Ecology is the actual study of living systems and the way that various organisms and flora and fauna interact and support one another. It is not nearly as focused on individual organisms or the past history of various organisms but much more on the present and the way various organisms interact.
Environmentalism is focused on the preservation of or conservation of various types of environments or ecosystems. It is much less scientific and much more about politics and all the other various aspects of conservation, etc., besides just the ecosystems themselves.
They can be related in that ecology can inform environmentalists or be used to justify certain environmental efforts or policies, etc.
Ecology is a discipline of science or study concerned with the relationships that living things have with each other and with their physical environment.
Environmentalism refers to a philosophy and a social movement that is concerned with protecting and preserving the quality of environment. This includes concern for the physical environment by itself, as well as the impact of the environment on all living things.Environmentalists seek protect natural resources and ecosystems by various means such as political lobbying, activism, and education.
The study of ecology has substantial impact on the nature of thinking and actions of the environmentalists. It increases their understanding of the world and its life, and how ecological relationships impacts our survival and well-being throughout the world. Ecology helps environmentalists to understand how the physical environment affects living things, and aids them in assessing the impact of environmental problems.