In ecology, two parameters are used to measure changes in ecosystems: resistance and resilience. Human agricultural practices, air pollution, acid rain, global deforestation, overfishing, eutrophication, oil spills, and illegal dumping on land and into the ocean are all issues of concern to conservationists.Įquilibrium is the steady state of an ecosystem where all organisms are in balance with their environment and with each other. The impact of environmental disturbances caused by human activities is as important as the changes wrought by natural processes. For example, when lightning causes a forest fire and destroys part of a forest ecosystem, the ground is eventually populated by grasses, then by bushes and shrubs, and later by mature trees, restoring the forest to its former state. Many of these disturbances are a result of natural processes. They are routinely exposed to various disturbances, or changes in the environment that effect their compositions: yearly variations in rainfall and temperature and the slower processes of plant growth, which may take several years. (credit a: modification of work by Jay Galvin credit b: modification of work by Ingo Wölbern)Įcosystems are complex with many interacting parts. The desert in (a) Saguaro National Park, Arizona, has abundant plant life, while the rocky desert of (b) Boa Vista island, Cape Verde, Africa, is devoid of plant life. For example, there is great variation in desert vegetation: the saguaro cacti and other plant life in the Sonoran Desert, in the United States, are relatively abundant compared to the desolate rocky desert of Boa Vista, an island off the coast of Western Africa (Figure 2).įigure 2. Desert ecosystems, like all ecosystems, can vary greatly. Grouping these ecosystems into just a few biome categories obscures the great diversity of the individual ecosystems within them. Terrestrial ecosystems, also known for their diversity, are grouped into large categories called biomes, such as tropical rain forests, savannas, deserts, coniferous forests, deciduous forests, and tundra. Lakes, rivers, streams, and springs comprise these systems they are quite diverse, and they support a variety of fish, amphibians, reptiles, insects, phytoplankton, fungi, and bacteria. Such ecosystems exist even at the bottom of the ocean where light is unable to penetrate through the water.įreshwater ecosystems are the rarest, occurring on only 1.8 percent of the Earth’s surface. Although not as diverse as the other two, deep ocean ecosystems contain a wide variety of marine organisms. These two environments are especially important to aerobic respirators worldwide as the phytoplankton perform 40 percent of all photosynthesis on Earth. The shallow ocean ecosystems include extremely biodiverse coral reef ecosystems, and the deep ocean surface is known for its large numbers of plankton and krill (small crustaceans) that support it. Ocean ecosystems are the most common, comprising 75 percent of the Earth’s surface and consisting of three basic types: shallow ocean, deep ocean water, and deep ocean surfaces (the low depth areas of the deep oceans). Within these broad categories are individual ecosystem types based on the organisms present and the type of environmental habitat. There are three broad categories of ecosystems based on their general environment: freshwater, ocean water, and terrestrial. (credit a: modification of work by “takomabibelot”/Flickr credit b: modification of work by Ivan Mlinaric) Ecosystems can be small, such as the tide pools found near the rocky shores of many oceans, or large, such as the Amazon Rainforest in Brazil (Figure 1).įigure 1: A (a) tidal pool ecosystem in Matinicus Island in Maine is a small ecosystem, while the (b) Amazon Rainforest in Brazil is a large ecosystem. These are all important environmental variables that determine which organisms can exist within a particular area.Īn ecosystem is a community of living organisms and their interactions with their abiotic (non-living) environment. Other critical factors influencing community dynamics are the components of its physical and geographic environment: a habitat’s latitude, amount of rainfall, topography (elevation), and available species. The resources for which organisms compete include organic material from living or previously living organisms, sunlight, and mineral nutrients, which provide the energy for living processes and the matter to make up organisms’ physical structures. Competition in communities (all living things within specific habitats) is observed both within species and among different species. Life in an ecosystem is often about competition for limited resources, a characteristic of the theory of natural selection.
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