| A | B | 
| Organ | An anatomical unit composed of tissues serving a common function. | 
| Organ System | anatomical system composed of a group of organs that work together | 
| Organelle | A subunit within a cell that has a specialized function. | 
| Organic Molecule | A molecule containing carbon that is a part of or produced by living systems. | 
| Organism | A form of life; an animal, plant, fungus, protist or bacterium. | 
| Osmosis | movement of H2O through membranes from an area of higher concentration to an area of lower concentration | 
| Passive Transport | The transportation of materials across a plasma membrane without using energy. | 
| pH | measure of acidity or alkalinity (basicity) of an aqueous solution | 
| Phenotype | The observable expression of a genotype. | 
| Photosynthesis | process in which solar radiation is chemically captured by chlorophyll molecules | 
| Plasma Membrane | thin, phospholipid and protein molecule bilayer that encapsulates a cell | 
| Plastids | group of membrane‐bound organelles commonly found in photosynthetic organisms, responsible for storage of food | 
| Point Mutation | A single‐base substitution causing the replacement of a single‐base nucleotide with another nucleotide | 
| Polygenic Trait | A trait in which the phenotype is controlled by two or more genes on different chromosomes. | 
| Population | A group of individuals of the same species living in a specific geographical area and reproducing. | 
| Population Dynamics | study of short‐ and long‐term changes in the number of individuals for a given population, | 
| Principle (Scientific) | A concept based on scientific laws and axioms (rules assumed to be present, true, and valid) | 
| Producer (Ecological) | An organism that uses a primary energy source to conduct photosynthesis | 
| Prokaryote | A single‐celled organism that lacks a membrane‐bound nucleus and specialized organelles. | 
| Protein | A macromolecule that performs a variety of structural and regulatory functions for cells | 
| Protein Synthesis | process in which amino acids are arranged in a linear sequence | 
| Pumps (Ion or Molecular) | mechanisms in which ions/molecules are transported across a membrane, requires energy | 
| Punctuated Equilibrium | Occasionally there are rapid changes that affect some species which can quickly result in a new species. |