We are indebted to Lamarck and Treviranus for the basis and name of the new science that after 1802 came to be called Biology. What was formerly referred to as Natural History was reformulated by Haeckel in 1869 when it began to form part of Biology under the name of e. This branch of knowledge studies the relationship between organisms and the environment in which they live. Today, e. studies the adaptations of species related to their need for energy, food and reproduction. As an academic discipline, e. is divided into plant, animal and human e. In general terms, e. is concerned with the adaptation of species and the environmental factors affecting them (soil, climate, other species, etc.). One of the fundamental themes of e. is ecosystems (the ensemble of living and non-living beings which are interrelated within and linked to the same environment). Ecosystems are thermodynamically open systems which receive energy from outside and transmit it to neighboring ecosystems. The study of ecosystems is based on systems theory and cybernetics. The ecosystem includes a body of biotic (species) and abiotic elements which are in a state of constant interaction. Today, interest in e. has spread beyond the cloisters of academia, reaching large sectors of the population. The excesses of companies that pollute have been duly documented. They have and continue to perpetrate serious imbalances that threaten existing flora and fauna, dumping toxic wastes and non-biodegradable residues, manipulating nuclear power plants as sources of energy, and unleashing environmental contamination and acid rain. To this must be added the growth of the mega-cities, the damage to the productivity of farmland irrationally over-treated with pesticides and chemical fertilizers, the desertification of vast areas, etc. All of these factors constitute a serious focus of concern for those interested in protecting the flora, fauna and climate in a balanced environment that will ensure human survival. The practice of calling attention to the growing ecological difficulties that societies are today experiencing, which has been generically termed environmentalism, signifies an important advance in the increasing consciousness of the people regarding one of the most critical problems of these times. Even if, among the teachers and leaders of environmentalism, there is not a single, homogeneous interpretation of the deterioration of the environment or the methods to be followed to overcome this dangerous situation, a collective sensibility has begun to emerge that has led to the passage of increasing amounts of legislation against anti-environmental activities. Of course, these dangerous activities will not be fully resolved until they come to be understood as crimes against humanity. Moreover, although we can advance in that direction, we need to understand that the inhuman system in which we live today carries within its own development the seeds of its own decomposition and that of everything it takes possession of. The need for a radical change in the structure of power and in the organization of societies becomes evident in the face of the growing ecological disaster.