Explore these resources to teach students about marine organisms, their relationship with one another, and with their environment. A keystone species helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether. Biodiversity refers to the variety of living species on Earth, including plants, animals, bacteria, and fungi. Students are introduced to ecosystems, food webs, and keystone species. They draw a simple food web and predict the impact keystone species have on an ecosystem.
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Predators Predators help control the populations of prey species, which in turn affects the quantity of plants and animals further along the food web. Ecosystem Engineers An ecosystem engineer is an organism that creates, changes, or destroys a habitat. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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View Activity. Biology The Elements of an Ecosystem Species. Linica Uday. Oct 6, Explanation: A keystone species has a disproportionately large effect on its environment relative to its abundance. Related questions Why is species identification important? How does mass extinction differ from species extinction? How do species adapt to their environment?
What are some examples of species? What is a species? Do any frogs live in salty waters? This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Leveled by. Thursday, September 5, A keystone species is an organism that helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether.
Keystone species have low functional redundancy. This means that if the species were to disappear from the ecosystem, no other species would be able to fill its ecological niche. The ecosystem would be forced to radically change, allowing new and possibly invasive species to populate the habitat. Any organism, from plants to fungi, may be a keystone species; they are not always the largest or most abundant species in an ecosystem.
However, almost all examples of keystone species are animals that have a huge influence on food webs. The way these animals influence food webs varies from habitat to habitat. A keystone species is often, but not always, a predator. Just a few predators can control the distribution and population of large numbers of prey species. The entire concept of keystone species was founded on research surrounding the influence of a marine predator on its environment. American zoology professor Robert T.
Paine's research showed that removing a single species, the Pisaster ochraceus sea star, from a tidal plain on Tatoosh Island in the U. Pisaster ochraceus , commonly known as purple sea stars, are a major predator of mussels and barnacles on Tatoosh Island. With the sea stars gone, mussels took over the area and crowded out other species, including benthic algae that supported communities of sea snails, limpets, and bivalves.
Another example of a predator acting as a keystone species is the presence of gray wolves in the Greater Yellowstone Ecosystem. The GYE includes active geothermal basins, mountains, forests, meadows, and freshwater habitats. The elk, bison, rabbit, and bird species in the Greater Yellowstone Ecosystem are at least partly controlled by the presence of wolves.
The feeding behavior of these prey species, as well as where they choose to make their nests and burrows, are largely a reaction to wolf activity. Scavenger species, such as vultures, are also controlled by the wolf activity. When the U. The last remaining wolf pups in Yellowstone were killed in This started a top-down trophic cascade in the Greater Yellowstone Ecosystem.
A trophic cascade describes changes in an ecosystem due to the addition or removal of a predator. A bottom-up trophic cascade describes changes that result from the removal of a producer or primary consumer. Lacking an apex predator , elk populations in Yellowstone exploded. Elk herds competed for food resources, and plants such as grasses, sedges, and reeds did not have time or space to grow.
Overgrazing influenced the populations of other species, such as fish, beaver, and songbirds. These animals rely on plants and their products—roots, flowers, wood, seeds—for survival. The physical geography of the Greater Yellowstone Ecosystem was also impacted by the loss of wolves and subsequent elk overgrazing.
Stream banks eroded as wetland plants failed to anchor valuable soil and sediments. Lake and river temperatures increased as trees and shrubs failed to provide shaded areas. Starting in the s, the U. The results have been noteworthy. Elk populations have shrunk, willow heights have increased, and beaver and songbird populations have recovered.
Herbivores can also be keystone species. Their consumption of plants helps control the physical and biological aspects of an ecosystem. In African savannas such as the Serengeti plains in Tanzania, elephants are a keystone species. Elephants eat shrubs and small trees, such as acacia , that grow on the savanna. Even if an acacia tree grows to a height of a meter or more, elephants are able to knock it over and uproot it.
This feeding behavior keeps the savanna a grassland and not a forest or woodland. With elephants to control the tree population, grasses thrive and sustain grazing animals such as antelopes, wildebeests, and zebras. Smaller animals such as mice and shrews are able to burrow in the warm, dry soil of a savanna. Predators such as lions and hyenas depend on the savanna for prey. Keystone mutualists are two or more species that engage in mutually beneficial interactions.
A change in one species would impact the other, and change the entire ecosystem. Keystone mutualists are often pollinators, such as bees. Pollinators often maintain gene flow and dispersal throughout widespread ecosystems. In the woody grasslands of Patagonia at the southern tip of South America a species of hummingbird and indigenous plants act together as keystone mutualists. Local trees, shrubs, and flowering plants have evolved to only be pollinated by Sephanoides sephanoides , a hummingbird known as the green-backed firecrown.
Pockets of the existing Patagonian habitat would collapse without green-backed firecrowns, because their functional redundancy is nearly zero—no other pollinator has adapted to pollinate these plants. In addition to keystone species, there are other categories of organisms crucial to their ecosystems' survival. Umbrella species are often conflated with keystone species.
Both terms describe a single species on which many other species depend. The key distinction between umbrella species and keystone species is that the value of an umbrella species is tied to its geographic species range.
Umbrella species have large habitat needs, and the requirements of that habitat impact many other species living there. Most umbrella species are migratory , and their range may include different habitat types. The identification of an umbrella species can be an important aspect of conservation. The minimum species range of an umbrella species is often the basis for establishing the size of a protected area. The species range includes heavily forested ecosystems in both temperate and boreal subarctic biomes.
Corals are a key example of a foundation species across many islands in the South Pacific Ocean.
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