How does competition affect population

The physical environment differs between upper and lower inter-tidal locations. Perhaps the niche of Chthamalus is high in this zone; the niche of Balanus is low in this zone. Barnacles have a larval stage, and larvae settle out of the water column onto hard substrates, metamorphose, and begin to grow.

Larvae of each species settle in the zone of the other, but no adults are found Figure 3. Does this mean neither can live in the zone occupied by the other? Chthamalus Figure 3. This study helped to pioneer the approach of field experiments. Using cages to exclude one or the other species, and by transferring slabs of rock from one region to the other, it was established that Chthamalus could thrive in the lower zone if protected from Balanus.

Otherwise, Balanus, which is a larger and more robust species, crushed neighboring Chthamalus as it grew in size. Chthamalus was competitively excluded from the lower inter-tidal. At the upper limit, however, both species were limited by their ability to withstand desiccation. Chthamalus, the inferior competitor, was better adapted to desiccation and so occupied the higher portion of the inter-tidal zone. Mechanisms of Competition Competition often takes place via the using up or depleting of resources by members of one species, making those resources unavailable to members of the second species.

Resources would include nest sites, food items, water or minerals in the soil. This is called indirect competition. It is likely to be most severe between individuals with similar needs for example, two species occupying the same trophic level, and with similar ecological roles or niches.

Direct competition occurs when members of one species interfere with or directly harm members of a second species. Examples include fights over space among animals, release of chemicals by plants e. Competition and Evolutionary Specialization Competition is likely to result in evolutionary divergence and specialization among closely related species. Consider the process of speciation , which is thought often to be gradual and include a period of selection for reproductive isolation once geographic isolation no longer separates the two diverging populations.

We should expect those two species to occupy very similar ecological niches, hence to be likely to compete. Quite possibly, one species will eliminate the other. It also is possible, however, that the two species will diverge ecologically, perhaps via divergence in traits such as bill size that affects the size of food items consumed.

This is known as character divergence. The Galapagos Finches The Galapagos finches appear to be good examples of character divergence. Three species of ground finches make a particularly strong case. If we assume there are seeds of different sizes -- small to large -- it makes sense that beaks of different sizes -- also small to large -- permit efficient handling and cracking of seeds in a specific size range.

If only one species of finch exists, perhaps it will occupy the "middle ground" of beak and seed size. However, once speciation occurs, should one species be slightly smaller and one slightly larger, natural selection should favor individuals that are smaller than average within one species, larger than average within the other.

Over time, beak size the character that determines which portion of the resource spectrum is consumed will diverge. There is a complication, however. Suppose our large and small finches arose independently somewhere else, and happened to colonize various islands in one's, two's and three's. In the absence of competition, both a small and a large species might evolve towards an intermediate size.

This is known as ecological release. Whether one is observing character displacement or ecological release then depends on the order and independence of speciation events. This is hard to know, but a good cladogram would resolve the issue. Summary - The Consequences of Competition Competition can be a powerful force affecting the growth, distribution, and abundance of populations in nature.

This is supported by evidence from laboratory "bottle' experiments, field observations, and field experiments. Laboratory studies lead to the formation of the competitive exclusion principle no two species can long occupy the same niche , while field observations suggest that niche differences, while sometimes subtle, are invariably found between co-existing species.

Microsatellite analysis indicated that, after the reproductive season, many colonies in the experimental plots were headed by a young queen that was the mother of the brood but not of the old workers, indicating that reduction in colony density stimulated fission of the remaining colonies.

Finally, at the end of the experiment, 14 months after experimental reduction in density, colonies that derived from fission were smaller in the experimental than in the control plots, suggesting that the former had undergone fission at a smaller size than in control plots, which presumably allowed them to colonize the emptied areas.

We conclude that colonies adjust resource allocation and colony fission to the degree of intraspecific competition. Abstract Intraspecific competition is a pervasive phenomenon with important ecological and evolutionary consequences, yet its effect in natural populations remains controversial. Publication types Research Support, Non-U. Skip to content Home Sociology How does competition affect population growth?

Ben Davis November 5, How does competition affect population growth? How can competition result in a decrease in population growth? How does competition affect a population quizlet? How can limiting factors affect a population? What are the 5 limiting factors? What are the main causes of population growth? How can we fight overpopulation?

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