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All The Vocab You Need To Know For The Bio Regents

Terms

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biological magnification
increasing concentration of a harmful substance in organisms at higher trophic levels in a food chain or food web
rumen
stomach chamber in cows and related animals in which newly swallowed plant food is stored and processed
cone
in gymnosperms, a seed-bearing structure; in the retina of the eye, a photoreceptor that responds to light of different colors, producing color vision
reflex
quick automatic response to a stimulus
bilateral symmetry
body plan in which only a single, imaginary line can divide the body into two equal halves; characteristic of worms, arthropods, and chordates
acid rain
rain containing nitric and sulfuric acids
pharynx
muscular tube at the end of the gastrovascular cavity, or throat, that connects the mouth with the rest of the digestive tract and serves as a passageway for air and food
nucleotide
monomer of nucleic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base
anal pore
region of the cell membrane of a ciliate where waste-containing food vacuoles fuse and are then emptied into the environment
urethra
tube that carries urine from the bladder and releases it from the body; in males, tube through which semen is released from the body
struggle for existence
competition among members of a species for food, living space, and the other necessities of life
coral reef
diverse and productive environment named for the coral animals that make up its primary structure
molecular clock
model that uses DNA comparisons to estimate the length of time that two species have been evolving independently
commensalism
symbiotic relationship in which one member of the association benefits and the other is neither helped nor harmed
frond
large leaf of a fern
multiple alleles
three or more alleles of the same gene
viviparous
term used to refer to animals that bear live young that are nourished directly by the mother's body as they develop
corpus luteum
name given to a follicle after ovulation because of its yellow color
nucleolus
small, dense region within most nuclei in which the assembly of proteins begins
Punnett square
diagram showing the gene combinations that might result from a genetic cross
vertebrate
animal that has a vertebral column, or backbone
extracellular digestion
process in which food is broken down outside the cells in a digestive tract
sensory receptor
neuron that reacts to a specific stimulus, such as light or sound, by sending impulses to other neurons and eventually to the central nervous system
hominoid
anthropoid group that includes apes and humans
scolex
head of an adult tapeworm; can contain suckers or hooks
gametophyte
haploid, or gamete-producing, phase of an organism
resting potential
electrical charge across the cell membrane of a resting neuron
myelin sheath
insulating membrane surrounding the axon in some neurons
extinction
disappearance of a species from all parts of its geographical range
endoplasmic reticulum
internal membrane system in cells in which lipid components of the cell membrane are assembled and some proteins are modified
fish
aquatic vertebrate characterized by paired fins, scales, and gills
prophage
the viral DNA that is embedded in the host cell's DNA
amoeboid movement
type of locomotion used by amoebas
acetylcholine
neurotransmitter that diffuses across a synapse and produces an impulse in the cell membrane of a muscle cell
incomplete dominance
situation in which one allele is not completely dominant over another
prion
infectious particle made up of protein rather than RNA or DNA
fossil
preserved remains or evidence of an ancient organism
photosystem
light-collecting units of the chloroplast
alternation of generations
process in which many algae switch back and forth between haploid and diploid stages of their life cycles
ecological succession
gradual change in living communities that follows a disturbance
specialized cell
cell that is uniquely suited to performing a particular function
cochlea
fluid-filled part of the inner ear; sends nerve impulses to the brain through the cochlear nerve
tendon
tough connective tissue that joins skeletal muscles to bones
era
one of several subdivisions of the time between the Precambrian and the present
brain stem
structure that connects the brain and spinal cord; includes the medulla oblongata and the pons
loop of Henle
section of the nephron tubule that conserves water and minimizes the volume of urine
primary growth
type of plant growth that occurs at the tips of roots and shoots
zonation
prominent horizontal banding of organisms that live in a particular habitat
single-gene trait
trait controlled by a single gene that has two alleles
ventricle
lower chamber of the heart that pumps blood out of the heart
pith
parenchyma cells inside the ring of vascular tissue in dicot stems
rhizome
creeping or underground stem in ferns
semicircular canal
one of three structures within the inner ear that help monitor the position of the body
cell-mediated immunity
immunity against abnormal cells and pathogens inside living cells
seminiferous tubule
one of hundreds of tiny tubules in the testes in which sperm are produced
temperate zone
moderate climate zone between the polar zones and the tropics
phototropism
tendency of plants to grow toward a source of light
drug
any substance, other than food, that causes a change in the structure or function of the body
bacteriophage
virus that infects bacteria
plankton
tiny, free-floating organisms that occur in aquatic environments
bacteria
domain of unicellular prokaryotes that have cell walls containing peptidoglycans
selective breeding
method of breeding that allows only those individual organisms with desired characteristics to produce the next generation
synapse
location at which a neuron can transfer an impulse to another cell
cerebrum
area of the brain responsible for all voluntary activities of the body
fission
form of asexual reproduction in which an organism splits into two, and each half grows new parts to become a complete organism
mitosis
part of eukaryotic cell division during which the cell nucleus divides
phytochrome
plant pigment responsible for photoperiodism
prokaryote
unicellular organism lacking a nucleus
foot
muscular part of a mollusk
exon
expressed sequence of DNA; codes for a protein
karyotype
photograph of chromosomes grouped in order in pairs
community
assemblage of different populations that live together in a defined area
polymerase chain reaction (PCR)
technique that allows molecular biologists to make many copies of a particular gene
pedigree
chart that shows the relationships within a family
appendage
structure, such as a leg or antenna, that extends from the body wall
hypotonic
when comparing two solutions, the solution with the lesser concentration of solutes
exocrine gland
gland that releases its secretions through tubelike structures called ducts
convergent evolution
process by which unrelated organisms independently evolve similarities when adapting to similar environments
puberty
period of rapid growth and sexual maturation during which the reproductive system becomes fully functional
producer
organism that can capture energy from sunlight or chemicals and use it to produce food from inorganic compounds; also called an autotroph
autotroph
organism that can capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer
conjugation
form of sexual reproduction in which paramecia and some prokaryotes exchange genetic information
protist
any eukaryote that is not a plant, an animal, or a fungus
lytic infection
process in which a virus enters a cell, makes a copy of itself, and causes the cell to burst
epididymis
structure in the male reproductive system in which sperm fully mature and are stored
spontaneous generation
hypothesis (disproven) stating that life could arise from nonliving matter
trichome
tiny cellular projection on the surfaces of some leaves that helps protect the leaf and also gives it a fuzzy appearance
cell culture
group of cells grown in a nutrient solution from a single original cell
Calvin cycle
reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars
population
group of individuals of the same species that live in the same area
ascus
structure within the fruiting body of an ascomycete in which two nuclei of different mating types fuse
herbicide
compound that is toxic to plants
hair follicle
tubelike pocket of epidermal cells that extends into the dermis; cells at the base of hair follicles produce hair
ecosystem
collection of all the organisms that live in a particular place, together with their nonliving environment
vein
in plants, a cluster of vascular tissue in leaves; in animals, a blood vessel that returns blood to the heart
activation energy
energy needed to get a reaction started
invertebrate
animal that does not have a backbone or vertebral column
pH scale
measurement system used to indicate the concentration of hydrogen ions (H+) in solution; ranges from 0 to 14
mycorrhiza
symbiotic association of plant roots and fungi
Krebs cycle
second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
mangrove swamp
coastal wetland dominated by mangroves, salt-tolerant woody plants
learning
alterations in behavior as a result of experience; also called acquired behavior
photosynthesis
process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches
extinct
term used to refer to a species that has died out
radula
tongue-shaped structure used for feeding by snails and slugs
habituation
learning process by which an animal decreases or stops its response to a repetitive stimulus that neither rewards nor harms it
hypothesis
possible explanation for a set of observations or possible answer to a scientific question
atom
basic unit of matter
clone
member of a population of genetically identical cells produced from a single cell
xylem
vascular tissue that carries water upward from the roots to every part of a plant
biodiversity
biological diversity; the sum total of the variety of organisms in the biosphere
phagocyte
white blood cell that engulfs and digests foreign cells
suspension
mixture of water and nondissolved materials
cyclin
one of a family of closely related proteins that regulate the cell cycle in eukaryotic cells
ectotherm
animal that relies on interactions with the environment to help it control body temperature
taproot
primary root found in some plants that grows longer and thicker than other roots
gibberellin
growth-promoting substance produced by plants
true-breeding
term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate
accessory pigment
compound other than chlorophyll that absorbs light at different wavelengths than chlorophyll
green revolution
the development of highly productive crop strains and the use of modern agricultural techniques to increase yields of food crops
frameshift mutation
mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide
organ
group of tissues that work together to perform closely related functions
endoderm
innermost germ layer of most animals; develops into the linings of the digestive tract and much of the respiratory system
aggression
threatening behavior that one animal uses to gain control over another
rod
photoreceptor in eye that is sensitive to light but not to colors
tympanic membrane
eardrum of amphibians inside the skull; vibrates in response to sound, allowing hearing
hominid
primate that walks upright, has opposable thumbs, and possesses a large brain; only living members are humans
smog
mixture of chemicals that occurs as a gray-brown haze in the atmosphere
axon
long fiber that carries impulses away from the cell body of a neuron
vaccine
a preparation of weakened or killed pathogens
classical conditioning
learning process in which an animal makes a mental connection between a stimulus and some kind of reward or punishment
photoautotroph
organism that uses energy from sunlight to convert carbon dioxide and water to carbon compounds
radioactive dating
technique in which scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains
genetic engineering
process of making changes in the DNA code of living organisms
gemma
small cup-shaped structure in liverworts that contains many haploid cells; used for asexual reproduction
carcinogen
chemical compound known to cause cancer
Hardy-Weinberg principle
principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change
adaptation
inherited characteristic that increases an organism's chance of survival
threshold
minimum level of a stimulus required to activate a neuron
speciation
formation of new species
pseudocoelom
body cavity between the endoderm and mesoderm tissues that is partially lined with mesoderm tissue
root hair
tiny projection from the outer surface, or epidermis, of a root
annual
flowering plant that completes a life cycle within one growing season
centromere
area where the chromatids of a chromosome are attached
leaf
photosynthetic organ that contains one or more bundles of vascular tissue
pellicle
cell membrane in euglenas
platelet
cell fragment released by bone marrow that helps in blood clotting
apical meristem
group of undifferentiated cells that divide to produce increased length of stems and roots
allergy
overreaction of the immune system to antigens
myocardium
thick middle muscle layer of the heart; pumps blood through the circulatory system
cilium
short hairlike projection similar to a flagellum; produces movement in many cells
lipid bilayer
double-layered sheet that forms the core of nearly all cell membranes
pioneer species
first species to populate an area during primary succession
transgenic
term used to refer to an organism that contains genes from other organisms
systemic circulation
pathway of circulation between the heart and the rest of the body except the lungs
cell
collection of living matter enclosed by a barrier that separates the cell from its surroundings; basic unit of all forms of life
biology
science that seeks to understand the living world
macroevolution
large-scale evolutionary changes that take place over long periods of time
water vascular system
system of internal tubes in echinoderms that carries out essential functions such as feeding, respiration, circulation, and movement
species diversity
number of different species in the biosphere
resource
any necessity of life, such as water, nutrients, light, food, or space
DNA polymerase
enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule
exoskeleton
external skeleton; tough external covering that protects and supports the body of many invertebrates
theory
well-tested explanation that unifies a broad range of observations
larynx
structure in the throat containing the vocal cords
plasma
straw-colored fluid that makes up about 55 percent of blood
punctuated equilibrium
pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change
allele
one of a number of different forms of a gene
transfer RNA (tRNA)
type of RNA molecule that transfers amino acids to ribosomes during protein synthesis
genetic equilibrium
situation in which allele frequencies remain constant
zooplankton
tiny animals that form part of the plankton
immigration
movement of individuals into an area occupied by an existing population
flower
seed-bearing structure of an angiosperm
chyme
mixture of stomach fluids and food produced in the stomach by contracting stomach muscles
binocular vision
ability to merge visual images from both eyes, which provides depth perception and a three-dimensional view of the world
caste
group of individual insects specialized to perform particular tasks, or roles
cytokinesis
division of the cytoplasm during cell division
mitochondrion
cell organelle that converts the chemical energy stored in food into compounds that are more convenient for the cell to use
sexually transmitted disease (STD)
disease spread from one person to another during sexual contact
uterus
organ of the female reproductive system in which a fertilized egg can develop
blastula
hollow ball of cells formed when a zygote undergoes a series of divisions
gravitropism
response of a plant to the force of gravity
sporangium
structure in ferns and some fungi that contains spores
ecology
scientific study of interactions among organisms and between organisms and their environment
root
underground organ in plants that absorbs water and minerals
segregation
separation of alleles during gamete formation
filtration
process by which a liquid or gas passes through a filter to remove wastes
estuary
wetlands formed where rivers meet the ocean
vertebra
individual segment of the backbone; encloses and protects the spinal cord
lysosome
cell organelle filled with enzymes needed to break down certain materials in the cell
coastal ocean
marine zone that extends from the low-tide mark to the end of the continental shelf
Plantae
kingdom of multicellular photosynthetic autotrophs that have cell walls containing cellulose
neurotransmitter
chemical used by a neuron to transmit an impulse across a synapse to another cell
biennial
flowering plant that completes its life cycle in two years
intracellular digestion
process in which food is digested inside cells
subcutaneous fat
layer of fat cells beneath the skin that helps conserve body heat
histamine
chemical released by activated mast cells that increases the flow of blood and fluids to the surrounding area
gastrulation
process of cell migration by which a third layer of cells is formed within the cavity of a blastocyst
target cell
cell that has a receptor for a particular hormone
phenotype
physical characteristics of an organism
vascular cylinder
central region of a root that includes the vascular tissue—xylem and phloem
replication
copying process by which a cell duplicates its DNA
atrium
upper chamber of the heart that receives and holds blood that is about to enter the ventricle
benthos
organisms that live attached to or near the ocean floor
fetus
name given to a human embryo after eight weeks of development
zygospore
resting spore that contains zygotes formed during the sexual phase of a mold's life cycle
chromosome
"threadlike structure within the nucleus containing the genetic information that is passed from one generation of cells to the next
tetrad
structure containing 4 chromatids that forms during meiosis
food vacuole
small cavity in the cytoplasm of protists that temporarily stores food
demographic transition
change in a population from high birth and death rates to low birth and death rates
invasive species
plants and animals that have migrated to places where they are not native
habitat
the area where an organism lives, including the biotic and abiotic factors that affect it
primary productivity
rate at which organic matter is created by producers in an ecosystem
cellular respiration
process that releases energy by breaking down glucose and other food molecules in the presence of oxygen
global warming
increase in the average temperatures on Earth
guard cell
specialized cell in the epidermis of plants that controls the opening and closing of stomata by responding to changes in water pressure
cheliped
one of the first pair of legs of decapods
dicot
angiosperm whose seeds have two cotyledons
hydrostatic skeleton
layers of circular and longitudinal muscles, together with the water in the gastrovascular cavity, that enable movement
swim bladder
internal gas-filled organ in many bony fishes that adjusts their buoyancy
nondisjunction
error in meiosis in which homologous chromosomes fail to separate
pigment
light-absorbing molecule
society
group of closely related animals of the same species that work together for the benefit of the group
fertilization
process in sexual reproduction in which male and female reproductive cells join to form a new cell
gamete
specialized cell involved in sexual reproduction
isotope
atom of an element that has a number of neutrons different from that of other atoms of the same element
archaeocyte
specialized cell in a sponge that makes spicules
adenosine triphosphate (ATP)
one of the principal chemical compounds that living things use to store and release energy
natural selection
process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest
osculum
large hole at the top of the sponge through which water leaves the sponge
controlled variable
factor in an experiment that a scientist purposely keeps the same
plasmid
small circular piece of DNA
pituitary gland
gland in the base of the skull that secretes nine hormones that directly regulate many body functions and control the actions of several other endocrine glands
amniotic egg
egg composed of shell and membranes that create a protected environment in which the embryo can develop out of the water
wetland
ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year
proteinoid microsphere
tiny bubble, formed of large organic molecules, that has some characteristics of a cell
trophic level
step in a food chain or food web
neuromuscular junction
point of contact between a motor neuron and a skeletal muscle cell
pedipalps
pair of mouthparts in chelicerates that are usually modified to grab prey
paleontologist
scientist who studies fossils
epiphyte
plant that is not rooted in soil but instead grows directly on the body of another plant
chordate
member of the phylum Chordata; animal that has, for at least some stage of its life, a dorsal hollow nerve cord, a notochord, pharyngeal pouches, and a muscular tail
mesophyll
specialized ground tissue that makes up the bulk of most leaves; performs most of a plant's photosynthesis
chemical bond
link that holds together atoms in compounds
evaporation
process by which water changes from a liquid into an atmospheric gas
opposable thumb
thumb that enables grasping objects and using tools
communication
passing of information from one organism to another
tube foot
suction-cuplike structure attached to radial canals of echinoderms; used to walk and to open shells
genetic drift
random change in allele frequencies that occurs in small populations
aorta
large blood vessel in mammals through which blood travels after it leaves the left ventricle
fruiting body
slender reproductive structure that produces spores and is found in some funguslike protists; reproductive structure of fungus that develops from a mycelium
artery
large blood vessel that carries blood from the heart to the tissues of the body
phycobilin
accessory pigment found in red algae that is especially good at absorbing blue light
nervous tissue
tissue that receives messages from the body's external and internal environment, analyzes the data, and directs the response
electron
variety of habitats, living communities, and ecological processes in the living world
myosin
protein that makes up the thick filaments in striations in skeletal muscle cells
ossification
process of bone formation, during which cartilage is replaced by bone
NAD+ (nicotinamide adenine dinucleotide)
electron carrier involved in glycolysis
humus
material formed from decaying leaves and other organic matter
chloroplast
organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy
nymph
immature form that lacks functional sex organs and other adult structures
meristematic tissue
plant tissue found only in the tips of shoots and roots; responsible for plant growth
rhizoid
in fungi, a rootlike hypha that penetrates the surface of an object; in mosses, a long, thin cell that anchors the moss to the ground and absorbs water and minerals from the surrounding soil
phagocytosis
process in which extensions of cytoplasm surround and engulf large particles and take them into the cell
antigen
substance that triggers an immune response
codominance
situation in which both alleles of a gene contribute to the phenotype of the organism
messenger RNA (mRNA)
RNA molecule that carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell
descent with modification
principle that each living species has descended, with changes, from other species over time
vegetative reproduction
method of asexual reproduction used by many flowering plants
sclerenchyma
type of ground-tissue cell with an extremely thick, rigid cell wall that makes ground tissue tough and strong
xerophyte
plant that lives in the desert biome
fetal alcohol syndrome
group of birth defects caused by the effects of alcohol on a fetus
cnidocyte
stinging cell of cnidarians; used for defense and to capture prey
emphysema
disease in which the tissues of the lungs lose elasticity, making breathing very difficult
photic zone
well-lit upper layer of the oceans
spirillum
spiral or corkscrew-shaped prokaryote
nucleic acid
macromolecule containing hydrogen, oxygen, nitrogen, carbon, and phosphorus
epithelial tissue
tissue that covers the surface of the body and lines internal organs
antibiotic
compound that blocks the growth and reproduction of bacteria
gullet
indentation in one side of a ciliate that allows food to enter the cell
cerebrospinal fluid
fluid in the space between the meninges that acts as a shock absorber that protects the central nervous system
ion
atom that has a positive or negative charge
chromatid
one of two identical "sister" parts of a duplicated chromosome
fitness
ability of an organism to survive and reproduce in its environment
ATP synthase
large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP
facilitated diffusion
movement of specific molecules across cell membranes through protein channels
codon
three-nucleotide sequence on messenger RNA that codes for a single amino acid
pollination
transfer of pollen from the male reproductive structure to the female reproductive structure
genotype
genetic makeup of an organism
carrying capacity
largest number of individuals of a population that a given environment can support
spore
haploid reproductive cell
hypertonic
when comparing two solutions, the solution with the greater concentration of solutes
anus
opening through which wastes leave the digestive tract
pulmonary circulation
pathway of circulation between the heart and the lungs
aphotic zone
permanently dark layer of the oceans below the photic zone
abiotic factor
physical, or nonliving, factor that shapes an ecosystem
gene pool
"combined genetic information of all the members of a particular population
operant conditioning
learning process in which an animal learns to behave in a certain way through repeated practice, in order to receive a reward or avoid punishment; also called trial-and-error learning
meristem
cluster of tissue that is responsible for continuing growth throughout a plant's lifetime
hypothalamus
brain structure that acts as a control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature
DNA fingerprinting
analysis of sections of DNA that have little or no known function, but vary widely from one individual to another, in order to identify individuals
mutation
change in a DNA sequence that affects genetic information
valve
flap of connective tissue between an atrium and a ventricle, or in a vein, that prevents backflow of blood
sieve tube element
phloem cell that is joined end-to-end to similar cells to form a continuous sieve tube
medulla oblongata
area of the brain that controls the functioning of many internal organs
shell
structure in mollusks made by glands in the mantle that secrete calcium carbonate
hermaphrodite
individual that has both male and female reproductive organs
substrate
reactant of an enzyme-catalyzed reaction
swimmerets
flipperlike appendages used by decapods for swimming
lipid
macromolecule made mainly from carbon and hydrogen atoms; includes fats, oils, and waxes
diabetes mellitus
condition that occurs when the pancreas produces too little insulin, resulting in an increase in the level of blood glucose
node
point on a stem where a leaf is attached
competitive exclusion principle
ecological rule that states that no two species can occupy the same exact niche in the same habitat at the same time
nucleus
the center of the atom which contains the protons and neutrons; in cells, structure that contains the cell's genetic material (DNA) and controls the cell's activities
responding variable
factor in an experiment that a scientist wants to observe, which may change in response to the manipulated variable; also known as a dependent variable
ectoderm
outermost germ layer of most animals; gives rise to outer layer of the skin, sense organs, and nerves
embryo sac
female gametophyte within the ovule of a flowering plant
cell specialization
the process in which cells develop in different ways to perform different tasks
viroid
single-stranded RNA molecule that has no surrounding capsids
siphon
tubelike structure through which water enters and leaves a mollusk's body
product
element or compound produced by a chemical reaction
evolutionary classification
method of grouping organisms together according to their evolutionary history
contractile vacuole
cavity in the cytoplasm of some protists that collects water and discharges it from the cell
larva
immature stage of an organism that looks different from the adult form
internode
region between nodes on plant stems
buffer
weak acid or base that can react with strong acids or bases to help prevent sharp, sudden changes in pH
Golgi apparatus
stack of membranes in the cell that modifies, sorts, and packages proteins from the endoplasmic reticulum
cephalothorax
region of a crustacean formed by the fusion of the head with the thorax
consumer
organism that relies on other organisms for its energy and food supply; also called a heterotroph
anaerobic
process that does not require oxygen
migration
periodic movement and return of animals from one place to another
courtship
type of behavior in which an animal sends out stimuli—such as sounds, visual displays, or chemicals—in order to attract a member of the opposite sex
disease
any change, other than an injury, that disrupts the normal functions of the body
vagina
in the human female reproductive system, a canal that leads from the uterus to the outside of the body
plastron
ventral part of a turtle's or tortoise's shell
survival of the fittest
process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection
connective tissue
tissue that holds organs in place and binds different parts of the body together
cell cycle
series of events that cells go through as they grow and divide
bipedal
term used to refer to two-footed locomotion
vacuole
cell organelle that stores materials such as water, salts, proteins, and carbohydrates
lichen
symbiotic association between a fungus and a photosynthetic organism
soil erosion
wearing away of surface soil by water and wind
interferon
one of a group of proteins that help cells resist viral infection
cell wall
strong supporting layer around the cell membrane in plants, algae, and some bacteria
abscission layer
layer of cells at the petiole that seals off a leaf from the vascular system
bacillus
rod-shaped prokaryote
gymnosperm
seed plant that bears its seeds directly on the surfaces of cones
spicule
spike-shaped structure that makes up the skeletons of harder sponges; made of either chalklike calcium carbonate or glasslike silica
ethylene
plant hormone that stimulates fruits to ripen
seed
embryo of a living plant that is encased in a protective covering and surrounded by a food supply
tumor
mass of growing tissue
lymph
fluid lost by the blood into surrounding tissue
photoheterotroph
organism that is photosynthetic but needs organic compounds as a carbon source
exocytosis
process by which a cell releases large amounts of material
antibody
protein that helps destroy pathogens
diploid
term used to refer to a cell that contains both sets of homologous chromosomes
kingdom
large taxonomic group, consisting of closely related phyla
Malpighian tubule
saclike organ in most terrestrial arthropods that extracts wastes from the blood, adding them to feces that move through the gut
cell fractionation
technique in which cells are broken into pieces and the different cell parts are separated
Animalia
kingdom of multicellular eukaryotic heterotrophs whose cells do not have cell walls
reproductive isolation
separation of species or populations so that they cannot interbreed and produce fertile offspring
conservation
wise management of natural resources, including the preservation of habitats and wildlife
cellular slime mold
slime mold whose individual cells remain separated during every phase of the mold's life cycle
air sac
one of several sacs attached to a bird's lungs into which air moves when a bird inhales; allows for the one-way flow of air through the respiratory system
vestigial organ
organ that serves no useful function in an organism
bone marrow
soft tissue inside the cavities within bones
angiosperm
flowering plant; bears its seeds within a layer of tissue that protects the seed
notochord
long supporting rod that runs through a chordate's body just below the nerve cord
germination
early growth stage of a plant embryo
heartwood
older xylem near the center of a woody stem that no longer conducts water
catalyst
substance that speeds up the rate of a chemical reaction
asthma
chronic respiratory disease in which the air passageways become narrower than normal
immune response
the body's specific defenses that attack a disease-causing agent
monoculture
farming strategy in which large fields are planted with a single crop, year after year
differentiation
process in which cells become specialized in structure and function
cell theory
idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells
anther
flower structure in which haploid male gametophytes are produced
active immunity
immunity produced by exposure to an antigen, as a result of the immune response
visceral mass
area beneath the mantle of a mollusk that contains the internal organs
compound
substance formed by the chemical combination of two or more elements in definite proportions
hormone
substance produced in one part of an organism that affects another part of the same organism
Eubacteria
kingdom of unicellular prokaryotes whose cell walls are made up of peptidoglycan
lateral bud
meristematic area on the side of a stem that gives rise to side branches
genus
group of closely related species, and the first part of the scientific name in binomial nomenclature
cohesion
attraction between molecules of the same substance
circadian rhythm
behavioral cycle that occurs in a daily pattern
cuticle
in plants, a thick waxy layer on exposed outer surfaces of cells that protects them against water loss and injury
sexual reproduction
process by which cells from two different parents unite to produce the first cell of a new organism
population density
number of individuals per unit of area
antheridium
male reproductive structure in some algae and plants
conidium
tiny fungal spore that forms at the tips of specialized hyphae in ascomycetes
hybrid
offspring of crosses between parents with different traits
reflex arc
sensory receptor, sensory neuron, motor neuron, and effector that are involved in a quick response to a stimulus
eukaryote
organism whose cells contain nuclei
order
group of similar families
coelom
fluid-filled body cavity lined with mesoderm
cork cambium
lateral meristematic tissue that produces the outer covering of stems
monotreme
egg-laying mammal
bryophyte
nonvascular plant; examples are mosses and their relatives
nitrogen fixation
process of converting nitrogen gas into ammonia
independent assortment
independent segregation of genes during the formation of gametes
ascospore
haploid spore produced within the ascus of ascomycetes
budding
asexual process by which yeasts increase in number; process of attaching a bud to a plant to produce a new branch
placenta
organ in placental mammals through which nutrients, oxygen, carbon dioxide, and wastes are exchanged between embryo and mother
cell body
largest part of a typical neuron; contains the nucleus and much of the cytoplasm
renewable resource
resource that can regenerate quickly and that is replaceable
keratin
tough, fibrous protein found in skin
feedback inhibition
process in which the product or result stops or limits the process
stamen
male part of the flower; made up of an anther and a filament
histone
protein molecule around which DNA is tightly coiled in chromatin
bird
endothermic animal that has an outer covering of feathers, two legs covered with scales that are used for walking or perching, and front limbs modified into wings
joint
place where one bone attaches to another
phylogeny
the study of evolutionary relationships among organisms
period
unit of time into which eras are subdivided
reabsorption
process in which liquid is taken back into a vessel
mesoderm
middle germ layer of most animals; gives rise to muscles and much of the circulatory, reproductive, and excretory systems
phloem
vascular tissue responsible for the transport of nutrients and the carbohydrates produced by photosynthesis
intron
sequence of DNA that is not involved in coding for a protein
calorie
amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius
coccus
spherical prokaryote
diaphragm
large, flat muscle at the bottom of the chest cavity that helps with breathing
endoskeleton
structural support located inside the body of an animal
binary fission
"type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells
predator-prey relationship
mechanism of population control in which a population is regulated by predation
petiole
thin stalk by which a leaf blade is attached to a stem
response
single, specific reaction to a stimulus
micronucleus
the smaller of a ciliate's two nuclei; contains a "reserve copy" of all of the cell's genes
Haversian canal
one of a network of tubes running through compact bone that contains blood vessels and nerves
habitat fragmentation
splitting of ecosystems into small fragments
anaphase
the third phase of mitosis, during which the chromosome pairs separate and move toward opposite poles
facultative anaerobe
organism that can survive with or without oxygen
taxonomy
discipline of classifying organisms and assigning each organism a universally accepted name
ligament
strip of tough connective tissue that holds bones together at a joint
permafrost
layer of permanently frozen subsoil in the tundra
thigmotropism
response of plants to touch
proglottid
one of the segments that make up most of a tapeworm's body
endotherm
animal that generates its own body heat and controls its body temperature from within
stoma
opening in the underside of a leaf that allows carbon dioxide and oxygen to diffuse into and out of the leaf
Fallopian tube
one of two fluid-filled tubes in human females through which an egg passes after its release from an ovary
spongy mesophyll
loose tissue beneath the palisade layer of a leaf; has many air spaces between its cells
aquaculture
the raising of aquatic organisms for human consumption
glomerulus
small network of capillaries encased in the upper end of a nephron; where the filtration of blood takes place
greenhouse effect
natural situation in which heat is retained in Earth's atmosphere by carbon dioxide, methane, water vapor, and other gases
ureter
tube that carries urine from the kidney to the urinary bladder
seta
bristle attached to the segments of many annelids
controlled experiment
a test of the effect of a single variable by changing it while keeping all other variables the same
vaccination
injection of a weakened or mild form of a pathogen to produce immunity
homeostasis
process by which organisms maintain a relatively stable internal environment
internal fertilization
process in which eggs are fertilized inside the female's body
Protista
kingdom composed of eukaryotes that are not classified as plants, animals, or fungi
implantation
process in which a blastocyst attaches itself to the wall of the uterus
cytoplasm
"material inside the cell membrane—not including the nucleus
genetic diversity
sum total of all the different forms of genetic information carried by all organisms living on Earth today
hybridization
breeding technique that involves crossing dissimilar individuals to bring together the best traits of both organisms
fruit
wall of tissue surrounding an angiosperm seed
passive immunity
short-term immunity caused when antibodies produced by other animals for a pathogen are injected into the body
septum
internal wall between the segments of an annelid's body
penis
external male reproductive organ
stigma
sticky portion at the top of the style where pollen grains frequently land
agriculture
the practice of farming
cerebral cortex
outer layer of the cerebrum of a mammal's brain; center of thinking and other complex behaviors
external fertilization
process in which eggs are fertilized outside the female's body
saprobe
organism that obtains food from decaying organic matter
food chain
series of steps in an ecosystem in which organisms transfer energy by eating and being eaten
vector
animal that carries pathogens from person to person
germ theory of disease
idea that infectious diseases are caused by microorganisms, or germs
long-day plant
plant that flowers when days are long
inflammatory response
nonspecific defense reaction to tissue damage caused by injury or infection
immunity
ability of the body to resist a specific pathogen
Bowman's capsule
cup-shaped structure in the upper end of a nephron that encases the glomerulus
insight learning
also called reasoning; learning process in which an animal applies something it has already learned to a new situation without a period of trial and error
ribonucleic acid (RNA)
single-stranded nucleic acid that contains the sugar ribose
probability
likelihood that a particular event will occur
binomial nomenclature
classification system in which each species is assigned a two-part scientific name
electron transport chain
a series of proteins in which the high-energy electrons from the Krebs cycle are used to convert ADP into ATP
collenchyma
type of ground tissue cell with a strong, flexible cell wall; helps support larger plants
mutualism
symbiotic relationship in which both species benefit from the relationship
tolerance
organism's capacity to grow or thrive when subjected to an unfavorable environmental factor
age-structure diagram
graph of the numbers of males and females within different age groups of a population
protonema
mass of tangled green filaments in mosses that forms during germination
obligate anaerobe
organism that cannot live in the presence of oxygen
lateral line system
sensitive receptor system that enables fish to detect gentle currents and vibrations in the water
aerobic
process that requires oxygen
drug abuse
intentional misuse of any drug for nonmedical purposes
imprinting
learning based on early experience; once imprinting has occurred, the behavior cannot be changed
stimulus
a signal to which an organism responds
dendrite
extension of the cell body of a neuron that carries impulses from the environment or from other neurons toward the cell body
emigration
movement of individuals out of an area
transpiration
loss of water from a plant through its leaves
promoter
region of DNA that indicates to an enzyme where to bind to make RNA
language
system of communication that combines sounds, symbols, or gestures according to a set of rules about word order and meaning
endocytosis
process by which a cell takes material into the cell by infolding of the cell membrane
nonrenewable resource
resource that cannot be replenished by natural processes
molecule
smallest unit of most compounds
testis
male gonad that produces sperm
flame cell
specialized cell that filters and removes excess water from the body of a flatworm
homozygous
term used to refer to an organism that has two identical alleles for a particular trait
nephron
"blood-filtering unit in the renal cortex of the kidney
parenchyma
type of ground-tissue cell with a thin cell wall and large central vacuole
nephridium
excretory organ of an annelid that filters fluid in the coelom
gene
sequence of DNA that codes for a protein and thus determines a trait
short-day plant
plant that flowers when daylight is short
variable
factor in an experiment that can change
tracheal tube
one of many branching, air-filled tubes that extend throughout the bodies of many terrestrial arthropods
solvent
substance in which a solute is dissolved to form a solution
archegonium
female reproductive structure in some plants, including mosses and liverworts
mandible
mouthpart adapted for biting and grinding food
embryo
organism in its early stage of development
monocot
angiosperm whose seeds have one cotyledon
index fossil
distinctive fossil used to compare the relative ages of fossils
common descent
principle that all living things were derived from common ancestors
action potential
reversal of charges across the cell membrane of a neuron; also called a nerve impulse
taiga
biome in which the winters are cold but summers are mild enough to allow the ground to thaw
villus
folded projection that increases the surface area of the walls of the small intestine
muscle tissue
"tissue that controls the internal movement of materials in the body, as well as external movement
vitamin
organic molecule that helps regulate body processes
acellular slime mold
slime mold that passes through a stage in which its cells fuse to form large cells with many nuclei
transformation
process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria
amino acid
compound with an amino group (−NH2) on one end and a carboxyl group (−COOH) on the other end
Casparian strip
waterproof strip that surrounds plant endodermis cells
thalamus
brain structure that receives messages from the sense organs and relays the information to the proper region of the cerebrum for further processing
mantle
thin layer of tissue that covers most of a mollusk's body
capillary action
tendency of water to rise in a thin tube
epidermis
outer layer of the skin
electron microscope
microscope that forms an image by focusing beams of electrons onto a specimen
genetics
scientific study of heredity
companion cell
phloem cell that surrounds sieve tube elements
protostome
animal whose mouth is formed from its blastopore
gill
filamentous organ in aquatic animals specialized for the exchange of gases with water
tracheid
hollow plant cell in xylem tissue with thick cell walls that resist pressure
restriction enzyme
enzyme that cuts DNA at a specific sequence of nucleotides
cerebellum
region of the brain that coordinates body movements
inbreeding
continued breeding of individuals with similar characteristics to maintain the desired characteristics of a line of organisms
directional selection
form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve
deciduous
term used to refer to a tree that sheds its leaves during a particular season each year
cladogram
diagram that shows the evolutionary relationships among a group of organisms
abdomen
posterior part of an arthropod's body
acoelomate
animal lacking a coelom, or body cavity
trichocyst
small, bottle-shaped structure used for defense by paramecia
innate behavior
instinct, or inborn behavior; behavior that appears in a fully functional form the first time it is performed
basidium
spore-bearing structure of a basidiomycete
founder effect
change in allele frequencies as a result of the migration of a small subgroup of a population
polymer
large compound formed from combinations of many monomers
biome
group of ecosystems that have the same climate and dominant communities
pollen tube
structure grown by a pollen grain; contains two haploid sperm nuclei
oviparous
term used to refer to animals whose eggs hatch outside the mother's body
biosphere
part of Earth in which life exists including land, water, and air or atmosphere
risk factor
anything that increases the chance of disease or injury
carpel
innermost part of a flower that produces the female gametophytes
molting
process in which an arthropod sheds its exoskeleton and manufactures a larger one to take its place
active transport
energy-requiring process that moves material across a cell membrane against a concentration difference
ribosome
small particle in the cell on which proteins are assembled; made of RNA and protein
carbohydrate
compound made up of carbon, hydrogen, and oxygen atoms; major source of energy for the human body
carnivore
organism that obtains energy by eating animals
endosymbiotic theory
theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms
menstruation
phase of the menstrual cycle during which the lining of the uterus, along with blood and the unfertilized egg, is discharged through the vagina
polysaccharide
large macromolecule formed from monosaccharides
biomass
total amount of living tissue within a given trophic level
macronucleus
the larger of a ciliate's two nuclei, contains multiple copies of most of the genes that the cell needs in its day-to-day existence
chitin
complex carbohydrate that makes up the cell walls of fungi; also found in the external skeletons of arthropods
vessel element
in angiosperms, xylem cell that forms part of a continuous tube through which water can move
chromatin
granular material visible within the nucleus; consists of DNA tightly coiled around proteins
polyp
usually sessile stage of the life cycle of a cnidarian that has a cylindrical body with armlike tentacles
complete metamorphosis
type of insect development in which the larvae look and act nothing like their parents and also feed in completely different ways
choanocyte
specialized cell in sponges that uses a flagellum to move a steady current of water through the sponge
stimulant
drug that speeds up the actions regulated by the nervous system
book lung
organ that has layers of respiratory tissue that is used by some terrestrial arthropods for the exchange of gases
primary succession
succession that occurs on surfaces where no soil exists
species
group of similar organisms that can breed and produce fertile offspring
haploid
term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes
fever
elevated body temperature that occurs in response to infection
monomer
small unit that can join together with other small units to form polymers
ionic bond
bond formed when one or more electrons are transferred from one atom to another
understory
layer in a rain forest formed by shorter trees and vines
chelicerae
pair of mouthparts in chelicerates that contain fangs and are used to stab and paralyze prey
limiting factor
factor that causes the growth of a population to decrease
salt marsh
temperate-zone estuary dominated by salt-tolerant grasses above the low-tide line and by seagrasses under water
cytoskeleton
network of protein filaments within some cells that helps the cell maintain its shape and is involved in many forms of cell movement
density-dependent limiting factor
limiting factor that depends on population size
chemosynthesis
process by which some organisms, such as certain bacteria, use chemical energy to produce carbohydrates
bark
tree structure that includes all tissues outside the vascular cambium, including phloem, the cork cambium, and cork
sepal
outermost circle of flower parts that encloses a bud before it opens and protects the flower while it is developing
scrotum
external sac containing the testes
esophagus
food tube connecting the mouth to the stomach
organ system
group of organs that work together to perform a specific function
decomposer
organism that breaks down and obtains energy from dead organic matter
pupil
small opening in the middle of the iris through which light enters the eye
cell membrane
thin, flexible barrier around a cell; regulates what enters and leaves the cell
denitrification
conversion of nitrates into nitrogen gas
prehensile
term used to refer to a long tail that can grasp branches
artificial selection
selection by humans for breeding of useful traits from the natural variation among different organisms
microscope
device that produces magnified images of structures that are too small to see with the unaided eye
cephalization
concentration of sense organs and nerve cells at the front of an animal's body
Fungi
kingdom composed of heterotrophs; many obtain energy and nutrients from dead organic matter
genetic marker
gene that makes it possible to distinguish bacteria that carry a plasmid with foreign DNA from those that don't
gemmule
group of archaeocytes surrounded by a tough layer of spicules; produced by some sponges
sex-linked gene
gene located on the X or Y chromosome
retrovirus
virus that contains RNA as its genetic information
prostaglandin
hormonelike modified fatty acid produced by a wide range of cells; generally affects only nearby cells and tissues
disruptive selection
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle
niche
full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions
fibrous root
part of a root system in which roots branch to such an extent that no single root grows larger than the rest
reactant
element or compound that enters into a chemical reaction
obligate aerobe
organism that requires a constant supply of oxygen in order to live
meiosis
process by which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
microfossil
microscopic fossil
RNA polymerase
enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription
parasite
organism that lives within or on another organism and harms that organism by feeding on it
hox genes
series of genes that controls the differentiation of cells and tissues in an embryo
predation
interaction in which one organism captures and feeds on another organism
centriole
one of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope
spiracle
small opening located along the side of the body through which air enters and leaves the body of many terrestrial arthropods
liver
large organ just above the stomach that produces bile, a fluid loaded with lipids and salts
basidiospore
spore in basidiomycetes that germinates to produce haploid primary mycelia
pupa
stage of metamorphosis in which an insect changes from a larva into an adult
tropism
response of a plant to an external stimulus
marsupial
mammal which bears live young that complete their development in an external pouch
isotonic
when the concentration of two solutions is the same
telophase
fourth and final phase of mitosis, during which the chromosomes begin to disperse into a tangle of dense material
dermis
inner layer of the skin
trochophore
free-swimming larval stage of an aquatic mollusk
pathogen
disease-causing agent
metric system
decimal system of measurement based on certain physical standards and scaled on multiples of 10
pseudopod
temporary projection of cytoplasm, or a "false foot," used by some protists for feeding or movement
protein
macromolecule that contains carbon, hydrogen, oxygen, and nitrogen; needed by the body for growth and repair and to make up enzymes
cytokinin
plant hormone produced in growing roots and in developing fruits and seeds
fossil record
information about past life, including the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived
base
compound that produces hydroxide ions (OH+) in solution
Koch's postulates
series of guidelines used to identify the microorganism that causes a specific disease
eyespot
group of cells that can detect changes in the amount of light in the environment
fermentation
process by which cells release energy in the absence of oxygen
humoral immunity
immunity against antigens and pathogens in the body fluids
base pairing
principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine
element
substance consisting entirely of one type of atom
feather
structure made mostly of protein that develops from a pit in a bird's skin
Archaebacteria
kingdom of unicellular prokaryotes whose cell walls do not contain peptidoglycan
vascular bundle
plant stem structure that contains xylem and phloem tissue
nicotine
stimulant drug in tobacco that increases heart rate and blood pressure
hemoglobin
iron-containing protein in red blood cells that transports oxygen from the lungs to the tissues of the body
compound light microscope
microscope that allows light to pass through a specimen and uses two lenses to form an image
anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
virus
particle made up of nucleic acid, protein, and in some cases lipids that can replicate only by infecting living cells
homologous
term used to refer to chromosomes that each have a corresponding chromosome from the opposite-sex parent
closed circulatory system
system in which blood is contained within a network of blood vessels
logistic growth
growth pattern in which a population's growth rate slows or stops following a period of exponential growth
domain
most inclusive taxonomic category; larger than a kingdom
crop
in earthworms, part of the digestive system in which food can be stored; in birds, structure at the lower end of the esophagus in which food is stored and moistened
neuron
cell that carries messages throughout the nervous system
open circulatory system
system in which blood is not always contained within a network of blood vessels
prosimian
with few exceptions, small, nocturnal primate that has large eyes for seeing in the dark
ovule
structure in seed cones in which female gametophytes develop
bud
plant structure containing undeveloped tissue that can produce new stems and leaves
covalent bond
bond formed by the sharing of electrons between atoms
reptile
any vertebrate that has dry scaly skin, lungs, and terrestrial eggs with several protective membranes
equilibrium
when the concentration of a solute is the same throughout a solution
demography
scientific study of human populations
heterotroph
organism that obtains energy from the foods it consumes; also called a consumer
gel electrophoresis
procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel
petal
brightly colored structure just inside the sepals; attracts insects and other pollinators to a flower
omnivore
organism that obtains energy by eating both plants and animals
polar zone
cold climate zone where the sun's rays strike Earth at a very low angle
melanin
dark-brown pigment found in skin
endocrine gland
gland that releases its secretions directly into the bloodstream
ovary
in plants, a flower structure that contains one or more ovules from which female gametophytes are produced; in animals, the female gonad that produces eggs
cancer
disorder in which some of the body's own cells lose the ability to control growth
behavioral isolation
form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding
secondary growth
pattern of plant growth in which stems increase in width
Eukarya
domain of all organisms whose cells have nuclei, including protists, plants, fungi, and animals
pinocytosis
process by which a cell takes in liquid from the surrounding environment
temporal isolation
form of reproductive isolation in which two populations reproduce at different times
desertification
in areas with dry climates, a process caused by a combination of poor farming practices, overgrazing, and drought that turns productive land into desert
meninges
three layers of connective tissue in which the brain and spinal cord are wrapped
behavior
the way an organism reacts to changes in its internal condition or external environment
addiction
uncontrollable dependence on a drug
inference
logical interpretation based on prior knowledge and experience
endangered species
species whose population size is rapidly declining and will become extinct if the trend continues
anthropoid
primate group made up of humans, apes, and most monkeys
pancreas
gland that produces hormones that regulate blood sugar; produces enzymes that break down carbohydrates, proteins, lipids, and nucleic acids; and produces sodium bicarbonate, a base that neutralizes stomach acid
glycolysis
first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid
taste bud
sense organ that detects the flavor of a substance
double fertilization
fertilization in angiosperms, in which two distinct fertilization events take place between the male and female gametophytes
deforestation
destruction of forests
zygote
fertilized egg
herbivore
organism that obtains energy by eating only plants
depressant
drug that decreases the rate of functions regulated by the brain
photoperiodism
response of plants to periods of light and darkness
filament
in algae, a long threadlike colony formed by many green algae; in plants, a long, thin structure that supports an anther
seed cone
cone that produces female gametophytes
retina
innermost layer of the eye; contains photoreceptors
crossing-over
process in which homologous chromosomes exchange portions of their chromatids during meiosis
acid
compound that forms hydrogen ions (H+) in solution
operon
group of genes operating together
prophase
first and longest phase of mitosis, during which the chromosomes become visible and the centrioles separate and take up positions on the opposite sides of the nucleus
microclimate
climate within a small area that differs significantly from the climate of the surrounding area
limiting nutrient
single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem
pressure-flow hypothesis
hypothesis that considers plants in terms of where they produce and use materials from photosynthesis
stabilizing selection
form of natural selection by which the center of the curve remains in its current position; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end
science
organized way of using evidence to learn about the natural world; also, the body of knowledge that scientists have built up after years of using this process
nerve net
loosely organized network of nerve cells that together allow cnidarians to detect stimuli
thorax
body part of a crustacean that lies just behind the head and houses most of the internal organs
ovoviviparous
term used to refer to animals whose young are born alive after developing in eggs inside the mother's body
secondary succession
succession following a disturbance that destroys a community without destroying the soil
interphase
period of the cell cycle between cell divisions
phytoplankton
population of algae and other small, photosynthetic organisms found near the surface of the ocean and forming part of plankton
kelp forest
coastal ocean community named for its dominant organism—kelp, a giant brown alga
point mutation
gene mutation involving changes in one or a few nucleotides
sporangiophore
specialized hyphae where sporangia are found
nictitating membrane
movable transparent membrane in amphibians located inside the regular eyelid; protects the surface of the eye from damage under water and keeps it moist on land
amylase
enzyme in saliva that breaks the chemical bonds in starches
mixture
material composed of two or more elements or compounds that are physically mixed together but not chemically combined
apical dominance
phenomenon in which the closer a bud is to the stem's tip, the more its growth is inhibited
ovulation
process in which an egg is released from the ovary
biotic factor
biological influence on organisms within an ecosystem
observation
use of one or more of the senses—sight, hearing, touch, smell, and sometimes taste—to gather information
detritivore
organism that feeds on plant and animal remains and other dead matter
adhesion
attraction between molecules of different substances; in plants, attraction between unlike molecules
family
group of genera that share many characteristics
canopy
dense covering formed by the leafy tops of tall rain forest trees
thylakoid
saclike photosynthetic membrane found in chloroplasts
neurulation
development of the nervous system
clitellum
band of thickened, specialized segments in annelids that secretes a mucus ring into which eggs and sperm are released
density-independent limiting factor
limiting factor that affects all populations in similar ways, regardless of population size
organelle
specialized structure that performs important cellular functions within a eukaryotic cell
metabolism
set of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes
asexual reproduction
process by which a single parent reproduces by itself
lens
transparent object behind the iris that changes shape to help adjust the eye's focus to see near or distant objects
parasitism
symbiotic relationship in which one organism lives in or on another organism (the host) and consequently harms it
ecological pyramid
diagram that shows the relative amounts of energy or matter within each trophic level in a food chain or food web
geographic isolation
form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water
autosome
chromosome that is not a sex chromosome
vascular cambium
lateral meristematic tissue that produces vascular tissues and increases the thickness of the stem over time
pollutant
harmful material that can enter the biosphere through the land, air, or water
evolution
change in a kind of organism over time; process by which modern organisms have descended from ancient organisms
translation
decoding of a mRNA message into a polypeptide chain
nuclear envelope
layer of two membranes that surrounds the nucleus of a cell
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
spinneret
organ in spiders that contains silk glands
endosperm
food-rich tissue that nourishes a seedling as it grows
chlorophyll
principal pigment of plants and other photosynthetic organisms; captures light energy
sorus
cluster of sporangia on the underside of a fern frond
enzyme
protein that acts as a biological catalyst
solute
substance that is dissolved in a solvent to make a solution
sporophyte
diploid, or spore-producing, phase of an organism
climate
average, year-after-year conditions of temperature and precipitation in a particular region
capillary
smallest blood vessel; brings nutrients and oxygen to the tissues and absorbs carbon dioxide and waste products
cell division
process by which a cell divides into two new daughter cells
fat
lipid; made up of fatty acids and glycerol; protects body organs, insulates body, and stores energy in the body
concentration
the mass of solute in a given volume of solution, or mass/volume
monosaccharide
single sugar molecule
ozone layer
atmospheric layer in which ozone gas is relatively concentrated
nutrient
chemical substance that an organism requires to live
carapace
in crustaceans, the part of the exoskeleton that covers the cephalothorax; in turtles and tortoises, the dorsal part of the shell
trait
specific characteristic that varies from one individual to another
tropical zone
warm climate zone that receives direct or nearly direct sunlight year round
cortex
spongy layer of ground tissue just inside the epidermis of a root
relative frequency
number of times an allele occurs in a gene pool compared with the number of times other alleles occur
epidermal cell
cell that makes up the dermal tissue, which is the outer covering of a plant
periosteum
tough layer of connective tissue surrounding a bone
perennial
flowering plant that lives for more than two years
lymphocyte
type of white blood cell that produces antibodies that help destroy pathogens
coniferous
term used to refer to trees that produce seed-bearing cones and have thin leaves shaped like needles
incomplete metamorphosis
type of insect development characterized by a similar appearance throughout all stages of the life cycle
diffusion
process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated
Archaea
domain of unicellular prokaryotes that have cell walls that do not contain peptidoglycan
taxon
group or level of organization into which organisms are classified
transcription
process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA
sustainable development
using natural resources at a rate that does not deplete them
coevolution
process by which two species evolve in response to changes in each other
phylum
group of closely related classes
actin
a protein that mainly makes up the thin filaments in striations in skeletal muscle cells
derived character
characteristic that appears in recent parts of a lineage, but not in its older members
lysogenic infection
process by which a virus embeds its DNA into the DNA of the host cell and is replicated along with the host cell's DNA
class
group of similar orders
operational definition
description of how a particular variable is to be measured or how a term is to be defined
deoxyribonucleic acid (DNA)
nucleic acid that contains the sugar deoxyribose
data
evidence; information gathered from observations
madreporite
sievelike structure through which the water vascular system of an echinoderm opens to the outside
large intestine
colon; organ that removes water from the undigested materials that pass through it
blade
thin, flattened section of a plant leaf that collects sunlight
mammary gland
gland in mammals that produces milk to nourish the young
gizzard
in earthworms, part of the digestive system in which food is ground into smaller pieces; in birds, a muscular organ that helps in the mechanical breakdown of food
territory
specific area occupied and protected by an animal or group of animals
weather
condition of Earth's atmosphere at a particular time and place
nematocyst
stinging structure within each cnidocyte of a cnidarian that is used to poison or kill prey
polyploidy
condition in which an organism has extra sets of chromosomes
manipulated variable
factor in an experiment that a scientist purposely changes; also known as independent variable
chemoautotroph
organism that makes organic carbon molecules from carbon dioxide using energy from chemical reactions
osmosis
diffusion of water through a selectively permeable membrane
alveolus
tiny air sac at the end of a bronchiole in the lungs that provides surface area for gas exchange to occur
hypha
tiny filament that makes up a multicellular fungus or a water mold
food web
network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem
NADP+ (nicotinamide adenine dinucleotide phosphate)
one of the carrier molecules that transfers high-energy electrons from chlorophyll to other molecules
pollen grain
male gametophyte in seed plants
tissue
group of similar cells that perform a particular function
relative dating
method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock
pacemaker
small group of cardiac muscle cells in the right atrium that "set the pace" for the heart as a whole; also known as the sinoatrial node
dormancy
period of time during which a plant embryo is alive but not growing
sex chromosome
one of two chromosomes that determine an individual's sex; females have two X chromosomes; males have one X chromosome and one Y chromosome
menstrual cycle
cycle during which an egg develops and is released from an ovary and the uterus is prepared to receive a fertilized egg
mass extinction
event in which many types of living things become extinct at the same time
polygenic trait
trait controlled by two or more genes
gametangium
gamete-producing structure found in black bread mold
grafting
use of a stem as a scion
trachea
windpipe; tube through which air moves
follicle
cluster of cells surrounding a single egg in the human female reproductive system
root cap
tough structure that protects a root as it forces its way through the soil
plasmodium
structure with many nuclei formed by acellular slime molds
peristalsis
rhythmic muscular contractions that squeeze food through the esophagus into the stomach
exponential growth
growth pattern in which the individuals in a population reproduce at a constant rate
zoosporangium
spore case
pollen cone
cone in gymnosperms that produces male gametophytes in the form of pollen grains
endospore
type of spore formed when a bacterium produces a thick internal wall that encloses its DNA and a portion of its cytoplasm
cotyledon
first leaf or first pair of leaves produced by the embryo of a seed plant
detritus
particles of organic material that provide food for organisms at the base of an estuary's food web
half-life
length of time required for half of the radioactive atoms in a sample to decay
homologous structures
structures that have different mature forms in different organisms but develop from the same embryonic tissues
bronchus
passageway leading from the trachea to a lung
cloaca
a muscular cavity at the end of the large intestine through which digestive wastes, urine, and eggs or sperm leave the body
dependent variable
factor in an experiment that a scientist wants to observe, which may change because of the manipulated variable; also known as a responding variable
stomach
large muscular sac that continues the mechanical and chemical digestion of food
Calorie
term used by scientists to measure the energy stored in foods; 1000 calories
mycelium
many hyphae tangled together into a thick mass; comprises the bodies of multicellular fungi
deuterostome
"animal whose anus is formed from the blastopore of a blastula
chemoheterotroph
organism that must take in organic molecules for both energy and carbon
cartilage
strong connective tissue that supports the body and is softer and more flexible than bone
light-dependent reactions
reactions of photosynthesis that use energy from light to produce ATP and NADPH
auxin
substance produced in the tip of a seedling that stimulates cell elongation
van der Waals forces
a slight attraction that develops between the oppositely charged regions of nearby molecules
radial symmetry
body plan in which body parts repeat around the center of the body; characteristic of sea anemones and sea stars
symbiosis
relationship in which two species live closely together
endodermis
layer of cells that completely encloses vascular tissue
stroma
region outside the thylakoid membranes in chloroplasts
solution
mixture of two or more substances in which the molecules of the substances are evenly distributed
stolon
in fungi, a stemlike hypha that runs along the surface of an object; in plants, a long, trailing stem that produces roots when it touches the ground
capsid
outer protein coat of a virus
medusa
motile stage of the life cycle of a cnidarian that has a bell-shaped body
ribosomal RNA (rRNA)
type of RNA that makes up the major part of ribosomes
ganglion
group of nerve cells
geologic time scale
scale used by paleontologists to represent evolutionary time
chemical reaction
process that changes one set of chemicals into another set of chemicals
lignin
substance in vascular plants that makes cell walls rigid
gene map
diagram showing the relative locations of each known gene on a particular chromosome
operator
region of chromosome in an operon to which the repressor binds when the operon is "turned off"
spindle
fanlike microtubule structure that helps separate the chromosomes during mitosis
vas deferens
tube that carries sperm from the epididymis to the urethra
heterozygous
term used to refer to an organism that has two different alleles for the same trait
amphibian
vertebrate that, with some exceptions, lives in water as a larva and on land as an adult, breathes with lungs as an adult, has moist skin that contains mucus glands, and lacks scales and claws
sapwood
area in plants that surrounds heartwood and is active in fluid transport
kidney
organ that removes urea, excess water, and other waste products from the blood and passes them to the ureter
mineral
inorganic nutrient the body needs, usually in small amounts
ecosystem diversity
variety of habitats, living communities, and ecological processes in the living world
recombinant DNA
DNA produced by combining DNA from different sources
seed coat
structure that surrounds and protects a plant embryo and keeps it from drying out
vascular tissue
type of plant tissue specialized to conduct water and nutrients throughout a plant
stem
supporting structure that connects roots and leaves and carries water and nutrients between them
gastrovascular cavity
digestive chamber with a single opening, in which cnidarians, flatworms, and echinoderms digest food
pheromone
specific chemical messenger that affects the behavior or development of other individuals of the same species
palisade mesophyll
layer of tall, column-shaped mesophyll cells just under the upper epidermis of a leaf
oogonium
specialized structure formed by hyphae that produces female nuclei
adaptive radiation
process by which a single species or small group of species evolves into several different forms that live in different ways; rapid growth in the diversity of a group of organisms
independent variable
factor in an experiment that a scientist purposely changes; also known as a responding variable
style
narrow stalk of the carpel in a flower
urinary bladder
saclike organ in which urine is stored before being excreted
algal bloom
an immediate increase in the amount of algae and other producers that results from a large input of a limiting nutrient
small intestine
digestive organ in which most chemical digestion takes place
atherosclerosis
condition in which fatty deposits called plaque build up on the inner walls of the arteries
metaphase
second phase of mitosis, during which the chromosomes line up across the center of the cell
pharyngeal pouch
one of a pair of structures in the throat (pharynx) region of a chordate

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