At the very end of the cladogram at the very top of a clade in the middle of a clade along the main trunk of the cladogram
A dense growth of plant life in a aquatic ecosystem which many animals living there die(due to lack of enough oxygen present in water) and the ecosystem gets completely disrupted.
Eutrophication excessive richness of nutrients in a lake or other body of water, frequently due to run-off from the land, which causes a dense growth of plant life.
Replication Fork! Is the answer! Hope this helps!