Ecology
Ecology (from Greek: οἶκος, "house", or "environment"; -λογία, "study of") is the branch of biology which studies the interactions among organisms and their environment. Objects of study include interactions of organisms with each other and with abiotic components of their environment. Topics of interest include the biodiversity, distribution, biomass, and populations of organisms, as well as cooperation and competition within and between species. Ecosystems are dynamically interacting systems of organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis, nutrient cycling, and niche construction, regulate the flux of energy and matter through an environment. These processes are sustained by organisms with specific life history traits. Biodiversity means the varieties of species, genes, and ecosystems, enhances certain ecosystem services.
Nature
Nature, in the broadest sense, is the natural, physical, or material world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are part of nature, human activity is often understood as a separate category from other natural phenomena.
Ecology
If there are favourable habitats and favorable forms of association for animals and plants, as ecology demonstrates, why not for men? If each particular natural environment has has its own balance; is there not perhaps an equivalent of this in culture?
Lewis Mumford, The Culture of Cities, Secker & Warburg, 1938.
Nature
See one promontory (said Socrates of old), one mountain, one sea, one river, and see all.
Robert Burton, The Anatomy of Melancholy (1621), Part I, Section 2. Memb. 4. Subsec. 7.