Me ! what is the last stage of speciation? a. the populations become adapted to different enviornments and eventually become so different that they cannot interbreed and produce fertile offspring. b the populations are isolated and thus they do not interbreed. c the populations have become totally seperated from one another. d the populations interbreed successfuly

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.