Life Science Vocabulary: Unit 2
PART ONE:
Organism: a living thing
Cell: the basic unit of structure and function in living things
Unicellular: an organism with one single cell
Multicellular: an organism with many cells
Stimulus: a change in an organisms surroundings that causes the organism to
react
Response: An action or change in behavior that occurs in reaction to a stimulus
Development: the process of change that occurs during an organism’s life to
produce a more complex organism
Spontaneous Generation: the mistaken idea that living things arise from nonliving sources
Homeostasis: the maintenance of stable internal conditions in an organism
Classification: the process of grouping things based on their similarities
Taxonomy: the scientific study of how living things are classified
Binomial Nomenclature: the system for naming organisms in which each
organism is given a unique, two-part scientific name
Genus: a classification grouping that consists of a number of similar, closely
related species (the first part of the name ALWAYS STARTS WITH A CAPITAL
LETTER)
Species: a group of organisms that are physically similar and can mate and
produce offspring that can also mate and reproduce (the second part of the name
always with a lowercase letter)
PART TWO:
Prokaryote: an organism whose cells lack a nucleus and some other cell
structures
Eukaryote: an organism whose cells contain nuclei
Cell Theory: a widely accepted explanation of the relationship between cells and
living things
Organelle: a tiny cell structure that carries out a specific function within a cell
Cell Wall: a ridged layer of nonliving material that surrounds the cells of plants
and some other organisms
Cell Membrane: the outside cell boundary that controls which substances can
either enter or leave a cell
Cytoplasm: the material within a cell apart from the nucleus
Mitochondria: rod-shaped cell structures that convert energy in food molecules
to energy the cell can use to carry out its functions
Endoplasmic Reticulum: a cell structure that forms passageways in which
proteins and other materials are carried through the cell
Ribosome: a small grain-like structure in the cytoplasm of a cell where proteins
are made
Golgi Body: a structure in a cell that receives proteins and other newly formed
materials from the endoplasmic reticulum, packages them, and distributes them
to other parts of the cell
Chloroplast: a structure in the cells of plants and other organisms that captures
energy from sunlight and uses it to produce food
Vacuole: a sac inside a cell that acts as a storage area
Lysosome: a small, round cell structure containing chemicals that break down
large food particles into smaller ones
Nucleus: the control center of a eukaryotic cell that directs the cell’s activities
and contains the information that determines the cell’s form and function
PART THREE:
Element: any substance that cannot be broken down into simpler substances
Compound: 2 or more elements that are chemically combined
Carbohydrate: an energy-rich organic compound made of the elements carbon,
hydrogen, and oxygen
Lipid: energy-rich organic compound, such as fat, oil, or wax, that is made of
carbon, hydrogen, and oxygen
Protein: large organic molecule made of carbon, hydrogen, oxygen, nitrogen,
and some sulfur
Amino Acid: a small molecule that is linked chemically to other amino acids to
form proteins
Enzyme: a protein that speeds up chemical reactions in living things
Nucleic Acid: very large organic molecule made up of carbon, oxygen, hydrogen,
nitrogen, and phosphorus, that contains the instructions cells need to carry out
all the functions of life
DNA: deoxyribonucleic acid; the genetic material that carries information about
an organism and is passed from parent to offspring
RNA: ribonucleic acid; a nucleic acid that plays an important role in the
production of proteins
Selectively Permeable: a property of cell membranes that allow some substances
to pass through while others cannot
Diffusion: the process by which molecules move from an area of higher
concentration to an area of lower concentration
Osmosis: the diffusion of water molecules through a selectively permeable
membrane
Passive Transport: the movement of materials through a cell membrane without
using the cell’s energy
Active Transport: the movement of materials through a cell membrane using
energy
PART FOUR
Photosynthesis: the process in which some organisms use water along with
sunlight and carbon dioxide to make their own food
Autotroph: an organism that makes its own food
Heterotroph: an organism that cannot make its own food
Chlorophyll: a green pigment found in the chloroplasts of plants, algae, and
some bacteria
Stomata: small openings on a leaf through which oxygen and carbon dioxide
move
Pigment: a colored chemical that absorbs light