energy needed to start a chemical reaction; lowered by enzymes
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active transport
movement of molecules across a membrane requiring energy to be expended by the cell
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adaptation
inherited characteristic that increases an organism's chance of survival
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allele
the different forms of a gene; could be dominant or recessive
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amino acid
basic building blocks of proteins
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analogous structures
structures that do not have a common evolutionary origin but are similar in form or function
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anaphase
the third phase of mitosis, during which the chromosome pairs separate and move toward opposite poles
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antibiotic
compound that blocks the growth and reproduction of bacteria
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antibody
a substance produced by the body that destroys or inactivates a pathogen that has entered the body
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antigen
substance (usually foreign) that stimulates the production of an antibody
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archaea
domain of unicellular prokaryotes that have cell walls that do not contain peptidoglycan
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ATP
a nucleotide that stores and transfers energy within cells
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autotroph
organism that can capture energy from sunlight or chemicals and use it to produce its own food; also called a producer
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bacteria
domain of unicellular prokaryotes that have cell walls containing peptidoglycans
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bacteriophage
virus that infects bacteria
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base deletion
mutation which results in the loss of nucleotide pairs in a gene; have a major effect on the resulting protein
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base insertion
mutation which results in the addition of nucleotide pairs in a gene; have a major effect on the resulting protein
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base-pair substitution
a type of point mutation where one nucleotide and its partner are replaced by another pair of nucleotides
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behavioral adaptation
an inherited behavior that helps an organism survive; like escaping from predators or find a mate
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binary fission
asexual reproduction in prokaryotes by which one cell divides into two identical cells
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fetus
an unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal
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fever
a rise in the temperature of the body
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fitness
the ability of an individual to survive and reproduce in its specific environment
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food chain
a series of steps in which organisms transfer energy by eating and being eaten
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food web
a diagram that shows the feeding relationships between organisms in an ecosystem
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fossil
the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil
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gamete
egg or sperm sex cell that contains a single set of chromosomes (haploid), one from each homologous pair
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gene
sequence of DNA that codes for a protein and thus determines a trait
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binomial nomenclature
Classification system in which each species is assigned a two-part scientific name including the genus and species
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biodiversity
the variety of different species in a given area
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biogeochemical cycle
process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from one part of the biosphere to another; like the carbon and nitrogen cycle
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biomass
the total amount of living matter within a given trophic level
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capsid
the outer covering of protein surrounding the nucleic acid of a virus
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carbohydrate
organic compound used by cells to store and release energy; composed of carbon, hydrogen, and oxygen
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carbon cycle
the organic circulation of carbon from the atmosphere into organisms and back again
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carnivore
a consumer that only eats other consumers
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catalyst
substance that speeds up the rate of a chemical reaction; like an enzyme
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cell
basic unit of life
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cell cycle
the cycle of growth and reproduction of a cell, consisting of interphase (g1, s, g2) and mitosis (division of the nucleus-prophase, metaphase, anaphase, and telophase) and cytokinesis (division of cytoplasm)
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cell division
the process by which a cell divides into two new daughter cells
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cell membrane
The lipid bilayer that forms the outer boundary of the cell
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cell wall
a rigid structure that surrounds the cell membrane and provides support to the cell; made of carbohydrates
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cellular respiration
process that releases energy by breaking down glucose and other food molecules in the presence of oxygen
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centriole
organize the spindle fibers to separate chromosomes during animal cell mitosis
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centromere
area where the chromatids of a chromosome are attached
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chlorophyll
green pigment in plants that absorbs light energy used to carry out photosynthesis
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chloroplast
organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy
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chromatid
one of two identical "sister" parts of a duplicated chromosome
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gradualism
a model of evolution in which gradual change over a long period of time leads to biological diversity
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guard cell
Pairs of cells that surround stomata and control their opening and closing.
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habitat
the place where an organism lives
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haploid number
half the normal number of chromosomes; found in sex cells
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herbivore
consumer that eats only producers; also called a primary consumer
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heterozygous
having two different alleles for a trait
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homeostasis
process by which organisms maintain a relatively stable internal environment
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chromosome
condensed threads of genetic material formed from chromatin as a cell prepares to divide
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climax community
a relatively stable long-lasting community reached in a successional series
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codon
in RNA, a three-base "word" that codes for one amino acid
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commensalism
symbiotic relationship in which one member of the association benefits and the other is neither helped nor harmed
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competition
the struggle between organisms to survive in a habitat with limited resources
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concentration gradient
difference in concentration of a substance on two sides of a membrane
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conclusion
a summary of what you have learned from an experiment
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consumer
an organism that obtains energy by feeding on other organisms
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crossing over
exchange of genetic material between homologous chromosomes during prophase I of meiosis
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cytokinesis
division of the cytoplasm
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cytoplasm
a jellylike fluid inside the cell in which the organelles are suspended
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data
information gathered from observations
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decomposer
organism that breaks down and obtains energy from dead organic matter
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deforestation
the removal of trees
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differentiation
process in which cells become specialized in structure and function
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diffusion
the process by which molecules move from an area of higher concentration to an area of lower concentration; passive
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dihybrid cross
genetic cross using two traits with two alleles each
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diploid number
cell condition in which two of each type of chromosome are present
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disturbance
A discrete event that disrupts an ecosystem or community. Examples of natural disturbances include fires, hurricanes, tornadoes, droughts, and floods. Examples of human-caused disturbances include deforestation, overgrazing, and plowing.
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DNA
deoxyribonucleic acid, the material that contains the information that determines inherited characteristics
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kingdom
large taxonomic group, consisting of closely related phyla
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learned behavior
a behavior an animal learns from its parents
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lipid
macromolecule made mainly from carbon and hydrogen atoms; includes fats, oils, and waxes
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lysosome
cell organelle filled with enzymes needed to break down certain materials in the cell
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macromolecule
any large complex organic molecule
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meiosis
Cell division that produces reproductive cells in sexually reproducing organisms
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mRNA
messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome
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metaphase
second phase of mitosis, during which the chromosomes line up across the center of the cell
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domain
Most inclusive taxonomic category; larger than a kingdom
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dominant
trait that will show up in an organism's phenotype if gene is present
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double helix
two strands of nucleotides wound about each other; structure of DNA
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ecological succession
gradual change in living communities that follows a disturbance
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ecosystem
living and nonliving things in an environment, together with their interactions
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egg
Female sex cell
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embryo
organism in its early stage of development
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embryology
study of multicellular organisms as they develop from fertilized eggs to fully formed organisms
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endocytosis
process by which a cell takes in a substance by surrounding it with the cell membrane; active transport
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endoplasmic reticulum
a system of membranes that is found in a cell's cytoplasm and that assists in the production, processing, and transport of proteins and in the production of lipids
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energy pyramid
a diagram that shows the amount of energy that moves from one feeding level to another in a food web
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enzyme
protein that speeds up a chemical reaction
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equilibrium
When the concentration of a solute is the same throughout a solution
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eukaryote
A cell that contains a nucleus and membrane bound organelles
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eutrophication
rapid growth of algae in bodies of water, due to high levels of nitrogen and often phosphate
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evolution
the gradual change in a species over time
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exocytosis
process by which vesicles release their contents outside the cell; active transport