Intro to Cellular and Molecular Biology Terms

Life

The ability of an entity made of cells to conduct metabolism, sense changes in the environment and respond, and reproduce, and for populations to evolve

Metabolism

The chemical reactions and other processes that enable organisms to take in resources and process them in ways that make growth and reproduction possible

Organism

A living thing

Evolution

A change in the genetic characteristics of a population/change in allele frequencies

Fossil record

Any trace of an organism that lived in the past

Adaptation

A heritable trait that increases the ability to survive and reproduce in a particular environment

Natural selection

The process that changes allele frequencies when certain heritable traits are associated with different levels of reproductive success

Directional selection

Natural selection that favors an extreme phenotype

Stabilizing selection

Natural selection that favors the average phenotype in the population and acts against extreme phenotypes

Theory

An explanation or set of hypotheses that attempt to explain a large and pervasive phenomenon, they tie together a large suite of observations about how the natural world works

Fitness

The ability to produce viable offspring

Artificial selection

When humans actively select which individuals will be the parents of the next generation

Element

A distinct type of substance or matter, each element has atoms that contain a unique number of protons in the nucleus

Atom

The fundamental unit of an element, made of protons, neutrons and electrons

Ion

An atom or molecule that carries a full charge—positive if it contains more protons than electrons and negative if it contains more electrons than protons

Molecule

A structure made of two or more atoms held together by covalent bonds

Covalent bond

An attraction between two atoms based on shared electrons

Electronegativity

The tendency for an atom’s nucleus to attract the shared electrons in a covalent bond

Polar covalent bond

An asymmetry in the position of shared elections due to differences in the electronegativities of the atoms involved that creates a partial positive charge on one atom and a partial negative charge on the second atom

Nonpolar covalent bond

Equal sharing of electrons due to equal or roughly equal electronegativities of the atoms involved

Hydrogen bond

An attraction between a partial positive charge on a hydrogen atom and a partial negative charge on another atom