Lecture 4 (Conditions and Resources) - Part 1.pdf -...

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Conditions and Resources
Lecture Objectives Describe how organisms respond to the range of conditions (e.g. temperature), Explain how the response of photosynthetic organisms to resources such as solar radiation, water, nutrients, and carbon dioxide are intertwined, Describe how different body compositions affect: the consumption of plants by animals, defenses employed by animals to reduce the rate that they are eaten by other animals, Describe the effects of intraspecific competition for resources, Explain how responses to conditions and resources interact to determine ecological niches.
Environmental Conditions Conditions are physico -chemical features of the environment such as its temperature, humidity, pH, or, in aquatic environments, salinity Organisms sometimes alter the conditions in their immediate environment— sometimes on a very large scale and sometimes only on a microscopic scale, But conditions are not consumed nor used up by the activities of organisms.
An example of organisms changing the conditions Lake Erie
Eutrophication and harmful algal blooms (HABs) result in changes to oxygen conditions! Limiting nutrient in marine ecosystems? Limiting nutrient in freshwater ecosystems?
Algae modify pH Matson, Paul G.; Washburn, Libe; Martz, Todd R.; Hofmann, Gretchen E. (2014): Model estimates of pH effect due to photosynthesis by algal community over a 24 h period in relation to sea ice algal biomass. Figure_8.tif. PLOS ONE. 10.1371/journal.pone.0107239.g008.
Algae change the conditions (pH) of their environment During the day, photosynthesis takes place, due to the presence of sunlight, Algae draw carbon dioxide from the water to utilize during photosynthesis, promoting cell growth, Removal of carbon dioxide from the water raises the pH levels, as a result of the reduction in carbonate and bicarbonate levels of water, since they are used to replenish the lost carbon dioxide, Depletion of inorganic carbon from water by algae results in high pH levels, as evidenced by the rise in pH levels of natural waters, which can go up to 10 or beyond in the presence of algae .
Acid Base Chemistry CO 2 + H 2 O  H 2 CO 3 * , K a = 10 -1.5 mol/(atm L) Plants remove CO 2 for photosynthesis If pH increases from say 8 to 9 how much will [H + ] drop? Carbonic acid
Acid Base Chemistry H 2 CO 3 *  HCO 3 - + H + K a1 = 10 -6.3 mol/ l HCO 3 - ,  CO 3 2- , + H + K a2 = 10 -10.3 mol/L H + gets used up, So…… pH rises! bicarbonate carbonate
If the pH of water is too high or too low, the aquatic organisms living within it will die. pH can also affect the solubility and toxicity of chemicals and heavy metals in the water. The majority of aquatic creatures prefer a pH range of 6.5-9.0, though some can live in water with pH levels outside of this range. pH - Tolerance Ranges
Environmental Resources Environmental resources , by contrast, are “consumed “ by organisms in the course of their growth and reproduction, The plant’s resources are thus carbon dioxide, water, nutrients, and solar radiation, Rabbits are a resource for eagles, and a rabbit

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