B Biological TERMS 
bacilli(singular, bacillus) Rod-shaped bacteria.
Bacteria The domain (major group) that contains single-celled, microscopic organisms that superficially resemble archaea but are genetically quite different. These are the bacteria that are familiar to us.
bacteriophage A type of virus that infects bacteria and is used in biotechnology to put foreign DNA into bacterial cells, therefore serving as a cloning vector.
ball-and-stick model A picture showing the three-dimensional structure of a molecule, with the atoms drawn as balls and the bonds between them drawn as sticks. This type of representation clearly shows the relationship of the atoms to each other.
bark Everything outside the vascular cambium in woody plants, consisting of cork cambium, cork, phelloderm, and secondary phloem.
base Any substance that accepts hydrogen ions in solution. A base has a number higher than 7 on the pH scale.
Batesian mimicry A type of mimicry in which one species evolves to resemble a species that has superior protection against predators.
behavioral biology The study of the behavior of animals.
bell curve A distribution of values that is symmetrically largest around the average.
benthic zone The ocean floor, where bottom-dwellers live.
beta pleated sheet A common secondary structure of proteins that resembles the folds of an accordion. Silk is a protein made up almost entirely of beta pleated sheets lying stacked like pancakes on top of each other.
biennial A type of plant that goes through its life cycle in about two years, flowering in the second year.
bilateral symmetry A bodily symmetry in which opposite sides of a sagittal plane are mirror images of one another. Animals generally are bilaterally symmetrical.
bile A substance produced by the liver that aids in the digestion of fats. Bile can enter the small intestine through ducts directly from the liver, or from a storage organ, the gallbladder.
binary fission The form of cell division carried out by prokaryotic cells in which the chromosome replicates and the cell pinches between the attachment points of the two chromosomes to form two new cells. In this type of simple cell-splitting, each pair of daughter cells is an exact replica of the parental cell.
binding site An area of a protein, located at the surface of the plasma membrane, with a particular conformation that recognizes only one molecule or a closely related group of molecules. Binding sites enable specificity of cell communication.
binomial nomenclature The system of naming species that uses two names (genus and species) for each species. This system helps identify groupings among living things.
biodegradable Capable of being broken down by living organisms.
biodiversity The diversity of living things. This includes species diversity, diversity of distributions, and genetic diversity.
biogeochemical cycling The movement of water and nutrients back and forth between biotic and abiotic systems.
biological legacy A living thing, or product of a living thing, that survives a major ecological disturbance. Biological legacies proved to be crucial in the process of succession that occurred at Washington State's Mount St. Helens following its eruption in 1980.
