Community (ecology)

Many different living things live together.

They share the same home at the same time. This group is called a community.

Plants are the first part of the group. They make their own food.

Then, animals come to eat. Some eat only plants. Others eat other animals.

Every living thing has a special job. This job helps them live without fighting too much. If two animals want the exact same food, one might win.

This changes how the whole group works. It is amazing how everyone fits together.

Many living things live in the same place. They share that home at the same time. This group is called a community.

Every species has a niche. A niche is a special role. It tells us how a species uses its home. It also shows how it interacts with others. Species can live together by using different niches. This is called niche partitioning. For example, one animal might hunt at night. Another might hunt during the day. This helps them avoid fighting for the same food.

Communities also have trophic levels. These are steps in a food web.

At the bottom are producers. These are mostly plants. They make their own power. Next are herbivores. These animals eat plants for power. Then come carnivores. These animals eat other animals. At the very top is the apex predator. This animal is not eaten by any others in the group.

Some species are very important. Keystone species have a big effect on the group. If they are gone, the whole community changes.

Beavers are also special. They are ecological engineers. They change the land by building dams. This makes new homes for other animals.

A biological community is a group of different living things that live in the same area at the same time.

Scientists study these groups through community ecology. This field looks at how species interact and how many of them live in a space. It also looks at how they are spread out. These interactions depend on the traits of the animals and plants. Scientists must also look at non-living things like soil pH or temperature. For example, desert plants look very different from rainforest plants because of how much it rains.

Every species in a community has a niche. A niche is the specific role a species plays in its environment. This role helps determine how a species interacts with its home. Species can live together by using niche partitioning. This means they use different resources so they do not fight. One species might hunt at a certain time of day. Another might eat a different type of food. If two species have the exact same niche, one will likely outcompete the other. The more different niches that are filled, the higher the biodiversity will be.

Energy moves through a community in steps called trophic levels. At the bottom are autotrophs, or primary producers. These are living things like plants that make their own energy. Next are herbivores, which are primary consumers that eat plants. Then come carnivores, which are secondary or tertiary consumers. Some animals are omnivores because they eat both plants and animals. At the very top of the food web is the apex predator. This is an animal that is not eaten by any other species in that community.

Some species have a much bigger impact on their community than others. Keystone species are animals that have a huge influence on their surroundings. If a keystone species is removed, it can cause a trophic cascade. This is a chain reaction that changes the whole community. For example, wolves are keystone species in Yellowstone National Park. When wolves were gone, the elk population grew too large. The elk then ate too much vegetation, which hurt other animals.

Other species, called foundation species, change the physical environment. Red mangroves create nurseries for young fish. Whitebark pine trees provide shade and food for grizzly bears.

Scientists have different ideas about how communities are built. Frederic Clements proposed the holistic theory. He thought a community acted like a single unit where every part depends on the others. On the other hand, Henry Gleason developed the individualistic theory. He believed species join together more by chance based on the environment. Another idea is the neutral theory by Stephen P. Hubbell. This theory suggests that many species are functionally the same. In this view, changes in a population happen due to random events like births and deaths.

In ecology, a community is a group of different populations living in the same area at the same time. Scientists sometimes call this a biocoenosis or a life assemblage. Community ecology, also known as synecology, is the study of how these species interact. Researchers look at the distribution, structure, and abundance of these coexisting populations. They also study how species' traits, or phenotypes, influence their interactions. To understand a community, scientists must also consider abiotic factors. These are non-living elements like annual temperature or soil pH. For instance, precipitation levels determine why desert plant communities differ from tropical rainforests.

Every species within a community occupies a specific niche. A niche is the role a species plays and how it interacts with its environment. Species can coexist through a process called niche partitioning. This happens when species use different resources to avoid direct competition. For example, two species might hunt at different times of day. This reduces interspecific competition, which is the struggle between different species. Instead, they experience intraspecific competition, which is the struggle between members of the same species. The number of available niches determines the total biodiversity of the community. If two species share the exact same niche, one will eventually outcompete the other.

Energy moves through a community via different trophic levels. At the base are autotrophs, or primary producers, which create energy through photosynthesis or chemosynthesis. Next are herbivores, known as primary consumers, which eat the producers. These are followed by carnivores and omnivores, which act as secondary or tertiary consumers. At the very top sits the apex predator, an animal not consumed by any other species in that community.

Energy is passed up these levels, but some is lost at each step due to ecological inefficiencies. Decomposers, such as bacteria and fungi, play a vital role by recycling nutrients back to the producers. They feed on dead organisms from all trophic levels to keep the cycle moving.

Some organisms belong to a guild. A guild is a group of species that use the same resources in a similar way. While many guild members are closely related by common descent, this is not always the case. For example, all herbivores form a basic guild. A more specific guild might include all vertebrates that forage for ground-dwelling arthropods. Even flowering plants can form a guild if they share the same pollinator. Because they share resources, species within a guild often experience intense competition.

Certain species have a much larger impact on their community than others. Keystone species have a disproportionate influence relative to their abundance. They are often apex predators, and their removal can cause a top-down trophic cascade.

In Yellowstone National Park, the loss of wolves due to overhunting caused the elk population to increase. This led to overgrazing, which harmed many other organisms. Reintroducing wolves helped restore the community to optimal functioning. Other influential species include foundation species, which create physical changes to the habitat. Red mangroves, for example, provide nursery grounds for young fish. Whitebark pines provide shade and food for grizzly bears.

Ecological engineers also play a major role by modifying the physical environment. Beavers are classic examples of these engineers. By building dams, they change the flow of water in a community. This creates new habitats and increases biodiversity in the riparian zone. These physical changes can help other organisms, like frogs, move more easily between habitats. Such species actively maintain or create aspects of the community that others rely on.

Scientists use different theories to explain how these communities are structured. Frederic Clements developed the holistic theory, viewing the community as a single unit or "superorganism." He believed species were interdependent and that community formation was non-random. In contrast, Henry Gleason proposed the individualistic theory. He argued that species associate somewhat randomly based on environmental gradients. Finally, Stephen P. Hubbell introduced the neutral theory. This theory suggests that species in a community are functionally equivalent. In this view, population changes are driven by stochastic, or random, processes like births and deaths.