Scientific Method and Experimental Design

Key Vocabulary and Concepts

The scientific method is a systematic approach used in biology to investigate phenomena, acquire new knowledge, or correct and integrate previous knowledge. Understanding the terminology and steps is essential for designing and interpreting experiments.

• Precision: The degree to which repeated measurements under unchanged conditions show the same results.

• Accuracy: The closeness of a measured value to a standard or known value.

• Dependent Variable: The variable being tested and measured in an experiment; it is affected by changes in the independent variable.

• Independent Variable: The variable that is changed or controlled in a scientific experiment to test its effects on the dependent variable.

• Controlled Experiment: An experiment in which only one variable is changed at a time, while all other variables are kept constant.

• Hypothesis: A testable statement or prediction about the relationship between variables.

Metric System and Measurement

• Understand metric system conversions: grams, liters, and meters are the basic units of measure in science.

• Be able to convert between kilo-, centi-, milli-, micro-, and nano- units, and write numbers in scientific notation.

• Example: 1 kilometer (km) = 1,000 meters (m); 1 milligram (mg) = 0.001 grams (g).

Graphing and Data Analysis

• Know the basic rules for graphing data:

  • X-axis: Independent variable

  • Y-axis: Dependent variable

  • Include title, units, and scale

• Types of graphs: bar graph, line graph, scatter plot, pie chart

Scientific Method Steps

• Observation

• Hypothesis formation

• Experimentation

• Conclusion

Laboratory Equipment

• Be able to recognize, name, and use common laboratory equipment:

  • Graduated cylinder

  • Beaker

  • Pipette

  • Electronic balance

  • Meter stick

Atoms, Molecules, and Chemical Reactions

Key Vocabulary and Concepts

Understanding the structure and behavior of atoms and molecules is fundamental to biology, as all living things are composed of chemical substances.

• Atom: The basic unit of a chemical element.

• Molecule: Two or more atoms bonded together.

• Molecular Structure: The arrangement of atoms within a molecule.

• Covalent Bond: A chemical bond formed by the sharing of electron pairs between atoms.

• Ionic Bond: A chemical bond formed by the transfer of electrons from one atom to another.

• Hydrogen Bond: A weak bond between two molecules resulting from an electrostatic attraction.

• Chemical Reaction: A process that leads to the transformation of one set of chemical substances to another.

• Dissociation: The process by which a molecule splits into smaller particles such as atoms, ions, or radicals.

• Electrolyte: A substance that produces an electrically conducting solution when dissolved in water.

• Solute: The substance dissolved in a solution.

• Solution: A homogeneous mixture composed of two or more substances.

Atomic Structure and Periodic Table

• Be able to diagram atoms from periodic table information.

• Predict products of a mixture of ionic compounds when mixed in an aqueous solution.

• State possible physical changes that can occur from a chemical reaction.

• Determine the formula for compounds from combinations of ions.

• Write the structural formula of an organic compound from its chemical formula.

Density and the Scientific Method

Key Vocabulary and Concepts

• Density: The mass per unit volume of a substance.

• Displacement: The method of measuring the volume of an object by the amount of fluid it displaces.

• Volume: The amount of space an object occupies.

• Mass: The amount of matter in an object.

Calculating Density

• Measure mass and volume of an object (cube, rectangle, sphere) using a balance and displacement method.

• Use the formula:

• Units: g/cm3 or g/mL

Application

• Determine density by measuring mass and volume.

• Understand how density affects whether an object sinks or floats.

Buffers and pH

Key Vocabulary and Concepts

• pH: A measure of the hydrogen ion concentration; a measure of acidity or alkalinity.

• Buffer: A solution that resists changes in pH when acid or base is added.

• Acid: A substance that increases the hydrogen ion concentration of a solution.

• Base: A substance that decreases the hydrogen ion concentration of a solution.

• Acidic Solution: pH less than 7

• Basic Solution: pH greater than 7

Calculating pH

• pH is calculated as:

• Be able to calculate pH of an acid or base from a given concentration of H+.

Buffer Function

• Understand how buffers work and explain what will occur with the addition of acid and/or base to a given buffer.

• Compare buffered versus non-buffered solutions in terms of pH stability.

Introduction to Microscopes

Compound Microscope Parts and Function

Microscopes are essential tools in biology for observing cells and microorganisms. Understanding their parts and how to use them is fundamental for laboratory work.

• Identify and know the function of:

  • Base

  • Arm

  • Coarse/fine focusing knobs

  • Objective lenses

  • Stage

  • Condenser

  • Iris diaphragm

  • Lamp

Microscope Calculations

• Field of view (FOV), depth of field, contrast, resolution

• How to calculate total magnification:

• Determine FOV diameter for a particular objective given FOV diameter for another objective.

Types of Samples

• Know what types of samples are viewed on a compound microscope (thin, stained slides) versus a dissecting microscope (large specimens such as rocks, twigs, or animal organs).

Cell Structure and Function

Key Vocabulary and Concepts

• Cytoplasm Streaming: Movement of the fluid substance within a plant or animal cell.

• Cilia: Short, hair-like structures that help with movement.

• Pseudopodia: Temporary projections of eukaryotic cell membranes or unicellular protists for movement or feeding.

• Photosynthesis: The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.

• Thylakoid: Membrane-bound compartments inside chloroplasts and cyanobacteria; site of the light-dependent reactions of photosynthesis.

Cell Types and Staining

• Distinguish between plant cells and animal cells (no cell wall in animal cells).

• Know the reasons why stains are used in cells (to enhance contrast and visualize structures).

• Distinguish between the following types of cells:

  • Cyanobacteria – Oscillatoria

  • Amoeba

  • Spirogyra

  • Onion cell

  • Epithelial (Cheek Cell)

  • Paramecium

  • Elodea

Diffusion and Osmosis

Key Vocabulary and Concepts

• Diffusion: The movement of molecules from an area of higher concentration to an area of lower concentration.

• Osmosis: The diffusion of water across a selectively permeable membrane.

• Hypotonic Solution: Lower concentration of solutes compared to the cell; water enters the cell.

• Hypertonic Solution: Higher concentration of solutes compared to the cell; water leaves the cell.

• Isotonic Solution: Equal concentration of solutes inside and outside the cell; no net movement of water.

• Crenation: Shrinking of animal cells in a hypertonic solution.

• Plasmolysis: Shrinking of plant cell cytoplasm away from the cell wall in a hypertonic solution.

• Concentration Gradient: The difference in concentration of a substance across a space.

• Solvent: The substance in which the solute is dissolved.

• Solution: A homogeneous mixture of two or more substances.

Diffusion and Osmosis Experiments

• Understand the results of diffusion experiments using starch, glucose, and iodine.

• Explain how substances move across membranes and the role of concentration gradients.

• Be able to predict direction and rate of osmosis and diffusion based on solution type.

• Recognize visual effects of different solution concentrations on plant cells.

Summary Table: Solution Types and Effects on Cells