primary and secondary succesion
Primary Succesion is where a forest or a comunity of orgianisms is started on bare rock. This happenes when birds and other creatures drop seeds in the cracks of rocks. After years and years the rocks are broken down and the plants begin to grow causing more plants to grow and eventually making a forest.
Secondary Succsesion is where there is a forest and say a forest fire occures so that there are no more trees. Well there is still soil so birds and other creatures accidantly drop seeds and eventually a new forest is there.