Why is change necessary in an ecosystem?

Why is there undigested food in the rectum which would be passed out of the body? What is human exhalation? What type of the cells form the intercellular substance of the pulp? Are there outlets on electricity poles? Is moldy bread unicellular or multicellular? Is selenium odorless? Why hydrazine does not use as solution? What are small leaves an adaptation in a desert environment? What is the Magnetic property of alkali metal at room temperature? What are the two steps involved in dissolving a solid? What tool is use for measure weight? Do ticks lay eggs from their mouths? Who explored Antarctica? Did Jacques cousteau have dyslexia? What is HG215 steel? What word meaning large body that resolves around the sun do you connect with planetarium? What is the element that makes rotten eggs smell badly? What happened to the matter at the center of the nebula? What was The Production Era is recognized for? What components in an IED creates an electrical charge?