ABSTRACT
Ecology is the science of the relationships of organisms to the surrounding world. This discipline is concerned with the interaction of organisms and their environment. Ecology is often divided into physiological ecology, population biology, community ecology and ecosystem ecology. For nutrient cycles, consumption must balance production, e.g., nutrients can be recycled from dead biomass through inorganic forms and back into living organisms. Much of the Earth’s Oxygen is in the form of molecular oxygen. There are three types of photosynthèses: Calvin cycle which occurs in C4 plants, Hatch and Slack cycle which is a characteristic of C3 plants and Crassulacean metabolism which is prevêlant in succulents. Lightning and certain photochemical reactions can transform molecular nitrogen to derivatives which are usable by organisms. Plants can take up sulfur from the soil and water as the sulfate anion. Sulfur in plants can be incorporated into animals via ingestion. Sulfur occurs in various compounds in both plants and animals.
