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strengths and weaknesses of ecological theory
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Competition and predation are two key factors that affect the stability of an ecosystem, such as a lake. There are three theories on the affects of competition. Competition may lead to competitive exclusion, stable coexistence, or niche differentiation. It has been shown that in marine environments, species are strong competitors for both light and nutrients and thus competition leads only to competitive exclusion (Passarge et al. 2006). The competitive exclusion principle states that if two species compete for the same resource in the same location, then one of those species will go extinct because one species will be the better competitor (Jenson 2010). Another factor in ecosystem diversity is predation. The predator and prey relationship is a complicated one. Populations go through cycles of high abundance and low abundance. Many data seem to indicate that predators are able to reduce prey populations in density-dependent situations (Freeman 2008). One example of this is the study of the snowshoe hair and the lynx. This study proved that the hair populations and the lynx...
Mills, Scott L., Daniel F. Doak, and Michael E. Soule. "The Keystone-species Concept in Ecology and Conservation." BioScience 43.4 (1993): 219-25. Apr. 1993. Web. 30 Oct. 2011.
Predation refers to the consumption of one organism known as the prey by another known as the predator in which the prey is alive when the predator first attacks it. Predation is beneficial to the predator and harmful to the prey. This is a broad group which covers a wide variety of interactions and numerous types of predators. For the purpose of this essay we will concentrate on classifying predators according to their individual taxonomic and functional responses.
Sea otters (Enhydra lutris) are marine mammals capable of spending their entire lives in water. Being carnivorous in nature, they feed on sea urchins, crabs, fishes, mussels and clams. They are referred to as keystone species due to their profound impact on marine ecology. The interaction between sea otters, sea urchins and kelp forests has been studied as a model for the impact of predator-prey interactions on community ecology. Sea otters are keystone predators, whose presence has a far-reaching influence on the marine food web by affecting the populations of sea urchins, which indirectly affects the populations of kelp forests & other marine organisms. There has been a steep decline in sea otter populations due to water pollution and exploitation for furs. This has affected marine ecology adversely. It is therefore suggested that sea otters should be included in the endangered species list to protect them from further exploitation. This study focuses on the community ecology of sea otters and their impact on marine ecology. The need for their inclusion in the Endangered Species list and the implications of such an intervention are also evaluated.
For a species to survive and flourish within a given environment, it not only needs to replace itself but also all the other species around it exclusively. Hence, if one species completely replaces another species, the result is a single dominant species, a monoculture (source 2). According to Gause’s law, every species in a given environment occupies different niches for survival. Therefore, two separate species competing for similar resources cannot fundamentally coexist (source Gause). This is known as the competitive exclusion principle. When comparing animal niche’s to that of different autotrophic plants, one can rather easily differentiate adequate ecological niches for the animal species merely based on food-requirements (P.J. Grubb). On the contrary, many autotrophic plants contradict the competitive exclusion principle by sharing similar ecological niches such as sunlight, carbon dioxide, water, and alike mineral nutrients (p.j. grubb).
...resides or benefit from forested habitat will possibly loss their home thus may decline in numbers. Another example would be a development of reservoirs within a river system. This type of development will benefit still water fish but at the same time adversely affects the fish habitat who are accustomed to the free flowing water.
Fish habitat is the underwater world which many people do not see. It is just like the world that people live. Fish and plants reproduce, eat, and live in this environment, and even face challenges such as invasive species. It is said that “Invasive species are non-native species that threaten the diversity or abundance of native species due to their uncontrollable population growth, causing ecological or economic impacts” (“Invasive” par. 1). Vegetation plays a big role for fish habitat and for a lake itself. Aquatic habitat provides living space for not only fish but also for many aquatic insects. These insects then in turn provide fish and other species of animals with food (“Native” par. 4).
As if there weren’t enough problems for scientists trying to save the Great Lakes Eco System. Many non-native species have entered the eco system and many of them are harmful. Every species in itself has played a role in the eco system. These non-native species make it increasingly difficult for the Great Lakes Eco System to be regulated.
This would be food chains. Food chains are a key part in any wildlife around the world. They are a system that shows what eats what from the plant-small prey-Large predators. In our lakes smaller fish eat aquatic plants , the smaller fish are eaten by larger predators and so on. But if one part of the food chain is messed up, like if all of the large predatory fish were fished out, there would be nothing to eat the small prey fish. This would cause the small prey fish to overpopulate and more mouths to feed. This would cause the aquatic plant population to decline. Now you see how one slight change of a part of a food chain can screw everything up. Which brings us to our next
Studies have shown both support and refutation for sea otters being the main reason for trophic cascades within kelp forests. However; there are many changes that could be made to improve previous studies, which would help confirm the true role that sea otters play. Many studies need to be duplicated to confirm the results that were seen. The focus of the studies needs to be shifted from sea otters to kelp and urchin populations. This will lead to a smaller sampling error due to the fact that otters are roving predators so determining abundance is harder than measuring sedentary organisms like kelp and urchins (Estes et al., 2010). Looking into complex and multistep food web interactions, such as the study on the rock greenling, will provide further insight into the possible far reaching effects of sea otter predation. Finally, research on the different equilibrium states needs to be addressed further in other locations to confirm the viability of the urchin
Trade-offs often occur when the members of a system are competing with each other. It is one of the most prevailing acknowledgements for coexistence in the communities. The ‘Darwinian demon’ theory indicated that “Trade-offs between survival and reproduction, however, constraints any organism from realistically resembling that creature.” Similarly, ‘Hutchinson demon’ theory also pinpointed whereby “one species in a community dominates because it is best colonizing new patches, utilizing all the resources, avoiding predators and resisting stresses.” Trade-offs in a community can be controlled by several limiting factors, such as scarce of resources, abiotic factors like pH, salinity, presence of sunlight, and presence of competitors. Interspecific trade-offs are typically thought to be a requirement for species coexistence in communities at small spatial scales. Within meta-community context, trade-offs are still often harbingered as imperative for coexistence at a regional scale rather than local scale. There are three elements of trade-offs among competing species within a trophic level like the interaction between local and regional trade-offs, regional-scale coexistence and trade-offs and species diversity at multiple spatial scales (alpha, beta, gamma).
The susceptibility of an aquatic ecosystem to becoming infested with an invasive species is also a topic of interest in the research of how zebra mussel populations spread. A study done on aquatic invasive species implies that resistance of a native community to invasion by non-native species is related to competition, predation, and parasitism. (Havel, et al., 2015)
If a prey species decreases in abundance, this leads to increased intraspecific and interspecific competition, which could have negative impacts on the species. One area of concern is the effects of climate change on the abundance and behaviour of krill, one of the leopard seal’s source of food during the winter (Siniff, et al., 2008).
Co-evolution occurs in nature as an evolutionary arms race with an ongoing cycle of response and selection between two species. In most situations when two species co-evolve, the two species will have a predator and prey relationship. In a predator and prey relationship there is a constant struggle for the predator to catch the prey and for the prey to deter or evade the predator. As a result, either the predator or prey will eventually acquire a trait via natural selection that will give them an edge over their counterpart. The new advantage developed will elicit a response from the other species to naturally select a counter adaptation. The natural selection of advantageous traits of one over the other and the selected response of the counterpart
Populations contain very delicate and reactive relationships between species. These populations can be largely impacted by small changes such as weather or climate. Most populations stay relatively balanced by predators or limited food sources. Populations are sometimes directly correlated to each other and when one gets too large they either get killed by the other or starve from competition over food. Our experiment was designed to answer the question, which factors affect the stability of a predator-prey population size relationship? This shows how populations balance each other out. Our claim was that if there is a higher amount of time needed for the re-growth of the grass, the amount of sheep, and therefore wolves, will go down.
off of just one host but very few predators can feed on the same prey(1973). In