Competition (biology)

Animals often want the same things.

They may want the same food or the same home. This is called competition.

Sometimes animals fight to win.

Large animals may use strength to keep others away. This helps them stay safe and fed.

Other times, animals do not fight. They just use things up fast. One animal might eat all the food first. This leaves nothing for the others.

Sometimes, a shared hunter causes trouble. If one animal group grows, more hunters come. These hunters might then eat a different animal group too.

Nature is a busy place. Animals must find their own way to live.

In nature, living things often need the same resources. They may want the same food, water, or space. This is called competition.

There are three main ways this happens. The first way is interference competition. This is when animals fight directly.

Large animals often use strength to win. For example, male red deer fight each other. Some ants even block the holes to other ant homes. Plants can also fight using chemicals. This is called allelopathy.

The second way is exploitation competition. This is a more indirect way to compete. Animals do not fight. Instead, they just use up the food or light first. This leaves less for everyone else. Smaller animals are often good at this because they can find food very fast.

The third way is apparent competition. This is not a fight for food. Instead, it happens because of a shared predator.

If one group of prey grows, more predators will come to the area. These new predators might then eat a different group of animals. This can make the second group shrink, even if they do not want the same food.

In nature, living things must often share. When two or more living things need the same resource, they are in competition. These resources might be food, water, or a place to live. Because these things are in limited supply, one living thing's use of them leaves less for others. This can lower the fitness of everyone involved. Competition is a major part of how communities are built. It helps decide which species live in a certain area and how many of them there are.

There are three main ways this works. The first way is interference competition, which is a direct fight. Organisms interact through aggression to protect what they need. For example, large aphids can push smaller ones away from good leaves. Some ants even plug the holes of other colonies with rocks. In plants, this happens through allelopathy, which is using chemicals to stop neighbors. The second way is exploitation competition. This is an indirect way of competing by using up a resource first.

A plant might grow fast to take all the sunlight. Smaller animals often win this way because they can find food very quickly.

Scientists have studied these patterns for a long time. In 1977, an ecologist named Robert D. Holt used a new term. He called the third way "apparent competition." Before this, people thought different prey species were fighting for food. Holt showed they were actually just sharing the same predator. This idea helps explain why some species disappear from certain places. For example, in the late 1960s, researchers looked at hares in Newfoundland. They found that snowshoe hares could change where arctic hares lived. This happened because the snowshoe hares led to more lynx predators.

Competition can happen between members of the same species. This is called intraspecific competition. It can also happen between different species, which is called interspecific competition. Some competition is even asymmetric. This means one species is hurt much more than the other. In the Mojave Desert, human garbage helped raven populations grow. This led to more ravens, which then harmed young desert tortoises. This is a very extreme version of apparent competition.

Scientists use data from space and isotopes to study these shifts. Even the bacteria inside our own bodies can compete this way.

Understanding competition helps us see how the world stays in balance. It is not just about winning a fight. It is about how every living thing finds its niche. A niche is the specific area or resources a species can actually use. Sometimes, animals avoid fighting by using resources at different times. Red deer females and babies do this to stay safe from males. Other times, species change where they live to avoid others. This complex web of interactions keeps nature moving and changing.

In biology, competition is an interaction between organisms or species. It occurs when they require one or more resources that are in limited supply. These resources can include food, water, or territory. Because these supplies are finite, the presence of one organism reduces the amount available to others. This process lowers the fitness of all organisms involved. Competition is a vital factor in community ecology. It influences community structure, species diversity, and population dynamics, which are shifts in a population over time.

Ecologists categorize competition into three major mechanisms. These are interference, exploitation, and apparent competition. Interference and exploitation are considered "real" forms of competition. This is because the organisms are actually interacting with the same resource. Apparent competition is different. In this case, organisms do not share a resource. Instead, they share a common predator. Scientists also distinguish between intraspecific competition, which happens within a single species, and interspecific competition, which occurs between different species.

Interference competition, also called contest competition, involves direct interaction. Organisms fight or use aggression to secure scarce resources. For example, large aphids defend feeding sites on cottonwood leaves by ejecting smaller aphids. In the animal kingdom, this strategy is often used by larger, stronger organisms. This can lead to adult-driven generation cycles. In these cycles, the growth of juveniles is stunted by larger adults. Once juveniles reach adulthood, they experience a secondary growth cycle. Some animals use temporal resource partitioning to avoid this. Red deer does and fawns forage for food only when adult males are not present.

Plants use a different method for interference competition called allelopathy. This involves the production of biochemicals to inhibit neighbors. Exploitation competition, or scramble competition, is an indirect mechanism. Organisms do not fight; instead, they compete by depleting a common resource. This rewards organisms that claim the resource first. This mechanism is often size-dependent. Smaller organisms are often favored because they typically have higher foraging rates. This can lead to juvenile-driven generation cycles. In these cycles, individual juveniles succeed and grow quickly, but are outcompeted once they mature.

Apparent competition occurs when two unrelated prey species share a predator. This can change the abundance of each species. If species A increases, the population of predator C might also increase. Because there are now more predators, species B will be hunted at higher rates. This makes it seem like species A is outcompeting species B. However, they are actually just sharing a predator. The term "apparent competition" was coined in 1977 by Robert D. Holt. He noted that ecologists were wrongly attributing these interactions to niche partitioning.

Apparent competition can shape a species' realized niche. A realized niche is the area or resources a species can actually persist in due to interactions. In the late 1960s, researchers studied snowshoe hares in Newfoundland. They found that snowshoe hares reduced the habitat range of native arctic hares. This happened because snowshoe hares caused an explosion in lynx populations. Since arctic hares have weaker defenses, they were excluded from woodlands by the increased predation. This interaction can be symmetric or asymmetric. Symmetric competition affects both species equally. Asymmetric competition affects one species much more than the other.

Human activity can cause extreme asymmetric apparent competition. In the Mojave Desert, human garbage caused common raven populations to increase. This led to an indirect negative effect on juvenile desert tortoises. This happens because the increased raven population affects the tortoise. Apparent competition can even occur within the human body. The human immune system can act as a generalist predator. A high abundance of certain bacteria can induce an immune response. This response can then damage all pathogens in the body. Understanding these complex links helps scientists understand how biodiversity is maintained.