BIOLOGY 220 LECTURE #22 - Niche Concept and Community Level Interactions - 11-17-07

BIOLOGY 220 LECTURE #22 - Niche Concept and Community Level Interactions - 11-17-07

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BIOLOGY 220 – LECTURE #22 – THE NICHE CONCEPT AND COMMUNITY – LEVEL INTERACTIONS FIRST MAJOR THEME: NICHE How niches work, how they are defined, what they are CONCEPT OF THE NICHE – 3 Physical elements of the environment that an organism lives in: o Wind conditions, o How much light does it need o What temperatures are best o Frost free growing days, o Precipitation Chemical elements/restrictions o Need nutrients o Need a certain pH Biological aspect: o Interactions it has Competitors, Predators Symbionts Mates Prey Pathogens All these elemental factors help us to predict the distribution of an organism (where it is found) Also, the number of organisms in a space CONCEPT OF THE NICHE – 4 Limiting factors – light, temperature, water, or nutrients o A resource that is scarce while others are in adequate supply Liebig’s Law of the Minimum : o Growth is limited by the limiting factor o Test by adding other nutrients other than the limiting factor o Add limiting factor, we get growth o In regards to plants… Shelfor’ds Law of Toleration o If we have an abiotic factor (physical or chemical) and we have an organism, there is a minimum, optimum, and maximum of the concentration of that particular factor.
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CONCEPT OF THE NICHE – 5 If we are talking about any limiting abiotic factor 1.) Lower lethal limit – A certain level that if we have a low enough concentration of that factor, at this point nothing happens, nothing grows. Population won’t grow. Taken away that much of this abiotic factor, nothing happens. 2.) Critical Minimum – If we increase the concentration of the limiting abiotic factor, we start to see population growth, we start to see individuals growing and reproducing. The region in which this happens is between 1 and 2. 3.) Physiological optimum : The preferred range – The level of concentration in which the population grows very quickly and the growth stabilizes – population becomes very large – all resources are in the optimum concentration range. (Range of 3) 4.) Critical maximum – Too much of the limiting abiotic factor can be bad – A lot of population growth, but also a lot of excretion (a lot of waste) – toxins build up in environment – poisoning of population 5.) Upper lethal limit – WAAAAY too much of the limiting abiotic factor and everything dies. To survive, organism must live somewhere between 2 and 4.
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This note was uploaded on 04/15/2008 for the course BIO 220 taught by Professor Cassiemajetic during the Fall '07 term at Allegheny.

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BIOLOGY 220 LECTURE #22 - Niche Concept and Community Level Interactions - 11-17-07

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