General Biology: Foundations, Chemistry of Life, and Properties of Water

Introduction to Biology

What is Life?

Biology is the scientific study of life, seeking to answer fundamental questions about living organisms and their interactions.

• Key Questions: How does a single cell develop into an organism? How do organisms interact with their environment? How does evolution shape life?

• Life is recognized by what living things do, not a single property.

Themes in the Study of Life

Biology is unified by several major themes:

1. Organization

2. Information

3. Energy and Matter

4. Interactions

5. Evolution

Organization: New Properties Emerge at Successive Levels

Biological Organization

• The biosphere: all living organisms on Earth

• Ecosystems: communities of organisms in an area and their environment

• Communities: all organisms in a specific location

• Populations: all individuals of a species in an area

• Organisms, organs, tissues, cells, organelles, molecules

Emergent properties arise from the arrangement and interaction of parts within a system.

Reductionism is breaking down complex systems into simpler components for study.

Cells: The Basic Unit of Life

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic cells: No nucleus, no membrane-bound organelles, generally smaller (e.g., bacteria, archaea).

• Eukaryotic cells: Have a nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).

Genetic Information and DNA

DNA: The Genetic Material

• DNA contains genes, the units of inheritance.

• Each DNA molecule is a double helix made of four building blocks: A, T, C, G.

• Gene expression: The process of converting information from gene to cellular product (DNA → RNA → Protein).

Genomics: Large-Scale Analysis

• Genomics: Study of sets of genes within and between species.

• Proteomics: Study of sets of proteins encoded by the genome.

Evolution: The Core Theme of Biology

Unity and Diversity of Life

• All life shares a common ancestor; diversity arises from evolutionary change.

• Three domains: Bacteria, Archaea, Eukarya.

Charles Darwin and Natural Selection

• Individuals vary in traits; more offspring are produced than survive; species adapt to their environment.

• Natural selection leads to adaptation and evolution.

Scientific Inquiry

Hypotheses and Theories

• Hypothesis: A testable explanation for an observation.

• Theory: Broader than a hypothesis, supported by a large body of evidence.

Scientific Method

• Observation → Question → Hypothesis → Prediction → Experiment → Analysis

• Inductive reasoning: Generalizations from observations.

• Deductive reasoning: Predictions from general premises.

Experimental Design

• Controlled experiments compare experimental and control groups.

• Variables: Independent (manipulated), dependent (measured), controlled (kept constant).

The Chemical Context of Life

Elements and Compounds

• Element: Substance that cannot be broken down by chemical reactions.

• Compound: Substance consisting of two or more elements in a fixed ratio.

The Elements of Life

• Major elements: C, H, O, N, (P, S, Ca, K, etc.)

Atomic Structure

• Atoms consist of protons (+), neutrons (0), electrons (−).

• Atomic number: Number of protons.

• Mass number: Protons + neutrons.

• Isotopes: Atoms with same number of protons, different neutrons.

Energy Levels and Electron Shells

• Electrons have potential energy based on their position in electron shells.

• Valence electrons determine chemical behavior.

Chemical Bonds

• Covalent bonds: Sharing of electron pairs.

• Ionic bonds: Transfer of electrons, forming ions.

• Hydrogen bonds: Attraction between hydrogen and electronegative atom.

• Van der Waals interactions: Weak attractions due to transient charges.

Molecular Shape and Function

• Molecular shape determines biological function and interactions.

Water: The Medium of Life

Properties of Water

• Cohesion: Water molecules stick together via hydrogen bonds.

• Adhesion: Water molecules stick to other substances.

• High specific heat: Water resists temperature change.

• Evaporative cooling: Loss of hottest molecules cools surface.

• Expansion upon freezing: Ice is less dense than liquid water.

• Versatile solvent: Water dissolves many substances.

Acids, Bases, and pH

• Acid: Increases H+ concentration.

• Base: Reduces H+ concentration.

• pH scale: Measures H+ concentration; $\text{pH} = -\log[\text{H}^+]$

• Buffers: Substances that minimize changes in pH.

Biological Importance of pH

• Organisms are sensitive to pH changes; buffers help maintain homeostasis.

• Ocean acidification is a concern due to increased CO2 absorption.