Bacteria would be considered a(n) species.
r- selected
k-selected

K and r Reproductive Strategies. In the equations describing growth of populations of organisms, r represents the slope of the line representing exponential growth. The letter K represents the carrying capacity of a habitat for members of a given sort of organism. The population is still at low values relative to the carrying capacity of the environment and thus is growing exponentially with intrinsic reproductive rate r (when it is not subject to environmental perturbations.), hence the name r-strategist.As the name implies, r-selected species are those that place an emphasis on a high growth rate, and, typically exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood (i.e., high r, low K).

T cells are a class of leukocytes that play a large role in the secondary immune response. "T" is the abbreviation of the thymus, the organ in which their development ends.
They are responsible for cellular immunity: cells infected with a virus, for example, or cancer cells are known to be foreign to the body (that is, distinct from the cells that T cells have learned to tolerate when maturation) is destroyed by a complex mechanism.
T-cell needs the antigen MHC I molecule (present in all the nucleated cells), to be activated.
While The B cell needs the antigen presented by MHC II molecule present in antigen presenting cells.

T-cells bind 1 type of antigen (which is an endogenous antigen, as opposed to B cell which bind exogenous antigen) which must be presented by another cell.