Exam 1 Preparation: Key Concepts in General Biology

Themes in Biology & The Scientific Method

The scientific method is a systematic approach used in biology to investigate phenomena, acquire new knowledge, or correct and integrate previous knowledge. It involves making observations, forming hypotheses, conducting experiments, and analyzing results.

• Characteristics Shared by Living Things: Living organisms exhibit organization, metabolism, responsiveness, growth, reproduction, and adaptation.

• Hypothesis: A testable statement that explains observations and can be supported or refuted by experimentation.

• Prediction: A logical statement about what will happen if the hypothesis is correct.

• Difference Between Hypothesis and Prediction: A hypothesis proposes an explanation; a prediction states the expected outcome.

• Variables in Experiments:

  • Independent Variable: The factor that is changed or manipulated.

  • Dependent Variable: The factor that is measured or observed.

  • Controlled Variables: Factors kept constant to ensure a fair test.

• Data Analysis: Results are often presented in graphs or tables. Statistical analysis (e.g., p-values) determines significance.

• Inference vs. Statement of Results: An inference interprets the results; a statement of results describes what was observed.

Digestion & Absorption

Digestion involves the breakdown of food into smaller molecules that can be absorbed and utilized by the body. The process includes both mechanical and chemical digestion, occurring in various organs of the alimentary canal and accessory glands.

• Alimentary Canal: The continuous tube from mouth to anus, including the mouth, stomach, and duodenum.

• Accessory Organs: Organs such as the liver and pancreas that aid digestion.

• Functions: Digestion (breaking down food), secretion (releasing enzymes and fluids), absorption (uptake of nutrients).

• Enzymes: Biological catalysts that speed up digestion (e.g., pepsin, lipase).

• Absorption: Occurs mainly in the small intestine; microvilli increase surface area for absorption.

• Types of Biomolecules Digested: Carbohydrates, proteins, lipids.

• Fick's Law of Diffusion: Describes the rate of diffusion across membranes: Where J is the flux, D is the diffusion coefficient, and dC/dx is the concentration gradient.

• Peristalsis: Wave-like muscle contractions that move food through the digestive tract.

• Transport of Biomolecules: Nutrients are absorbed into blood or lymph and transported to organs.

Lipids & Cell Membranes

Cell membranes are composed primarily of lipids and proteins, providing structure and regulating the movement of substances into and out of cells.

• Types of Lipids: Fat, phospholipid, steroid.

• Phospholipid Bilayer: Forms the basic structure of cell membranes; hydrophilic heads face outward, hydrophobic tails face inward.

• Saturated vs. Unsaturated Fatty Acids:

  • Saturated: No double bonds; solid at room temperature.

  • Unsaturated: One or more double bonds; liquid at room temperature.

• Membrane Proteins: Include channels, carriers, and enzymes.

• Fluid Mosaic Model: Describes the dynamic nature of the cell membrane.

• Selective Permeability: Only certain molecules can cross the membrane freely.

• Transport Mechanisms:

  • Passive Transport: Diffusion and osmosis; no energy required.

  • Active Transport: Requires energy (ATP); e.g., Na-K ATPase pump.

  • Facilitated Diffusion: Uses membrane proteins to help substances cross.

• Osmosis: Movement of water across a semipermeable membrane from low to high solute concentration.

• Carrier Proteins: Transport specific molecules across membranes.

• Examples: GLUT1 (glucose transporter), aquaporin (water channel).

Carbon Skeletons & Functional Groups

Organic molecules are built from carbon skeletons and functional groups, which determine their chemical properties and biological functions.

• Carbon Skeletons: The backbone of organic molecules; can be straight, branched, or ring-shaped.

• Functional Groups: Specific groups of atoms that confer particular properties (e.g., hydroxyl, carboxyl, amino, phosphate).

• Polarity: Functional groups can make molecules polar or non-polar.

• Miller Experiment: Demonstrated that organic molecules could form under prebiotic conditions.

Cells: Prokaryotic vs. Eukaryotic

Cells are the basic units of life. They can be classified as prokaryotic or eukaryotic based on their structure and complexity.

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles; examples include bacteria.

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles; examples include plants, animals, fungi, and protists.

• Shared Characteristics: Plasma membrane, cytoplasm, genetic material, ribosomes.

Experimental Design & Data Representation

Experiments in biology require careful design, including identification of variables and appropriate data representation.

• Graphing Data: Use bar graphs, line graphs, or scatter plots to represent results.

• Practice: Draw and interpret graphs showing relationships between variables.

• Example: Camouflage experiment measuring predation rates on colored mice in different environments.

Vocabulary and Key Terms

Understanding key terms is essential for mastering biology concepts. Below is a table summarizing important vocabulary for this exam.

Additional info: Some definitions and explanations have been expanded for clarity and completeness.