LITE5_-_study_guide - Chapter 5 - Biodiversity, Species...

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Chapter 5 - Biodiversity, Species Interactions, and Population Control Core Case Study: Southern Sea Otter Southern sea otters, an endangered species, live in giant kelp beds in a small area of coastal California. These otters use stones to crack open shellfishes from underwater rockbeds, eating ¼ their weight daily in clams, mussels, crabs, urchins, and abalone. In the early 1900s, sea otters were hunted almost to extinction for their fur and to stop competition with humans for abalone. They have increased from 50 otters in 1937 to over 3,000 in 2007. Why should we be concerned about this species? 1) They generate millions of dollars a year in ecotourism dollars; 2) Ethics; many people believe it is wrong to cause the premature extinction of a species; and 3) otters are keystone species . The otter’s diet restricts sea urchins and other kelp-eating species, allowing development of kelp habitats that support large numbers of organisms. Species interact through: 1) Interspecific competition : when two or more species interact to gain access to the same limited resources , such as food, light, or space. 2) Predation : when one species, the predator, feeds directly on another species, the prey. 3) Parasitism : when one organism, the parasite, feeds on the body of another organism, the host, usually by living on or in the host. 4) Mutualism : when the interaction of two species is beneficial to both, providing food, shelter, or other resource. 5) Commensalism : when the interaction benefits one species, while having little effect on the other. These interactions affect the resource base, population size, and natural selection process (survival and reproduction) of organisms in an ecosystem. Competition : Competition for limited resources is the most common interaction. Evolving better abilities to acquire food or other resources over another species is the most common aspect of competition, not direct fighting. A species’ unique role in an ecosystem (or the resources it uses, remember the n-dimensional hypervolume) is its ecological niche , some species are generalists , with broad niches, and some are specialists , with very narrow niches, at least along one niche dimension. No two species can occupy the exactly same ecological niche, a concept known as competition exclusion principle . Humans compete with many species for food and habitat as we convert the earth to our uses and degrade, destroy, or fragment natural habitats. Predation : Producer species are plants and phytoplankton, which make their own food by photosynthesis. Consumer species include: herbivores (feed on plants), carnivores (feed on the flesh of other animals), omnivores (feed on plants and animals), and decomposers (detritivores and saprovores, which feed on detritus and dead bodies of organisms). Predator-prey interactions can include grizzly bears feeding on cutworm moths, but usually involve pursuit and ambush , such as a cheetah running down prey. Predators use camouflage and chemical
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This document was uploaded on 10/27/2011 for the course RNR 1001 at LSU.

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LITE5_-_study_guide - Chapter 5 - Biodiversity, Species...

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