| antibiotic | A chemical that kills bacteria or slows their growth without harming the body cells of humans |
| asexual reproduction | The reproductive process that involves only one parent and produces offspring that are identical to the parent |
| bacterium | A single-celled organism that is a prokaryote; it belongs to one of two kingdoms- Archaebacteria and Eubacteria |
| binomial nomenclature | The naming system for organisms in which each organism is given a two part name- a genus and species |
| classification | The process of grouping things based on their similarities |
| decomposer | An organism that breaks down large chemicals from dead organisms into small chemicals and returns important materials to the soil and water |
| flagellum | A long, whiplike structure that helps an unicellular organism move |
| genus | A classification grouping that consists of a number of similar, closely related species |
| infectious disease | A disease that can pass from one organism to another |
| parasite | An organism that lives on or in a host and causes harm to the host |
| sexual reproduction | The reproductive process that involves two parents who combine their genetic material to produce a new organism, which differs from both parents |
| species | A classification grouping that consists of members who can mate and produce fertile offpsring. |
| taxonomic key | A series of paired statements that describe the physical characteristics of different organisms |
| vaccine | A substance used in a vaccination that consists of pathogens that have been weakened or killed but can still trigger the immune system response |
| virus | A small, nonliving particle that invades and then reproduces inside a living cell |