In a scientific experiment, a VARIABLE changed is any factor that can change or be
They provide the immune system with "memory" against previously encountered pathogens.
T memory cells are necessary for protective immunity against invading pathogens
Ecological succession is a process of inhabiting a zoological area by a group of organisms. it involves many stages to reach the climax stage such as primary, secondary, tertiary names basing on the habitat where it occurs. once the organisms reach the most stable stage of the succession. thus it maintains equilibrium
Succession helps restore the equilibrium of an ecosystem by forming up new species, diversifying species, and basically by replacing the damaged, deranged, or disturbed community. For instance, when a sudden climate change occurred in a community, such as drought, dryness, fire, or heat waves, all living things that depends on water or survives in a cool, wet environment will die or migrate somewhere else. Thus, leaving that community vacant and/or unoccupied by any living things. Succession, then, will take place in that area by going through various stages until reaching the climax stage, in which the ecosystem is complete again. c: hope i helped :D