This figure with the plants, zebra, lion, and so forth illustrates the two main ideas about how ecosystems function: ecosystems have energy flows and ecosystems cycle materials. These two processes are linked, but they are not quite the same
Energy flows and material cycles.
Energy enters the biological system as light energy, or photons, is transformed into chemical energy in organic molecules by cellular processes including photosynthesis and respiration, and ultimately is converted to heat energy. This energy is dissipated, meaning it is lost to the system as heat; once it is lost it cannot be recycled. Without the continued input of solar energy, biological systems would quickly shut down. Thus the earth is an open system with respect to energy.
The importance of carbon dioxide extends from cellular to global levels of organization and potential ecological deterioration may be the result of increased CO2 in our atmosphere. Recently, the research emphasis shifted from studies of photosynthesis pathways and plant growth to ground-breaking studies of carbon dioxide balances in ecosystems, regions, and even the entire globe. Carbon Dioxide and Terrestrial Ecosystems addresses these new areas of research. Economically important woody ecosystems are emphasized because they have substantial influence on global carbon dioxide balances. Herbaceous ecosystems (e.g., grasslands, prairies, wetlands) and crop ecosystems are also covered. The interactions among organisms, communities, and ecosystems are modeled, and the book closes with an important synthesis of this growing nexus of research.Carbon Dioxide and Terrestrial Ecosystems is a compilation of detailed scientific studies that reveal how ecosystems generally, and particular plants specifically, respond to changed levels of carbon dioxide.
Nutrients and Water
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All living things need and water. Therefore, there must be a substrate, such as soil, that can retain water and nutrients. Healthy soil can support healthy plants that will thrive on abundant water and nutrients. Herbivores, or plant-eaters, can eat the plants and will also need a water source such as a lake or stream. Carnivores, or meat-eaters, can eat the plant-eaters and also share the water source. When any of these plants or animals die, decomposers must be present to break down the bodies into nutrients that will return to the soil.
Shelter
- Animals need shelter to survive. Since different animals prefer different types of shelters, it is important for there to be a wide variety of shelters available. Shelters may include empty logs, rocks and treetops. Animals will be able to rest, care for their young and hide from predators within these shelters. Shelter also often provides protection from the elements such as extreme heat or cold. If you are creating or maintaining an ecosystem for a particular animal, research what type of shelter it prefers and then provide a few of those types of shelters so the animal has options to choose from.
Space
- Animals and plants, just like people, need space to live comfortable and healthy lives. When organisms are overcrowded, they quickly run out of the resources, such as food, water and shelter that they need to survive. Each type of animal has particular space needs. For example, a deer that spends most of its day grazing on grass will need enough space to find all the food that it needs. That amount of space will probably be much more than the space needed by a smaller animal, such as a mouse, that can find enough food within a smaller area.
