General Biology Study Guide: Themes of Biology, Scientific Method, and Chemistry of Life

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Chapter 1 – Themes of Biology and Scientific Method

Characteristics of Life

Biology is the scientific study of life, and living organisms share several key characteristics that distinguish them from non-living matter.

Reproduction: Ability to produce offspring.
Growth and Development: Increase in size and change in form during life.
Energy Use: Metabolism and use of energy for cellular processes.
Order: Highly ordered structure.
Regulation (Homeostasis): Maintenance of stable internal conditions.
Response to Environment: Reacting to stimuli.
Evolution: Populations change over time.
Cell: The smallest unit that displays all characteristics of life.

Example: Escherichia coli (E. coli) is a single cell that can reproduce, metabolize, and respond to its environment.

Unity and Diversity of Life

Life on Earth is unified by common ancestry and diversified by adaptation to different environments.

Unity: Shared traits like DNA, ribosomes, and genetic code.
Diversity: Differences arise from adaptation and natural selection.

Example: Darwin’s theory of evolution explains both unity (common ancestry) and diversity (adaptation).

Levels of Biological Organization

Life is organized into hierarchical levels, each with emergent properties.

Emergent Properties: New properties that arise at each step upward in the hierarchy due to arrangement and interactions of parts.
Examples: Photosynthesis in chloroplasts, brain function in head trauma.

Definitions of Each Level

Level	Definition
Biosphere	All ecosystems and living things on Earth
Ecosystem	All organisms in a given area plus abiotic factors
Community	All organisms inhabiting a particular area
Population	Group of individuals of the same species in an area
Organism	Individual living thing
Organ System	Group of organs working together
Tissue	Integrated group of cells with a function
Cell	Fundamental unit of structure and function
Organelle	Membrane-bound structure with specialized function
Molecule	Two or more atoms held together by bonds

Scientific Method and Hypothesis Testing

The scientific method is a systematic way to investigate natural phenomena.

Steps: Making observations, asking questions, forming hypotheses, making predictions, testing hypotheses, drawing conclusions.
Hypothesis: 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.

Example: "All living things are made of cells" is a scientific theory.

Experimental Design

Experiments test relationships between variables and require careful control.

Experimental Group: Receives the treatment.
Control Group: Does not receive the treatment.
Independent Variable: Factor manipulated by the researcher.
Dependent Variable: Factor measured in the experiment.
Controlling Variables: Ensures results are due to the independent variable.

Term	Definition
Independent Variable	x-axis on graphs; manipulated variable
Dependent Variable	y-axis on graphs; measured variable

Example: In a mouse experiment, the percentage of mice attacked is the dependent variable.

Energy and Matter in Ecosystems

Energy flows and matter cycles through ecosystems.

Energy: Transformed from light to chemical energy (photosynthesis), then lost as heat.
Matter: Cycles in ecosystems; never created or destroyed, only changes form.

Example: Photosynthesis converts sunlight into chemical energy in plants.

Chapter 2 – Chemistry of Life and Properties of Water

Chemical Reactions and Conservation of Matter

Chemical reactions rearrange atoms but do not create or destroy matter.

Reactants: Starting molecules in a reaction.
Products: Final molecules formed.

Example Equation:

Ions and Chemical Bonds

Ions are charged atoms or molecules. Chemical bonds form between ions or atoms.

Anion: Negatively charged ion (more electrons than protons).
Cation: Positively charged ion (more protons than electrons).
Ionic Bond: Attraction between oppositely charged ions (e.g., Na+ and Cl- in NaCl).

Atomic Structure and Periodic Table

Atoms consist of protons, neutrons, and electrons. The chemical behavior of an atom is determined by the number of electrons in its valence shell.

Isotopes: Atoms of the same element with different numbers of neutrons.
Big 4 Elements in Biology: Oxygen, carbon, nitrogen, hydrogen.

Electron Shell	Maximum Electrons
First shell	2
Second shell	8
Third shell	8

Example: Phosphorus has 5 electrons in its outer shell.

Chemical Bonds: Covalent, Ionic, and Hydrogen

Atoms form bonds to achieve stable electron configurations.

Covalent Bond: Atoms share pairs of electrons.
Ionic Bond: Attraction between oppositely charged ions.
Hydrogen Bond: Attraction between a hydrogen atom and an electronegative atom (e.g., oxygen).

Strength (in water): Covalent > Ionic > Hydrogen

Electronegativity and Bond Polarity

Electronegativity is the attraction of an atom for electrons in a covalent bond.

Most Electronegative Atom: Oxygen
Nonpolar Covalent Bond: Electrons shared equally.
Polar Covalent Bond: Electrons shared unequally; creates partial charges.

Example: Water (H2O) has polar covalent bonds.

Bonds in Water and Other Molecules

Water: Polar covalent bonds
CO2: Nonpolar covalent bonds
O2: Nonpolar covalent bonds

CO2 Emissions and Ecosystems

CO2 emissions affect marine life and ecosystems by causing ocean acidification and altering carbonate concentrations, which impacts organisms that rely on calcium carbonate for shells and skeletons.

Ocean Acidification: CO2 dissolves in seawater, forming carbonic acid and lowering pH.
Impact: Reduces carbonate ions needed by marine organisms.

Example: Coral reefs are threatened by increased CO2 emissions.

Additional info: Some definitions and examples were expanded for clarity and completeness.