biology

Observation

process of noticing and describing events or processes in a careful, orderly way

Inference

a logical interpretation based on prior knowledge and experience

Hypothesis

possible explanation for a set of observations or possible answer to a scientific question

Controlled Experiment

experiment in which only one variable is changed

Independent Variable

factor in a controlled experiment that is deliberately changed; also called manipulated variable

Dependent Variable

variable that is observed and that changes in response to the independent variable; also called the responding variable

Control Group

group in an experiment that is exposed to the same conditions as the experimental group except for one independent variable

Data

evidence; information gathered from observations

Theory

well-tested explanation that unifies a broad range of observations and hypotheses, and enables scientists to make accurate predictions about new situations

Biology

scientific study of life

Sexual Reproduction

type of reproduction in which cells from two parents unite to form the first of a new organism

Asexual Reproduction

process of reproduction involving a single parent that results in offspring that are genetically identical to the parent

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.

Metabolism

the combination of chemical reactions through which an organism builds up or breaks down materials

Stimulus

a signal to which an organism responds

Homeostasis

relatively constant internal physical and chemical conditions that organisms maintain

Evolve

to change over time

Autotroph

organism that is able to capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer

Primary Producer

first producer of energy-rich compounds that are later used by other organisms

Consumer

organism that relies on other organisms for its energy and food supply; also called a heterotroph

Heterotroph

organism that obtains food by consuming other living things; also called a consumer

Food Chain

a series of steps in an ecosystem in which organisms transfer energy by eating and being eaten

Food Web

network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem

Trophic Level

each step in a food chain or food web

Habitat

area where an organism lives including the biotic and abiotic factors that affect it

Niche

full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions

Competitive Exclusion Principle

principle that states that no two species can occupy the same niche in the same habitat at the same time

Symbiosis

relationship in which two species live close together

Mutualism

symbiotic relationship in which both species benefit from the relationship

Commensalism

symbiotic relationship in which one organism benefits and the other is neither helped nor harmed

Parasitism

a symbiotic relationship in which one organism lives on or inside another organism and harms it

Ecological Succession

series of gradual changes that occur in a community following a disturbance

Primary Succession

succession that occurs in an area in which no trace of a previous community is present

Secondary Succession

type of succession that occurs in an area that was only partially destroyed by disturbances

Atom

the basic unit of matter

Nucleus

the center of an atom, which contains the protons and neutrons

Electron

negatively charged particle; located in the space surrounding the nucleus

Element

pure substance that consists entirely of one type of atom

Isotope

one of several forms of a single element, which contains the same number of protons but different numbers of neutrons

Compound

substance formed by the chemical combination of two or more elements in definite proportions

Ionic Bond

chemical bond formed when one or more electrons are transferred from one atom to another

Ion

atom that has a positive or negative charge

Covalent Bond

type of bond between atoms in which the electrons are shared

Molecule

smallest unit of most compounds that displays all the properties of that compound

Hydrogen Bond

weak attraction between a hydrogen atom and another atom

Adhesion

force of attraction between different kinds of molecules

Cohesion

attraction between molecules of the same substance

Mixture

material composed of two or more elements or compounds that are physically mixed together but not chemically combined

Solution

type of mixture in which all the components are evenly distributed

Solute

substance that is dissolved in a solution

Solvent

dissolving substance in a solution

Suspension

mixture of water and nondissolved material

pH Scale

scale with values from 0 to 14, used to measure the concentration of H+ ions in a solution; a pH of 0 to 7 is acidic, a pH of 7 is neutral, and a pH of 7 to 14 is basic

Acid

a compound that forms hydrogen ions (H+) in solution; a solution with a pH of less than 7

Base

a compound that produces hydroxide ions (OH-) in solution; a solution with a pH of more than 7

Buffer

a compound that prevents sharp, sudden changes in pH

Monomer

small chemical unit that makes up a polymer

Polymer

molecules composed of many monomers; makes up macromolecules

Carbohydrate

compound made up of carbon, hydrogen, and oxygen atoms; type of nutrient that is the major source of energy for the body

Lipid

macromolecule made mostly from carbon and hydrogen atoms; includes fats, oils, and waxes

Nucleotide

subunit of which nucleic acids are composed; made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base

Nucleic Acid

macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus

Protein

macromolecule that contains carbon, hydrogen, oxygen, and nitrogen; needed by the body for growth and repair

Amino Acid

compound with an amino group on one end and a carboxyl group on the other end

Chemical Reaction

process that changes, or transforms, one set of chemicals into another set of chemicals

Reactant

elements or compounds that enter into a chemical reaction

Product

elements or compounds produced by a chemical reaction

Activation Energy

energy that is needed to get a reaction started

Catalyst

substance that speeds up the rate of a chemical reaction

Enzyme

protein catalyst that speeds up the rate of specific biological reactions

Substrate

reactant of an enzyme-catalyzed reaction

Cell

basic unit of all forms of life

Cell Theory

fundamental concept of biology that states that all living things are composed of cells; that cells are the basic units of structure and function in living things; and that new cells are produced from existing cells

Cell Membrane

thin, flexible barrier that surrounds all cells; regulates what enters and leaves the cell

Eukaryote

organism whose cells contain a nucleus

Prokaryote

unicellular organism that lacks a nucleus

Cytoplasm

fluid portion of the cell outside the nucleus

Organelle

specialized structure that performs important cellular functions within a eukaryotic cell

Ribosome

cell organelle consisting of RNA and protein found throughout the cytoplasm in a cell; the site of protein synthesis

Smooth Endoplasmic Reticulum

internal membrane system found in eukaryotic cells; place where lipid components of the cell membrane are assembled and does not have ribosomes on its membrane

Rough Endoplasmic Reticulum

internal membrane system found in eukaryotic cells; place where lipid components of the cell membrane are assembled and does have ribosomes on its membrane

Golgi Apparatus

organelle in cells that modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell

Lysosome

cell organelle that breaks down lipids, carbohydrates, and proteins into small molecules that can used by the rest of the cell

Cytoskeleton

network of protein filaments in a eukaryotic cell that gives the cell its shape and internal organization and is involved in movement

Chloroplast

organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy

Mitochondrion

cell organelle that converts the chemical energy stored in food into compounds that are more convenient for the cell to use

Cell Wall

strong, supporting layer around the cell membrane in some cells

Lipid Bilayer

flexible double-layered sheet that makes up the cell membrane and forms a barrier between the cell and its surroundings

Selectively Permeable

property of biological membranes that allows some substances to pass across it while others cannot; also called semipermeable membrane

Homeostasis

relatively constant internal physical and chemical conditions that organisms maintain

Diffusion

process by which particles tend to move from an area where they are more concentrated to an area where they are less concentrated

facilitated diffusion

process of diffusion in which molecules pass across the membrane through cell membrane channels

Aquaporin

water channel protein in a cell

Osmosis

diffusion of water through a selectively permeable membrane

Isotonic

when the concentration of two solutions is the same

Hypertonic

when comparing two solutions, the solution with the greater concentration of solutes

Hypotonic

when comparing two solutions, the solution with the lesser concentration of solutes

Osmotic Pressure

pressure that must be applied to prevent osmotic movement across a selectively permeable membrane