Fill in the Blanks EcosystemsOnline version Complete the text by Valentina Arévalo Hernández 1 Ecology is the study of ecosystems . Ecosystems are said to be in when the flow of matter energy between biotic an abiotic factors is continuous . Ecosystems change over time through a process called ecological . During this process , both the biotic and abiotic factors chance . Ecological succession is and takes a long time to happen , but sometimes ecosystems experience that accelerate the process . Diturbances affecting ecosystems can be caused by natural or by human actions . Volcanic eruptions and tornadoes are natural . Overfishing and global warming are human .