Abiotic Factors: Precipitation
One of the two most important physical factors in an environment is precipitation. The amount of annual rainfall over a given area, and the frequency with which it falls, determines what plant life can grow and reproduce. In general, areas that receive less than 10 inches of rainfall per year are deserts. Deserts exist in areas like the southwest United States, where it is very hot, and on Antarctica, where it is very cold. Grasslands receive more rain than deserts, but not enough rain to support trees. Typical grassland environments, like the North American prairie or the steppes of Central Eurasia, receive between 20 and 35 inches of rain annually. Grasslands have extended dry spells when very little precipitation falls. Forests receive the greatest rainfall, ranging from 28 inches for deciduous forests to upwards of 28 feet for tropical rainforests. Since most trees cannot survive extended drought well, precipitation patterns are more consistent in forests than grasslands.
Abiotic Factors: Temperature
Ranging from a scorching maximum of 136 degrees Fahrenheit to a minimum of 129 below zero, Earth's temperatures vary widely. Just like precipitation, the range and duration of temperatures in a given area determine what plant life can grow and reproduce. Equatorial (as opposed to polar) deserts have the greatest one-day temperature ranges, reaching the century mark at midday and plunging to 25 degrees Fahrenheit at night. These daily extremes of hot and cold make plant life difficult to impossible for all but a relative few specially adapted species. Grasslands also have a wide range of temperatures, from -20 to 100 degrees Fahrenheit, but this environment feels these temperature ranges on a yearly, instead of daily, basis. Rainforests have the most consistent temperatures, not straying far from 60 to 100 degrees, and never dropping below freezing. Plants living in a rainforest environment never have to contend with freezing conditions, and are incredibly lush and diverse as a result.
Biotic Factors: Producers
The foundation for any terrestrial environment is the producer, or plant. Plants include grasses, flowers, trees, mosses, shrubs and forbs, all of which use the sun's energy to create glucose, which serves as a plant's source of food. Without plants, there would be no other life on Earth, because plants are the only creatures who can capture the energy from the Sun and use it to live, grow and reproduce. Plants adapt in many ways to a local climate, from grasses growing roots that extend 10 to 20 feet into the ground in a grassland to survive periods of drought, to trees growing leaves in patterns that block light from reaching the ground beneath them to ward off competing species.
Biotic Factors: Consumers
Aside from plants, all life on Earth gets energy by eating, or consuming, something else. Consumers inhabit a diverse array of ecological roles, from plant-eating herbivores like deer, to meat-eating predators like wolves, to nonselective omnivores like humans and bears, and finally to carcass- devouring decomposers like fungi and bacteria, who return dead biomass to the soil for future life to use. Since consumers must rely on a large biomass of plant life to support themselves (or their prey), consumers account for only about 10 percent of an environment's biomass, while producers make up the other 90 percent.