Rules of Life

The biosphere is the part of Earth's outer shell—including land, surface rocks, water, air and the atmosphere—within which life occurs, and which biotic processes in turn alter or transform. From the broadest geophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere (rocks), hydrosphere (water), and atmosphere (air). The entire Earth contains over 75 billion tons (150 trillion pounds or about 6.8×1013 kilograms) of biomass (life), which lives within various environments within the biosphere.

Although Earth is the only body within the Solar System known to support life, evidence suggests that in the distant past the planet Mars possessed bodies of liquid water on the surface.[93] For a brief period in Mars' history, it may have also been capable of forming life. At present though, most of the water remaining on Mars is frozen. If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist.

Animals and plants are often negatively affected by cars via habitat destruction and pollution. Over the lifetime of the average car, the "loss of habitat potential" may be over 50,000 square metres (540,000 sq ft) based on primary production correlations.[93][clarification needed] Animals are also killed every year on roads by cars, referred to as roadkill. More recent road developments are including significant environmental mitigation in their designs, such as green bridges (designed to allow wildlife crossings) and creating wildlife corridors.

Animals originally evolved in the sea. Lineages of arthropods colonised land around the same time as land plants, probably between 510 and 471 million years ago during the Late Cambrian or Early Ordovician.[57] Vertebrates such as the lobe-finned fish Tiktaalik started to move on to land in the late Devonian, about 375 million years ago.[58][59] Animals occupy virtually all of earth's habitats and microhabitats, including salt water, hydrothermal vents, fresh water, hot springs, swamps, forests, pastures, deserts, air, and the interiors of animals, plants, fungi and rocks.[60] Animals are however not particularly heat tolerant; very few of them can survive at constant temperatures above 50 °C (122 °F).[61] Only very few species of animals (mostly nematodes) inhabit the most extreme cold deserts of continental Antarctica.