Foundations of Biology and the Chemical Context of Life

Chapter 1: Evolution and Foundations of Biology

Introduction to Biology

Biology is the scientific study of life, encompassing the structure, function, growth, origin, evolution, and distribution of living organisms. The study of biology is organized around several unifying themes that help explain the diversity and complexity of life.

• Evolution: The central theory of biology, explaining the unity and diversity of life. All living organisms share a common ancestor and have evolved over time through natural selection.

• Life Processes: Activities that living organisms accomplish, such as growth, reproduction, and response to the environment.

Properties of Life

• Order: Living things exhibit complex but ordered organization.

• Evolutionary Adaptation: Organisms adapt to their environment over generations.

• Response to Environment: Organisms respond to environmental stimuli.

• Regulation: Organisms maintain homeostasis (stable internal conditions).

• Energy Processing: Organisms obtain and use energy for growth and maintenance.

• Growth and Development: Organisms grow and develop according to inherited instructions.

• Reproduction: Organisms reproduce their own kind.

Biological Organization

• Hierarchy of Life: Life is organized into a hierarchy from molecules to the biosphere.

• Emergent Properties: New properties emerge at each level of organization that are not present at the preceding level.

Cells: The Basic Unit of Life

• Cell Theory: All living things are composed of cells, and all cells come from pre-existing cells.

• Prokaryotic Cells: Lack a nucleus and membrane-bound organelles (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 molecule that stores genetic information in all living organisms.

• Genes: Units of inheritance made of DNA that encode instructions for building proteins.

• Gene Expression: The process by which information from a gene is used to synthesize a functional product (usually a protein).

• Central Dogma of Biology: DNA → RNA → Protein

Energy and Matter

• Energy Flow: Life requires the transfer and transformation of energy and matter.

• Producers: Organisms that produce their own food (e.g., plants via photosynthesis).

• Consumers: Organisms that obtain energy by feeding on other organisms.

Interactions and Ecosystems

• Interactions: Organisms interact with each other and their environment, affecting both their own survival and the ecosystem as a whole.

• Ecosystem: A community of organisms and their physical environment interacting as a system.

Classification of Life

• Taxonomy: The science of classifying organisms.

• Domains of Life: Bacteria, Archaea, Eukarya

• Kingdoms: Plantae, Fungi, Animalia (within Eukarya)

Scientific Method

• Observation: Gathering data about the natural world.

• Hypothesis: A testable explanation for an observation.

• Experimentation: Testing hypotheses through controlled experiments.

• Inductive Reasoning: Drawing general conclusions from specific observations.

• Deductive Reasoning: Making predictions based on general principles.

• Variables: Independent (manipulated), Dependent (measured), and Controlled (kept constant).

Chapter 2: The Chemical Context of Life

Introduction to Chemistry in Biology

All living organisms are composed of matter, which consists of chemical elements. Understanding the chemical basis of life is essential for studying biological processes.

Elements and Compounds

• Element: A substance that cannot be broken down into other substances by chemical means (e.g., carbon, hydrogen, oxygen, nitrogen).

• Compound: A substance consisting of two or more elements combined in a fixed ratio (e.g., water, H2O).

• Molecule: A structure formed when two or more atoms join together chemically.

Atoms and Subatomic Particles

• Atom: The smallest unit of an element that retains its properties.

• Subatomic Particles: Protons (positive charge), Neutrons (no charge), Electrons (negative charge).

• Atomic Number: Number of protons in an atom, determines the element.

• Mass Number: Sum of protons and neutrons in the nucleus.

• Isotopes: Atoms of the same element with different numbers of neutrons.

Electron Configuration and Chemical Bonds

• Electron Shells: Electrons are arranged in shells around the nucleus; the outermost shell determines chemical reactivity.

• Covalent Bonds: Atoms share pairs of electrons to achieve stability.

• Nonpolar Covalent Bonds: Equal sharing of electrons between atoms.

• Polar Covalent Bonds: Unequal sharing of electrons due to differences in electronegativity.

• Ionic Bonds: Transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other.

Key Elements in Biology

• Four elements make up about 96% of living matter: Carbon, Hydrogen, Oxygen, Nitrogen.

Summary Table: Types of Chemical Bonds

Bond Type	Description	Example
Covalent	Atoms share electrons	H2O (water)
Nonpolar Covalent	Equal sharing of electrons	O2 (oxygen gas)
Polar Covalent	Unequal sharing of electrons	H2O (water)
Ionic	Transfer of electrons	NaCl (table salt)

Additional info:

• Scientific method involves both inductive and deductive reasoning.

• Louis Pasteur's experiments disproved spontaneous generation, supporting the idea that all cells come from pre-existing cells.