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Biosphere
The biosphere refers to all living organisms on earth and is often called the global ecosystem. It is the sphere that includes all living organisms, from plants to bacteria to multicellular organisms. The biosphere interacts with other spheres, such as the lithosphere, atmosphere and hydrosphere.
- Hydrosphere: is the combined mass of water found on, under and above the surface of the earth. The hydrosphere is made up of oceans, seas, lakes, rivers and springs. The water in these bodies can be freshwater or salt water. The hydrosphere is home to a wide diversity of aquatic plant and animal life.
- Lithosphere: refers to the outermost surface of the Earth, the Earth’s crust. The oceanic lithosphereis associated with the oceanic crust and exists in oceanic basins. Continental lithosphere is associated with continental crust which covers the Earth’s landmass. The lithosphere shields living organisms from the heat of the Earth’s core and contains ionic compounds which allow plant and animal life to exist.
- Atmosphere: is the layer of gases surrounding the earth. The gases in the atmosphere allow organisms to respire and regulates the temperature of the planet. The atmosphere’s ability to absorb the ultraviolet rays of the sun is what allows life on earth to survive. The connections between spheres imply that disturbances in one sphere affect the other spheres. For example, excessive deforestation (biosphere) results in increased erosion of soil (the upper layer of the lithosphere- pedosphere) into rivers (hydrosphere). Deforestation also results in an increase in atmospheric carbon dioxide (atmosphere). Deforestation therefore is an example of how disturbances in one sphere produces effects in the hydrosphere, upper-lithosphere and atmosphere.
Biomes
The biosphere is divided up into a number of biomes. Biomes are regions with similar climate and geography. The key factors determining climate are average annual precipitation (rainfall) and temperature. These factors, in turn, depend on the geography of the region, such as the latitude and altitude of the region, and mountainous barriers. The specific conditions of biomes determine the plant and animal life found within them. The communities of plants, animals and soil organisms in a particular biome are collectively referred to as an ecosystem. Biomes can be aquatic or terrestrial.
Aquatic biomes
Water covers a major portion of the Earth’s surface, so aquatic biomes contain a rich diversity of plants and animals. Aquatic biomes are divided into two main groups depending on the amount of salt present in the water: freshwater and marine biomes.
- Freshwater
Freshwater biomes are defined by their low salt concentration, which is usually less than 1%1%. Examples include: ponds, lakes, streams, rivers and wetlands.
- Marine biomes
Marine bodies are salty, having approximately 35 grams of dissolved salt per litre of water (3,5%3,5%). Marine biomes are divided into oceans, coral reefs and estuaries. The vegetation of the marine biomes consists of the different types of algae, which is one of the major sources of oxygen in the world. Green algae also play a role in the removal of carbon dioxide from the atmosphere.
Oceans: are very large marine bodies that dominate the Earth’s surface and hold the largest ecosystems. The open ocean or sea covers nearly three-quarters of the earth’s surface and contains a rich diversity of living organisms. Examples of animals in the ocean biome include whales, sharks, octopuses, perlemoen, crabs and crayfish.
Coral reefs: are found in the warm, clear, shallow waters of tropical oceans around islands or along continental coastlines. Coral reefs are mostly formed underwater from calcium carbonate produced by living coral. Reefs provide food and shelter for other organisms and protect shorelines from erosion.
Estuaries: are partially enclosed areas of fresh water and silt from streams or rivers, which mix with salty ocean water. Estuaries represent a transition from land to sea and from freshwater to saltwater. Estuaries are biologically very productive areas and provide homes for a wide variety of plants, birds and animals.
Terrestrial biomes
Terrestrial biomes occur on land and can be of many types. Examples include: thicket, tundra, forest, grassland and desert. Terrestrial biomes are usually classified based on the dominant vegetation, climate or geographic location. The location and characteristics of the various biomes is mostly influenced by climatic conditions such as rainfall and temperature.
The most recent classification of the terrestrial biomes divides the region into the following eight biomes:
- Grassland
- Savannah
- Forest
- Desert
Environment
The environment refers to everything that surrounds us, including the place where we live. We usually use the term ‘environment’ to refer to the physical aspects of our surroundings, which may be living (biotic) or non-living (abiotic). This means that if you live in a city, the environment consists of the buildings, roads and other infrastructure, while if you live on a farm, your environment consists of you pastures, farm house etc.
Although an environment consists of non-living and living things, the term ‘environment’ really just describes one’s surroundings, but does not really define the relationships, connectedness or dynamic nature of those surroundings. To study how the living and non-living parts of the environment depend on and are influenced on each other, we need to understand a different concept- the ecosystem.