Biology Now, 2e

Glossary ■ (^) G3
cartilage A dense tissue of the skeleton that combines strength
with flexibility. It is found almost everywhere that two bones
meet and prevents them from grinding together.
catabolism Metabolic pathways that release chemical energy in
the process of breaking down complex biomolecules. Compare
anabolism.
causation A statistical relation indicating that a change in one
aspect of the natural world causes a change in another aspect.
Compare correlation.
cell The smallest and most basic unit of life—a microscopic, self-
contained unit enclosed by a water-repelling membrane.
cell cycle The sequence of events that make up the life of a typi-
cal eukaryotic cell, from the moment of its origin to the time it
divides to produce two daughter cells.
cell division The final stage of the cell cycle. Cell division
includes the transfer of DNA from the parent cell to the daugh-
ter cells.
cell theory One of the unifying principles of biology; a theory
stating that every living organism is composed of one or more
cells, and that all cells living today came from a preexisting cell.
cellular respiration The reciprocal process to photosynthesis, in
which sugars are broken down into energy usable by the cell.
cellulose A chemical substance that provides structural strength in
plant cells. Compare lignin.
centromere The central region of a chromosome that attaches
sister chromatids together.
chaparral A terrestrial shrubland biome characterized by cool,
rainy winters and hot, dry summers, and dominated by drought-
resistant plants.
chemical bond A force that holds two atoms together.
chemical compound A molecule that contains atoms from two
or more different elements.
chemical reaction The process of breaking existing chemical
bonds and creating new ones.
chemoautotroph See autotroph.
chemoheterotroph See heterotroph.
chlorophyll A green pigment that is specialized for absorbing light
energy.
chloroplast An organelle of plant cells and some protist cells that
captures energy from sunlight and uses it to manufacture food
molecules via photosynthesis.
chordates A large phylum that encompasses all animals with
backbones, such as fishes, birds, and mammals.
chorionic villus sampling (CVS) A prenatal genetic screening
technique in which cells are extracted by gentle suction from
the villi (a cluster of cells that attaches the pregnancy sac to the
wall of the uterus). Ultrasound is used to guide the narrow, flex-
ible suction tube through a woman’s vagina and into her uterus.
Compare amniocentesis.
chromatin fiber A chromosome in relaxed form, made up of DNA
and nucleosomes.
chromosomal abnormality Any change in the chromosome
number or structure, compared to what is typical for a species.
chromosome A DNA double helix wrapped around spools of
proteins.
chromosome theory of inheritance The theory that genes are
located on chromosomes, and that these chromosomes are the
basis for all inheritance.
citizen science Research that is assisted by members of the public,
who participate by collecting and sometimes analyzing data in
cooperation with professional scientists.
citric acid cycle See Krebs cycle.
clade A branch of an evolutionary tree, consisting of an ancestor
and all its descendants.
class The unit of classification in the Linnaean hierarchy above
order and below phylum.
climate The prevailing weather of a specific place over relatively
long periods of time (30 years or more).
climate change A large-scale and long-term alteration in Earth’s
climate, including such phenomena as global warming, change in
rainfall patterns, and increased frequency of violent storms.
climax community A mature community whose species compo-
sition remains stable over long periods of time.
codominance An interaction between two alleles of a gene that
causes a heterozygote to display a phenotype that clearly displays
the effects of both alleles. Compare incomplete dominance.
codon A unique sequence of three mRNA bases that either speci-
fies a particular amino acid during translation or signals the ribo-
somes where to start or stop translation. Compare anticodon.
coevolution The tandem evolution of two species that results
because interaction between the two so strongly influences their
survival.
commensalism A species interaction in one species benefits at no
cost to the other species. Compare competition, mutualism, and
predation.
common ancestor An organism from which many species have
evolved.
common descent The sharing of a common ancestor by two or
more different species.
community The populations of different species that live and
interact with one another in a particular place.
competition A species interaction in which both species may be
harmed. Compare commensalism, mutualism, and predation.
competitive exclusion principle The idea that different species
that use the same resource can coexist only if one of the species
adapts to using other resources.
complementary base-pairing The relationship between two
nucleic acid strands in which each purine on one strand hydro-
gen-bonds with a specific pyrimidine on the opposite strand. A
pairs with T or U, and C pairs with G.
complex trait A genetic trait whose pattern of inheritance cannot
be predicted by Mendel’s laws of inheritance.