The Science of Biology Chapter 1

Six Steps to Scientific Method 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 Experimentation Must have a variable or single factor being tested Experimental set: part of experiment that contains the variable. Control set: exactly like the experimental except NO VARIABLE. ppjpo

Variables INDEPENDENT Factor or value that is not affected by another variable. DEPENDENT Factor 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 : LAW : Theories & Laws Explanations to phenomena supported by evidence. LAW : A theory which has been accepted as true.

How do we know when something is ALIVE? 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 Offspring comes from a single parent Offspring is identical to parent. SEXUAL Offspring is usually a result of two parents. 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: Optical system Lenses 1.Objective lens low, med and high power 2. Ocular lens eyepiece

B. Mechanical system Base Arm Nosepiece Stage Clips Body tube Coarse adjustment knob Fine adjustment knob

C. Light System Mirror Internal light source Diaphragm

Magnification vs Resolution 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. Fixation Cutting material into small pieces and allowing it to soak in a fixative Embedded in liquid wax or plastic Sectioned or sliced Often stained

Phase-contrast microscope Allows the observer to see details in living specimens without staining.

Stereomicroscope Low magnification 3D images Great for dissections

Electron Microscopes 250,000 X Smaller magnification 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. Spectrophotometry Computers MRI (magnetic resonance imaging) CAT (computerized axial tomography) ultrasound