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The site on an enzyme that attaches to a substrate


In the presence of oxygen


Without oxygen


An organism that produces its own nutrients from inorganic substances or from the environment instead of consuming other organisms


Any organic compound that is made of carbon, hydrogen and oxygen and that provides nutrients to the cells of living things

Cellular Respiration

The process by which cells obtain energy from carbohydrates, atmospheric oxygen combines with glucose to form water and carbon dioxide

Cell Theory

The theory that states that all living things are made up of one or more cells, that cells are the basic units of organisms, that each cell in a multicellular organism has a specific job


A green pigment that is present in most plant cells, that gives plants their characteristic green color, and that reacts with sunlight, carbon dioxide, and water to form carbohydrates


The force that holds molecules of a single material together


The loss of a part of DNA from a chromosome


The movement of particles from regions of higher density to regions of lower density


A type of protein or RNA molecule that speeds up metabolic reactions in plant and animals without being permanently changed or destroyed

Energy pyramid

An ecologic or trophic pyramid. A graphical representation designed to show the biomass or productivity at each trophic level in a given ecosystem


In biology, a state that exists when the concentration of a substance is the same throughout a space


An organism that obtains organic food molecules by eating other organisms or their byproducts and that cannot synthesize organic compounds from inorganic material


Describes a solution whose solute concentration is higher than the solute concentration inside a cell


Describes a solution whose solute concentration is lower than the solute concentration inside a cell


A large, nonpolar organic molecule, including fats ad steroids; lipids store energy and make up cell membranes


A method of viral replication in which a viral genome is replicated as a provirus without destroying the host cell


A method of viral replication that results in the destruction of a host cell and the release of many new virus particles


The diffusion of water or another solvent from a more dilute solution to a more concentrated solution through a membrane that is permeable to the solvent


A range of values that are used to express the acidity or alkalinity of a system; each whole number on the scale indicates a tenfold change in acidity; a pH of 7 is neutral, a pH of less than 7 is acidic; and a pH of greater than 7 is alkaline.


The process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce carbohydrates and oxygen


An organic compound that is made of one or more chains of amino acids and that is a principal component of all cells


The process of becoming adapted to an environment; an anatomical, physiological, or behavioral trait that improves an organism's ability to survive and reproduce

Adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species


An anatomical structure in one species that is similar in function and appearance, but not in evolutionary origin, to another anatomical structure in another species


A diagram that is based on patterns of shared, derived straits and that shows the evolutionary relationships between groups of organisms

Convergent evolution

The process by which unrelated species become more similar as they adapt to the same kind of environment

Derived Characteristic

A feature that evolved only within a particular taxonomic group

Divergent Evolution

The process by which two or more related but reproductively isolated populations become more and more dissimilar


In a modern taxanomic system, the broadest category; the category that contains kingdoms


A heritable change in characteristics within a population from one generation to the next; the development of new types of organisms from preexisting types of organisms over time


The death of every member of a species


A traditional taxonomic system, the highest taxonomic category which contains a group of similar phyla

Natural Selection

The process by which individuals are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do; a theory to explain the mechanism of evolution


The evolutionary history of a species or taxonomic group; the relationships of ancestry among species or taxonomic groups

Punctuated Equilibrium

A model of evolution in which short periods of drastic change in species, including mass extinctions and rapid specialization, are separated by long periods of little or no change


A group of organisms that are closely related and can mate to produce fertile offspring; also the level to classification below genus and above subspecies


An particular group within a taxonomic system


The science of describing, naming and classifying organisms


One of the alternative forms of a gene that governs a characteristic, such as hair color


One of the two strands of a chromosome that becomes visible during meiosis or mitosis


The exchange of genetic material between homologous chromosomes during meiosis; can result in genetic recombination


A cross between individuals that have different alleles for the same gene


A cell that contains two haploid sets of chromosomes

F1 Cross

A cross that yields the first generation of offspring obtained from an experimental cross of two organisms that are both true-breeding

F2 Cross

The second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation


The entire genetic makeup of an organism; also the combination of genes for one or more specific traits


Describes a cell, nucleus, or organism that has only one set of unpaired chromosomes


Describes an individual that has two different alleles for a trait


Describes an individual that has identical alleles for a trait on both homologous chromosomes

Incomplete Dominance

A condition in which a trait in an individual is intermediate between the phenotype of the individual's two parents because the dominant allele is unable to express itself fully


A micrograph of the array of chromosomes visible in a cell during metaphase; a graphical display that shows an individual's chromosomes arranged in homologous pairs and in order of diminishing size

Nitrogen base

An organic base that contains nitrogen, such as a purine or pyrimidine; a subunit of a nucleotide in DNA and RNA


In a nucleic-acid chain, a subunit that consists of a sugar, a phosphate, and a nitrogenous base


A diagram that shows the occurrence of a genetic trait in several generations of a family


An organism's appearance or other detectable characteristic that results from the organism's genotype and the environment


Describes a characteristic that is influenced by many genes


A nitrogenous base that has a double-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; either adenine or guanine


A nitrogenous base that has a single-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; thymine, cytosine or uracil

Recombinant DNA

DNA molecules that are artificially created by combining DNA from different sources


The four chromatids in a pair of homologous chromosomes that come together as a result of synapsis during meiosis


The crossing of an individual of an unknown genotype with a homozygous recessive individual to determine the unknown genotype


The process of forming a nucleic acid by using another molecule as a template; particularly the process of synthesizing RNA by using one strand of a DNA molecule as a template


The portion of protein synthesis that takes place at ribosomes and that uses the codons in mRNA molecules to specify the sequence of amino acids in polypeptide chains

Abiotic factor

An environmental factor that is not associated with the activities of living organisms

Acid rain

Precipitation, such as rain, sleet, or snow, that contains a high concentrations of acids, often because of the pollution of the atmosphere


A large region characterized by a specific type of climate and certain types of plant and animal communities

Biotic factors

An environmental factor that is associated with or results from the activities of living organisms


An organism that eats other organisms or organic matter instead of producing its own nutrients or obtaining nutrients from inorganic sources


A community of organisms and their abiotic environment

Food Chain

The pathway of energy transfer through various stages as a result of the feeding patterns of series of organisms


The place where an organisms usually lives


The unique position occupied by a species, both in terms of its physical use of its habitat ad its function within an ecological community

Ozone layer

The layer of the atmosphere at an altitude of 15 to 40 km in which ozone absorbs ultraviolet solar radiation


A group of organisms of the same species that live in a specific geographical area and interbreed


An organism that can make organic molecules from inorganic molecules; a photosynthetic or chemosynthetic autotroph that serves as the basic source in an ecosystem

Water Cycle

The continuous movement of water between the atmosphere, the land and the oceans

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