Middle School Life Science: Ecosystem Dynamics - Ecosystem of Change — Flashcards

The towering trees in an old forest have been growing there for hundreds of years. It may seem as though the forest has been there forever. But no ecosystem is truly static. The numbers and types of species in most ecosystems change to some degree through time. This is called ecological succession.    
Two important cases of ecological succession are primary succession and secondary succession. Primary succession occurs in an area that has never before been colonized by living things. Generally, the area starts out as nothing but bare rock. This type of environment could come about when a landslide uncovers bare rock, a glacier retreats and leaves behind bare rock, or lava flows from a volcano and hardens into bare rock. Secondary succession occurs in a formerly inhabited area that was disturbed. Secondary succession could result from a fire, flood, or human action such as farming. For example, a forest fire might kill all the trees and other plants in a forest, leaving behind only charred wood and soil.    
Does a changing ecosystem ever stop changing? Does its community of organisms ever reach some final, stable state? Scientists used to think that ecological succession always ended at a stable state, called a climax community.    
Now their thinking has changed. Theoretically, a climax community is possible, but continued change is probably more likely for real-world ecosystems. Most ecosystems are disturbed too often to ever develop a climax community.