The striking molecular similarities that exist between earth's many diverse species can best be explained by a. random changes that occur separately in each species' genetic code. b. the sharing of common ancestors within the species' evolutionary history. c. the inability of the species to undergo evolutionary change over time. d. species mating with other species to produce offspring.

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.

This group of organisms perform the process of ammonifcation. a. herbivores b. decomposers c. carnivores c. plants

Match the pollutants. 1. a chlorofluorocarbon smoke 2. a biodegradable organophosphate insecticide freon 3. particle pollution paint 4. hazardous waste monoxide 5. carbon is completely burned malathion 6. carbon is incompletely burned dioxide