ABSTRACT
There is now a growing awareness that our use of nature's processes and resources must be adjusted to the limitations and requirements which it sets for us. Thus in the twentieth century we have become more interested in the ecological changes which human settlements and industry have brought about in the local and the world environment. In particular we are now concerned with the conservation of species in danger of extinction and the maintenance of ecological balance in environments which have been altered to suit our economic needs. The important and fundamental fact remains that all animal life, including Homo sapiens, ultimately depends on plant life, which alone is able to synthesize elements into the form of food.
