An Overview of Biomes

by Mrs. Ezzo

    Scientists classify large environmental areas with similar climates and ecological communities as biomes.  Although there is some variation in the agreed upon number of biomes in the world, common biomes include:  tundra, coniferous forests, deciduous forests, tropical rain forests, grasslands, deserts, marine biomes, freshwater biomes and wetlands/estuaries.  It is the climate, or weather patterns over time that determines what type of organisms will live in a particular area.  As the climate varies throughout the world, so do the plants that grow and the animals that live off of those plants and one another.

    In every biome, there are both abiotic (non-living) and biotic (living) elements.  Since the abiotic characteristics are so intertwined with the biotic portion of the environment it is sometimes difficult to identify them, but their impact is as follows.  First, most chemical reactions go faster in warm, moist climates, such as the tropics.  Because of more carbon dioxide, decomposition occurs more rapidly.  Since there is more oxygen, photosynthesis happens faster. Second, water, which is necessary for all living things in the biome, will evaporate more quickly in warm temperatures and affect weathering and erosion of mountains, rock and soil.  Third, the air around a biome can absorb energy from the sun, block excess UV-rays in ozone, and affect weather through pressure and wind.   Fourth, wind is responsible for dispersing pollutants and adds to erosion.  Fifth, the rocks and soil set limits as to which plants will grow in an area.  Finally, the nutrients that continually cycle through a biome and support the living portion of it are all abiotic elements.

    The biotic portion of any biome includes all of the living organisms from the microscopic bacterium to the largest animals.  All of these creatures live in complex organizations and depend on other members of the ecosystem for survival.  As a result, adaptations have developed over time that help organisms survive.  Some of these, such as thorns, toxins, the ability to camouflage, speed, shells, odors, etc., all developed to help protect would-be prey from predators. 

     There are additional adaptations that aid in survival against the climate of a biome.  For example, in excessively cold climates, where water in the cells of living things could freeze, which would result in expansion that would damage the cells, there are many ways to protect oneself.  Some plant species simply die-off, but return from seeds dispersed the previous year.  Others lose their leaves and store energy deep underground in their roots.  Still others have thick needles that provide more insulation than flat leaves.  Some animals will hibernate during the coldest months, while others are equipped with thick layers of differing types of feathers or fur.  Animals that will enter freezing water tend to have blubber, a thick layer of oily fat.  Finally, many plants and animals take advantage of the insulation provided by a covering or blanket of snow.

    In extreme heat, plants and animals must also have adaptations against both the temperature and the loss of water that usually accompanies it.  Plants tend to be able to store water, but do lose moisture through transpiration.  To prevent losing too much water during the day, desert plants such as cacti will keep their transpiration pores called stomata, closed until night.  In extreme heat, plants also tend to be thick and fleshy to be able to store large amounts of water.  Animal adaptations to extreme heat include resting in the shade, having light colored coats, flattened fur or feathers to trap less heat, and large ears to radiate heat out of the body.  Many animals are simply nocturnal, being active primarily at night when temperatures are cooler.

    The Earth contains a huge variety of living organisms. The placement of those organisms on the planet is not random, but determined by the surrounding climate.  While all organisms require non-living elements such carbon dioxide, oxygen, water, air, and nutrients, the variations in these because of climate will dramatically impact what can survive.  Part of what makes the Earth such a unique place is the variation that can be found on it.  This wiki contains a collection of research, divided up by biome, about that variety. 

Sources:

The Grolier Library of Environmental Concepts and Issues.  Danbury, CT:  Grolier Education Corporation, 1996.  pp 55-59.

Introduction to Ecosystems.  2007.  Internet Geography.  Feb. 5, 2008. www.geography.learnontheinternet.co.uk/topics/whatecosystem.html.

Prentice Hall.  Ecology:  Earth’s Living Resources.  Englewood Cliffs:  Prentice Hall, 1994.  pp 69-74.

Scott, Michael.  The Young Oxford Book of Ecology.  Oxford:  Oxford University Press, 1995.  pp 34-51.