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797 terms

Biology Praxis II Study

Biology: Principles & Explorations Holt, Rinehart, and Winston
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biology
The study of life.
cells
Highly organized, tiny structures with thin coverings called membranes. The smallest unit capable of life functions.
reproduction
The process by which organisms make more of their own kind from one generations to the next.
metabolism
The sum of all chemical reactions carried out in an organism. Almost all energy used by living organisms is captured from sunlight.
homeostasis
The maintenance of stable internal conditions despite changes in the external environment.
genes
Sets of inherited instructions for making proteins. Control when proteins are made and what proteins are made.
heredity
The passing of traits from parent to offspring.
mutation
A change in the DNA of a gene.
evolution
Change in the inherited traits of a species over time.
species
A group of genetically similar organisms that can produce fertile offspring.
natural selection
The process in which organisms with favorable genes are more likely to survive and reproduce.
ecology
The science that studies the interactions of living organisms with one another and with the nonliving part of their environment.
HIV
A virus that destroys the immune system, causing acquired immune deficiency disorder, or AIDS.
cystic fibrosis
A fatal disorder in which abnormally thick mucus builds up in many organs, including the lungs. Caused by a defective gene.
cancer
A growth disorder of cells that occurs when cells divide uncontrollably in the body.
observation
The act of noting or perceiving objects or events using the senses.
hypothesis
An explanation that might be true-a statement that can be tested by additional observations or experimentation.
prediction
The expected outcome of a test, assuming the hypothesis is correct.
pH
A description of how acidic a solution is. Measured on a scale of 0-14 with 7 being neutral. Solutions measuring below 7 are more acidic and those measuring above 7 are more basic.
experiment
A planned procedure to test a hypothesis.
control group
A group in an experiment that receives no experimental treatment.
independent variable
The factor that is varied in an experiment.
dependent variable
The variable that is measured in an experiment.
theory
A set of related hypotheses that have been tested and confirmed many times by many scientists.
atom
The smallest unit of matter than cannot be broken down by chemical means.
element
A substance made of only one kind of atom, and therefore a pure substance.
compound
A substance made of the joined atoms of two or more different elements.
molecule
A group of atoms held together by covalent bonds.
ion
a charged atom or molecule that has lost or gained one or more electrons.
cohesion
Attraction between substances of the same kind.
adhesion
Attraction between different substances.
solution
A mixture in which one or more substances are evenly distributed in another substance.
acids
Compounds that form hydrogen ions when dissolved in water.
bases
Compounds that reduce the concentration of hydrogen ions in a solution.
carbohydrate
Organic compounds made of carbon, hydrogen, and oxygen atoms in the proportion of 1:2:1.
monosaccharides
The building blocks of carbohydrates: simple sugars such as glucose and fructose.
lipids
Nonpolar molecules that are not soluble in water including fats, phospholipids, steroids, and waxes.
protein
A chain of amino acids linked together and folded into compact shapes.
amino acids
Molecules that are the building blocks of proteins.
nucleic acid
A long chain of smaller molecules called nucleotides.
nucleotide
Has three parts: a sugar, a base, and a phosphate group, which contains phosphorous and oxygen atoms.
DNA
Deoxyribonucleic acid. Consists of two strands of nucleotides that spiral around each other. The two strands are held together by hydrogen bonds between bases across from one another. Make up chromosomes.
RNA
Ribonucleic acid. Consists of a single strand of nucleotides. Plays several roles in cell function, including the manufacture of proteins.
ATP
Adeonsine triphosphate. A single nucleotide with two extra energy-storing phosphate groups. The main energy currency of cells.
energy
The ability to move or change matter.
activation energy
The energy needed to start a chemical reaction.
enzymes
Substances that increase the speed of chemical reactions. Most are proteins.
substrate
A substance on which an enzyme acts during a chemical reaction.
active sites
The pockets formed by the folds in a protein enzyme.
light microscope
A microscope in which light passes through one or more lenses to produce an enlarged image of a specimen.
electron microscope
A microscope which forms an image of a specimen using a beam of electrons.
magnification
The ability to make an image appear larger than its actual size.
resolution
A measure of the clarity of an image.
scanning tunneling microscope
Uses a needle-like probe to measure differences in voltage caused by electrons that leak, or tunnel, from the surface of the object being viewed.
cell theory
1. All living things are made of one or more cells.
2. Cells are the basic units of structure and function in organisms.
3. All cells arise from existing cells.
cell membrane
The outer boundary of a cell. Encloses the cell and separates the cell interior, called the cytoplasm, from its surroundings. Regulates what enters and leaves a cell-including gases, nutrients, and waste.
cytoplasm
The interior of a cell.
cytoskeleton
A system of microscopic fibers in which the structures inside a cell are suspended.
ribosomes
The cellular structures on which proteins are made.
prokaryote
A single-celled organism that lacks a nucleus and other internal compartments. The modern version would be a bacterium.
cell wall
In bacteria, fungi, and plants, surrounds the cell membrane providing structure and support.
flagella
Long, threadlike structures that protrude from the cell's surface and enable movement.
eukaryote
An organism whose cells have a nucleus.
nucleus
An internal compartment that houses the cell's DNA.
organelle
A structure that carries out specific activities in the cell.
cilia
Short hairlike structures protruding from the surface of some eukaryotic cells.
phospholipid
A lipid made of a phosphate group and two fatty acids.
lipid bilayer
A double layer of phospholipids. This arrangement forms the cell membrane.
endoplasmic reticulum
An extensive system of internal membranes that move proteins and other substances through the cell. It is made of a lipid bilayer with embedded proteins.
vesicle
A small, membrane-bound sac that transports substances in cells.
golgi apparatus
A set of flattened, membrane-bound sacs that serves as the packaging and distribution center of the cell.
lysosomes
Small, spherical organelles that contain the cell's digestive enzymes.
mitochondria
An organelle that harvests energy from organic compounds to make ATP.
chloroplasts
Organelles that use light energy to make carbohydrates from carbon dioxide and water.
central vacuole
A large, membrane-bound space taking up much of the space of a plant cell. When full it presses the cytoplasm against the cell wall, making the cell rigid, which enables plants to stand upright.
passive transport
Movement across the cell membrane that does not require energy from the cell.
concentration gradient
A difference in the concentration of a substance across a space.
equilibrium
A condition in which the concentration of a substance is equal throughout a space.
diffusion
The movement of a substance from an area of high concentration to an area of lower concentration caused by the random motion of particles of the substance.
osmosis
The diffusion of water through a selectively permeable membrane.
hypertonic solution
A solution that causes a cell to shrink because of osmosis.
hypotonic solution
A solution that causes a cell to swell because of osmosis.
isotonic solution
A solution that produces no change in cell volume because of osmosis.
ion channel
A doughnut shaped transport protein with a polar pore through which ions can pass.
carrier protein
A transport protein that can bind to a specific substance on one side of the cell membrane, carry the substance across the cell membrane, and release it on the other side.
facilitated diffusion
Transport of substances through a cell membrane down a concentration gradient aided by carrier proteins.
active transport
The transport of a substance across the cell membrane against its concentration gradient.
sodium-potassium pump
In a complete cycle transports three sodium ions, Na+, out of a cell and two potassium ions, K+, into the cell.
endocytosis
The movement of a substance into a cell by a vesicle.
exocytosis
the movement of a substance by a vesicle to the outside of a cell.
receptor protein
A protein that binds to a specific signal molecule, enabling the cell to respond to the signal molecule.
second messenger
A signal molecule in the cytoplasm.
photosynthesis
The process by which light energy is converted to chemical energy.
autotrophs
Organisms that use energy from sunlight or inorganic substances to make organic compounds.
heterotrophs
Organisms that must get energy from food instead of directly from sunlight or inorganic substances.
cellular respiration
A metabolic process similar to burning fuel. Releases much of the energy in food to make ATP.
pigments
Light-absorbing substances.
chlorophyll
The primary pigment involved in photosynthesis. Absorbs mostly blue and red light and reflects green and yellow light.
carotenoids
Pigments that produce yellow and orange fall leaf colors, as well as the colors of many fruits, vegetables and flowers. Absorbs wavelengths of light different from those absorbed by chlorophyll.
thylakoids
Disk-shaped structures in the membranes of plants where clusters of pigments are stored.
electron transport chains
The series of molecules through which excited electrons are passed along a thylakoid membrane.
NADPH
An electron carrier that provides the high energy electrons needed to make carbon-hydrogen bonds in the third stage of photosynthesis.
carbon dioxide fixation
The transfer of carbon dioxide to organic compounds.
aerobic
Metabolic process that require oxygen.
anaerobic
Metabolic processes that do not require oxygen.
glycolysis
A process in which glucose is broken down in the cytoplasm. An enzyme-assisted anaerobic process that breaks down one six-carbon molecule of glucose to two three-carbon pyruvates.
NADH
An electron carrier formed when a glucose is broken down, transferring some of its hydrogen atoms to an electron receptor called NAD+.
krebs cycle
A series of enzyme-assisted reactions involving Acetyl-CoA that produces electron carriers that temporarily store energy.
FADH2
An electron carrier created during the Krebs cycle.
fermentation
The recycling of NAD+ using an organic hydrogen acceptor.
gametes
An organism's reproductive cells, such as sperm or egg cells.
binary fission
A form a sexual reproduction that produces identical offspring.
gene
A segment of DNA that codes for a protein or RNA molecule.
chromosome
A coiled structure containing long strands of DNA and proteins.
chromatids
The two exact copies of DNA that make up each chromosome.
centromere
The point where to two chromatids of a chromosome are attached.
homologous chromosomes
Chromosomes that are similar in size, shape, and genetic content.
diploid
When a cell, such as a somatic cell, contains two sets of chromosomes.
haploid
When a cell, such as a gamete, contains one set of chromosomes.
zygote
A fertilized egg cell, the first cell of a new individual.
autosomes
Chromosomes that are not directly involved in determining the sex of an individual.
sex chromosome
One of the 23 pairs of chromosomes in humans containing genes that will determine the sex of the individual.
karyotype
A photo of the chromosomes in a dividing cell that shows the chromosomes arranged by size.
cell cycle
A repeating sequence of cellular growth and division during the life of an organism.
interphase
The first three phases of the cell cycle occurring before mitosis and cytokinesis.
mitosis
The process during cell division in which the nucleus of a cell is divided into two nuclei.
cytokinesis
The process during cell division in which the cytoplasm divides.
spindles
Cell structures made up of both centrioles and individual microtubule fibers that are involved in moving chromosomes during cell division.
meiosis
A form of cell division that halves the number of chromosomes when forming specialized reproductive cells, such as gametes or spores.
crossing-over
Occurs when portions of a chromatid on one homologous chromosome broken and exchanged with the corresponding portions on one of the chromotids of the other homologous chromosome.
independent assortment
The random distribution of homologous chromosomes during meiosis.
spermatogenesis
The process by which sperm are produced in male animals.
sperm
Male gametes.
oogenesis
The process by which gametes are produced in female animals.
ovum
The female gamete, more commonly known as an egg.
asexual reproduction
Reproduction in which a single parent passes copies of all of its genes to each of its offspring.
clone
An individual produced by asexual reproduction.
sexual reproduction
Reproduction in which two parents each form haploid reproductive cells.
life cycle
The entire span in the life of an organism from one generation to the next.
fertilization
A process in which the gametes (sperm and egg cells) join during the diploid life cycle.
sporophyte
In plants, the diploid phase in the life cycle that produces spores.
spore
A haploid reproductive cell produced by meiosis that is capable of developing into an adult without fusing with another cell.
gametophyte
The haploid phase that produces gametes by mitosis.
heredity
The passing of traits from parents to offspring.
genetics
The branch of biology that focuses on heredity.
monohybrid cross
A cross that involves one pair of contrasting traits.
true-breeding
Breeding in which all of the offspring display only one form of a particular trait.
P generation
the first of two individuals that are crossed in a breeding experiment.
F1 generation
The first offspring of the P generation.
F2 generation
The offspring resulting from the self-pollination of the F1 generation.
alleles
The different versions of a gene.
dominant
The expressed form of a trait.
recessive
The trait not expressed when the dominant form of the trait is present.
homozygous
An individual in which the two alleles of a particular gene present are the same.
heterozygous
An individual in which the alleles of a particular gene present are different.
genotype
The set of alleles that an individual has.
phenotype
The physical appearance of a trait.
law of segregation
The two alleles for a trait segregate (separate) when gametes are formed.
law of independent assortment
The alleles of different genes separate independently of one another during gamete formation.
punnett square
A diagram that predicts the expected outcome of a genetic cross by considering all possible combinations of gametes in the cross.
test cross
A cross in which an individual whose phenotype is dominant, but whose genotype is not known, is crossed with a homozygous recessive individual.
probability
The likelihood that a specific event will occur.
pedigree
A family history that shows how a trait is inherited over several generations.
sex-linked trait
A trait whose allele is located on the X chromosome. Most are recessive.
polygenic trait
A trait that is influenced by several genes.
incomplete dominance
When an individual displays a trait that is intermediate between the two parents.
codominance
When two dominant alleles are expressed at the same time and both forms of the trait are displayed.
multiple alleles
Genes with three or more alleles.
vaccine
A substance that is prepared from killed or weakened microorganisms and is introduced into the body to protect the body against future infections by the microorganisms.
virulent
Able to cause disease.
transformation
A change in phenotype caused when bacterial cells take up foreign genetic material.
bacteriophage
Also referred to as phage, viruses that infect bacteria.
double helix
Two strands twisted around each other, like a winding staircase.
nucleotides
The subunits that make up DNA.
deoxyribose
The five carbon sugar in DNA molecules.
base-pairing rules
The pairing arrangement of the nitrogen bases between the two strands of a DNA molecule.
complementary
The state of two bases in DNA which must be paired. The sequence of bases on one strand determines the sequence of bases on the other strand.
DNA replication
The process of making a copy of DNA
DNA helicases
Enzymes that are responsible for unwinding the double helix of a DNA molecule.
replication forks
The two areas on either end of the DNA where the double helix separates.
DNA polymerases
Enzymes that move along each of the DNA strands during replication, adding nucleotides to the exposed nitrogen bases, according to the base-pairing rules.
RNA
Ribonucleic acid. A nucleic acid - a molecule made of nucleotides linked together.
uracil
A nitrogen base found in RNA nucleotides.
transcription
A process in which instructions for making a protein are transferred from a gene to an RNA molecule.
translation
A process in which cells use two different types of RNA to read the instructions on an RNA molecule and put together the amino acids that make up a protein.
gene expression
The process by which proteins are made based on the information encoded in DNA - also known as protein synthesis.
RNA polymerase
An enzyme that adds and links complementary RNA nucleotides during transcription.
messenger RNA
A form of RNA that carries the instructions for making a protein from a gene and delivers it to the site of translation.
codons
A series of three-nucleotide sequences on an mRNA molecule on which RNA instructions are written.
genetic code
The amino acids and "start" and "stop" signals that are coded for by each of the possible 64 mRNA codons.
transfer RNA
Single strands of RNA that temporarily carry a specific amino acid on one end.
anticodon
A three-nucleotide sequence on a tRNA that is complementary to an mRNA codon.
ribosomal RNA
RNA molecules that are part of the structure of ribosomes.
operator
The piece of DNA that overlaps the promoter site and serves as the on-off switch.
operon
A group of genes that code for enzymes involved in the same function, their promoter site, and the operator that controls them all functioning together in a bacterium.
lac operon
The operon that controls the metabolism of lactose.
repressor
A protein that binds to an operator and physically blocks RNA polymerase from binding to a promoter site.
introns
Long segments of nucleotides that have no coding information.
exons
The portions of a gene that are translated (expressed) into proteins.
point mutations
Mutations that change one or just a few nucleotides in a gene on a chromosome.
genetic engineering
The process of manipulating genes for practical purposes.
recombinant DNA
DNA made from two or more different organisms.
restriction enzymes
Bacterial enzymes that recognize and bind to specific short sequences of DNA, and then cut the DNA between specific nucleotides within the sequences.
vector
An agent that is used to carry a gene of interest into another cell.
plasmids
Circular DNA molecules that can replicate independently of the main chromosomes of bacteria.
gene cloning
A process in which many copies of a gene of interest are made each time the host cell reproduces.
electrophoresis
A technique that uses an electrical field within a gel to separate molecules by their size and charge.
probes
Radioactive or fluorescent-labeled RNA or single-stranded DNA pieces that are complementary to the gene of interest.
vaccine
A solution containing all or part of a harmless version of a pathogen (disease-causing microorganism).
gene therapy
A technique that involves putting a healthy copy of a gene into the cells of a person whose copy of the gene is defective.
DNA fingerprint
A pattern of dark bands on a photographic film that is made when an individual's DNA fragments (RFLPs) are separated by gel electrophoresis, probed, and then exposed to an X-ray film.
human genome project
A project to determine the nucleotide sequence of the entire human genome and to map the location of every gene on each chromosome.
transgenic animals
Animals that have foreign DNA in their cells.
radiometric dating
The calculation of the age of an object by measuring the proportions of the radioactive isotopes of certain elements.
radioisotopes
Unstable elements (parent) that break up and give off energy in the form of charged particles (radiation).
half-life
The time it takes for one-half of a given amount of a radioisotope to change.
spontaneous origin
The process through which life is thought to have developed when molecules of nonliving matter reacted chemically during the first billion years of Earth's history.
microspheres
Tiny vesicles into which short chains of amino acids tend to gather.
fossil
The preserved or mineralized remains (bone, tooth, or shell) or imprint of an organism that lived long ago.
cyanobacteria
Photosynthetic bacteria.
eubacteria
Prokaryotes that contain a chemical called peptidoglycan in their cell walls and have the same type of lipids in their cell membranes as eukaryotes.
archaebacteria
Prokaryotes that lack peptidoglycan in their cell walls and have unique lipids in their cell membranes.
endosymbiosis
The theory proposing that mitochondria are the descendants of symbiotic, aerobic eubacteria.
protists
Members of the kingdom Protista, a large, varied group that includes both multicellular and unicellular organisms.
mass extinction
The death of all members of many different species, usually caused by a large ecological disaster.
mycorrhizae
Associations between fungi and the roots of plants.
mutualism
A relationship in which both organisms benefit.
arthropod
A kind of animal with a hard outer skeleton and jointed limbs.
vertebrates
Animals with a backbone.
continental drift
The movement of Earth's land masses over geologic time.
population
All the individuals of a species that live together in one place at one time.
natural selection
The process by which populations change in response to their environment. By surviving long enough to reproduce, individuals have the opportunity to pass on their favorable characteristics to offspring. In time, the favorable characteristics will increase in a population, and the nature of the population will gradually change.
adaptation
The changing of a species that results in its being better suited to its environment.
isolation
The condition in which two populations of the same species cannot breed with one another.
paleontologists
Scientists who study fossils.
vestigial structures
Bones or other structures present in an organism that are reduced in size and either have no use or have a less important function.
homologous structures
Structures that share a common ancestry.
gradualism
The model of evolution in which gradual changes over a long period of time lead to species formation.
punctuated equilibrium
The model of evolution in which periods of rapid change in species are separated by periods of little or no change.
industrial melanism
The darkening of populations of organisms over time in response to industrial pollution.
divergence
The accumulation of differences between groups.
speciation
The process by which new species form.
ecological races
Populations of the same species that differ genetically because of adaptations to different living conditions.
reproductive isolation
The inability of formerly interbreeding groups to mate or produce fertile offspring.
primates
The mammalian group that includes prosimians, monkeys, apes, and humans.
prosimian
A member of a group of mostly night-active primates that live in trees. Includes lorises, lemurs, and tarsiers.
diurnal
The pattern of being active at day and sleeping at night.
antropoids
Monkeys, together with apes and humans.
opposable thumb
A thumb that stands out at an angle from the other fingers and can be bent inward toward them to hold an object.
hominids
Primates that can walk upright on two legs.
bipedal
Able to walk upright on two legs.
taxonomy
The science of naming and classifying organisms.
binomial nomenclature
A two-word system for naming organisms. Consists of the genus followed by the species names.
genus
A taxonomic category containing similar species.
family
A taxonomic category containing similar genera.
order
A taxonomic category containing similar families.
class
A taxonomic category containing similar orders.
phylum
A taxonomic category containing similar classes.
kingdom
A taxonomic category containing similar phyla.
biological species
A group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.
convergent evolution
Evolution in which organisms evolve similar features independently, often because they live in similar habitats.
analogous characters
Similar features that evolved through convergent evolution.
phylogeny
The evolutionary history of a species.
cladistics
A system of taxonomy that reconstructs phylogenies by inferring relationships based on similarities.
derived traits
Unique characteristics found in a particular group of organisms.
cladogram
A branching diagram constructed from patterns of shared derived traits.
evolutionary systematics
A subjective analysis of evolutionary relationships.
population
All the individuals of a species that live together in one place at one time.
population size
The number of individuals in a population.
population density
The number of individuals that live in a given area.
dispersion
The way individuals of a population are arranged in space.
population model
A hypothetical population that attempts to exhibit the key characteristics of a real population.
exponential growth curve
A curve in which the rate of population growth stays the same, as result the population size increases steadily.
carrying capacity
(K) The population size that an environment can sustain.
density-dependent factors
Resources such as food and water for which a population model can be adjusted. The rate at which they become depleted depends upon the the population density of the population that uses them.
logistic model
A population model in which exponential growth is limited by a density-dependent factor.
density-independent factors
Environmental conditions such as weather and climate which limit growth but are not dependent on population density.
r-strategists
Species that grow exponentially when environmental conditions allow them to reproduce.
k-strategists
Populations that grow slowly and have small population sizes. Their population density is usually near the carrying capacity (K) of their environment.
Hardy-Weinberg principle
States that the frequency of alleles in a population do not change unless evolutionary forces act on the population.
gene flow
The movement of alleles into or out of a population due to the movement of individuals to or from a population, called migration.
nonrandom mating
A situation in which individuals mate with others that live nearby or are of their own phenotype.
genetic drift
Random changes in allele frequency in a population.
polygenic trait
A trait that is influenced by several genes.
normal distribution
A graph with a hill-shaped curve.
directional selection
A form of selection that causes the frequency of a particular trait to move in one direction.
stabilizing selection
A form a selection eliminating extremes at both ends of a range of phenotypes.
ecology
The study of the interactions of living organisms with one another and with their physical environment (soil, water, climate, and so on).
habitat
The place where a particular population of a species lives.
community
The many different species that live together in a habitat.
ecosystem
Consists of a community and all the physical aspects of its habitat, such as the soil, water, and weather. Also called an ecological system.
abiotic factors
The physical aspects of a habitat.
biotic factors
The living organisms in a habitat.
biodiversity
A measure of the number of species living within an ecosystem.
pioneer species
The first organisms to live in a new habitat. Typically small, fast-growing plants.
succession
A somewhat regular progression of species replacement.
primary succession
Succession that occurs where plants have not grown before.
secondary succession
Succession that occurs in areas where there has been previous growth, such as in abandoned fields or forest clearings.
primary productivity
The rate at which organic material is produced by photosynthetic organisms in an ecosystem.
producers
Organisms that first capture energy. Include plants, some kinds of bacteria, and algae. They make energy-storing molecules.
consumers
Those organisms that consume plants or other organisms to obtain the energy necessary to build their molecules.
trophic level
A group of organisms that have the same source of energy; a step in a food chain.
food chain
The path of energy through the trophic levels of an ecosystem.
herbivores
Animals that eat plants or other primary producers. Animals at the second trophic level.
carnivores
Animals that eat herbivores. Animals at the third trophic level.
omnivores
Animals that are both herbivores and carnivores.
detritivores
Organisms that obtain their energy from the organic waste and dead bodies that are produced at all trophic levels.
decomposers
Organisms that cause decay. Include bacteria and fungi.
food web
A complicated, interconnected group of food chains.
energy pyramid
A diagram in which each trophic level is represented by a block, and the blocks are stacked on top of one another, with the lowest trophic level on the bottom.
biomass
The dry weight of tissue and other organic matter found in a specific ecosystem.
biogeochemical cycle
cycle in which a substance, such as carbon or water, enters into an environment's living reservoir where it remains for a certain period of time and is returned to a nonliving reservoir.
ground water
water retained beneath the surface of the Earth.
transpiration
The process by which water evaporates from the leaves of plants after having passed through the plant.
nitrogen fixation
The process of combining nitrogen with hydrogen to form ammonia.
coevolution
Back-and-forth evolutionary adjustments between interacting members of an ecosystem.
predation
The act of one organism feeding on another.
parasitism
A special case of predation in which one organism feeds on and usually lives on or in another, typically larger, organism.
secondary compounds
Defensive chemicals in plants used to discourage herbivores.
symbiosis
In which two or more species live together in close, long-term associations.
mutualism
A symbiotic relationship in which both participating species benefit.
commensalism
A symbiotic relationship in which one species benefits and the other is neither harmed nor helped.
competition
Ecological interaction between two or more species that use the same scare resource such as food, light and water.
niche
The functional role of a particular species in an ecosystem.
fundamental niche
The entire range of conditions an organism is potentially able to occupy within an ecosystem.
realized niche
The part of its fundamental niche that a species occupies.
competitive exclusion
The elimination of a competing species. If two species are competing, the species that uses the resource more efficiently will eliminate the other.
biodiversity
The variety of living organisms present in a community.
climate
The prevailing weather conditions in any given area.
biome
A major biological community that occurs over a large area of land.
littoral zone
In a pond or lake, a shallow zone near the shore.
limnetic zone
In a pond or lake, the area that is farther away from the shore but close to the surface.
profundal zone
In a pond or lake, a deep-water zone that is below the limits of effective light penetration.
plankton
Bacteria, algae, fish larvae, and certain species of small animals drifting freely in the upper waters of the ocean.
acid rain
Rain and snow carrying sulfuric acid to Earth's surface. Coal burning power plants send smoke into the atmosphere. The smoke contains sulfur which combines with water vapor to create the sulfuric acid.
chlorofluorocarbons
Chemicals once used as a heat exchanger but found to be destroying the ozone layer.
greenhouse effect
The warming of the atmosphere that results from greenhouse gases.
biological magnification
Process by which molecules passing upward through the trophic levels of a food chain become increasingly concentrated.
aquifer
Porous rock reservoirs in which ground water is stored.
colonial organism
A group of cells that are permanently associated but that do not communicate with one another.
aggregation
A temporary collection of cells that come together for a period of time and then seperate.
multicellular organism
An organism composed of many cells that are permanently associated with one another, such as green algae.
differentiation
The process by which cells become specialized in form and function.
protists
Members of the kingdom Protista. Defined on the basis that they are eukaryotes that are not fungi, plants, or animals.
hyphae
slender filaments that are part of the body of a multicellular fungus.
septum
In fungi, a wall-like division between cells within a hypha; wall that internally divides body segments in annelids.
tissues
Distinct types of cells with a common structure and function.
organs
Specialized structures with specific functions into which tissues are organized.
organ systems
The various organs that carry out major body functions.
vascular tissue
A group of specialized cells that transport water and dissolved nutrients.
invertebrates
Animals that lack a backbone.
vertebrates
Animals with backbones.
virsues
Segments of nucleic acids contained in a protein coat.
capsid
The virus protein coat. May contain either RNA or DNA, but not both.
envelope
A membrane surrounding the capsid in a virus.
glycoproteins
Proteins with attached carbohydrate molecules that are derived from the host cell of a virus. Along with proteins and lipids they compose the envelope in a virus.
bacteriophages
Viruses that infect bacteria.
pathogen
Any agent that causes diseases.
lytic cycle
The cycle of viral infection, replication, and cell destruction.
provirus
The viral gene inserted into a host chromosome by a virus.
lysogenic cycle
Cycle in which a viral genome replicates as a provirus without destoring the host cell.
emerging viruses
Viruses that evolve in geographically isolated areas and are pathogenic to humans.
prions
Infectious particles composes of proteins with no nucleic acid.
viroid
A single strand of RNA that has no capsid.
pilus
a short, thick outgrowth on bactera which enables them to attach to surfaces or other surfaces.
bacillus
One of the basic shapes of a bacterium. A rod-shaped cell.
coccus
One of the basic shapes of a bacterium. A round-shaped cell.
spirillum
One of the basic shapes of a bacterium. A spiral cell.
capsule
A gel-like layer outside of the cell wall and membrane of a bacterium.
antibiotics
Chemicals that interfere with life processes in bacteria.
endospore
dormant bacterial cell enclosed by a tough coating that is highly resistant to environmental stress.
conjugation
A process in which two bacterium adhere to another bacterium.
anaerobic
Processes that do not require oxygen.
aerobic
Processes that require oxygen.
toxins
Chemicals secreted by bacteria that cause disease.
protozoa
Heterotrophic protists.
algae
Photosynthetic protists.
zygospore
Diploid zygote that results from the pairing of gametes of opposite mating types.
alternation of generations
A reproductive cycle characterized by two distinct multicellular phases: a diploid, spore-producing phase, called the sporophyte generation, and a haploid, gamete-producing phase, called the gametophyte generation.
sporangia
Reproductive cells of an adult sporophyte algae.
amoebas
Members of the phylum Rhizopoda; protists that move by using flexible, cytoplasmic extensions.
pseudopodia
Flexible, cytoplasmic extensions used by certain protists for movement.
diatom
Members of the phylum Bacillariophyta; photosynthetic, unicellular protists with unique double shells.
zoomastigotes
Members of the phylum Zoomastigina; unicellular heterotrophs that have at least one flagellum.
euglenoids
Members of the phylum Euglenophyta; freshwater protists with two flagella.
cilia
Tightly packed rows of short flagella used for movement.
plasmodium
A mass of cytomplasm that looks like an oozing slime.
sporozoite
One of three stages of Plasmodium that lives in mosquitoes and is injected into humans. Infects the lliver where they divide rapidly producing millions of cells.
merozoite
The second stage of Plasmodium in humans. Infects red blood cells and divide rapidly.
chitin
Tough polysaccharide found in the walls of fungi and the hard outer covering of insects.
hyphae
The slender filaments composing the bodies of all fungi except yeast.
mycelium
A tangled mass formed when hyphae grow.
zygosporangia
Thick-walled sexual structures found in members of the phylum Zygomycota.
stolons
The mycelia that grow along the surface of bread.
rhizoids
The hyphae that anchor the fungus in the bread.
ascus
A saclike structure in which haploid spores are formed in ascomycetes.
yeast
Unicellular ascomycetes.
budding
A form of asexual reproduction in which a small cell forms from a large cell and pinches itself off from the large cell.
basidium
The club-shaped sexual reproductive structure for which the basidiomycetes are named. Spores are produced on this structure.
mycorrhiza
A type of mutualistic relationship formed between fungi and vascular plant roots.
lichen
A symbiosis between a fungus and a photosynthetic partner such as a green alga, a cyanobacterium, or both.
cuticle
A waxy layer that covers the nonwoody aboveground parts of most plants. Does not let oxygen or carbon dioxide pass through it. Reduces water loss.
stomata
Pores that permit plants to exchange oxygen and carbon dioxide.
guard cells
Specialized cells that border each stomata.
vascular system
A system of well-developed vascular tissues that distributes water and other materials in plants.
nonvascular plants
Relatively small plants with no vascular system.
vascular plants
Plants that have a vascular system.
seed
A structure that contains the embryo of a plant.
embryo
An early stage in the development of plants and animals.
seed plants
Vascular plants that produce seeds.
flower
A reproductive structure that produces pollen and seeds.
phloem
Type of vascular tissue in plants that contains soft-walled conducting cells through which organic compounds are transported throughout the body of a plant.
xylem
Type of vascular tissue in plants that contains hard-walled conducting cells that transport water and dissolved minerals upward from the roots to the leaves.
shoot
The part of a plant's body that grows mostly upward.
root
The part of a plant's body that grows downward.
meristems
Zones of actively dividing plant cells.
rhizoids
Hairlike projections in nonvascular plants that anchor gametophytes to the surfaces on which they grow.
rhizomes
Horizontal underground stems found in early seedless vascular plants.
fronds
The roots and leaves in ferns that anchor rhizomes.
cone
Clusters of nongreen spore-bearing leaves found in some species of club moss.
gymnosperms
Seed plants whose seeds do not develop within a sealed container (a fruit).
angiosperms
Flowering plants which produce seeds that develop while they are enclosed within a specialized structure.
fruits
The structures in which the seeds of angiosperms develop.
endosperm
The supple of stored food used by the seeds of angiosperms at some time during their development.
monocots
Flowering plants that produce seeds with one seed leef (cotyledon).
dicots
Flowering plants that produce seeds with two seed leaves (cotyledons).
vegetative part
Any nonreproductive part of a plant.
cereals
Grasses that are grown as food for human and livestock.
grain
A type of edible, dry fruit produced by cereal grasses.
archegonium
reproductive structure that produces eggs in seedless plants.
anteridium
reproductive structure that produces sperm in seedless plants.
sorus
A cluster of sporangia on a fern frond.
pollen grain
Structure consisting of a few haploid cells surrounded by a thick protective wall that contains a male gametophyte of a seed plant.
ovule
Structure of a seed plant sporophyte in which a female spore forms and then develops into a female gametophyte that contains an egg; structure in the ovary of a pistil that develops into a seed.
pollination
Transportation of pollen grains from a male reproductive structure of a flower to a female reproductive structure of a flower.
pollen tube
Structure that grows from a pollen grain to an ovule, enabling a sperm to pass directly to an egg.
seed coat
The protective, outer covering of a seed.
cotyledon
Leaflike structures of a plant embryo functions in the transfer of stored nutrients to the embryo, in which food is stored.
sepal
Structure of a flower that encloses and protects a flower bud.
petal
Structure of a flower that is often colorful and may attract pollinators to the flower.
stamen
Male reproductive part of a flower.
anther
Sac at the tip of a stamen in which pollen grains form.
pistil
Female reproductive part of a flower; consisting of an ovary, style, and stigma.
ovary
Reproductive structure that produces eggs; in flowering plants, the lower part of a pistil that produces eggs in ovules.
double fertilization
Process by which two sperm fuse with cells of the female gametophyte, producing both a diploid (2n) zygote and a triploid (3n) endosperm.
vegetative reproduction
The reproduction of plants from vegetative parts.
plant propagation
Growing new plants from seed or from vegetative parts.
tissue culture
A technique in which pieces of plant tissue are placed on a sterile medium and used to grow new plants.
dermal tissue
Tissue that forms the protective outer layer of a plant.
ground tissue
Tissue that makes up much of the inside of the nonwoody parts of a plant, including roots, stems, and leaves.
epidermis
The "skin" on the nonwoody parts of a plant formed from dermal tissue.
cork
Several layers of dead cells that form the dermal tissue on woody stems and roots of plant.
vessel
Conducting strand in xylem that consists of a series of vessel cells stacked end to end.
sieve tube
The conducting strands in phloem.
cortex
The ground tissue surrounding the vascular tissue in plants.
root hair
Extension of an epidermal cell near the root tip that aids in the absorption of water.
root cap
A mass of cells that covers and protects the actively growing root tip.
herbaceous plant
A plant with stems that are flexible and usually green.
vascular bundle
Bundles of xylem and phloem found in herbaceous plants.
pith
The ground tissue inside the ring of vascular bundles in herbaceous plants.
heartwood
The wood in the center of a mature stem of tree trunk.
sapwood
Wood that lies outside the heartwood and contain vessel cells that can conduct water.
petiole
A stalk which attaches the blade to the stalk in leaves.
mesophyll
The ground tissue in leaves.
transpiration
The loss of water vapor from a plant.
source
A part of a plant that provides organic compounds for other parts of the plant.
sink
A part of a plant that organic compounds are delivered to.
translocation
The movement of organic compounds within a plant from a source to a sink.
germination
Resumption of growth by the plant embryo in a seed.
perennial
A plant that lives for several years.
annual
A plant that completes its life cycle (grows, flowers, and produces fruits and seeds) and then dies within one growing season.
biennial
A flowering plant that takes two growing seasons to complete its life cycle.
primary growth
Growth that increases the length of height of a plant.
secondary growth
Growth that increases the width of stems and roots.
apical meristem
Structures located at the tips of stems and roots and produce primary primary growth through cell division.
cork cambium
A meristem that lies within the bark and produces cork cells.
vascular cambium
A meristem that lies under the bark and produces vascular tissues.
annual ring
Layers of secondary xylem, or wood, that form each year producing rings.
mineral nutrients
Elements absorbed mainly as inorganic ions. Plants require small amounts of 13 of these.
auxin
The growth-promoting chemical that causes stems to bend.
hormone
A chemical that is produced in one part of an organism and transported to another part, where it causes a response.
apical dominance
Inhibition of lateral bud growth on the stem of a plant by auxin produced in the terminal bud.
tropism
A response in which a plant grows either toward or away from a stimulus.
photoperiodism
The response of a plant to the length of days and nights.
dormancy
The condition in which a plant or a seed remains inactive, even when conditions are suitable for growth.
blastula
Hollow ball of cells that gives rise to all the tissues and organs of an adult body.
ectoderm
In animals, the outer layer of embryonic tissue from which the skin and nervous system develop.
endoderm
Inner layer of embryonic tissue from which the digestive organs develop in animals.
mesoderm
Middle Layer of embryonic tissue in animals from which the skeleton and muscles develop.
body plan
An animal's shape, symmetry, and internal organization.
asymmetrical
Irregular in shape.
radial symmetry
Arrangement of body parts around a central axis.
bilateral symmetry
Arrangement of body parts so there are distinct left and right halves that mirror each other
cephalization
In bilaterally symmetric animals, the development of a head end with a concentration of nerves and sensory structures.
coelom
Fluid-filled body cavity that forms between the body wall and the digestive tract.
acoelomate
An animal that lacks a coelom, or body cavity.
pseudocoelomate
Animal with a body cavity located between the endoderm and the mesoderm.
coelomate
Animal with a body cavity located entirely within the mesoderm.
phylogenetic tree
Branching diagram that shows how animals are related through evolution.
gastrovascular cavity
A digestive cavity with only one opening.
respiration
The uptake of oxygen and the release of carbon dioxide.
gill
Extremely thin projections of tissue that are rich in blood vessels, providing a large surface for gas exchange.
open circulatory system
System in which blood leaves the blood vessels and bathes the body's tissues.
closed circulatory system
System in which the blood does not leave the blood vessels and materials diffuse across the walls of the vessels.
hydrostatic skeleton
A framework for supporting a body consisting of water that is contained under pressure in a closed cavity, such as a gastrovascular cavity or a coelom.
exoskeleton
A rigid external skeleton that encases the body of an animal.
hermaphrodites
Animals with both testes and ovaries.
external fertilization
Fertilization that occurs when animals release the male and female gametes near one another in the water.
internal fertilization
Fertilization in which the union of the sperm and egg occurs within the female's body.
endoskeleton
A skeleton composed of a hard material, such as bone, embedded within an animal.
ostia
Tiny pores on sponges through which water enters.
oscula
Larger openings on sponges through which water exits.
sessile
Describes an organism that remains attached to a surface for its entire life.
choanocyte
A layer of flagellated cells lining the internal cavity of a sponge. Also called collar cells.
amoebocyte
Sponge cells that have irregular amoeba-like shapes.
spongin
A resilient, flexible protein fiber that makes of the skeletons of most sponges.
spicule
Tiny needs of silica or calcium carbonate that make of the skeletons of some sponges.
gemmule
Clusters of amoebocytes encased in protective coats formed by sponges during harsh living conditions to ensure their survival.
medusa
Free-floating forms of cnidarians that are jellylike and often umbrella shaped.
polyp
Tubelike forms of cnidarians that are usually attached to a rock or some other object.
cnidocytes
Stinging cells found on the tentacles of cnidarians.
nematocyst
A small barbed harpoon located within each cnidocyte of a chindarian.
basal disk
An area of the body on animals of the genus Hydra which produces a sticky secretion used to attach to rocks or water plants.
planulae
Free swimming larvae developed from medusa zygotes.
proglottid
Rectangular body sections produced for growth by tapeworms.
fluke
Parasitic worms of the largest flatworm class, Trematoda.
tegument
A thick protective covering of cells found on endoparasites and used to avoid being digested by their host.
trochophore
A larval stage in mollusks and annelids which develops from a fertilized egg.
visceral mass
A central section of a mollusk that contains the mollusk's organs.
mantle
A heavy fold of tissue that wraps around the visceral mass in mollusks.
foot
A muscular region in mollusks that is used primarily for locomotion.
radula
A rasping tongue-like organ located in the mouth s of all mollusks except bivalves.
nephridia
Tiny tubular structures into which coelomic fluid is pulled by beating cilia in mollusks.
adductor muscle
Two thick muscles connecting the valves of bivalves. These muscles contract they cause the valves to close tightly.
siphon
Hollow tubes used by bivalves for processing sea water.
cerebral ganglion
A primitive brain located in one anterior segment of an annelid.
septa
Internal body walls that separate the segments of most annelids.
seta
External bristles found on most annelids.
parapodium
Fleshy appendages on some annelids.
appendage
Structures that extend from the arthropod's body wall.
thorax
The mid-body region.
cephalothorax
A body region consisting of a head fused with a thorax.
compound eye
An eye made of thousands of individual units, each with its own lens and retina.
molting
A process in which an arthropod sheds and discards its exoskeleton periodically so that it may grow.
trachea
A network of fine tubes through which most terrestrial arthropods respirate.
spiracle
Structures through which air enters into an arthropod's trachea.
Malpighian tubule
Slender, fingerlike extensions from the arthropod's gut that are bathed by the blood that surrounds them.
chelicerae
Mouthparts in members of the subphylum Chelicerata that are modified into fangs or pincers.
pedipalps
Appendages on members of the subphylum Chelicerata that are modified to catch and handle prey.
spinneret
Specially modified appendages on spiders that secrete sticky strands of silk.
mandible
Chewing mouthparts found in terrestrial athropods (subphylum Uniramia).
metamorphosis
Dramatic physical change through which an immature organism passes as it grows to adulthood.
chrysalis
Protective capsule enclosing the transforming larva in insects.
pupa
Stage of complete metamorphosis in which an insect changes from larva to adult.
nymph
Juvenile stage of some insects that is a smaller version of the adult.
caste
Role played by an individual insect in a colony.
nauplius
Larval form of a crustacean.
krill
Small marine crustacean that is the chief food source for many marine species.
blastopore
Opening in the gastrula of protosomes that develops into a mouth.
protostome
An animal whose mouth develops from or near the blastospore. the opening in the gastrula.
deuterostome
An animal whose anus forms form the blastospore.
ossicle
Calcium-rich plates that compose the endoskeleton of echinoderms.
water-vascular system
Water-filled system of interconnected canals and tube feet that aids echinoderms in movement.
skin gill
Small, fingerlike projections that grow between the spines of echinoderms.
chordate
Deuterostome with a completely internal endoskeleton, notochord, pharyngeal slits, and post anal tail.
notochord
Flexible rod of tissue along the back of a chordate that aids in locomotion.
pharyngeal slit
Opening in the wall of the pharynx in chordates.
invertebrate chordate
chordates without a backbone; tunicates and lancelets.
vertebrae
The individual segments of a backbone.
agnathans
The earliest fishes. Had neither jaws nor paired fins.
acanthodians
Spiny fishes. Appeared about 430 million years ago. Had strong jaws with jagged bony edges that served as teeth.
cartilage
A lightweight, strong, flexible, tissue.
terrestrial
Having to do with land.
thecodont
An extinct group of crocodile-like reptiles from which dinosaurs evolved.
pangea
A single giant supercontinent in which all the continents were joined during the time of dinosaurs.
ectothermic
Animals whose metabolism is too slow to produce enough heat to warm their bodies. Such animals must absorb heat from their environment, and their body temperature changes as the temperature of their environment changes.
endothermic
Animals that maintain a high, constant body temperature by producing heat internally through a faster metabolism.
therapsids
An extinct order of reptiles that were probably endotherms and from which mammals evolved.
gill filament
Fingerlike projections from a gill where respiratory gases enter and leave the blood.
gill slit
Opening at the rear of a fish's cheek cavity where water exits.
countercurrent flow
Arrangement in fish respiratory system where water going over the gills and blood in the gill filaments flows in opposite directions.
nephron
Tubelike structure in the kidneys that filters wastes from the body and retains useful molecules; also regulates the body's salt and water balance.
lateral line
Specialized sensory system running the length of both sides of a fish's body.
operculum
Hard plate that covers the gills on each side of the head of bony fishes.
swim bladder
The gas-filled sac of bony fishes used to regulate their buoyancy.
teleost
Group of bony fishes with highly mobile fins, thin scales, a swim bladder, and symmetrical tails; largest group of living fishes.
lung
Internal, baglike respiratory organ of a vertebrate that enables gas exchange between the air and the blood.
pulmonary vein
Vessel that carries oxygen-rich blood from the lungs to the heart.
septum
Thick wall that divides the heart's atrium or ventricle into right and left halves.
amniotic egg
Egg containing a water and food supply, key to reproduction on land.
alveoli
microscopic air sacs in the lung where oxygen and carbon dioxide are exchanged.
oviparous
Term that describes organisms that produce eggs that hatch outside the mother's body.
ovoviviparous
Term that describes organisms that produce eggs that are retained in the mother's body until hatching or just before hatching.
carapace
Dorsal part of a turtle's shell; shieldlike plate covering the cephalothorax of decapods.
plastron
The bottom, or ventral, portion of a turtle's shell.
contour feather
Feather that provides insulation and shape to adult birds.
down feather
Feather that covers young birds and insulates adult birds.
preen gland
In birds, a special gland that secretes oil that birds spread over their feathers to clean and waterproof them.
hair
In mammals, filament of dead cells and keratin used for insulation.
mammary gland
Gland located in the chest or abdomen of female mammals that secretes milk to nourish her young.
weaning
The time when a female mammal stops nursing its young.
placenta
Organ through which the mother nourishes an embryo or fetus.
gestation period
In mammals, length of time between fertilization and birth.
ungulate
Mammal with hoofs.
cud
Partly digested food that is regurgitated, rechewed, and reswallowed for further digestion by mammals with a rumen.
behavior
An action or series of actions performed by an animal in response to a stimulus.
innate behavior
Genetically programmed behavior; instinct.
fixed action pattern behavior
An innate behavior that always occurs the same way.
learning
The development of behaviors through experience.
conditioning
Learning by association.
reasoning
the ability to analyze a problem and think of a possible solution.
imprinting
Learning that can occur only during a specific period early in an animal's life and cannot be changed once learned.
sexual selection
Evolutionary mechanism by which traits that increase the ability of individuals to attract or acquire mates appear with increasing frequency in a population.
epithelial tissue
Thin, flat tissue layer that lines most body surfaces and protects other tissues from dehydration and physical damage.
nervous tissue
Nerve cells and their supporting cells.
connective tissue
Tissue that supports, protects, and insulates the body.
muscle tissue
Body tissue that enables movement.
body cavity
Fluid-filled spaces that house and protect major internal organs.
axial skeleton
Bones of the skull, spine, ribs and sternum.
appendicular skeleton
Bones of the arms and legs.
bone marrow
Soft tissue inside bones where red blood cells are produced.
periosteum
Tough exterior membrane of bones.
haversian canal
Hollow channel in bone through which blood vessels pass.
osteocyte
Cell that maintains the mineral content of bone.
osteoperosis
Reduction of bone mass that produces porous bone.
joint
Junction of two or more bones.
ligament
Band of connective tissue that holds together the bones of a joint.
tendon
Dense connective tissue that attaches muscles to bones.
flexor
Skeletal muscle that causes a joint to bend.
extensor
Skeletal muscle that causes a joint to straighten.
actin
Thin protein filament found in muscles that functions in contraction.
myosin
thick protein filament in muscle that functions in contraction.
myofibril
Cylindrical components of muscle, containing many myosin and actin filaments.
sarcomere
The functional unit of muscle contraction.
epidermis
Outermost layer of tissue, consisting of from one to several layers of dead cells.
keratin
Protein that makes skin tough and waterproof.
melanin
pigment that helps determine skin color.
dermis
Thick, functional layer of skin beneath the epidermis.
hair follicle
Specialized dermal structure that produces hair.
subcutaneous tissue
Layer of fat-rich cells just below the dermis.
sebum
Oily secretion that lubricates the skin; released by oil glands in the dermis.
artery
Vessel that carries blood away from the heart to the body's organs.
capillary
Tiny blood vessel that allows exchange between blood and cells in tissue.
vein
Large vessel that carries blood toward the heart.
valve
Flap of tissue that ensures that the blood or fluid that passes through does not flow back.
lymphatic system
System of the body that collects and recycles fluids leaked from the cardiovascular system and is involved in fighting infections.
plasma
Noncellular portion of blood.
red blood cell
Cell in the blood that carries oxygen.
anemia
Condition in which the oxygen-carrying ability of red blood cells is reduced.
white blood cell
Cell in blood whose primary job is to defend the body against disease.
platelet
Un-nucleated cell fragment that aids in blood clotting.
ABO blood group system
A system used to classify human blood by proteins found on the surface of red blood cells.
Rh factor
Protein antigen on the surface of red blood cells.
atrium
A chamber that receives blood returning to the heart.
ventricle
Thick-walled heart chamber that pumps blood away from the heart.
vena cava
One of two large veins that collect all of the oxygen-poor blood from the body.
aorta
Main artery in the body; receives blood from the left ventricle.
coronary artery
Artery that branches from the aorta and carries oxygenated blood to the heart muscle.
sinoatrial node
A small cluster of cardiac muscle cells in the upper wall of the right atrium that initiates and regulates contraction of the heart.
blood pressure
Force exerted by blood as it moves through vessels.
pulse
Series of pressure waves within an artery caused by a contraction of the left ventricle; indicator of heart rate.
heart attack
When an area of the heart muscle dies and stops working.
stroke
A sudden attack of weakness of paralysis that occurs when an area of the brain dies after blood flow to the brain is interrupted.
pharynx
Upper portion of the throat leading to the esophagus.
trachea
Tube that carries air from the larynx to the lungs.
bronchus
One of the two branches of the trachea that leads to the lungs.
alveolus
Microscopic air sac in the lung where oxygen and carbon dioxide are exchanged.
diaphragm
In mammals, sheet of muscle at the bottom of the rib cage that aids in respiration.
nutrient
Substance needed by the body for energy growth, repair, and maintenance.
digestion
The process of breaking food down into molecules the body can use.
calorie
Amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. The Calorie used to indicate the energy content of food is a kilocalorie.
vitamin
Organic substance that enhances the activity of enzymes and that occurs naturally in food.
mineral
Naturally occurring inorganic substance used to make certain body structures and substances, for normal nerve and muscle function, to maintain osmotic balance, and for enzyme function.
amylase
Enzyme that breaks down starches into sugars.
esophagus
Tube that connects the mouth to the stomach.
peristaltic contraction
Contraction of the smooth muscle in the wall of the gut that moves food through the digestive system.
pepsin
Digestive enzyme that secreted by the stomach that cuts single protein strands into smaller chains of amino acids.
ulcer
Hole in the lining of the stomach or small intestine.
lipase
Enzyme that breaks down fat molecules into fatty acids and glycerol.
villus
One of many fine, finger-like projections that cover the lining of the small intestine, increasing its absorptive surface.
colon
Organ that compacts waste for excretion; also called the large instestine.
hepatitis
Inflammation of the liver.
excretion
The process of eliminating waste.
urea
Principal nitrogenous waste of mammals and a chief component of urine.
nephron
Tubelike structure in the kidneys that filters wastes from the body and retains useful molecules; also regulates the body's salt and water balance.
urine
Water and metabolic wastes left after filtering process of the kidneys; expelled from the body.
ureter
Tube through which urine produced in the kidneys passes to the bladder.
urinary bladder
Hollow, muscular sac that stores urine.
urethra
Tube through which urine leaves the bladder and exits the body.
pathogen
A disease-causing agent.
mucous membrane
Layer of epithelial tissue covering internal surfaces of the body that secretes mucus and functions in nonspecific defense.
inflammatory response
Series of events, initiated by an injury or local infection, that suppress infection and promote healing.
histamine
Chemical released by injured cells in an inflammatory response.
complement system
Defensive proteins that circulate in the bloodstream.
interferon
Protein released by cells that inhibits viruses.
neutrophil
White blood cell that kills pathogens and itself through the release of chemicals.
macrophage
Large white blood cell that engulfs pathogens.
natural killer cell
Immune system cell that attacks cells infected with pathogens.
cytotoxic T cell
White blood cell that attacks and kills infected cells.
B cell
White blood cell that labels pathogens for destruction by macrophages.
helper T cell
White blood cell that activates cytotoxic T cells and B cells in an immune response.
antigen
Substance that triggers an immune response.
plasma cell
Cell that releases antibodies in response to a specific antigen.
antibody
Defensive protein released by plasma cells during an immune response.
koch's postulates
Four-stage procedure used to identify specific pathogens.
immunity
Resistance to a disease.
vaccination
The application of a vaccine to produce immunity.
vaccine
Substance prepared from weakened or killed pathogens and introduced into a body to produce immunity.
antigen shifting
Production of new antigens by a virus as it mutates over time.
autoimmune disease
Disease in which the immune system cannot distinguish body cells from pathogens.
AIDS
(Acquired immunodeficiency syndrome) disease caused by infection by HIV that results in a depressed immune system.
HIV
Human immunodeficiency virus; the infectious virus that causes AIDS.
CD4
Receptor protein on human cells targeted by HIV.
allergy
A reaction by the body's immune system to a harmless antigen.
neuron
Cell that transmits nerve impulses.
dendrite
Cytoplasmic extension of a neuron that receives stimuli.
axon
An elongated extension of a neuron that conducts nerve impulses.
nerve
Bundle of neurons that appears as a fine white thread to the unaided eye.
membrane potential
Difference in electrical charge across a cell membrane.
resting potential
Membrane potential of a neuron that is not conducting a nerve impulse.
action potential
Sudden reversal of polarity across a neuron membrane.
synapse
Junction at which a neuron meets another cell.
neurotansmitter
Signal molecule that transmits nerve impulses across a synapse.
central nervous system
Controls the body; system composed of the brain and spinal cord.
peripheral nervous system
System of sensory and motor neurons that branch throughout the body.
sensory neuron
Neuron that sends information from the sense organs to the central nervous system.
motor neuron
Neuron that sends motor responses from the central nervous system to muscles. glands, and other organs.
brain
Body's main processing center; major organ of the nervous system.
cerebrum
Largest portion of the brain; center of memory, learning, emotion, and other highly complex functions.
cerebellum
Region of the brain that controls coordination and balance.
brain stem
The part of the brain that connects to the spinal cord; contains nerves controlling breathing, swallowing, digestive processes, heartbeat, and blood vessel diameter.
thalamus
Part of the brain that directs incoming sensory information to the proper region of the cerebral cortex.
hypothalamus
Region of the brain located below the thalamus that coordinates that activities of the nervous and endocrine systems and that controls many body activities related to homeostasis.
spinal cord
Cable of nerve tissue extending from the base of the brain through the backbone, to level just below the ribs.
reflex
Sudden, rapid, and involuntary self-protective response to a stimulus.
interneuron
A neuron that links neurons to each other.
sensory receptor
Specialized neurons that detect sensory information.
retina
Light-sensitive area at the back of the eye that contains photoreceptors.
rod
Photoreceptor in the eye that responds to dim light.
cone
In animals, photoreceptor of the retina of the eye that detects color.
optic nerve
Nerve that transmits signals from the eye to the brain.
cochlea
Fluid-filled chamber of the inner ear that is involved in hearing.
semicircular canal
Fluid-filled chamber in the inner ear that contains hair cells involved in maintaining equilibrium.
psychoactive drug
Drug that alters the functioning of the central nervous system.
addiction
Physiological dependence on a drug.
tolerance
Condition of drug addiction in which increasing amounts of the drug are needed to achieve the desired effect.
withdrawal
Set of symptoms associated with the removal of an addictive drug from the body.
stimulant
Drug that increases the activity of the central nervous system.
depressant
Drug that decreases the activity of the central nervous system.
hormone
Substance secreted by cells that acts to regulate the activity of other cells.
endocrine gland
Ductless gland in the body that releases its product directly into the bloodstream of the fluid around the cells.
target cell
A specific cell a hormone binds to and acts on to produce a specific effect.
amino-acid-based hormone
Water-soluble hormone made of amino acids.
steroid hormone
Fat-soluble hormone derived from cholesterol.
second messenger
Signal molecule produced in response to the binding of a chemical signal; alters the chemical activity within the cell.
negative feedback
Mechanism used in homeostasis to keep a monitored variable within a certain range. A change in one direction stimulates two control mechanisms to counteract further change in the same direction.
hypothalamus
Region of the brain located below the thalamus that coordinates the activities of the nervous and endocrine systems and that controls many body activities related to homeostasis.
pituitary gland
Endocrine gland at the base of the brain that stores and releases hormones produced by the hypothalamus and hormones that control endocrine glands elsewhere in the body.
adrenal gland
Endocrine gland located above each kidney.
epinephrine
Amino-acid based hormone released by the adrenal medulla in times of stress; formerly called adrenaline.
norepinephrine
Amino-acid based molecule released as a hormone by the adrenal medulla in times of stress and as a neurotransmitter in the nervous system; formerly called noradrenaline.
insulin
Amino-acid based hormone produced by the islets of Langerhans in the pancreas that lowers blood glucose levels by promoting the accumulation of glycogen in the liver.
glucagon
A peptide hormone produced by the pancreas that causes liver cells to release glucose stored in glycogen.
diabetes mellitus
Serious disorder in which cells are unable to obtain glucose from the blood; caused by a deficiency of insulin or lack of response to insulin.
testes
Gamete-producing organs of the male reproductive system.
seminiferous tubules
Tightly coiled tubes within the testes in which sperm are produced.
epididymis
Long, coiled tube on the surface of the testes where sperm mature.
vas deferens
Tube through which sperm move from the epididymis to the urethra.
seminal vesicles
Glands of male reproductive system that produce fluid rich in sugars to nourish sperm cells.
prostate gland
Gland in males that secretes an alkaline fluid necessary to neutralize the acids produced by the female reproductive tract.
bulbourethral gland
Glands in male reproductive system that secrete a fluid that neutralizes traces of acidic urine in the urethra.
semen
The mixture of secretions and sperm produced by male reproductive organs.
penis
Male reproductive organ that delivers sperm to the female reproductive tract.
ovary
In animals, the gamete-producing organ of the female reproductive system.
ovum
A mature egg cell.
fallopian tube
Organs of the female reproductive system that lead from the ovaries to the uterus.
uterus
Hollow, muscular organ of the female reproductive system in which the embryo and fetus develop.
vagina
Muscular tube that leads from the uterus to the outside of the female body.
ovarian cycle
Series of hormone-induced changes in which the ovaries prepare and release a mature ovum each month.
ovulation
The release of an ovum from a follicle.
follicle
Cluster of cells that surrounds an immature egg cell in an ovary.
corpus luteum
Structure that forms from the ruptured follicle in the ovary after ovulation and releases hormones.
menstrual cycle
Series of hormone-induced changes that prepare the uterine lining for a possible pregnancy each month.
menstruation
Discharge of blood and discarded uterine tissue during the menstrual cycle.
cleavage
In development, the rapid, mitotic division of the zygote.
blastocyte
Hollow-ball embryo that becomes implanted in the uterus.
implantation
Burrowing of a blastocyst into lining of the uterus.
gestation
Period of human development; pregnancy.
pregnancy
Period of time in which embryonic and fetal development occur.
embryo
Early stage in the development of plants and animals; term for a developing human during the first 8 weeks of pregnancy.
placenta
Organ through which the mother nourishes an embryo or fetus.
fetus
Developing human from 8 weeks until birth.
gonorrhea
Sexually transmitted disease caused by bacteria that results in inflammation of the mucous membranes in the urinary and reproductive tracts.
syphilis
STD caused by the bacterium Treponema pallidum.
chyamydia
Bacterial STD marked by painful urination and vaginal discharge.
pelvic inflammatory disease
Severe inflammation of the uterus, ovaries, fallopian tubes, or pelvic cavity usually caused by bacterial STDs.
genital herpes
STD caused by the herpes simplex virus.