Biology, 9th ed, Sylvia Mader Chapter 48 Chapter 48 Ecosystems & Human Interferences Ecosystems & Human Interferences

The Nature of Ecosystems Outline The Nature of Ecosystems Biotic Components Autotrophs Heterotrophs Energy Flow Ecological Pyramids Global Biogeochemical Cycles Hydrologic Cycle Carbon Cycle Nitrogen Cycle Phosphorus Cycle

Nature of Ecosystems Biosphere is the organism-containing part of the Atmosphere Hydrosphere, and Lithosphere An ecosystem is a place where organisms interact with the physical environment Ecosystems characterized by: Cyclical flow of materials from abiotic environment through biotic community and back One-way flow of energy

Ecosystems

Biotic Components: Autotrophs Producers are autotrophs Require only inorganic nutrients and an outside energy source to produce organic nutrients Photoautotrophs Chemoautrophs

Biotic Components: Heterotrophs Consumers are heterotrophs Require a source of preformed organic nutrients Herbivores - Feed on plants Carnivores - Feed on other animals Omnivores - Feed on plants and animals Decomposers are also heterotrophs Bacteria and fungi Break down dead organic matter

Biotic Components

Energy Flow and Chemical Cycling Nutrients pass one-way through food chain from one level to another Each level retains some energy The rest is converted to heat, which dissipates into the environment Chemicals cycle as organic nutrients Once used, they are returned back to the producers by Excretion Death Cellular Respiration

Nature of an Ecosystem

Energy Balances

Grazing & Detrital Food Webs

Ecological Pyramids A trophic level Composed of all the organisms that feed at the same level in a food chain Only about 10% of the energy of one trophic level is useable to the next trophic level Explains why few top carnivores can be supported in a food web

Ecological Pyramid

Global Biogeochemical Cycles Chemical cycling may involve: Reservoir - Source normally unavailable to producers Fossil Fuels Minerals Sediments Exchange Pool - Source from which organisms generally take chemicals Atmosphere Soil Water Biotic Community - Chemicals remain in food chains, perhaps never entering a pool

Model for Chemical Cycling

Hydrologic Cycle Fresh water evaporates from bodies of water Precipitation on land enters the ground, surface waters, or aquifers Water eventually returns to the oceans

The Hydrologic (Water) Cycle

Atmosphere is an exchange pool for carbon dioxide Carbon Cycle Atmosphere is an exchange pool for carbon dioxide The total amount of carbon dioxide in the atmosphere has been increasing every year Thought to be due to fossil fuel combustion Transfer Rate

The Carbon Cycle

Greenhouse Effect Greenhouse gases If Earth’s temperature rises Carbon dioxide, nitrous oxide, methane Allow sunlight to pass through atmosphere Reflect infrared back to earth Trap heat in atmosphere If Earth’s temperature rises More water will evaporate More clouds will form, and Setting up a potential positive feedback loop

Earth’s Radiation Balances

Atmospheric nitrogen is fixed by bacteria Nitrogen Cycle Atmospheric nitrogen is fixed by bacteria Make it available to plants Nodules on legume roots Nitrification - Production of nitrates Denitrification - Conversion of nitrate to nitrous oxide and nitrogen gas Balances nitrogen fixation

The Nitrogen Cycle

Nitrogen and Air Pollution Acid Deposition Nitrogen oxides and sulfur dioxide are converted to acids when they combine with water vapor Acid rain dramatically reduces pH of surface waters in some areas Causes heavy metals to leach out of rocks, poisoning aquatic organisms Kills plants and causes fish to be unfit for human consumption Smog

Acid Deposition

Thermal Inversion

Phosphorus does not enter the atmosphere Phosphorus Cycle Phosphorus does not enter the atmosphere Sedimentary cycle Phosphate taken up by producers incorporated into a variety of organic molecules Can lead to water eutrophication Biomagnification

The Phosphorus Cycle

Sources of Water Pollution

The Nature of Ecosystems Review The Nature of Ecosystems Biotic Components Autotrophs Heterotrophs Energy Flow Ecological Pyramids Global Biogeochemical Cycles Hydrologic Cycle Carbon Cycle Nitrogen Cycle Phosphorus Cycle

Biology, 9th ed, Sylvia Mader Chapter 48 Ending Slide Chapter 48 Ecosystems & Human Interferences Ecosystems & Human Interferences