Because of biogeochemical cycling,
a. human activity has no effect on elements, chemical compounds, and other forms of matter.
b. living organisms are not limited by any one nutrient.
c. nutrients are circulated throughout the biosphere.
d. many nutrients do not reach toxic concentrations in the biosphere.

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.

What is the function of the root cap? a. extra-absorbent cells in the root cap absorb more water and nutrients b. protect the meristematic area of the stem c. contains sensors for sunlight d. increases surface area of the root

Which soil would most likely be found in the arctic? andisols gelisols histosols spodosols