The Living World

Overview
Glossary
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Species diversity
Introduction Species diversity is a measure of the diversity within an ecological community that incorporates both species richness (the number of species in a community) and the evenness ...
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Biome
Biomes organize the biological communities of the earth based on similarities in the dominant vegetation, climate, geographic location, and other characteristics. Aspects of the physical environment s...
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Terrestrial biome
Introduction Many places on Earth share similar climatic conditions despite being found in geographically different areas. As a result of natural selection, comparable ecosystems have deve...
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Freshwater biomes
Introduction Freshwater is defined as having a low salt concentration — usually less than 1%. Aquatic plants and animals in freshwater regions are adjusted to the low salt content and would...
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Marine biomes
Introduction Marine regions cover about three-fourths of the Earth's surface and include oceans, coral reefs, and estuaries. Marine algae supply much of the world's oxygen supply and take in a h...
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Tundra biome
The tundra biome is the coldest of all the biomes. Tundra comes from the Finnish word tunturi, meaning treeless plain. It is noted for its frost-molded landscapes, extremely low temperatures, littl...
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Grassland biome
Grasslands are characterized as lands dominated by grasses rather than large shrubs or trees. In the Miocene and Pliocene Epochs, which spanned a period of about 25 million years, mountains rose i...
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Desert biome
Desert biomes cover about one fifth of the Earth's surface and are defined to occur where rainfall is less than 50 centimeters (cm) per year. Although most deserts, such as the Sahara of North A...
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Forest biome
About 420 million years ago, during the Silurian Period, ancient plants and arthropods began to occupy the land. Over the millions of years that followed, these land colonizers developed and adapte...
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Photosynthesis
Introduction Photosynthesis is a process in plants, algae, and some prokaryotes, that coverts solar insolation into chemical energy stored in glucose or other organi...
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Biodiversity
Introduction The word "biodiversity" is a contracted version of "biological diversity". The Convention on Biological Diversity defines biodiversity as:&...
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Natural selection
Introduction Natural selection Natural selection is an agent of microevolutionary change in which a population of an organism becomes better adapted to its habitat by genetic inheritance o...
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Biodiversity and ecosystem services
Biodiversity is being threatened at an unprecedented scale by global environmental change brought about by human societies. In addition to the many moral reasons to preserve it for its own sake, ...
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Carbon cycle
All life is based on the element carbon. Carbon is the major chemical constituent of most organic matter, from fossil fuels to the complex molecules (DNA and RNA) that control genetic reproduction ...
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Nitrogen cycle
The nitrogen cycle represents one of the most important nutrient cycles found in ecosystems. (Figure 1). Nitrogen is a required nutrient for all living organisms to produce a number of complex organic...
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Hydrologic cycle
The hydrologic cycle is a conceptual model that describes the storage and movement of water between the biosphere, atmosphere, lithosphere, and the hydrosphere (see Figure 1). Water on our planet can ...
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Natural biogeochemical cycles
Energy flow
Ecosystem Structure
Ecosystem diversity
Natural ecosystem change