General Biology Study Guide: Life, Chemistry, Cells, and Membranes (Chapters 1-2)

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Chapter 1 – Themes of Biology and Scientific Method

Characteristics of Life

Biology is the study of living organisms and their interactions with the environment. All living things share certain characteristics that define life.

Reproduction: The ability to produce offspring.
Growth and Development: Organisms increase in size and complexity.
Energy Use: Living things obtain and use energy for metabolism.
Order: Living things have organized structures.
Regulation (Homeostasis): Maintenance of stable internal conditions.
Response to the Environment: Ability to sense and react to stimuli.
Evolution: Populations change over generations.
The Cell: The basic unit of life.

Unity and Diversity of Life

Life on Earth is both unified and diverse. Unity is demonstrated by shared traits (e.g., DNA, ribosomes, genetic code), while diversity arises from evolutionary processes such as natural selection.

Evolution: The process by which different kinds of living organisms develop and diversify from earlier forms.
Common Ancestry: Shared traits indicate descent from a common ancestor.

Levels of Biological Organization

Biological systems are organized into a hierarchy from molecules to the biosphere.

Level	Definition
Biosphere	All life on Earth and all places where life exists.
Ecosystem	All living things in a particular area, plus nonliving components with which they interact.
Community	All organisms in an ecosystem.
Population	Individuals of the same species in a given area.
Organism	An individual living thing.
Organ System	Group of organs working together.
Organ	Body part with a specific function.
Tissue	Group of similar cells performing a function.
Cell	Smallest unit of life.
Organelle	Membrane-bound structure with specialized function.
Molecule	Chemical structure of two or more atoms.

Emergent Properties

Emergent properties are new characteristics that arise at each level of organization due to the arrangement and interactions of parts.

Example: Photosynthesis occurs in chloroplasts, not in individual molecules.
Example: The brain can process information, but individual neurons cannot.

The Scientific Method

The scientific method is a systematic approach to understanding the natural world.

Steps: Observation, hypothesis formation, prediction, experimentation, data collection, analysis, and conclusion.
Hypothesis: A testable explanation for a set of observations, must be falsifiable and testable.
Scientific Theory: Broader in scope than a hypothesis, supported by a large body of evidence.

Experimental Design

Experiments are designed to test hypotheses by manipulating variables and controlling conditions.

Independent Variable: The factor manipulated by the researcher (x-axis).
Dependent Variable: The factor measured in response (y-axis).
Control Group: The group not exposed to the experimental treatment, used for comparison.
Experimental Group: The group exposed to the treatment.

Controlling variables ensures that results are due to the independent variable, not other factors.

Energy and Matter in Ecosystems

Energy flows through ecosystems, while matter cycles within them.

Energy: Enters as sunlight, converted to chemical energy by producers, transferred through food webs, and lost as heat.
Matter: Cycles between living and nonliving components; is not created or destroyed.

Chapter 2 – Chemistry of Life and Properties of Water

Chemical Reactions and Matter

All matter is composed of elements, which combine to form compounds through chemical reactions.

Chemical Reaction: Process in which chemical bonds are broken and reformed, producing new substances.
Reactants: Starting materials in a reaction.
Products: Substances formed from a reaction.
Conservation of Matter: Atoms are not created or destroyed in chemical reactions.

Example Equation:

Ions and Chemical Bonds

Anion: Negatively charged ion (gains electrons).
Cation: Positively charged ion (loses electrons).
Ionic Bond: Attraction between oppositely charged ions.
Covalent Bond: Sharing of electron pairs between atoms.
Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom.

Bond Strength (in water): Covalent > Ionic > Hydrogen

Atomic Structure and Elements

Atoms: Composed of protons, neutrons, and electrons.
Isotopes: Atoms of the same element with different numbers of neutrons (e.g., carbon-13, carbon-14).
Major Elements in Life: Oxygen, carbon, nitrogen, hydrogen.
Electron Shells: First shell holds 2 electrons, second and third hold up to 8 each.

Valence Electrons and Chemical Behavior

The chemical behavior of an atom is determined by the number of electrons in its valence shell.

Valence Electrons: Electrons in the outermost shell, involved in bonding.
Example: Phosphorus has 5 electrons in its valence shell.

Electronegativity

Electronegativity is the attraction of an atom for electrons in a covalent bond. Oxygen is typically the most electronegative atom in organic molecules.

Properties of Water

Water's unique properties are essential for life:

Cohesion: Water molecules stick together via hydrogen bonds.
Adhesion: Water molecules stick to other substances.
High Specific Heat: Water resists temperature change.
High Heat of Vaporization: Large amount of energy needed to convert water from liquid to gas.
Solvent Properties: Water dissolves many substances due to its polarity.

These properties support processes such as temperature regulation, nutrient transport, and chemical reactions in living organisms.