BIOL 101 7986
Kenneth Galicia
Week 6 Discussion.
1. In terms of ecological science, what is a "niche?"
A niche can be defined as the specific position a species holds within the hierarchy of a local area. To clarify, it encompasses not only where the species physically exists but also what it eats, who its predators are, who its competitors are, how it mates/reproduces, and any factors that influence these things. How a species or population responds to the pressures placed on it by the environment it is in such as resource scarcity, competition for territory or food, predation, parasitism, etc. are all part of what can be considered its Niche within that ecological community. A niche, therefore, also encompasses behavioral adaptations to its surroundings and environmental pressures. Various scientists have defined specific parameters for defining a niche, including; Grinnell who proposed a niche can be defined as the environment a species lives in and its behavioral responses to that environment, Elton who focused on predation and competition stating that “The 'niche' of an animal means its place in the biotic environment, its relations to food and enemies”, and arguably the most complex being the Hutchinson explanation which puts forth an n-dimensional hypervolume who’s parameters are defined by the environmental conditions and resources available.
2. Give a brief example of parasitism, mutualism, and symbiosis.
Parasitism is the ecological relationship which can be defined most simply as a plus for one species and a minus for the other; that is one species benefits directly at the detriment of the other species. An example would be the Tapeworm (Cestota) a class of parasitic flatworms which infect their host and directly steal nutrients by inhabiting their intestinal tract and intercepting whatever the host eats. This obviously causes malnutrition and other issues for the host. Mutualism could be defined as a plus-plus ecological relationship in which both species benefit from the interaction. A good example of this would be pilot fish that eat dead skin and microbes off the hide of whales, the whale gaining better health through hygiene and the pilot fish gaining a reliable food source and measure of safety from predators. Symbiosis is similar to mutualism but involves a direct, close, physical association between the species; a good example would be plants that enter a symbiotic relationship with Arbuscular Myccohhrizal Fungi. The Fungi gain carbohydrates from the plant’s photosynthesis and the plant gains access to nutrients and minerals the fungi takes up from the soil that would otherwise be inaccessible. 3. E. O. Wilson noted that whenever a species becomes extinct, we have no idea what effect the loss of that species will have on the remainder of the gene pool in the long term. Explain what Wilson meant by that statement. E.O. Wilson was describing the interconnectedness of species within a community and even globally in our increasingly “shrinking” world. His statement reflects the idea that when one species is lost, the effects reverberate throughout the entire “food web” or consumer-resource interactions. This is especially true for what are termed “keystone” species or species that, if removed, would cause the entire ecological infrastructure in the area to collapse. The trophic interactions between species in an environment are very complex and not just a linear plants-herbivores-predators-top tier predators pattern. Top tier predators for example also eat primary consumers and in