abiotic factors
Nonliving components of environment.
amino acids
Building blocks of proteins; 20 different types in the human body.
biotic factors
All the living organisms that inhabit an environment.
aerobic
Process that requires oxygen.
anaerobic
Process that does not require oxygen.
homeostasis
A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level.
asexual reproduction
Process by which a single parent reproduces by itself.
sexual reproduction
A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents.
active transport
Energy-requiring process that moves material across a cell membrane against a concentration difference.
allele
Different forms of a gene.
antigen
A protein that, when introduced in the blood, triggers the production of an antibody.
bilateral symmetry
Body plan in which only a single, imaginary line can divide the body into two equal halves.
biome
A group of ecosystems that share similar climates and typical organisms.
biodiversity
The variety of life in the world or in a particular habitat or ecosystem.
biomass
Total amount of living tissue within a given trophic level.
bone marrow
A soft tissue inside the bone that produces blood cells.
Calvin Cycle
Reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars.
carbohydrates
The starches and sugars present in foods.
carrying capacity
Largest number of individuals of a population that an environment can support.
catalyst
Substance that speeds up the rate of a chemical reaction.
cell wall
A rigid layer of nonliving material that surrounds the cells of plants and some other organisms.
cellular respiration
Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.
cellulose
A substance (made of sugars) that is common in the cell walls of many organisms.
centromere
Area where the chromatids of a chromosome are attached.
cerebrum
Area of the brain responsible for all voluntary activities of the body.
chlorophyll
A green pigment found in the chloroplasts of plants, algae, and some bacteria.
chloroplast
An organelle found in plant and algae cells where photosynthesis occurs.
chromatin
Clusters of DNA, RNA, and proteins in the nucleus of a cell.
chromosomes
Threadlike structures made of DNA molecules that contain the genes.
circulatory system
Transports oxygen, waste, nutrients, hormones, heat, etc. around the body.
codon
A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid.
coniferous forest
Forest populated by cone-bearing evergreen trees; mostly found in northern latitudes.
commensalism
A relationship between two organisms in which one organism benefits and the other is unaffected.
community
All the different populations that live together in an area.
cytokinesis
Division of the cytoplasm during cell division.
cytolysis
The bursting of a cell.
cytoplasm
A jellylike fluid inside the cell in which the organelles are suspended.
deciduous
(Of plants and shrubs) shedding foliage at the end of the growing season.
desert
Can be hot or cold; receives less than 30 cm of precipitation per year.
diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
digestion
Breakdown of food substances into simpler forms that can be absorbed and used.
dihybrid cross
A cross between individuals that have different alleles for the same gene.
dominant allele
An allele whose trait always shows up in the organism when the allele is present.
ecology
Scientific study of interactions among organisms and between organisms and their environment.
ecosystem
A biological community of interacting organisms and their physical environment.
ectothermic
Cold blooded. Cannot regulate its own body temperature.
Electron Transport Chain
A sequence of electron carrier molecules (membrane proteins) that shuttle electrons during the redox reactions that release energy used to make ATP.
endothermic
Absorbs heat.
epidermis
Outer layer of skin.
excretion
Process by which metabolic wastes are eliminated from the body.
flagellate
To whip; to lash.
fruit
A mature ovary of a flower that protects dormant seeds and aids in their dispersal.
food chain
A series of steps in which organisms transfer energy by eating and being eaten.
food web
A community of organisms where there are several interrelated food chains.
gene
A segment of DNA on a chromosome that codes for a specific trait.
genetics
The scientific study of heredity.
genotype
Genetic makeup of an organism.
gestation
Growth process from conception to birth.
gonad
Female or male reproductive organ that produces sex cells and hormones; ovary or testis.
hermaphrodite
An organism that has both male and female reproductive organs.
hibernation
Long-term resting state that is an adaptation to winter cold and food scarcity.
hydrophobic
“Water-fearing”; pertaining to nonpolar molecules (or parts of molecules) that do not dissolve in water.
isotonic solution
A solution in which the concentration of solutes is essentially equal to that of the cell which resides in the solution.
lysosome
A small, round cell structure containing chemicals that break down large food particles into smaller ones.
lipids
Energy-rich organic compounds, such as fats, oils, and waxes, that are made of carbon, hydrogen, and oxygen.
meiosis
Cell division that produces reproductive cells in sexually reproducing organisms.
membrane
Thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.
messenger RNA
RNA molecule that carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell.
metabolism
All of the chemical reactions that occur within an organism.
mitosis
Part of eukaryotic cell division during which the cell nucleus divides.
monohybrid cross
A cross between individuals that involves one pair of contrasting traits.
monosaccharides
Simple sugars (glucose, fructose, galactose).
mutualism
A relationship between two species in which both species benefit.
NADPH
An electron carrier involved in photosynthesis.
nervous system
A conglomeration of billions of cells specifically designed to provide a communication network within the human body.
neurotoxins
Toxic substances, such as lead or mercury, that specifically poison nerve cells.
niche
An organism’s particular role in an ecosystem, or how it makes its living.
nucleotides
Basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases.
nucleus
A part of the cell containing DNA and RNA and responsible for growth and reproduction.
osmosis
Diffusion of water through a selectively permeable membrane.
parasite
An organism that lives in or on another organism; one who lives off another person.
parasitism
A relationship between two organisms of different species where one benefits and the other is harmed.
passive transport
The movement of substances across a cell membrane without the use of energy by the cell.
pathogen
An organism that causes disease.
phenotype
An organism’s physical appearance, or visible traits.
phospholipid
A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.
phototropism
A growth response to light.
placenta
A structure that allows an embryo to be nourished with the mother’s blood supply.
plankton
Tiny organisms that float in the water.
plasma membrane
A selectively-permeable phospholipid bilayer forming the boundary of the cells.
pollen
A fine dust that contains the sperm of seed-producing plants.
pollination
The transfer of pollen from male reproductive structures to female reproductive structures in plants.
population
A group of individuals that belong to the same species and live in the same area.
primary consumer
An organism that eats producers.
primary succession
Succession that occurs on surfaces where no soil exists.
proteins
Nutrients the body uses to build and maintain its cells and tissues.
quaternary consumer
An organism that eats tertiary consumers.
recessive allele
An allele that is masked when a dominant allele is present.
regeneration
The ability to regrow a missing part of the body.
respiration
Inhalation and exhalation of air.
respiratory system
The organ system that brings oxygen to body cells and removes waste gas.
secondary consumer
An organism that eats primary consumers.
secondary succession
Type of succession that occurs in an area that was only partially destroyed by disturbances.
species
A group of similar organisms that can breed and produce fertile offspring.
symbiosis
A close relationship between two species that benefits at least one of the species.
skeletal system
Protects and supports body organs and provides a framework the muscles use to support movement. Made up of bones and joints.
taxonomy
The scientific study of how living things are classified.
temperate forest
Biome characterized by broad-leaved, deciduous trees, well-defined seasons, and average yearly precipitation of 75-150 cm.
temperate grassland
A community (or biome) that is dominated by grasses, has few trees, and is characterized by cold winters and rainfall that is intermediate between that of a forest and a desert.
tertiary consumer
An organism that eats secondary consumers.
transformation
A change in genotype and phenotype due to the assimilation of external DNA by a cell.
transpiration
Evaporation of water from the leaves of a plant.
tropical forest
Warm, long days; very diverse; over 200 cm of precipitation per year.
vaccine
A harmless variant or derivative of a pathogen that stimulates a host’s immune system to mount defenses against the pathogen.
vacuole
Cell organelle that stores materials such as water, salts, proteins, and carbohydrates.
ventricle
Bottom portion of the heart, thicker walled and larger.
virus
A tiny, nonliving particle that invades and then reproduces inside a living cell.
zooplankton
Tiny floating organisms that are either small animals or protozoa.
zygote
The fertilized egg; it enters a 2-week period of rapid cell division and develops into an embryo.
