Chapter 1

Six Steps to Scientific Method

1. Defining the Problem:

• Be specific

• Research the topic

2. Formulating a hypothesis

Hypothesis = a possible explanation for an observed set of facts.

3. Testing the hypothesis

ExperimentationMust have a variable or

single factor being tested

1) Experimental set: part of experiment that contains the variable.

2) Control set: exactly like the experimental except NO VARIABLE. ppjpo

Variables

INDEPENDENTFactor or value that

is not affected by another variable.

DEPENDENTFactor or value that

is affected or determined by another factor or variable.

4. Observing and Measuring

Be specific with observations.Write down all data. 5. Analyzing & Drawing

Conclusions A chart or graph is often used to

help clarify information.

6. Reporting Observations

* If an experiment cannot be repeated the results cannot be considered valid.

THEORY :Explanations to

phenomena supported by evidence.

LAW :A theory which has

been accepted as true.

How do we know when something is ALIVE?

1) Made of one or more cells A small collection of living matter

enclosed by a barrier. Organisms can be either unicellular or

multicelluar.

2. Living things reproduce

ASEXUAL

1. Offspring comes from a single parent

2. Offspring is identical to parent.

SEXUAL

1. Offspring is usually a result of two parents.

2. Offspring is often similar to parents but not identical.

3. Living things are based on a genetic code.

Inheritance of traits are carried by a molecule of nucleic acid.

Usually DNA (deoxyribonucleic acid)

4. Growth and Development

All living things can increase in size (growth) and change over time (development)

All living things have a finite life span.

5. Living things obtain and use materials and energy

Metabolism : All of the chemical reactions and processes that build up and break down materials in an organism

6. Living things can respond to the environment

7. Living things try to maintain an internal balance

• Known as homeostasis

8. Living things evolve over time

As a species, living organisms can change over a given amount of time.

Tools of the Biologist

Section 4

The Light Microscope

Simple Microscope

Only one lens.

Compound Microscope

Uses two lenses, an optical system, a mechanical system, and a light system.

Parts of the microscope:

A. Optical system

Lenses

1.Objective lens

low, med and high power

2. Ocular lens

eyepiece

B. Mechanical system

BaseArmNosepieceStageClipsBody tubeCoarse adjustment knobFine adjustment knob

C. Light System

MirrorInternal light sourceDiaphragm

Magnification vs Resolution

Magnification:

enlargement of the object’s image

Resolution:

sharpness of an image; the ability to distinguish between separate points

Preparation of Specimens

Must be thin enough for light to pass through.

FixationCutting material into small pieces and

allowing it to soak in a fixativeEmbedded in liquid wax or plasticSectioned or sliced

Often stained

Phase-contrast microscope

Allows the observer to see details in living specimens without staining.

Stereomicroscope

Low magnification3D imagesGreat for dissections

Electron Microscopes

Transmission electron

– 250,000 X

Scanning electron

– Smaller magnification

– Can see many many fine details

SEM images

Human red blood cells and a housefly.

Lab techniques

Centrifugation = used to separate materials of different densities.

Tissue culture = used to maintain living cells outside an organism’s body.

Chromatography = separation of different substances on the basis of their chemical or physical properties.

Techniques continued…

Electrophoresis = an electric current is used to separate

substances.SpectrophotometryComputers

– MRI (magnetic resonance imaging)– CAT (computerized axial tomography)– ultrasound

ASSIGNMENT:

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