Introduction to Biology

stimuli/stimulus

a change in the environment producing a response

DNA

deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

gamete

specialized cell involved in sexual reproduction

genes

DNA segments that serve as the key functional units in hereditary transmission.

differentiation

process in which cells become specialized in structure and function

photosynthesis

Conversion of light energy from the sun into chemical energy.

cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

atoms

Basic unit of matter

molecule

A group of atoms bonded together

macromolecules

A very large organic molecule composed of many smaller molecules

organelle

A tiny cell structure that carries out a specific function within the cell

cell

The basic unit of structure and function in living things

tissue

A group of similar cells that perform the same function.

organ

A collection of tissues that carry out a specialized function of the body

organ system

A group of organs that work together in performing vital body functions.

organism

Any living thing

species

A group of similar organisms that can breed and produce fertile offspring.

population

A group of individuals that belong to the same species and live in the same area

community

All the different populations that live together in an area

ecosystem

A system formed by the interaction of a community of organisms with their physical environment

biosphere

Consists of all life on Earth and all parts of the Earth in which life exists, including land, water, and the atmosphere.

plasma membrane

a microscopic membrane of lipids and proteins that forms the external boundary of the cytoplasm of a cell and that regulates the passage of molecules in and out of the cytoplasm.

cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended

ribosome

Particles that synthesize proteins.

cell wall

A rigid structure that surrounds the cell membrane and provides support to the cell

nucleoid region

The region in a prokaryotic cell consisting of a concentrated mass of DNA.

capsule

A sticky layer that surrounds the cell walls of some bacteria, protecting the cell surface and sometimes helping to glue the cell to surfaces.

flagellum

A long, hairlike structure that grows out of a cell and enables the cell to move.

pili

Appendages that allow bacteria to attach to each other and to transfer DNA

nucleus

A part of the cell containing DNA and RNA and responsible for growth and reproduction

biodiversity

The number of different species in an area

bacteria

single-celled organisms that lack a nucleus; prokaryotes

archaea

One of two prokaryotic domains, the other being Bacteria.

eukarya

Domain of all organisms whose cells have nuclei, including protists, plants, fungi, and animals

phylogenetic tree

A family tree that shows the evolutionary relationships thought to exist among groups of organisms

binomial nomenclature

Classification system in which each species is assigned a two-part scientific name