General Biology: Foundations, Cell Theory, Evolution, and Chemistry of Life

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Introduction to Biology

Definition and Scope

Biology is the scientific study of life and living organisms. The term "biology" comes from "bio" meaning life and "-ology" meaning the study of. It encompasses a wide range of topics, from the molecular mechanisms within cells to the interactions of organisms within ecosystems.

Characteristics of Life: All living things share certain characteristics, including cellular organization, metabolism, energy use, replication, information transfer, and evolution.
Cells: The basic unit of life; viruses are not made of cells and are therefore not considered alive.
Theory of Evolution: Explains how species change over time; major developments occurred in the mid-1800s.
Chromosomal Theory of Inheritance: Developed in the late 1800s to early 1900s, it describes how genetic information is passed through chromosomes.

Theory: An explanation about something we see that is backed by a wide body of evidence.

Hypothesis: A testable proposal with explanation or prediction based on previous knowledge or observations.

Law: A set of mathematical explanations to describe how something in the world works.

Cell Theory

Foundations and Contributors

Cell theory is a fundamental concept in biology stating that all living organisms are composed of cells, and all cells arise from pre-existing cells.

James Watson and Francis Crick: Proposed that DNA is a double-stranded helix.
Robert Hooke: Developed early microscopes and observed cells in cork.
Anton van Leeuwenhoek: Improved microscopes and observed microorganisms in pond water.
Cell: A highly organized compartment bound by a plasma membrane, containing concentrated chemicals in an aqueous solution.

Cell Theory Statements:

All organisms are made of cells.
All cells come from pre-existing cells.

Theory of Evolution by Natural Selection

Key Concepts

Evolution by natural selection explains how populations change over time due to heritable traits that affect survival and reproduction.

Natural Selection: Individuals vary in characteristics that are heritable and can be passed on. Certain traits help with reproduction more than others.
Fitness: The ability of an individual to produce offspring.
Adaptation: A trait that increases the fitness of an individual in a particular environment.
Evolutionary Change: Natural selection acts on individuals, but evolutionary change occurs in populations. Speciation occurs when populations diverge to form new species.

Phylogeny: The evolutionary relationships among species, often depicted as a phylogenetic tree.

Prokaryotes: Bacteria and Archaea; cells do not have a membrane-bound nucleus.
Eukaryotes: Eukarya; cells have a membrane-bound nucleus.

Taxonomy: The science of naming and classifying organisms. Domains include Bacteria, Archaea, and Eukarya.

Nature of Science

Scientific Method and Experimentation

Science is based on formulating hypotheses and testing them through experiments and observations. Well-designed experiments include control groups, experimental groups, and repetition.

Hypothesis: A question that can be answered by measurement or data collection.
Experiment: Tests the effect of a factor on a phenomenon.
Prediction: Measurable or observable result that must be correct if a hypothesis is valid.

Water and Carbon: The Chemical Basis of Life

Atoms, Ions, and Molecules

All living organisms are composed of atoms and molecules. The most common elements in living organisms are hydrogen, carbon, nitrogen, and oxygen.

Atoms: Basic units of matter, made up of protons, neutrons, and electrons.
Protons: Positively charged particles in the nucleus.
Neutrons: Neutral particles in the nucleus.
Electrons: Negatively charged particles in orbitals surrounding the nucleus.
Atomic Number: Number of protons in an atom.
Mass Number: Number of protons and neutrons in an atom.

Isotopes: Forms of an element with different numbers of neutrons.

Valence Electrons: Electrons in the outermost shell, important for chemical bonding.

Electron Shells: Most stable when filled; outermost shell can hold about 8 electrons.

Chemical Bonds

Covalent Bonds: Atoms share electrons to fill their valence shells.
Ionic Bonds: Electrons are transferred from one atom to another, creating ions that attract each other.
Polar Covalent Bonds: Electrons are shared unequally, creating partial charges.

Water and Its Properties

Hydrogen Bonds: Weak attractions between the partial positive charge of hydrogen and the partial negative charge of another atom (often oxygen or nitrogen).
Hydrophilic: Molecules that dissolve in water (water-loving).
Hydrophobic: Molecules that do not dissolve in water (water-fearing).

Acids, Bases, and pH

Acids: Substances that give up protons during chemical reactions and raise hydronium ion concentration.
Bases: Substances that acquire protons during chemical reactions and lower hydronium ion concentration.
pH Scale: Measures proton concentration in solution.
Buffers: Help maintain homeostasis by protecting against changes in pH.

Energy and Chemical Reactions

Types of Energy

Potential Energy: Stored energy due to position or structure.
Kinetic Energy: Energy of movement.
Exothermic Reaction: Releases heat.
Endothermic Reaction: Absorbs heat.

Important Equations and Concepts

Atomic Mass Unit (AMU):
Avogadro's Number:
Mole Concept: atoms or molecules
Atomic Mass: Average mass of all naturally occurring isotopes of an element

HTML Table: Comparison of Prokaryotes and Eukaryotes

Feature	Prokaryotes	Eukaryotes
Nucleus	No membrane-bound nucleus	Membrane-bound nucleus
Domains	Bacteria, Archaea	Eukarya
Cell Size	Generally smaller	Generally larger

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