Ecosystems Chapter 20 Part A

The Nature of Ecosystems Ecosystems are an association of communities and their physical environment interconnected by an ongoing flow of energy and a cycling of nutrients

One-way flow of energy Cycling of nutrients

The Nature of Ecosystems Ecosystems are open systems because they require ongoing inputs of energy There is a one-way flow of energy through ecosystems Sun  producers  consumers  decomposers Some energy escapes as heat Energy for living organisms is continually resupplied from the sun

The Nature of Ecosystems Primary producers (autotrophs) Photoautotrophs capture and convert the sun’s energy to chemical bond energy Build glucose and other compounds Plants, algae, and photosynthetic bacteria Chemoautotrophs capture energy from get energy and carbon from deep-sea vents

The Nature of Ecosystems Primary production The rate that energy is captured and stored Anything affecting producer growth will impact primary production Terrestrial production: temperature and moisture Aquatic production: nutrient availability Factors can vary seasonally causing productivity to vary from ecosystem to ecosystem

The Nature of Ecosystems Consumers Feed on producers or other consumers Described by their diet Herbivore = plants Carnivore = flesh of animals Omnivores = plant and animals Parasites = live in or on and eat their host Detritovores = bits of decaying organic matter (detritis) Decomposers = wastes and remains

Food Chains and Webs Pathways showing the transfer of energy and nutrients from organism to organism within an ecosystem Shows the trophic structure of an ecosystem Troph means nourishment Each trophic level represents the number of energy transfers away from the original energy input into that system

Food Chains and Webs Trophic Structure First trophic level Primary producers (autotrophs) Photosynthesis or chemosynthesis Second trophic level Primary consumers (heterotrophs) Herbivores, omnivores Third trophic level Secondary consumers (heterotrophs) Carnivores (primary level), omnivores Fourth trophic level Third level consumers (heterotrophs) Carnivores (second level)

Fig. 38.13

Figure 42.5 Computer model for a land food web in East River Valley, Colorado. Balls signify species. Their colors identify trophic levels, with producers (coded red) at the bottom and top predators ( yellow) at top. The connecting lines thicken, as they go from an eaten species to the eater. Fig. 42.5, p. 713

Food Chains and Webs Trophic Structure The number of trophic levels is limited based on the efficiency of energy transfers Only 5-30% of the energy in one level ends up in the next level Some energy is used to reproduce Some energy escapes as metabolic heat Some energy is bound up in body parts that can’t be digested (bone, lignin, hair, etc)

Ecological Pyramids Depict the distribution of materials and energy between trophic levels

top carnivores (gar and bass) 1.5 11 carnivores (smaller fishes, invertebrates) 37 herbivores (plant-eating fishes, invertebrates, turtles) detritivores (crayfish) and decomposers (bacteria) 5 Biomass pyramid (grams per square meter) 809 producers (algae and aquatic plants) Figure 42.6 Ecological pyramids for Silver Springs, an aquatic ecosystem in Florida. Stepped Art Fig. 42.6a, p. 713

detritivores + decomposers = 5,060 carnivores 383 21 top carnivores detritivores + decomposers = 5,060 carnivores 383 3,368 herbivores 20,810 producers Energy flow pyramid (kilocalories per square meter per year) Figure 42.6 Ecological pyramids for Silver Springs, an aquatic ecosystem in Florida. Stepped Art Fig. 42.6b, p. 713

Answer the questions based on the figure What trophic level is the sparrow? What consumer level is the coyote? Approximately what percentage of energy does the grasshopper get from the grass? Which organism is an herbivore? If the coyote also eats the grasshopper would that make it an omnivore? If insecticide was sprayed reducing the number of grasshoppers what would that do to the number of coyotes? To the amount of grass?

Biogeochemical Cycles Elements essential for life move between a community and the environment Cycle from environmental reservoirs, through organisms, and then back to the reservoirs

Biogeochemical Cycles Water Needed for all cellular fluids Required for photosynthesis

Biogeochemical Cycles Water Found as vapor in the atmosphere (atmospheric cycle) Condenses into droplets causing rain Rain water seeps into the ground (and is tapped by plant roots) Drains into aquifers Runs off into rivers, lakes, and the ocean Soil water which is tapped by roots Evaporation due to solar energy returns the water to atmospheric vapor

Precipitation into ocean Atmosphere Precipitation onto the land Windborne water vapor Evaporation from ocean Evaporation from land plants (transporation) Precipitation into ocean Surface and groundwater flow Figure 42.8 The water cycle. Water moves from the ocean to the atmosphere, land, and back. The arrows identify processes that move water. Land Ocean Stepped Art Fig. 42.8, p. 715

Biogeochemical Cycles Water Conservation Concerns Limited amounts of fresh water Using aquifer water faster than it accumulates Contaminated water sources

Biogeochemical Cycles Carbon Essential part of all organic molecules

Biogeochemical Cycles Carbon Found in the atmosphere (atmospheric cycle) Carbon enters terrestrial food webs when plants take up CO2 from the air for use in photosynthesis to make glucose (C6H12O6) Carbon enters aquatic food webs by dissolving in seawater and being used by aquatic producers Carbon returns to the air/water as CO2 when organisms carry out aerobic respiration Burning of fossil fuels also puts carbon in the air

death, burial, compaction over millions of years Fossil fuels burning fossil fuels 6 Land food webs Atmospheric CO2 photosynthesis 1 aerobic respiration 2 Dissolved carbon in ocean diffusion between atmosphere and ocean 3 Marine organisms 4 sedimentation Earth’s crust 5 Figure 42.10 The carbon cycle. Most carbon is in Earth’s crust, where it is largely unavailable to living organisms. Stepped Art Fig. 42.10, p. 716

Biogeochemical Cycles Carbon Conservation Concerns More CO2 is being released into the atmosphere than is being taken up Adds to the greenhouse gasses Group of gasses (CO2, CFC, CH4, and N2O) that act like a pane of glass in a greenhouse Visible light can pass through Infrared wavelengths (heat) can’t escape Help shape global temperatures

Greenhouse Effect Sun’s rays Some heat escapes Increased gasses, less escapes

Biogeochemical Cycles Nitrogen Essential for amino acids (protein), chlorophyll and hemoglobin

Biogeochemical Cycles Nitrogen N2 is found in the atmosphere (atmospheric cycle) Not a useable form for most organisms Plants and animals can not break the bonds between the two nitrogen atoms

Biogeochemical Cycles Nitrogen Nitrogen fixation Certain bacteria can break the bonds of N2 and form ammonia (NH4+) Nitrogen fixing bacteria live in aquatic habitats, soils, and as mutualistic partners with fungi (lichens) and legumes (form root nodules)

Biogeochemical Cycles Nitrogen Plants take up NH4 and use it in metabolic reactions Consumers get nitrogen by eating plants or one another Nitrogen returns to the soil Wastes and remains

Biogeochemical Cycles Nitrogen Denitrification Some bacteria use nitrogen in energy producing pathways that release N2 into the atmosphere

Land food webs denitrification by bacteria Waste and remains 6 Waste and remains decomposition by bacteria and fungi 3 nitrogen fixation by bacteria 1 uptake by producers 2 uptake by producers 5 Figure 42.12 Nitrogen cycle in a land ecosystem. nitrification by bacteria Soil nitrates (NO3–) 4 Soil ammonium (NH4+) Stepped Art Fig. 42.12, p. 718

Biogeochemical Cycles Nitrogen Conservation concerns Not enough nitrogen in the soil and aquatic habitats lowers productivity Too much nitrogen can run off soils and enter aquatic ecosystems Causes algal blooms and eutrophication N2O (nitrous oxide) is a greenhouse gas

Biogeochemical Cycles Phosphorus Essential for energy (ATP), genetics (DNA, RNA), and structure of living things

Biogeochemical Cycles Phosphorous Found in rocks and sediments (sedimentary cycle) Weathering releases phosphorous to soils, lakes, rivers, and ultimately the oceans Producers take up phosphorous Consumers obtain phosphorous by eating producers and other consumers Returns to the soil in wastes and remains

uplifting over geologic time Rocks on land excretion, death, decomposition uptake by producers Land food webs 5 6 uplifting over geologic time Rocks on land 4 1 weathering, erosion Phosphates in seawater leaching, runoff 2 Marine food web 7 8 Phosphates in soil, lakes, rivers Figure 42.13 The phosphorus cycle. Marine sediments 3 Stepped Art Fig. 42.13, p. 719

Biogeochemical Cycles Phosphorous Conservation concerns Can be a limiting factor for plant growth Found in fertilizers Too much phosphorous can run off into aquatic ecosystems Sources include fertilizer, sewage, detergents Causes algal blooms and eutrophication

Questions Reservoir in rocks and soil Bacteria are required to “fix” it Water Impacts global temperatures Carbon Essential for DNA and RNA Nitrogen Released by excretion and decomposition Phosphorous Accumulates in ocean sediments

Summary Nature of Ecosystems Food Webs Biogeochemical Cycles Producers and consumers Food Webs Trophic levels Biogeochemical Cycles H2O, C, N, P

10% X 10% = 1% 1% X 10% X 10% X 10% = 0.001% 10% 10% 10% 1% SUN