Ecology II Chapter 34 PDF

The biotic components of ecosystems Populations of an ecosystem – Autotrophs- primary producers Require an energy source and inorganic nutrients to produce organic food molecules Green plants and algae-photosynthesis Bacteria-chemoautotrophs – Heterotrophs- c...

The biotic components of ecosystems Populations of an ecosystem – Autotrophs- primary producers Require an energy source and inorganic nutrients to produce organic food molecules Green plants and algae-photosynthesis Bacteria-chemoautotrophs – Heterotrophs- consumers Consume organic nutrients – Herbivores, carnivores, omnivores Decomposers- fungi, bacteria – Break down decaying matter releasing nutrients 34-1  Biotic components Fig. 34.1 34-2  The biotic components of ecosystems cont’d. Energy flow and chemical cycling – Energy enters ecosystem in the form of sunlight absorbed by producers – Chemicals enter when producers absorb inorganic nutrients – Producers then make organic nutrients for themselves and all other organisms in the ecosystem Consumers (herbivores and omnivores) gain nutrients and energy from eating producers Higher level consumers (carnivores) then gain nutrients and energy from eating herbivores and omnivores – A lot of energy (90%) is released at each level to the environment in the form of heat and waste products. Only 10% is usable at that trophic level. 34-3  Energy flow and chemical cycling Fig. 34.2 34-4  Energy balances Fig. 34.3 34-5  The biotic components of ecosystems cont’d. The following two slides illustrate food webs – Food webs illustrate the interrelationships between organisms in the food chain – Identify the producers, primary consumers, and secondary consumers Laws of thermodynamics – First law- energy is neither created nor destroyed Ecosystems depend on continual outside source of energy – Second law- with every transformation, some energy is given off as heat The amount of available energy at each successive trophic level is less than the one below it 34-6  Grazing food webs 34-7 Fig. 34.4  Detritis food web Fig. 34.5 34-8  34.2 Energy flow Trophic levels – Trophic level is composed of all organisms that feed at a particular link in the food chain Primary producers- first trophic level Primary consumers- second trophic level Secondary consumers- third trophic level Ecological pyramids – Represent amount of available energy in each trophic level – Producers are at the base- the most available energy Energy is given off in less usable forms as producers are eaten by primary consumers, etc. – Biomass- the number of organisms at each level multiplied by their weight 34-9  Ecological pyramid Fig. 34.6 34-10 34.3 Global biogeochemical cycles Biogeochemical cycles – 2 main types of cycles Gaseous cycle-drawn from and returns to the atmosphere Sedimentary cycle-element is drawn from soil by plant roots, eaten by consumers, returned to soil by decomposers 34-11  Global biogeochemical cycles cont’d. The water cycle – Freshwater evaporates from bodies of water – Precipitation over land enters ground, surface waters, aquifers – Eventually returns to oceans over time – Hydrologic cycle is illustrated on the following slide Note that size of arrow is proportional to rate of transfer – Human impact In arid southwest and southern Florida, water mining is occurring – Aquifers are being drained faster than they can be naturally replenished 34-12  The hydrologic cycle Fig. 34.8 34-13  Global biogeochemical cycles cont’d. The phosphorus cycle – Phosphate enters soil as rocks undergo weathering process – Picked up by producers and cycles through consumers and finally decomposers – Human impact Accelerated transfer rate due to phosphate mining, supplementation on farm fields, detergents – Cultural eutrophication- over-enrichment » Can lead to increased algal bloom » As algae die off, decomposers consume high levels of oxygen in the water » Results in massive fish kills – Phosphorus cycle is illustrated on the following slide 34-14  The phosphorus cycle Fig. 34.9 34-15  Global biogeochemical cycles cont’d. The nitrogen cycle – Nitrogen fixation-conversion of nitrogen gas N2 to ammonium NH4+ by bacteria – 78% of atmosphere is nitrogen gas, but unusable by plants – Root nodules of legumes house nitrogen-fixing bacteria – Nitrification-production of nitrates which plants can also use Nitrogen gas converted to nitrate in atmosphere by lighting, meteor trails, cosmic radiation Ammonium in soil converted to nitrate by nitrifying bacteria – Denitrification-conversion of nitrate back to nitrogen gas by denitrifying bacteria 34-16  The nitrogen cycle Fig. 34.10 34-17  Global biogeochemical cycles cont’d. The carbon cycle – Photosynthesis takes up carbon dioxide from the atmosphere – Cell respiration returns it to the atmosphere – Reservoirs of carbon Dead organisms- fossil fuels Forests – Human activities More carbon dioxide is being deposited in atmosphere than is being removed – Due to deforestation and burning of fossil fuels Increased carbon dioxide in atmosphere contributes to global warming 34-18  The carbon cycle Fig. 34.11 34-19