Key Concepts in Biology and the Scientific Method

Scientific Method

Steps in Order: Observation: Identifying and noting a phenomenon. Hypothesis: A testable statement predicting a possible explanation. Experiment: Testing the hypothesis through controlled experiments. Conclusion: Analyzing the results to determine if they support the hypothesis. Scientific Theory: A well-substantiated explanation acquired through repeated experiments and observations.

Biological Organization

Hierarchical Structure: Domain: Highest level (e.g., Eukarya, Bacteria, Archaea). Kingdom: Broad taxonomic category (e.g., Animalia, Plantae). Phylum: Grouping organisms based on major body plans. Class: Division within a phylum (e.g., Mammalia). Order: Further classification within a class (e.g., Primates). Family: Grouping of related genera (e.g., Hominidae). Genus: Group of closely related species. Species: Most specific level of organism classification.

Properties of Life

Growth and Development: Organisms grow and undergo changes. Hierarchical Organization: Life is organized into complex structures: Cells -> Tissues -> Organs -> Organ Systems -> Organisms. Additional Properties: Sensitivity or response to stimuli: Reacting to environmental changes. Reproduction: Ability to produce new individuals. Adaptation: Evolutionary changes for survival. Regulation: Coordinating internal functions. Homeostasis: Maintaining a stable internal environment. Energy Processing: Using energy for metabolic activities. Order: Organized structures within organisms.

Experimental Purpose

Main Purpose: To support or not support a hypothesis with evidence. Experiments: Collect data and test hypotheses.

Hypothesis

An educated guess predicting a phenomenon.

Scientific Theory

A well-established explanation based on evidence.

Virus Characteristics

Not Living: Viruses can't respond to the environment and rely on host cells for replication.

Levels of Biological Organization

From Most Complex to Simplest: Biosphere: All ecosystems on Earth. Community: Different species living together. Organism: Individual living entity. Organ System: Group of organs working together.

Prokaryotic Cells

Simple, no nucleus (e.g., Bacteria).

Eukaryotic Cells

Complex, with nucleus (e.g., Plants, Animals).

Macromolecules

Backbone Element: Carbon. Roles: Lipids: Insulation, energy storage. Proteins: Structure, enzymes, transport. Carbohydrates: Primary energy source. Nucleic Acids: Genetic information storage (DNA, RNA).

Ionic Bonds

Electrical attraction between charged ions.

pH

Lower pH: More acidic.

Neutral pH

Pure water has equal concentrations of hydroxide (OH-) and hydrogen (H+) ions.

Endomembrane System

Group of membranes and organelles that work together to modify, package, and transport lipids and proteins.

Cytoplasm

A gel-like substance in which organelles are suspended.

Flagella

Long, hair-like structures used to move an entire cell.

Cytoskeleton

Network of microtubules, actin filaments, and intermediate filaments that organize the internal contents of the cell.

Ribosomes

Site of protein synthesis in the cytoplasm or attached to the cytoplasmic side of the endoplasmic reticulum.

Endoplasmic Reticulum

Interconnected membranes that modify proteins and synthesize lipids.

Rough Endoplasmic Reticulum (RER)

Has a studded appearance due to ribosomes.

Smooth Endoplasmic Reticulum (SER)

Synthesizes carbohydrates and lipids, stores calcium ions.

Plasma Membrane

Phospholipid bilayer with embedded proteins, separates the external environment from the internal contents of the cell.

Cilia

Short hair-like structures used to move an entire cell or substances along the outer surface of the cell.

Nucleus

Contains chromatin, directs the synthesis of proteins and ribosomes, most prominent organelle.

Lysosome

Contain digestive enzymes and are involved in phagocytosis, cell's garbage disposals.

Cytosol

Contents of the cell between the plasma membrane and the nuclear envelope.

Vesicles

Small membrane-bound sacs for transport of materials, fuse with membranes of other cellular components.

Golgi Apparatus

Sorting, packaging, and distributing lipids and proteins.

Vacuole

Larger membrane-bound sacs for storage, do not fuse with other cellular membranes.

Nucleolus

Site of ribosome assembly inside the nucleus.

Mitochondria

Site of ATP synthesis, powerhouse of the cell.

Peroxisomes

Small round organelles enclosed by single membranes, break down fatty acids and amino acids.

Nuclear Envelope

Double membrane structure, outermost portion of the nucleus.

Cellular Respiration Equation

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy.

ATP

Produced during cellular respiration.

Glycolysis

First step, breakdown of glucose into pyruvate, net gain of 2 ATP.

Electron Transport Chain

Final electron acceptor is oxygen.

Active Site

Where the substrate fits into the enzyme.

Coupled Reaction

One reaction releases energy to drive another.