509 terms

Barron's AP Biology Complete Glossary

A complete rendition of all terms and definitions in the Glossary provided by Barron's AP Biology, 4th Edition
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ABA (abscisic acid)
Plant hormone that inhibits growth, closes stomates during times of water stress and counteracts breaking of dormancy
Abiotic
Nonliving and includes temperature, water, sunlight, wind, rocks, and soil
Abscission
The process of leaves falling off a tree or bush
Acetylcholine
One of many neurotransmitters (ACC)
Acid rain
Caused by pollutants in the air from combustion of fossil fuels; the pH is less than 5.6
Actin
Thin protein filaments that interact with myosin filaments in the contraction of skeletal muscles
Action potential
A rapid change in the membrane of a nerve or muscle cell when a stimulus causes an impulse to pass
Active immunity
The type of immunity when an individual makes his or her own antibodies after being ill and recovering or after being given an immunization or vaccine
Adaptive radiation
The emergence of numerous species from one common ancestor introduced into an environment
Adenine
A nucleotide that binds to thymine and uracil; it is a purine
Adipose
Fat tissue
Allopatric speciation
The formation of new species caused by separation in geography, such as mountain ranges, canyons, rivers, lakes, glaciers, altitude, or longitude
Allosteric
A type of enzyme that changes its conformation and its function in response to a modifier
Amoebocytes
Found in sponges, these cells are mobile and perform numerous functions, including reproduction, transport of food particles to nonfeeding cells, and secretion of material that forms the spicules
Amphipathic
A molecule with both a positive and negative pole
Anaerobic respiration
The anaerobic breakdown of glucose into pyruvic acid with the release of a small amount of ATP
Analogous structures
Structures, such as a bat's wing and a fly's wing, that have the same function, but the similarity is superficial and reflects an adaptation to similar environments, not a common ancestry
Aneuploidy
Any abnormal number or a particular chromosome
Angiosperms
Flowering plants
Anode
The positive pole in an electrolytic cell
Antenna pigment
Accessory photosynthetic pigment that explains the wavelengths of light that can be used to power photosynthesis
Anterior pituitary
Gland in the brain that releases many hormones, including growth hormone, luteinizing hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, and follicle-stimulating hormone
Anther
Part of a flowering plant that produces male gametophytes
Antheridia
Structures in plants that produce male gametes
Antibodies
Produced by B lymphocytes and destroy antigens
Anticodon
The three-base sequence of nucleotides at one end of a tRNA molecule
Antidiuretic hormone
Released by the posterior pituitary, its target is the collecting tube of the nephron
Apical dominance
The preferential growth of a plant upward (toward the sun), rather than laterally
Apoptosis
Programmed cell death
Aposematic coloration
The bright, often red or orange coloration of poisonous animals as a warning that predators should avoid them
Archegonia
Structures in plants that produce female gametes
Artificial selection
The intentional selection of specific individuals with desired traits for breeding
Associative learning
One type of learning in which one stimulus becomes linked, through experience, to another
ATP-synthase channels
Located in the cristae of mitochondria and thylakoids of chloroplasts, these are membrane channels that allow protons to diffuse down a gradient in the production of ATP
Autonomic nervous system
The branch of the vertebrate peripheral nervous system that controls involuntary muscles
Autotrophs
Organisms that synthesize their own nutrients
Auxin
A plant hormone that stimulated stem elongation and growth, enhances apical dominance, and is responsible for tropisms
Bacteriophage
A virus that attacks bacteria
Balanced polymorphism
The presence of two or more phenotypically distinct forms of a trait in a single population, such as two varieties of peppered moths, black ones and white ones
Barr body
An inactivated X chromosome seen as a condensed body lying just inside the nuclear envelope
Batesian mimicry
The copycat coloration where one harmless animal mimics the coloration of one that is poisonous; an example is the viceroy butterfly, which is harmless but looks similar to the monarch butterfly
Binomial nomenclature
A scientific naming system where every organism has a unique name consisting of two parts: a genus name and a species name
Biological magnification
A trophic process in which substances in the food chain become more concentrated with each link of the food chain
Biomes
Very large regions of the earth, names for the climatic conditions and for the predominant vegetation; examples are marine, tropical rain forest, and desert
Biotic potential
The maximum rate at which a population could increase under ideal conditions
B lymphocyte
A lymphocyte that produces antibodies
Bottleneck effect
An example of genetic drift that results from the reduction of a population, typically by natural disaster; the surviving population is no longer genetically representative of the original one
Botulinum
The genus name for the bacterium that produces botulism, a very serious form of food poisoning
Bryophytes
Nonvascular plants like mosses
Bulk flow
The general term for the overall movement of a fluid in one direction in an organism, such as sap flowing in a tree or blood flowing in a human
Bundle sheath cell
A type of photosynthetic plant cell that is tightly packed around the veins in a leaf
C-3 plant
The common type of plant, different from C-4 and CAM plants
C-4 plant
A plant with the anatomical and biochemical modifications for a dry environment that differ from C-3 and CAM plants; examples are sugarcane and corn
Calvin cycle
A cyclic metabolic pathway in the dark reactions of photosynthesis that fixes or incorporates carbon into carbon dioxide and produces phosphoglyceraldehyde (PGAL), a three-carbon sugar
CAM (crassulacean acid metabolism)
A form of photosynthesis that is an adaptation to ry conditions; stomates remain closed during the day and open only at night
Capsid
The protein shell that encloses viral DNA or RNA
Carbon fixation
Carbon becomes fixed or incorporated into a molecule of PGAL; this happens during the Calvin cycle
Carbonic acid anhydrase
An enzyme found in red blood cells that catalyzes the conversion of carbon dioxide and water into carbonic acid as part of the system that maintains blood pH at 7.4
Carotenoid
Accessory photosynthetic pigment that is yellow or orange
Carrying capacity
The limit to the number of individuals that can occupy one area at a particular time
Catalase
An enzyme produced in all cells to decompose hydrogen peroxide, a by-product of cell respiration
Cathode
The negative pole in an electrolytic cell
CDKs (cyclin-dependent kinases)
A kinase whose activity depends on the level of cyclins and that controls the timing of cell division
Cell plate
A double membrane down the midline of a dividing plant cell between which the new cell wall will form
Centriole
One of two structures in animal cells involved with cell division
Centromere
A specialized region in a chromosome that holds the two chromatids together
Chemiosmosis
The process by which ATP is produces from the flow of protons through an ATP-sythase channel in the thylakoid membrane of the chloroplast during the light reactions of photosynthesis and in the cristae membrane if the mitochondria during cell respiration
Chemokines
A chemical secreted by blood vessel endothelium and monocytes during an immune response to attract phagocytes to an area
Chiasma/chiasmata
The site at which crossover and recombination occurs
Chitin
A structural polysaccharide found in cell walls, i.e., cell walls of fungi and exoskeletons of arthropods
Chlorophyll a
One type of chlorophyll that participates directly in the light-dependent reactions of photosynthesis
Chlorophyll b
One type of chlorophyll that acts as an antenna pigment, expanding the wavelengths of light that can be used to power photosynthesis
Chloroplast
The site of photosynthesis in plant cells
Choanocytes
Collar cells that line the body cavity and have flagella that circulate water in sponges
Chromatid
Either of the two strands of a replicated chromosome joined at the centromere
Chromatin network
The complex of DNA and protein that makes up a eukaryotic chromosome; when the cell is not dividing, chromatin exists as long, thin strands, and is not visible with the light microscope
Cilia
Hairlike extensions from the cytoplasm used for cell locomotion
Citric acid cycle
Another name for the Krebs cycle
Cladogenesis
Branching evolution occurs when a new species branches out from a parent species
Classical conditioning
One type of associative learning that is widely accepted because of the ingenious work of Ivan Pavlov associating a novel stimulus with an innately recognized one
Cleavage furrow
A shallow groove in the cell surface in an animal cell where cytokinesis is taking place
Climax community
The final, stable community in an ecosystem
Cline
A variation in some trait of individuals coordinated with some gradual change in temperature or other factor over a geographic range
Clonal selection
A fundamental mechanism in the development of immunity; antigenic molecules select or bind to specific B or T lymphocytes, activating them; the B cells then differentiate into plasma cells and memory cells
Cnidocytes
Stinging cells in all cnidarians
Codominance
The type of inheritance when there is no trait that dominates over another; both traits show
Codons
The three-base sequence of nucleotides in mRNA
Coelom
The body cavity that arises from within the mesoderm and is completely surrounded by mesoderm tissue
Coevolution
Evolution that is caused by two species that interact and influence each other; all predator-prey relationships are examples
Cohesion tension
Force of attraction between molecules of water due to hydrogen bonding
Collaboration
Two genes interact to produce a novel phenotype
Collenchyma cells
Plant cells with unevenly thickened primary cell walls that are alive at maturity and that function to support the growing stem
Commensalism
A symbiotic relationship where one organism benefits and one is unaware of the other organism (+/o)
Community
All the organisms living in one area
Companion cell
Connected to each sieve tube member in the phloem and nurtures the sieve tube elements
Complement
An important part of the immune system, a group of about twenty proteins that assists in lysing cells
Complementary genes
The expression of two or more genes where each depends upon the alleles of the other in order for a trait to show
Conformation
The particular three-dimentional shape of a protein molecule
Conjugation
A primitive form of sexual reproduction that is characteristic of bacteria and some algae
Convergent evolution
Evolution that occurs when unrelated species occupy the same environment and are subjected to similar selective pressures and show similar adaptations
Countercurrent mechanism
A mechanism or strategy to maximize the rate of diffusion; this is a major strategy to transport substances across membranes passively, such as in the nephron
Cristae
The internal membranes of the mitochondria that are the site of the electron transport chain
Crop
Part of the digestive tract of many animals where food is temporarily stored until it can continue to the gizzard
Crossing-over
The reciprocal exchange of genetic material between nonsister chromatids during synapsis of meiosis I
Cutin
The main component of the waxy cuticle covering leaves to minimize water loss
Cyclic phosphorylation
Part of the light-dependent reactions in photosynthesis where electrons travel on a short-circuit pathway to replenish ATP levels only
Cyclin
A regulatory protein whose levels fluctuate cyclically in a cell, in part, related to the timing of cell division
Cystic fibrosis
The most common lethal genetic disease in the United States; characterized by a buildup of extracellular fluid in the lungs and digestive tract
Cytochrome
An iron-containing pigment present in the electron transport chain of all aerobes
Cytokines
Chemicals that stimulate helper T cells, B cells, and killer T cells
Cytokinesis
Division of the cytoplasm
Cytokinins
Plant hormone that stimulates cell division and delays senescence (aging)
Cytosine
A nucleotide that binds with guanine; a pyrimidine
Cytoskeleton
A complex network of protein filaments that gives a cell its shape and helps it move
Cytotoxic T cells
A type of lymphocyte that kills infected body cells and cancer cells
Decomposers
Organisms, like bacteria and fungi, that recycle nutrients back to the soil
Deletion
A chromosomal mutation where a fragment is lost during cell division
Dendrites
The sensory processes of a neuron
Denitrifying bacteria
Convert nitrates (NO3) into free atmospheric nitrogen
Density-dependent factors
Factors, such as starvation, that increase directly as the population density increases
Density-dependent inhibition
A characteristic of normal cells grown in culture that causes cell division to cease when the culture becomes too crowded
Density-independent factors
Factors, such as earthquakes, whose occurrence is unrelates to the population density
Depolarization
An electrical state where the inside of an excitable cell is made less negative compared with the outside; if an axon is depolarized, an impulse is passing
Detrivores
Consumers that derive their nutrition from nonliving, organic matter
Deuterostomes
Animals in which the blastopore becomes the anus during early embryonic development
Dicotyledon
A subdivision of flowering plants whose members possess an embryonic seed leaf made of two halves or cotyledons
Dihybrid cross
A cross between individuals that are hybrid for two different traits, such as height and seed color
Diploblastic
An organism whose body is made of only two cell layers, the ectoderm and the endoderm; the two are connected by a noncellular layer called the mesoglea; animal phyla that are this are the Porifera (sponges) and the Cnidaria (jellyfish and hydra)
Directional selection
Selection here one phenotype replaces another in the gene pool
Disruptive selection
Selection that increases the extreme types in a population at the expense of intermediate forms
Divergent evolution
Evolution that occurs when a population becomes isolated (for any reason) from the rest of the species, becomes exposed to new selective pressures, and evolves into a new species
DNA ligase
An enzyme that permanently attaches pieces of DNA together
Dopamine
A neurotransmitter (dopa)
Down syndrome
A genetic condition caused by trisomy 21
Duodenum
The first 12 inches (30 cm) of the human small intestine
Ecdysone
A hormone that helps control metamorphosis in insects
Ecological succesion
The sequential rebuilding of an entire ecosystem after a disaster
Ecosystem
All the organisms in a given area as well as the abiotic (nonliving) factors with which they interact
Ectoderm
The germ layer that gives rise to the skin and nervous system
Effectors
Muscles or glands
Electron transport chain
A sequence of membrane proteins that carry electrons through a series of redox reactions to produce ATP
Endergonic
Any process that absorbs energy
Endoderm
The embryonic germ layer that gives rise to the viscera, the digestive tract, and other internal organs
Endodermis
The tightly packed layer of cells that surrounds the vascular cylinder in the root of a plant
Endoplasmic reticulum
A system of transport channels inside a eukaryotic cell
Endosperm
The food source for the growing embryo in monocots
Endosymbiosis
This theory states that mitochondria and chloroplasts were once free-living prokaryotes that took up residence inside larger prokaryotic cells in a permanent, symbiotic relationship
Endotherms
Animals that can raise their body temperature, although they cannot maintain a stable body temperature
Envelope
Cloaks the capsid of a virus and aids the virus in infecting the host; the envelope is derived from membranes of host cells
Enzyme
A protein that serves as a catalyst
Epicotyl
Part of the developing embryo that will become the upper part of the stem and the leaves of a plant
Epinephrine
A neurotransmitter (EpiPen)
Epiphytes
Photosynthetic plants that grow on other trees rather than supporting themselves
Epistasis
Two separate genes control one trait, but one gene masks the expression of the other gene
Esterase
An enzyme that breaks down excess neurotransmitter
Ethylene
A gaseous plant hormone that promotes fruit ripening and opposes auxins in its actions
Eukaryotes
Cells with internal membranes
Eutrophication
Translates as "true feeding"; a process begun by the entrance of large amounts of nutrients into a lake, ultimately ending with the death of the lake
Exocytosis
The process by which cells expel substances
Exons
Stands for expressed sequences of DNA; these are genes
Exothermic
Any process that gives off energy
Expressivity
The range of expression of mutant genes
Extranuclear genes
Genes outside the nucleus, in the mitochondria and chloroplasts
Facultative anaerobes
Organisms that can live without oxygen in the environment
FAD (flavin adenine dinucleotide)
A coenzyme that carries protons or electrons from glycolysis and the Krebs cycle to the electron transport chain
Fermentation
A synonym for anaerobic respiration; the processing of pyruvic acid following glycolysis to yield more NAD+ so that glycolysis has material for NADH and, significantly, can continue the process
of making ATP
Fixed action pattern
An innate, highly stereotypic behavior, which when begun is continued to completion, no matter how useless
Flagella
The tail-like structure that propels some single-celled organisms; these consist of microtubules
Follicle-stimulating hormone (FSH)
A hormone released from the anterior pituitary that stimulates the ovarian follicle
Food chain
The pathway along which food is transferred from one trophic level to the next
Food pyramid
A model of the food chain that demonstrates the interaction of the organisms and the loss of energy
Food web
The interconnected feeding relationships of organisms in an ecosystem
Founder effect
An example of genetic drift, when a small population breaks away from a larger one to colonize a new area; it is most likely not genetically representative of the original larger population
Frameshift
One type of mutation caused by a deletion or addition where the entire reading sequence of DNA is shifted; AAA TTT CCC GGG could become AAT TTC CCG GG
Frequency-dependent selection
A form of selection that acts to decrease the frequency of the more-common phenotypes and increase the frequency of the less-common ones
Fruit
A ripened ovary of a flowering plant
Fungi
The kingdom that consists of heterotrophs that carry out extracellular digestion and have walls made of chitin; includes mushrooms and yeast
GABA (gamma-aminobutyric acid)
A neurotransmitter (gamma-aminobutyric acid)
Gametangia
A protective jacket of cells that prevents some plants' gametes and zygotes from dryingout
Gametophyte
The monoploid generation of a plant
Gastrodermis
Cells that line the gastrovascular cavity in cnidarians
Gastrovascular cavity
A digestive cavity with only one opening, characteristic of cnidarians
Gated-ion channel
A channel in the plasma membrane for one specific ion, such as sodium or calcium; in the terminal branch of a neuron, it is responsible for the release of neurotransmitter into the synapse
Gene flow
the movement of alleles into or out of a population
Genetic drift
Change in the gene pool due to chance
Genetic engineering
The technology of manipulating genes for practical purposes
Genomic imprinting
Certain traits whose expression varies, depending on the parent from which they are inherited; diseases that result from imprinting are Prader-Willi and Angelman syndromes
Genotype
The types of genes an organism has
Gibberellins
Plant hormone that promotes stem elongation
Gizzard
Part of the digestive tract of many animals; it is the site of mechanical digestion
Glial cells
Cells that nourish neurons
Gluteraldehyde
A chemical fixative often used in the preparation of tissue for electron microscopy
Glycocalyx
The external surface of a plasma membrane that is important for cell-to-cell communication
Glycolysis
A nine-step, anaerobic process that breaks down one glucose molecule into two pyruvates and four ATP
Golgi apparatus
An organelle in eukaryotes that lis near the nucleus and that packages and secretes substances for the cell
Gonadotropic-releasing hormone
A hormone released by the hypothalamus that stimulates other glands to release their hormones
Gradualism
The theory that organisms descend from a common ancestor gradually, over a long period of time, in a linear or branching fashion
Grana
Stacks of thylakoid disks in the chloroplast where light reactions occur
Greenhouse effect
The warming of the planet because of the accumulation of atmospheric carbon dioxide
Ground tissue
The most common tissue type in a plant, functions mainly in support and consists of parenchyma, collenchyma, and sclerenchyma in cells
GTP (guanosine triphosphate)
A molecule closely related to ATP that provides the energy for translation
Guanine
A nucleotide that bonds with cytosine; a purine
Guttation
Due to root pressure, droplets of water appear in the morning on the leaf tips of some herbaceous plants
Gymnosperms
Conifers or cone-bearing plants
Habitat isolation
Separation of two or more organisms of the same species living in the same area but in separate habitats, such as in the water and on land
Habituation
One of the simplest forms of learning in which an animal comes to ignore a persistent stimulus
Halophiles (halobacteria)
Anaerobic bacteria that thrive in environments with very high salt concentrations
Hatch-Slack pathway
An alternate biochemical pathway found in C-4 plants; its purpose is to remove CO2 from the airspace near the stomate
Head-foot
The part of the body of mollusks that contains both sensory and motor organs
Helicase
An enzyme that untwists the double helix at the replication fork
Helper T cells
One type of T lymphocyte that activates B cells and other T lymphocytes
Hemocoels
Blood-filled cavities within the body of arthropods and mollusks with open circulatory systems
Hemophilia
An inherited genetic disease caused by the absence of one or more proteins necessary for normal blood clotting
Hermaphrodite
Organisms possessing both male and female sex organs
Heterosporous
A plant that produces two kinds of spores, male and female
Heterotroph hypothesis
This theory states that the first cells on earth were heterotrophic prokaryotes
Heterotrophs
Organisms that must ingest nutrients rather than synthesize them
Histamine
A chemical released by the body during an inflammatory response that causes the blood vessels to dilate
Homeotherms
Organisms that maintain a consistent body temperature
Homologous structures
Structures in different species that are similar because they have a common origin
Homosporous
A plant that produces a singe bisexual spore
Huntington's disease
A degenerative, inherited, dominant disease of the nervous system that results in certain and early death
Hybrid vigor
A phenomenon in which the hybrid state is selected because it has greater survival and reproductive success; also known as heterosis
Hydrophilic
Having an affinity for water
Hyperpolarized
An electrical state where the inside of the excitable cell is made more negative compared with the outside of the cell and the electric potential of the membrane increases (gets more negative)
Hypertonic
Having a greater concentration of solute than another solution
Hypocotyl
Part of the developing embryo that will become the lower part of the stem and roots
Hypothalamus
Gland locates in the brain above the pituitary that is the bridge between the endocrine and the nervous systems
Hypotonic
Having a lesser concentration of solute than another solution
Immunological memory
The capacity of the immune system to generate a secondary immune response against a specific antigen for a lifetime
Imprinting
A type of learning that is responsible for the bonding between the mother and offspring; common in birds, it occurs during a sensitive or critical period in early life
Incomplete dominance
The type of inheritance that is characterized by blending traits; for instance, one gene for red plus one gene for white results in a pink four o'clock flower
Indoleacetic acid (IAA)
IAA; a naturally occurring auxin
Inflammatory response
A nonspecific defensive reaction of the body to invasion by a foreign substance that is accompanied by the release of histamine, fever, and red, itchy areas
Interferons
A class of chemicals that block viral infections
Interneuron
AKA an association neuron, resides within the spinal chord and receives sensory stimuli and transfers the information directly to a motor neuron or to the brain for processing
Interphase
The longest stage of the life cycle of a cell; it consists of G1, S, and G2
Introns
Intervening sequences, the noncoding regions of DNA that are sometimes referred to as junk
Inversion
A chromosome mutation where a chromosomal fragment reattaches to its original chromosome but in the reverse orientation
In vitro
In the laboratory
In vivo
In the living thing
Isotonic
Two solutions containing equal concentrations of solutes
Karyotype
A procedure that analyzes the size, number, and shape of chromosomes
Kinase
An enzyme that transfers phosphate ions from one molecule to another
Kinetochore
A disc-shaped protein on the centromere that attaches the chromatid to the mitotic spindle during cell division
Klinefelter's syndrome
A genetic condition in males in which there is an extra X chromosome; the genotype is XXY
Kranz anatomy
Refers to the structure of C-4 leaves and differs from C-3 leaves. In C-4 leaves, the bundle sheath cells lie under the mesophyll cells, tightly wrapping the vein deep within the leaf, where CO2 is sequestered
Krebs cycle
AKA the citric acid cycle, it completes the breakdown of pyruvic acid into CO2, with the release of a small amount of ATP
Lactic acid fermentation
The process by which pyruvate from glycolysis is reduced to form lactic acid or lactate; this is the process that the dairy industry uses to produce yogurt and cheese
Lateral meristem
Growth region of a plant that provides secondary growth, increase in girth
Law of dominance
One of Mendel's laws; it states that when two organisms, each purebred for two opposing traits, are crossed, the offspring will be hybrid but will exhibit only the dominant trait
Law of independent assortment
States that each allelic pair separates during gamete formation; applies when genes for two traits are not on the same chromosome
Law of segregation
During the formation of gametes, allelic pairs for two traits (from the same gene on sister chromosomes) separate
Learning
A sophisticated process in which the responses of the organism are modifies as a result of experience
Linked genes
Genes that are on the same chromosome
Luteinizing hormone
Triggers the ovulation of the secondary oocyte from the ovary
Lysosomes
Sacs of hydrolytic enzymes and the principal site of intracellular digestion
Lytic cycle
A type of viral infectious cycle that results in the lysing of the host cell and the release of new phages that will infect other cells
Macroevolution
The development of an entirely new species
Macrophage
While acting as an antigen-presenting cell, it engulfs bacteria by phagocytosis and presents a fragment of the bacteria on the cell surface by an MHC II molecule
Malpighian tubules
The organ of excretion in insects
Mantle
The part of the body of mollusks that contains specialized tissue that surrounds the visceral mass and secreted the shell
Map unit
The distance on a chromosome within which recombination occurs 1 percent of the time
Marsupials
Animals whose young are born very early in embryonic development and where the joey completes its development nursing in the mother's pouch; includes kangaroos
Matrix
The inner region of the mitochondrion, where the Krebs cycle occurs
Medusa
The free-swimming, upside-down, bowl-shaped stage in the life cycle of the cnidarians; an example is the jellyfish
Megaspores
In flowering plants, these produce the ova
Meiosis
Occurs in sexually reproducing organisms and results in cells with half the chromosome number of the parent cell
Membrane potential
A measurable difference in electrical charge between the cytoplasm (negative ions) and extracellular fluid (positive ions)
Memory cells
A long-lived form of a lymphocyte that bear receptors to a specific antigen and that remains circulating in the blood in small numbers for a lifetime
Meristem
Actively dividing cells that give rise to other cells such as xylem and phloem
Mesoderm
The germ layer that gives rise to the blood, bones and muscles
Methanogens
Prokaryotes that synthesize methane from carbon dioxide and hydrogen gas
MHC (major histocompatibility complex)
A collection of cell surface markers that identify the cells as self; no two people, except identical twins, have the same of these kind of markers; AKA HLA (human leukocyte antigens)
Microevolution
Refers to the changes in one gene pool of a population
Microfilaments
Solid rods od the protein actin that make up part of the cytoskeleton
Micropyle
The opening to the ovule in a flowering plant
Microspores
In flowering plants, these produce sperm
Microtubules
A hollow rod of the protein tubulin in the cytoplasm of all eukaryote cells that make up cilia, flagella, spindle fibers, and other cytoskeletal structures of cells
Middle lamella
A distinct layer of adhesive polysaccharides that cements adjacent plant cells together
Mitchell hypothesis
An attempt to explain how energy is produced during the electron transport chain by oxidative phosphorylation
Mitochondria
The site of cell respiration and ATP synthesis in all eukaryotic cells
Mitosis
Produces two genetically identical daughter cells and conserves the chromosome number (2n)
Monera
No longer used as the name of the kingdom that contains all the prokaryotes, including bacteria
Monoclonal antibodies
Antibodies produced by a single B cell that produces a single antigen in huge quantities; they are important in research and in treating and diagnosing certain disease
Monocotyledon
A subdivision of flowing plants whose members possess one embryonic seed leaf of cotyledon
Monocytes
A type of white blood cell that transforms into macrophages, extends pseudopods, and engulfs huge numbers of microbes over a long period of time
Monohybrid cross
This is the cross between two organisms that are each hybrid for one trait
Monotremes
Egg-laying mammals where the embryo derives nutrition from the yolk, like the duck-billed platypus
Motor neuron
A neuron that stimulates effectors (muscles or glands)
Mucosa
The innermost layer of the human digestive tract; in some parts of the digestive system, it contains mucus-secreting cells and glands that secrete digestive enzymes
Müllerian mimicry
Two or more poisonous species resemble each other and gain an advantage from their combined numbers; predators learn more quickly to avoid any prey with that appearance
Multiple alleles
More than two allelic forms of a gene
Mutagenic agents
Substances that cause mutations
Mutation
Change in DNA
Mutualism
A symbiotic relationship where both organisms benefit (+/+)
Mycorrhizae
The symbiotic structures consisting of the plant's roots intermingled with the hyphae (filaments) of a fungus that greatly increase the quantity of nutrients that a plant can absorb
Myosin
Thick protein filaments that interact with actin filaments in the contraction of skeletal muscle
NAD (nicotinamide adenine dinucleotide)
A coenzyme that carries protons or electrons from glycolysis and the Krebs cycle to the electron transport chain
NADP (nicotinamide nucleotide phosphate)
Carries hydrogen from the light reactions to the Calvin cycle in the dark reactions of photosynthesis
Natural killer (NK) cell
Part of the nonspecific immune response that destroys virus-infected body cells (as well as cancerous cells)
Natural selection
A theory that explains how populations evolve and how new species develop
Neuromuscular junction
The place where a neuron synapses on a muscle
Neurotransmitter
The chemical held in presynaptic vesicles of the terminal branch of the axon that is released into a synapse and that excites the postsynaptic membrane
Neutrophils
A type of white blood cell that engulfs microbes by phagocytosis
Niche
Organisms that live in the same area and use the same resources
Nitric oxide
Acts as a local signaling molecule
Nitrifying bacteria
Convert the ammonium ion into nitrates
Nitrogen-fixing bacteria
Convert free nitrogen into the ammonium ion
Nondisjunction
Homologous chromosomes fail to separate as the should during meiosis
Norepinephrine
A neurotransmitter; IEE, NE
Notochord
A rod that extends the length of the body and serves as a flexible axis in all chordates
Nucleoid
Nuclear region in prokaryotes
Nucleolus
Located in the nucleus and is the site of protein synthesis
Nucleotides
The building blocks of nucleic acids; they consist of a five-carbon sugar, a phosphate, and a nitrogenous base: adenine thymine (in DNA), cytosine, guanine, or uracil (in RNA)
Obligate anaerobes
Prokaryotes that cannot live in the presence of oxygen
Okazaki fragments
Pieces of DNA created by the lagging strand in DNA replication; these are fused together by DNA ligase
Omnivores
Organisms, like humans, that eat both plants and animals
Operant conditioning
A type of associative learning in which an animal learns to associate one of its own behaviors with a reward or punishment and then tends to repeat or avoid that behavior; also called trial-and-error learning
Operator
In an operon, the binding site for the repressor
Operon
Consist of a promoter region, operator, and structural genes; these allow prokaryotes to regulate gene expression
Osmotic potential
The tendency of water to move across a permeable membrane into a solution
Outbreeding
Mating of organisms that are not closely related; this is a major mechanism of maintaining variation within a species
Oxidative phosphorylation
The production of ATP using energy derived from the electron transport chain
Oxytocin
Hormone released by the posterior pituitary that stimulates labor and the production of milk from mammary glands
Parallel evolution
Evolution that occurs when two related species have made similar evolutionary adaptations after their divergence from a common ancestor
Parasitism
A symbiotic relationship (+/-) where one organism, the parasite, benefits while the other organism, the host, is harmed
Parasympathetic
One of two branches of the autonomic nervous system that has a relaxing effect
Parenchyma cells
Traditional plant cells with primary cell walls that are thin and flexible and that lack secondary cell walls
Passive immunity
Immunity is transferred to an individual from someone else
Pathogens
Organisms that cause disease
Pedigree
A family tree that indicated the phenotype of one trait being studied for every member of a family and will help determine how a particular trait is inherited
Peroxisomes
Organelles in both plants and animals that break down peroxide, a toxic byproduct of cell respiration
Phage
Bacterio-this; a type of virus that attacks bacteria
Phagocytes
A type of white blood cell that ingests invading microbes
Phagocytosis
The process by which a cell engulfs large particles using pseudopods
Phenotype
The appearance of an organism
Phenylketonuria
An inborn inability to break down the amino acid phenylalanine; it requires elimination of phenylalanine from the diet, otherwise serious mental retardation will result
Phloem
Transport vessels in plants that carry sugars from the photosynthetic leaves to the rest of the plant by active transport
Phosphodiester linkages
The bonds that join nucleotides in DNA
Phosphofructokinase (PFK)
An allosteric enzyme important in glycolysis (PFK)
Phosphoglyceraldehyde (PGAL)
A three-carbon sugar, the first stable carbohydrate to by produced by photosynthesis
Photolysis
The process of splitting water, providing electrons to replace those lost from chlorophyll a in P680; this is powered by the light energy absorbed during the light-dependent reactions
Photoperiod
The environmental stimulus a plant uses to detect the time of year and the relative lengths of day and night
Photophosphorylation
The process of generating ATP by means of a proton motive force during the light reactions of photosynthesis
Photorespiration
A process that occurs when rubisco binds with O2 instead of CO2; it is a dead-end process because no ATP is produced and no sugar formed
Photosynthesis
The process by which light energy is converted to chemical bond energy
Photosystem I (P700)
Energy,with average wavelength of 700nm, is absorbed in this photosystem and transferred to electrons that move to a higher energy level
Photosystem II (P680)
Energy,with average wavelength of 680nm, is absorbed in this photosystem and transferred to electrons that move to a higher energy level
Photosystems
Light-harvesting complexes in the thylakoid membranes of chloroplasts; they consist of a reaction center containing chlorophyll a and a region containing several hundred antenna pigment molecules that funnel energy into chlorophyll a
Phycobilin
A photosynthetic antenna pigment common in red and blue-green algae
Phytochrome
The photoreceptor responsible for keeping track of the length of day and night; there are two forms of this, Pr (red light absorbing) and Pfr (infrared light absorbing)
Pili
Cytoplasmic bridges the connect one cell to another and that allow DNA to move from one cell to another in a form of primitive sexual reproduction called conjugation
Pinocytosis
A type of endocytosis in which a cell ingests large, dissolved molecules
Pioneer organisms
The first organisms, such as lichens and mosses, to inhabit a barren area
Pistil
Part of a flowering plant that produces female gametes
Placental mammals
Animals whose young are born and where the embryo develops internally in a uterus connected to the mother by a placenta where nutrients diffuse from mother to embryo; also called eutherians
Plasma cells
A short-lived form of a lymphocyte that secretes antibodies
Plasmid
Foreign, small, circular, self-replicatind DNA molecule that inhabits a bacterium and imparts characteristics to the bacterium such as resistance to antibodies
Plasmodesmata
An open channel in the cell walls of plant cells allowing for connections between the cytoplasm of adjacent cells
Plasmolysis
Cell shrinking
Plastids
Organelles in plant cells, including chloroplasts, chromoplasts, and leucoplasts
Plastoquinone
A proton and electron carrier in the electron transport chain during the light reactions of photosynthesis
Pleiotropy
One single gene affects and organisms in several or many different ways
Poikilotherms
Cold-blooded animals
Point mutation
A change in one nucleotide in DNA
Polarized membrane
An axon membrane at rest where the inside of the cell is negative compared with the outside of the cell
Pollen
One of these grains contains three monoploid nuclei, one tube nucleus, and two sperm nuclei
Pollination
The transfer of pollen from the stamen to the pistil
Polygenic
Genes that vary along a continuum, like skin color or height
Polymerase chain reaction (PCR)
A cell-free, automated technique by which a piece of DNA can be rapidly copied or amplified
Polyp
A vase-shaped body or the sessile phase in the life cycle or cnidarians
Polyploid
A chromosome mutation in which the organism possesses extra sets of chromosomes; the cell becomes 3n, 4n, 5n, and so on
Population
A group of individuals of one species living in one area
Predation
One animal eating another animal; this can also refer to animals eating plants
Primary consumer
The animal that directly eats the producer
Primary immune response
The initial immune response to an antigen
Primase
An enzyme that joins RNA nucleotides to make the primer
Prions
Infectious proteins that cause several brain diseases: scrapie in sheep, mad cow disease in cattle, and Creutzfeldt-Jacob disease in humans
Producer
Those photosynthetic organisms at the bottom of any food chain
Prokaryotes
Organisms with no internal membranes; bacteria are one example
Promoter
The binding site of RNA polymerase into an operon
Prophage
A phage genome that has been inserted into a specific site in a bacterial chromosome
Prostaglandin
A hormone that promotes blood supply to an area
Protista
The kingdom that consists of single-celled and primitive multicelled organisms, such as paramecium and amoeba
Proton pump
A mechanism in cells that uses ATP to pump protons across a membrane to generate a membrane or electric potential
Protostome
An animal in which the blastopore becomes the mouth during early embryonic development; literally, first opening
Pseudocoelomate
A body cavity with mesoderm on only one side, characteristic of nematodes
Pseudopods
Cellular extensions of amoeboid cells used in moving and feeding
Punctuated equilibrium
A theory that proposes that new species appear suddenly after long periods of stasis
Pyrimidines
A class of nucleotides that includes cytosine, thymine, and uracil
Pyrogens
A chemical released by certain leukocytes that increases body temperature to speed up the immune system and make it more difficult for microbes to function
Pyruvate
A variant of pyruvic acid
Pyruvic acid
A three-carbon molecule that is the product of glycolysis and is the raw material for the Krebs cycle
Radicle
In the embryonic root, the first organ to emerge from the germinating seed
Radula
A movable, tooth-bearing structure that acts like a tongue in mollusks
Receptor-mediated endocytosis
The uptake of specific molecules based on a cell's receptor proteins
Recessive trait
The trait that remains hidden in the hybrid state (Aa)
Recognition sequence
A specific sequence of nucleotides at which a restriction enzyme cleaves a DNA molecule
Recombinant chromosomes
Chromosomes that combine genes from both parents due to crossing-over
Recombination
The result of crossing-over
Reflex arc
The simplest nerve response; it is inborn, automatic, and protective
Refractory period
The period of time during which a neuron cannot respond to another stimulus because the membrane is returning to its polarized state
Replication bubbles
There are thousands of these along the DNA molecule that speed up the process of replication, they merge and join until there are two distinct DNA daughter molecules
Replication fork
A Y-shaped region where the new strands of DNA are elongating
Repressor
Binds to the operator of an operon and prevents RNA polymerase from binding to the promoter, thus blocking transcription
Resolution
A measure of the clarity of an image; the ability to see two objects as separate
Resource partitioning
The exploitation of environmental resources by organisms living in the same area so that each group of organisms can occupy a different niche
Restriction enzymes
Enzymes, naturally occurring in bacteria, that cut DNA at certain specific recognition sites
Restriction fragment length polymorphisms (RFLPs)
Noncoding regions of human DNA that vary from person to person; they can be used to identify a single individual; pronounced "riflips"
Restriction fragments
Fragments of DNA that result from the cuts made by restriction enzymes
Reverse transcriptase
An enzyme found in retroviruses that facilitates the production of DNA from RNA
Rhizobium
A symbiotic bacterium that lives in the nodules on roots of specific legumes and that incorporates nitrogen gas from the air into a form of nitrogen the plant requires
Ribosomes
The site of protein synthesis in the cytoplasm
RNA polymerase
The enzyme that binds to the promoter in DNA and that begins transciption
RNA primer
An already existing chain of RNA attached to DNA which DNA polymerase adds nucleotides to during DNA synthesis; these are changed from RNA to DNA language by a proofreader enzyme
Rubisco (ribulose biphosphate carboxylase)
The enzyme that catalyzes the first step in the Calvin cycle: the addition of RuBP (ribulose biphosphate) to CO2
Sarcolemma
The modified plasma membrane surrounding a skeletal muscle cell and that can propagate an action potential
Sarcomere
The basic functional unit of skeletal muscle
Sarcoplasmic reticulum
Modified ER in skeletal muscle cells
Satellite DNA
Short sequences of DNA that are tandemly repeated as many as 10 million times in the DNA; much of it is located in the telomeres
Schwann cells
Glial cells that are located in the peripheral nervous system and that form the myelin sheath around the axon of a neuron
Sclerenchyma cells
Plant cells with very thick primary and secondary walls fortified with lignin
Secondary consumer
The animal that eats the primary consumer
Seed
After fertilization, the ovule becomes this
Semiconservative replication
The way DNA replicates, each double helix separates and forms two new strands of DNA; each new molecule of DNA consists of one old strand and one new strand
Senescence
Aging
Sertoli cells
The cells found in the mammalian testes that nourish developing sperm cells, which contain no cytoplasm
Sessile
Nonmotile
Sex-influenced trait
The inheritance of a trait influenced by the sex of the individual carrying the trait
Sexual selection
Selection based on variation in secondary sexual characteristics related to or competing for and attracting mates
Sieve tube members
Along with companion cells, these make up the phloem
Single-stranded binding proteins
Proteins that act as scaffolding, holding two DNA strands apart during replication
snRNPs (small nuclear ribonucleoproteins)
Help to process RNA after it is formed and before it moves to the ribosome
Sodium-potassium pump
A protein pump within a plasma membrane of an axon that restores the membrane to its original polarized condition by pumping sodium and potassium ions across the membrane
Solute
The substance dissolved
Solvent
The substance doing the dissolving
Somatic cell
A body cell
Somatic nervous system
The branch of the vertebrate peripheral nervous system that controls skeletal (voluntary) muscles
Sori
Structures on the underside of the fern leaves that are clusters of sporangia containing monoploid spores
Specific heat
The amount of heat a substance must absorb to increase 1 gram of the substance by 1 degree Celsius
Spicules
Found in sponges, these consist of inorganic materials and support the animal
Spindle fibers
Made of microtubules that connect centrioles to kinetochores of chromosomes and that separate sister (mitosis) or homologous (meiosis) chromosomes during cell division
Spiracles
Openings in the exoskeleton of arthropods, such as the grasshopper, that connect to internal cavities called hemocoels where respiratory gases are exchanged
Splicesomes
Enzymes that (along with snRNPs) help process RNA after it is formed and before it moves to the ribosome
Spongocoel
Found in sponges, it is the central cavity into which water is drawn to filter nutrients
Sporopollenin
A tough polymer that protects plants in a harsh terrestrial environment
Stabilizing selection
Selection that eliminates the extremes and favors the more common intermediate forms
Stele
The vascular cylinder of the root, containing vascular tissue
Stroma
The site of the light-independent (dark) reactions in chloroplasts
Submucosa
A layer of the human digestive system that contains nerves, blood vessels, and lymph nodes
Survivorship curves
Show the size and composition of a population
Sympathetic nervous system
One of two branches of the autonomic nervous system that is generally excitatory
Sympatric speciation
The formation of new species without geographic isolation; such as polyploidy or behavioral isolation
Symplast
A continuous system of cytoplasm of cells interconnected by plasmodesmata
Synapsis
The process of pairing replicated homologous chromosomes during prophase I of meiosis
Systematics
Scientific study of the classification of organisms and their relationship to one another
Taq polymerase
A heat-stable form of DNA polymerase extracted from bacteria that live in hot environments, such as hot springs, that is used during PCR technique
Taxa
A particular group at a category level, such as kingdom or genus
Taxonomy
The study of classification of organisms
Tay-Sachs disease
An inherited genetic disease that is caused by lack of and enzyme necessary to break down lipids necessary for normal brain function and results in seizures, blindness, and early death; common in Ashkenazi Jews
Telomerase
An enzyme that catalyzes the lengthening of the telomeres at the ends of eukaryotic chromosomes
Telomeres
The protective ends of eukaryotic chromosomes
Tertiary consumer
The third trophic level of consumer in a food chain
Testcross
A cross is done to determine whether an individual plant or animal shown the dominant trait is homozygous dominant (B/B) or heterozygous (B/b); the individual in question (B/_) is crossed with a homozygous recessive individual
Tetanus
The smooth, sustained contraction of a skeletal muscle
Thermophiles
Prokaryotes that thrive in very high temperatures
Theta replication
The way in which prokaryotes replicate their DNA
Thylakoids
Membranes in chloroplasts that make up the grana, the site of the light reactions
Thymine
A nucleotide that bonds with adenine; it is a pyrimidine and is not present in RNA
T lymphocytes
One type of lymphocyte that fights pathogens by cell-mediated response
Tracheids
Long, thin cells that overlap and are tapered at the ends and that, along with vessel elements, make up xylem in a plant
Tracheophytes
Plants that have transport vessels, xylem and phloem
Transcription
The process by which RNA is made from a DNA template
Transduction
Transfer of bacterial DNA by phages from one bacterium to another
Transformation
The transfer of genes from one bacterium to another via genetic material (adrift) is taken up into a foreign bacterium and incorporated into the bacterium's DNA
Translation
The process by which the codons of an mRNA sequence are changed into an amino acid sequence
Translocation
A chromosomal mutation where a fragment of a chromosome becomes attached to a non-homologous chromosome; the transport of sugar in a plant from source to sink
Transpiration
Loss of water from stomata in leaves
Transpirational pull-cohesion tension theory
This theory describes the passive transport of water up a tree; for each molecule of water that evaporates from a leaf by transpiration, another molecule of water is drawn in at the root to replace it
Transposons
Transposable genetic elements, sometimes called jumping genes
Triploblastic
Having three cell layers: ectoderm, mesoderm, and endoderm
Triploid
A chromosomal mutation where an organism has three sets of chromosomes (3n) instead of two (2n)
Trisomy
A chromosomal condition in which a cell has an extra copy of one chromosome; the cel has three of that chromosome, instead of two
Trophic level
Any level of a food chain based on nutritional source
Tropic hormones
Hormones released by one endocrine gland that stimulate other endocrine glands to release their hormones
Tropism
The growth of a plant toward of away from a stimulus, for example, phototropism
T system
A set of tubules that traverse the skeletal muscle, conduct the action potential deep into the cell, and stimulate the sarcoplasmic reticulum to release calcium ions
Turgid
Firm; plant cells are swollen because they have absorbed water
Turner's syndrome
A genetic condition in females caused by a deletion of one of the two X chromosomes
Typhlosole
A large fold in the upper surface of the intestine of the earthworm that increases surface area to increase absorption
Ultramicrotome
An instrument used to cut very thin sections of tissue for use in the transmission electron microscope
Uracil
A nucleotide in only RNA that binds with adenine; it is a pyrimidine
Vacuoles
A membrane-enclosed sac for storage in all cells, particularly in plant cells
Vasolidation
The enlargement of blood vessels to increase blood supply
Vegetative propagation
Plants that can clone themselves or reproduce asexually from any vegetative part of the plant: the root, stem, or leaf
Vesicles
Small vacuoles
Vessel elements
Wide, short tubes that, along with tracheoids, make up the xylem
Vestigial structures
Structures of no importance, such as the appendix, that were once important to ancestors
Visceral mass
The part of the body of mollusks that contains the organs of digestion, excretion, and reproduction
Water potential
The tendency of water to move across a semipermeable membrane, phi; the "this" of pure water is zero; any solution has a value less that zero
Wave of depolarization
The wavelike reversal of the polarity of the membrane when an impulse passes
Wobble
Refers to the translation of mRNA to protein; the relaxation of base-pairing rules, i.e., the pairing rules for the third codon do not necessarily (as much) alter the resulting amino acid; for example, UUU and UUA both code for the amino acid phenylalanine
Xanthophyll
A photosynthetic antenna pigment common in algae that is a structural variant of a carotenoid
Xylem
Transport vessels in plants that carry water and minerals from the soil to the leaves
Z lines
These define the edges of a sarcomere in the muscle cell
Zone of cell division
The region of a plant's root with active dividing cells that grow down into the soil
Zone of differentiation
The region of root tip where cells undergo specialization
Zone of elongation
The region of root tip where cells elongate and that are responsible for pushing the root cap downward, deeper into the soil
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