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UVM BCOR 012 - Ecological Niches and Disturbances
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BCOR 12 1nd Edition Lecture 23Outline of Last Lecture I. Major Life History Traits RepeatedII. Human Population cont.III. Critical Perspective QuestionsIV. Community Ecology – Beginning of Chapter 54V. Intra- and Interspecific interactionsOutline of Current Lecture I. Competitive Exclusion II. Ecological Niche and Resource PartitioningIII. Fundamental Features of Community StructureIV. DisturbancesCurrent LectureCompetitive Exclusion- Competitive exclusion principle: when two populations of two similar species compete for same limited resources (food, space, etc.) one population will use resources more efficiently and have a reproductive advantage (in time an evolutionary advantage) o Result = the other species will be eliminated (over time)Ecological Niche and Resource Partitioning - Niche: sum of a species’ use of both biotic and abiotic resources in its environment (“ecological role”)o Habitat = where an organisms liveso Ecological niche = organism’s profession or job - Example: many different lizards living in the trees of the tropics all eat insects but they live in different parts of the tree (nicke-shift)- Resource partitioning: a pattern in which species whose niches overlap may diverge to minimize the overlap- Example: Lizards diverged to live in all parts of the trees to limit their competition with other lizards and led to speciation- Competitive exclusion principle is too simplistic to be seen in the natural worldThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Keystone species: a species that exerts strong control on the community structure by thenature of its nicheo Example: The sea otter in the North Pacific. When it was almost completely eliminated by orca whales, the sea urchins’ (that sea otters prey on) population grew quickly and diminished the kelp forests. This led to a decline in animal abundance for the kelp forests were a habitat to many animals. Sea otter = keystone species of North Pacific- The sea otter had a DIRECT, NEGATIVE effect on the sea urchins and an INDIRECT, POSITIVE effect on the kelpFundamental Features of Community StructureFundamental Community Properties:I. Species DiversityII. Tropic StructureSpecies diversity:- Species richness: number of different species in the community - Relative abundance: the proportion of each species in the community*Can have same species richness in two different communities BUT have different relative abundances of those species- Diverse communities are MORE stable and have increased productivity- Example: Minnesota Experiment set up 168 plots. Plots either had 1, 2, 4, 8, or 16 species of grass (perennial, native grasslands) and these plots were replicated.o Found: 16 species plots were 70% more productive when compared to a 1 species plot- Communities with higher diversity are:o Better able to withstand or recover from environmental stresseso More resistant to invasive species – organisms that become established outside their native rangeTropic structure:- Tropic structure: different feeding relationship in an ecosystemo Route of energy flowo Pattern of chemical cycling (driven by decomposers)- Food Chain:Primary Producers (autotrophs)Primary Producers (autotrophs)Primary Consumers (herbivores)Primary Consumers (herbivores)Secondary Consumers (Carnivores)Secondary Consumers (Carnivores)Tertiary Consumers (Carnivores)Tertiary Consumers (Carnivores)Quaternary Consumers (Carnivores)Quaternary Consumers (Carnivores)Disturbances- Disturbance: an event that changes a community by removing organisms from it or altering resource availabilityo Influences species diversity and composition- Succession: the predictable process of recovery after a disturbance (natural or unnatural)- Pioneer species: first species to colonize a disturbed areao Bryophytes are most abundant pioneer species due to the fact they don’t need soil for they don’t have roots and were the first to colonize land- Succession, following a disturbance, species colonize and transform the habitat in a predictable


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UVM BCOR 012 - Ecological Niches and Disturbances

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