Introduction to Biology

What is Biology?

Biology is the study of all living things, including plants, animals, and bacteria. It seeks to understand the characteristics and processes that define life.

• Reproduction: The ability to produce offspring.

• Energy Input: Living things require energy (e.g., food, sunlight) to bring in nutrients.

• Respiration or Gas Exchange: Processes like breathing and photosynthesis.

• Homeostasis/Regulation: Maintaining a stable internal environment.

• Adaptation: The ability to evolve over time.

• Response to Stimuli: Reacting to environmental changes.

• Growth and Development: Increase in size and complexity.

• Order: Organized structure, even in the face of chaos or disorder.

All these processes occur at the cellular level.

Levels of Biological Organization

• Cells: The smallest unit of life.

• Organelles: Structures within cells (e.g., mitochondria).

• Molecules: Combinations of atoms (e.g., proteins, carbohydrates, lipids).

• Atoms: The smallest unit of matter, forming molecules.

• Matter: Anything that takes up space and has mass.

The Hierarchy of Life

• Atoms make up Molecules.

• Molecules make up Organelles.

• Organelles make up a Cell.

• Cells form Tissues.

• Tissues make up Organs.

• Organs make up Organ Systems.

• Organ systems make up an Organism.

• Organisms make up Populations.

• Populations make up Communities.

• Communities make up Ecosystems (including abiotic and biotic factors).

• Ecosystems make up the Biosphere.

Abiotic: Non-living Biotic: Living

DNA and water are essential for life.

Cell Types and Classification

Two Different Types of Cells

• Prokaryote

  • No nucleus; DNA is in the nucleoid region.

  • Primitive/prehistoric cell type; among the earliest forms of life.

  • Small and simple structure.

  • Made up of DNA, proteins, and ribosomes.

  • Ribosomes are non-membrane-bound organelles.

  • Examples: Bacteria, Archaea.

• Eukaryote

  • Has a nucleus containing linear DNA.

  • Contains membrane-bound organelles (including the nucleus).

  • Larger and more complex than prokaryotes.

  • Examples: Plants, Animals, Fungi, Protists.

Biological Classification: Domains and Kingdoms

All living things are classified into domains and kingdoms based on shared characteristics.

• The Three Domains

  • Archaea (prokaryotic)

  • Bacteria (prokaryotic)

  • Eukarya (eukaryotic)

• Kingdoms (Domain Eukarya)

  • Protista: Single-celled organisms (e.g., Amoeba, Paramecium).

  • Fungi: Multi-cellular decomposers (e.g., molds, mushrooms).

  • Plantae: Multi-cellular producers (e.g., plants).

  • Animalia: Multi-cellular consumers (e.g., humans, animals).

Mnemonic: "King Philip Came Over For Good Soup" helps remember the order of classification: Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Domain

• Kingdom

• Phylum (e.g., Chordata: animals with a backbone)

• Class (e.g., Mammalia: mammals)

• Order (e.g., Carnivora: meat eaters)

• Family (e.g., Felidae: cats)

The Scientific Method

Steps of the Scientific Method

• Observation and asking questions

• Forming a hypothesis

• Collecting data

• Producing a theory

Key Terms

• Data: Recorded observations or information.

• Qualitative: Descriptions without numbers.

• Quantitative: Measurements with numbers.

• Hypothesis: A testable explanation based on observations.

• Theory: A broad explanation supported by a large body of evidence.

• Experiment: A scientific test under controlled conditions.

Reasoning in Science

• Inductive Reasoning: Using specific observations to form a general rule or conclusion.

• Deductive Reasoning: Using a general principle to reach a specific conclusion.

Example: Inductive: All observed swans are white, so all swans are white. Deductive: All birds have feathers; a sparrow is a bird, so it has feathers.

Controlled Experiments

• Controlled Experiment: Compares an experimental group with a control group.

• Control Group: Lacks the experimental variable.

• Variables: Factors that can change in an experiment.

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

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

Hypothesis vs. Theory

• Hypothesis: A specific, testable prediction. Example: "Coat coloration well-matched to their habitat is an adaptation that protects mice from predators." Must be phrased so it can be tested.

• Theory: A broad explanation, supported by much evidence. Example: "Evolutionary adaptations arise by natural selection."

Cell Theory

• All living things are made up of at least one cell.

• All cells come from pre-existing cells.

• The cell is the basic unit of life.

Graphs in Biology

• Scatter Plot: Plots individual data points; shows relationships between two variables.

• Line Graph: Connects data points with a line; shows trends over time.

• Bar Graph: Uses bars to represent groups or categories.

• Mean: The average of data points.

• Standard Deviation: A measure of data spread.

• Variation: The amount of difference in data.

Proteins and Enzymes

Key Terms

• Catalyze: Speed up a chemical reaction.

• Amino Acids: Building blocks of proteins.

• Proteins: Chains of amino acids folded into 3D shapes.

• Enzymatic Protein (Enzyme): A protein whose shape allows it to act as a catalyst.

How Enzymes Work

• Enzymes lower the activation energy needed for reactions, making them faster and easier.

• They are specific to the reactions they catalyze.

Amino Acids and Protein Structure

• Amino acids are like the letters in an alphabet; they combine to form words (proteins).

• Amino acids join together in chains (polypeptides).

• The sequence and shape of the chain determine the protein's function.

Example: One amino acid = "A"; many joined together = "APPLE" (a chain with meaning).

Protein Folding and Function

• Proteins fold into unique 3D shapes, often with an active site for catalysis.

• The shape of the protein determines its function.

• Enzymes are proteins with specific shapes that allow them to catalyze reactions.

Emergent Property: When amino acids fold into a protein, the new structure can catalyze reactions—a property not present in the individual amino acids.

Why Enzymes are Important

• Without enzymes, many reactions in the body would take years instead of seconds.

• Enzymes are essential for processes like digestion, DNA replication, and metabolism.

Summary Table: Prokaryotes vs. Eukaryotes

Key Equations and Concepts

• Mean (Average): where is each data point and is the number of data points.

• Standard Deviation: where is the mean.

Additional info: Some explanations and examples have been expanded for clarity and completeness, following standard introductory biology textbooks.