Keystone Species are the ones which impact the entire ecosystems and all the organisms with in it.
Keystone species are responsible for maintaining the overall structure and function of the ecosystem.
For example – small predators in any ecosystem which feed upon the herbivores organism in order to preserve the plant species act as key species. Their presence is essential for maintaining the dominant plant species in the ecosystem
Purines: Heterocyclic rings are synthesized one atom at a time, first atom attached to ribose phosphate (source is PRPP) and then all the other atoms are added .
Pyrimidines: Common intermediate, orotate, synthesized first, then orotate is attached to ribose phosphate (source is PRPP or 5-Phosphoribosyl-1-pyrophosphate).
