Environment:

Environment for environmentalists is the natural world  within which people, animals, and plant live. For ecologists, it is all external factors influencing the life of organisms, such as light or food supply . Social Scientists on the other hand believe that it is social and physical conditions that surround people and affect the way they live. In whatever way it is defined in is , in the broadest sense, all of the external factors affecting  an organism. These factors may be other living organisms or nonliving variables, such as temperature, rainfall, day length, wind, and ocean currents. The interactions of organisms with biotic and abiotic factors affecting an organism. These factors may be other living organisms or nonliving variables, such as temperature, rainfall, day length, wind, and ocean currents. The interactions of organisms with biotic and abiotic factors form an ecosystem. Even minute changes in any one factor in an ecosystem can influence whether or not a particular plant or animal species will be successful in its environment.    Scientists study the long-term consequences of human actions on the environment, while environmentalists- professionals in various fields, as well as concerned citizens- advocate ways to lessen the impact of human activity on the natural world. Understanding The Environment   The science of ecology attempts to explain why plants and animals live where they do and why their populations are the sizes they do and why their populations are the sizes they are. Understanding the distribution and population size of organisms helps scientists evaluate the health of the environment.   Population size and distribution may also be affected, either directly or indirectly, by the way species in an ecosystem interact with one another. In an experiment performed in the late 1960s in the rocky tidal zone along the Pacific Coast of the U.S, American ecologist Robert Paine studied an area that contained 15 species of invertebrates, including starfish, mussels, limpets, barnacles, and chitons. Paine found that in this ecosystem one species of starfish preyed heavily on a species of mussel, preventing that mussel population from multiplying and monopolizing space in the tidal zone. When Paine removed the starfish from the area, he found that the mussel population quickly increased in size, crowding out most other organisms from rock surfaces. The number of invertebrate species in the ecosystem soon dropped to eight species. Paine concluded that the loss of just one species, the starfish, indirectly led to the loss of an additional six species and a transformation of the ecosystem.    To better understand the impact of natural and human disruptions on the Earth, in 1991 the National Aeronautics and Space Administration (NASA) began to use artificial satellites to study global change. NASA's undertaking, called Earth Science Enterprise, is part of an international effort linking numerous satellites into a single Earth Observing System (EOS). EOS collects information about the interactions occurring in the atmosphere, on land, and in the oceans, and these data help scientists and lawmakers make sound environmental policy decisions.