C seeds because plants grow from seeds
#19 due to weathering and erosion the rock from the stream was smoothened and without as much the rock from deep underground was/is very rugged and natural.
#18 Due to wind patterns the sand dunes are blew around and the sands shift and fly around with nothing to keep the sand in place the sand can go long distances or come long distances.
(I am back lol)
Extinction of species reduces the number of different species in ecosystems, hence lowering the diversity of living things.