Introduction to Biology

What is Biology?

Biology is the scientific study of living things and the processes that sustain life. It encompasses the structure, function, growth, origin, evolution, and distribution of living organisms.

• Living things are made of cells, use energy, respond to their environment, grow, develop, reproduce, maintain homeostasis, and evolve over generations.

• The scientific method is used to investigate biological questions, involving observation, hypothesis formation, experimentation, analysis, and conclusion.

The Scientific Method

Steps of the Scientific Method

• Observation: Notice something in the world.

• Question: Ask why or how it happens.

• Hypothesis: Make an educated guess.

• Experiment: Test your hypothesis.

• Analyze: Collect and examine data.

• Conclusion: Decide if your guess was right.

• Repeat: Science is ongoing and self-correcting.

Chemistry in Biology

Main Elements and Water

Life is based on a few key elements and the unique properties of water.

• Main elements: Carbon, Hydrogen, Oxygen, Nitrogen (CHON).

• Water: A polar molecule, excellent at dissolving substances.

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other surfaces.

• Regulates temperature: Water helps maintain stable temperatures in organisms and environments.

Biomolecules

Macromolecules and Their Functions

• Carbohydrates: Sugars, energy source.

• Lipids: Fats, oils; store energy, make membranes.

• Proteins: Enzymes, structure, most cellular functions.

• Nucleic acids: DNA and RNA, store genetic information.

Cell Components

Types of Cells

• Prokaryotes: No nucleus (bacteria, archaea).

• Eukaryotes: Have a nucleus and organelles (plants, animals, fungi, protists).

Cell Parts and Organelles

• Nucleus: Contains DNA.

• Mitochondria: Makes energy (ATP).

• Cytoplasm: Fluid for reactions.

• Ribosomes: Make proteins.

• Cell membrane: Controls what enters and exits the cell.

Plant Cell Special Structures

• Cell wall: Structure and support.

• Chloroplasts: Site of photosynthesis.

• Large central vacuole: Storage of water and nutrients.

The Membrane and Cell Transport

Types of Transport

• Diffusion: Movement from high to low concentration, no energy needed.

• Osmosis: Diffusion of water across a membrane.

• Active transport: Requires energy (ATP), moves materials from low to high concentration.

Energy and Metabolism

Cellular Respiration

Cells convert glucose and oxygen into ATP (energy), water, and carbon dioxide.

• Equation:

Photosynthesis

Plants and algae use sunlight to make glucose and oxygen.

• Equation:

Genetics

DNA and Genes

• DNA: Double helix, bases are A, T, C, G.

• Genes: Code for traits.

• Chromosomes: Bundles of DNA; humans have 46.

Cell Division

• Mitosis: Cell division for growth and repair (2 identical cells).

• Meiosis: Cell division for reproduction (4 unique cells).

Evolution

Mechanisms of Evolution

• Evolution: Changes in species over generations.

• Natural selection: Best-adapted organisms survive and reproduce.

• Evidence: Fossils, DNA similarities, comparative anatomy.

Ecology

Levels of Organization

• Organism → Population → Community → Ecosystem → Biosphere

Energy Flow and Roles

• Producers: Plants, make their own food.

• Consumers: Animals, eat other organisms.

• Decomposers: Bacteria, fungi, break down dead matter.

• Energy flows from the sun to producers to consumers to decomposers.

Domains and Kingdoms

• Domains: Bacteria, Archaea, Eukarya.

• Kingdoms: Animals, Plants, Fungi, Protists, Bacteria, Archaea.