Comprehensive Biology Key Concepts: Cells, Ecosystems, and Scientific Methods

Biology

The scientific study of life; all living things share a set of properties.

Properties of life

Order, energy and matter processing, reproduction, growth and development, response to the environment, evolutionary adaptations.

Biosphere

All life on Earth and the environments that support it.

Ecosystem

All living organisms in an area plus nonliving components (soil, air, sunlight).

Community

All interacting populations of organisms in an ecosystem.

Population

A group of individuals of one species living in a specific area.

Organism

An individual living being.

Organ system

Group of organs working together to perform a vital body function.

Organ

Multiple tissues cooperating to perform a specific task.

Tissue

Integrated group of similar cells working together for a function.

Cell

The basic unit of life; can be unicellular or multicellular.

Organelle

A component of a cell that performs a specific function.

Molecule

A group of atoms bonded together; DNA is an essential molecule.

Atom

Smallest unit of an element that retains its properties, made of subatomic particles.

Energy and matter pathways

Living organisms take in energy and matter, convert it to useful forms, and expel waste.

Structure and function

The shape of a component provides insight into its function (e.g., lungs have a branched structure for gas exchange).

Information flow

DNA stores information; cells communicate via molecules; genetic info passed to offspring drives evolution.

Evolution

Species that are similar share a common ancestor; explained by natural selection.

Scientific method

A series of steps to investigate questions about the natural world: observation, question, hypothesis, experiment, results, conclusion, repeat.

Hypothesis

A testable and falsifiable proposed explanation for a set of observations.

Theory

A well-substantiated, comprehensive explanation supported by evidence and never proven false.

Variable

An aspect of a study that changes from one round to the next.

Independent variable

The variable being changed or tested.

Dependent variable

The variable being measured as the effect of the independent variable.

Control group

Baseline group used for comparison in an experiment.

Positive control

A group where change is expected.

Negative control

A group where no change is expected.

Blind experiment

Some information about the experiment is withheld from participants.

Single-blind experiment

Only the participant is unaware of group assignment.

Double-blind experiment

Both the participant and experimenter are unaware of group assignment.

Placebo

A medically ineffective treatment used as a control in studies.

Bar graph

Used to compare categories of data; error bars indicate statistical confidence.

Line graph

Displays data changing continuously over time.

Pie chart

Represents percentages; total adds up to 100%.

Observational study

Scientists observe subjects without manipulating them.

Epidemiological study

Examines health differences between exposed and unexposed groups over time.

Human clinical trial

Controlled experiment testing treatment effects on humans, often randomized.

Critical thinking

Unbiased analysis and evaluation of information to form a judgment.

Science

Follows the scientific method, has repeatable results, testable claims, and multiple lines of evidence.

Pseudoscience

Claims falsely presented as scientific; cannot be replicated or tested.

Peer review

Evaluation of scientific work by experts in the field.

Primary source

Original report or data presented for the first time.

Secondary source

Summary of information not from the original experimenter.

Matter

Anything that occupies space and has mass.

Element

A basic substance that cannot be broken down.

Compound

A substance made from two or more elements (e.g., NaCl).

Reactants

Starting materials in a chemical reaction.

Products

Resulting substances from a chemical reaction.

Prokaryotic cell

Small, simple, no membrane-bound organelles, DNA not in