What are the factors specific to the tropical rain forest biome that affect this ecosystem?
Abiotic FactorsThe abiotic factors of an ecosystem are considered nonliving, and they could be categorized as all of the chemical and physical factors: temperature, light, water, and nutrients. Abiotic factors influence the distribution and abundance of organisms in an ecosystem, therefore determining its biodiversity (2b). Organisms that have adaptations that enable them to survive in an ecosystem with certain abiotic conditions will have a higher reproductive success than those who do not have beneficial adaptations.
ExamplesLight:
For example, the intensity and amount of light that is received in the tropical rainforest biome determines which plant types will survive (5). In Manuel Antonio, there is an average of 5 hours of intense sunshine each day; however, the ground level of the forest is dark and shaded because only a small amount of light can penetrate through the leaves of the taller trees in the canopy. Because of the limited amount of light that reaches the ground level of the rainforest, only a few bushes and herbs are able to grow and survive. With that said, the majority of plant life in this ecosystem consists of trees such as the bully tree, black locust, cow tree, and silk cotton tree that vary between 30-40 meters in height, as they are fully exposed to the light (7). Precipitation: The rainforest ecosystem within the Manuel Antonio National Park neighbors four beaches: Espadilla Sur, Manuel Antonio, Escondito and Playita (1). There is a rainy season and a dry season in Manuel Antonio, and the dry season lasts from about January to March. In the dry season, the precipitation significantly decreases, and the hours of intense sunshine during the day increase (about 9 hours in March). Animals must look for food and water close to the beach areas listed above in order to survive due to the lack of water and food in the rainforest (7). This is a black locust tree in a neighborhood, but is also found in the tropical rainforest ecosystem of Manuel Antonio. The black locust is one of the more dominant tree types in this ecosystem (4)
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Biotic FactorsBiotic factors are organisms living in an environment that influence or affect the ecosystem (8). Biotic factors are not just a compiled list of all of the individual living organisms of the ecosystem, but more importantly how these living organisms affect their ecosystem, or affect the lives of other organisms within their ecosystem.
ExamplesAlgae on the Two-Toed Sloth:
The two-toed sloth is abundant in the tropical rainforest ecosystem of Manuel Antonio National Park. Sloths are very inactive in general, and are even the world's slowest mammal, so algae grows on the coat of the two-toed sloth. This gives the coat color of the sloth a greenish tinge, so the sloth appears to blend in with the colors of the rainforest. By coating the sloth's fur green, the algae (which is a living organism) allows for the sloth to be camouflaged while hanging still on a tree and avoid its predators. Without this ability to blend into the trees, sloths would not be able to escape the gripping claws of their predators because of their slow speed. Therefore, the algae is a biotic factor, as it effects the two-toed sloth's ability to avoid predators (8). A two-toed sloth hanging from a tree branch in a rainforest. Sloths spend their whole lives sleeping, eating, and hanging from trees! (5)
A three-toed sloth that is a better example of algae giving the sloth's coat color a green tint; the sloth is camoflauged very well and perfectly blends in to the tree color that it is clinging on to (6).
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Limiting Factors
Limiting factors limit the presence, success, and distribution of organisms in a population (resources in short supply) (10).
Density-dependentIf the population density rises and death rate rises as well, then that rate is density-dependent. For example, as the population density rises, competition for resources that are necessary for survival will increase and result in a lower birth rate in the population. This is because the organisms that are more "fit" in their environment (are able to obtain these limited resources) will have reproductive success, lowering the overall birth rate of the population. Also, a population with a high density will have an increased rate of infections by pathogens (2c).
ExamplesDecreasing Squirrel Monkey Birth Rate:
In this example, the population density of the endangered squirrel monkey increased, resulting in a decreasing birth rate. Manuel Antonio is Costa Rica's most popular National Park; it is also one of the smallest, measuring up to 682 hectares. Because of its very small size and limited amount of resources, it is difficult to sustain a healthy and growing population of certain animals, particularly the squirrel monkey. These monkeys needed to be able to travel outside of the park because of their high population density and competition for limited resources due to the size of the park. However, before the year 2000, monkeys were not able to travel outside of the park along monkey bridges to find food and shelter. And so, the death rate of these squirrel monkeys began to increase. The birth rate of the population also decreased because the monkeys competed for resources and only the "fit" would survive and reproduce (so less breeding would be able to occur) (12). |
Density-independentA death rate or birth rate that does not change with population density is considered density-independent. Regardless of the size of the population, an increase of the death rate within a population is mainly caused by the weather, deforestation, human interference, or natural disasters. These factors are all based on disturbances of an environment (2c).
ExamplesTropical Storm Devastation:
A great example of a density-independent limiting factor is a tropical storm. In 2010, Manuel Antonio National Park faced a devastating tropical storm that increased the death rate of a population of the endangered squirrel monkey. With this tropical storm, 30 monkey bridges were destroyed (1/4 of the bridges), and thousands of trees located in the rainforest collapsed or were broken. This made it very difficult for the squirrel monkeys to travel across the canopy and find food and shelter among the trees, so the death rate of the already endangered squirrel monkey population rose (11). Squirrel monkeys travelling across man-made monkey bridges through the canopy of the rainforest ecosystem of Manuel Antonio National Park (7).
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