Encyclopedia of Biology

located at regular intervals along the actin filament and allows actin to interact with myosin. See alsoCYTOSKELETON. actinomorp ...

adenylyl cyclase An enzyme, embedded in the plasma membrane, that converts ATP to cyclic adeno- sine monophosphate (cyclic AMP, ...

aerobic Any organism, environmental condition, or cellular process that requires atmospheric oxygen. Aer- obic microorganisms, c ...

Agonistic behavior is used to defend territories, areas that a dominant individual will defend for feeding, mating, rearing, or ...

societal indifference to the AIDS epidemic. Public atti- tude changed when heterosexuals became infected, and greater education ...

cells. While many lichen have a different fungi compo- nent, they often have the same algae species. Some common species of lich ...

Because the various forms of algae are now assigned to different phyla, the words algaand algae are used informally and have no ...

allochronic speciation Speciation that takes place related to time rather than space; populations that are reproductively isolat ...

encounter selection factors that are different from and perhaps more severe than that experienced by the par- ent because the is ...

complete turn every 3.6 amino acids. The distance between two turns is 0.54 nm. However, an alpha helix can also be left-handed. ...

proteins by transfer RNA according to the genetic code while messenger RNA is being decoded by ribo- somes. The amino acid conte ...

shown.) The residue in a peptide that has an amino group that is free, or at least not acylated by another amino acid residue (i ...

amniocentesis Amniocentesis is the removal of about two tablespoons of amniotic fluid via a needle inserted through the maternal ...

However, in 1988, herpetologists (scientists who study amphibians) from many parts of the world reported declines in amphibian p ...

larity in underlying structure (or origin) are called anal- ogous structures. For example, birds and bats each have their foreli ...

Angiosperms are divided into two large groups. The dicotyledonea, or dicotyledons (also called magno- liopsida), the larger of t ...

embryo, and a second fertilization event produces endosperm, a polyploid embryo-nourishing tissue found only in the angiosperms. ...

inthe bone marrow (also known as B lymphocytes, plasma cells) in response to an antigen (a foreign sub- stance). Antibodies are ...

anticodon A specialized sequence of three nucleotides on a tRNA (transfer ribonucleic acid) molecule. The anticodon associates w ...

apical dominance Concentration of growth at the tip of a plant shoot, where aterminal bud partially inhibits axillary bud growth ...