abiotic factors

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Levels of Organization

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Levels of Organization• Biosphere

– Sum of all ecosystems

1.4 Special Qualities of Biology

• Until the early nineteenth century, biology waslargely a descriptive science that mainlycatalogued and described the Earth’s livingthings.– Naturalists

Special Qualities of Biology

Special Qualities of Biology• Biology’s subject matter—the living world—is notable for its

complexity and diversity compared to other aspects of thenatural world (such as stars and atoms).– Estimated as many as 5-30 million species

• Some say 100 million– 1.5 million described (~5%)

Special Qualities of Biology• Evolution

– Biology’s chief unifying principle– The gradual modification of populations of living things over time.– This modification sometimes results in the development of new species.