A widespread occurrence of an infectious disease in a community at a particular time
a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron, but of opposite sign
A substance that cannot be broken down into simpler substances by chemical means
An infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host
has mass and takes up space
a group of organisms belonging to the same species that live in a particular area. May be described by their size, density, or distribution
a stable subatomic particle with a charge of negative electricity, found orbiting the nucleus of an atom
a crack in the earth's crust resulting from the displacement of one side with respect to the other
the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it
The substance that is dissolved in a solution
the name given to a horizontal row of the periodic table
an organism, either a green plant or bacterium, which is part of the first level of a food chain
the chemical processes that occur within a living organism in order to maintain life
repair and growth; a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth
reproduction; a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores
a subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen
the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock
A substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, its products, or a synthetic substitute, treated to act as an antigen without inducing the disease