Chapter 34 Nature of Ecosystems. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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1 Chapter 34 Nature of Ecosystems 1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 34.1 The Biotic Components of Ecosystems Ecosystems Abiotic components include sunlight, inorganic nutrients, soil type, water, temperature and wind Biotic components are the various populations of species that form a community

3 34.1 The Biotic Components of Ecosystems Populations Within an Ecosystem Autotrophs (producers) Require an energy source and inorganic nutrients to produce organic food molecules Manufacture organic nutrients for all organisms Green plants and algae carry on photosynthesis Some bacteria are chemoautotrophs

4 34.1 The Biotic Components of Ecosystems Populations of an Ecosystem Heterotrophs (consumers) Need a preformed source of organic nutrients Herbivores: graze directly on plants or algae Carnivores: feed on other animals Omnivores: feed on both plants and animals

5 34.1 The Biotic Components of Ecosystems Populations of an Ecosystem Decomposers Heterotrophic bacteria and fungi Break down nonliving organic matter They release inorganic matter to be used by producers Detritus: partially decomposed matter Earthworms and some beetles, termites, and maggots

6 Producers Herbivores Carnivores Decomposers

7 34.1 The Biotic Components of Ecosystems Energy flow and chemical cycling characterizes every ecosystem Energy enters ecosystem in the form of sunlight absorbed by producers Chemicals enter when producers take in inorganic nutrients

8 34.1 The Biotic Components of Ecosystems Energy Flow and Chemical Cycling 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 Some energy is released at each level to the environment in the form of heat and waste products

9 Energy Flow and Nutrient Cycling Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. solar energy heat producers consumers inorganic nutrient pool heat heat decomposers energy nutrients

10 Energy Balances Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Heat to environment growth and reproduction Energy to carnivores Energy to detritus feeders George D. Lepp/Photo Researchers, Inc.

11 34.2 Energy Flow The interconnecting paths of energy flow are represented by diagramming food webs Grazing food webs begin with producers Detrital food webs begin with detritus

12 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Autotrophs Herbivores/Omnivores Carnivores fruits and nuts birds hawks owls leaf-eating insects deer foxes leaves rabbits chipmunks detritus skunks snakes mice mice a. Grazing food web fungi and bacteria invertebrates carnivorous invertebrates salamanders shrews b. Detrital food web

13 34.2 Energy Flow Trophic Level Composed of all the organisms that feed at a particular link in a food chain. Grazing food chain Leaves caterpillars tree birds hawks Detrital food chain Detritus earthworms shrews Primary producers, primary consumers, secondary consumers

14 34.2 Energy Flow Ecological Pyramids Shortness of food chains can be attributed to the loss of energy between trophic levels In general, only about 10% of the energy of one trophic level is available to the next trophic level Large energy losses depicted as an ecological pyramid

15 Ecological Pyramid Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. top carnivores carnivores herbivores producers Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16 34.2 Energy Flow Ecological Pyramids Biomass: the number of organisms at each level multiplied by their weight Biomass of autotrophs much greater than herbivores Biomass of herbivores greater than carnivores

17 Ecological Pyramids 34.2 Energy Flow Inverted pyramids may be found in aquatic ecosystems Herbivores may have a greater biomass than the producers Over time, algae reproduces and are consumed rapidly Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. herbivores producers (algae) relative dry weight

18 34.3 Global Biogeochemical Cycles Biogeochemical Cycles Pathways by which chemicals circulate through ecosystems involve both biotic and abiotic components Reservoir: source unavailable to producers Exchange pool: source from which organisms take chemicals Biotic community: chemicals move through community along food chains

19 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reservoir fossil fuels mineral in rocks sediment in oceans Exchange Pool atmosphere soil water Community

20 34.3 Global Biogeochemical Cycles Biogeochemical Cycles Two Main Types of Cycles Gaseous cycle: chemical element is drawn from and returns to the atmosphere Sedimentary cycle: chemical element is drawn from soil by plant roots, eaten by consumers, returned to soil by decomposers Exception of water which exists in gas, liquid and solid forms

21 34.3 Global Biogeochemical Cycles The Water or Hydrologic Cycle Freshwater evaporates from bodies of water Condensation gas back to liquid - rain Eventually returns to oceans over time via precipitation Human Impact In arid West and southern Florida, groundwater mining is occurring Aquifers are being drained faster than they can be naturally replenished

22 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H 2 O in Atmosphere net transport of water vapor by wind transpiration from plants and evaporation from soil precipitation over land lake evaporation from ocean precipitation to ocean freshwater runoff Ice Ocean aquifer Groundwaters

23 34.3 Global Biogeochemical Cycles The Phosphorus Cycle Phosphorus moves from rocks on land to the oceans Gets trapped in sediments Phosphorus moves back onto land following a geological upheaval Phosphate is usually a limiting inorganic nutrient for plants

24 34.3 Global Biogeochemical Cycles The Phosphorus Cycle Human Activities Phosphates are used in fertilizers, animal feeds, and detergents Excess phosphates in water supplies can lead to cultural eutrophication (over-enrichment) Algal blooms that can lead to massive fish kills

25 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. mineable rock phosphate mining weathering geological uplift sewage treatment plants fertilizer plants runoff phosphate in solution animals and animal wastes Biotic Community phosphate in soil biota decomposers detritus sedimentation

26 34.3 Global Biogeochemical Cycles The Nitrogen Cycle Nitrogen gas makes up about 78% of the atmosphere Plants cannot use nitrogen gas, so nitrogen is a limiting inorganic nutrient for plants Nitrogen Fixation Carried out by some cyanobacteria and bacteria Conversion of nitrogen gas (N 2 ) to ammonium ions (NH 4+ ) Plants can use ammonium ions

27 34.3 Global Biogeochemical Cycles The Nitrogen Cycle Nitrification: production of nitrates (NO 3- ) which plants can also use Nitrogen gas converted to nitrate in atmosphere by lightning, meteor trails, cosmic radiation which provide the high energy needed for N to react with O Ammonium in soil converted to nitrate by nitrifying bacteria (chemoautotrophs) Denitrification: conversion of nitrate back to nitrogen gas by denitrifying bacteria

28 34.3 Global Biogeochemical Cycles The Nitrogen Cycle Human Activities Nitrogen is added to fertilizers Runoff that contains nitrogen also contributes to eutrophication Fertilizer use also results in the release of nitrous oxide (N 2 O), a greenhouse gas ozone shield depletion

29 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. N 2 (nitrogengas) in Atmosphere N 2 fixation nitrogen-fixing bacteria in nodules and soil human activities runoff N 2 fixation denitrification plants dead organisms and animal waste nitrification denitrifying bacteria NH 4 + (ammonium) decomposers Biotic Community denitrification cyanobacteria NH 4 + Biotic Community NO 3 phytoplankton nitrifying bacteria NO 2 (nitrite) NO 3 (nitrate) denitrifying bacteria sedimentation decomposers

30 34.3 Global Biogeochemical Cycles 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, shells, limestone

31 34.3 Global Biogeochemical Cycles The Carbon Cycle 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 Carbon dioxide and other gases absorb and radiate heat back to Earth greenhouse effect

32 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. combustion CO 2 in Atmosphere photosynthesis destruction of vegetation respiration decay Land plants diffusion runoff bicarbonate (HCO 3 ) Ocean coal Soils sedimentation oil natural gas dead organisms and animal waste