Unit_1.8-1.11_Energy_in_an_Ecosystem.pdf

Energy Flow in an Ecosystem  Energy Objectives After this section you should be able to: describe the processes of photosynthesis and respiration distinguish among the trophic levels that exist in food chains and food webs. quantify ecosystem productivity. explain energ...

Energy Flow in an Ecosystem  Energy Objectives After this section you should be able to: describe the processes of photosynthesis and respiration distinguish among the trophic levels that exist in food chains and food webs. quantify ecosystem productivity. explain energy transfer efficiency and trophic pyramids.  Ecosystem Ecology Examines Interactions Between the Living and Non-Living World Ecosystem- A particular location on Earth distinguished by its particular mix of interacting biotic and abiotic components. Biotic-living factors that affect the ecosystem Abiotic-non living factors that affect the ecosystem (sun, soil, wind, water) Objective/EKs/Skill  Photosynthesis Producers (autotrophs) are able to use the suns energy to produce usable energy through the process called photosynthesis.  In photosynthesis, plants convert radiant energy into chemical energy in the form of glucose sugar. Sunlight Carbon Glucose dioxide Water Carbon from carbon dioxide is combined with hydrogen from water molecules to form organic compounds like sugars. This carbon production is referred to as biomass. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 6  Respiration Cellular respiration is the process by which other organisms gain energy from eating the tissues of producers.  When cells utilize organic compounds they produce carbon dioxide and water as the products of cell respiration. These same two molecules are used by photosynthesis. Chemical energy and heat energy are normal products of respiration that recycle in the environment. Mitochondria are the organelles in eukaryotes where oxygen is used to finish oxidative respiration. NSF NASA Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 9  The tropical oceans are important carbon “sinks” where carbon dioxide can be absorbed from the atmosphere. Microscopic foraminifera use tons of CO2 to compose their shells or tests. Photo: National Biological Information Infrastructure Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 10  Gross primary production (GPP) represents all of the organic compounds produced by photosynthesis. When the organic compounds used through cellular respiration are subtracted, the result is net primary production (NPP). Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 11  As energy flows through each step of a food web, it becomes more unusable. The rate of conversion of solar energy into chemical energy is the amount of energy available, calculated as productivity. Gross productivity - respiration = net productivity given in units of g/m2/yr. G–R=N Biomass is the dry weight of all organic matter in living organisms it is used to estimate gross productivity. Respiration is the rate of energy used at each level to maintain life (estimated at 90% of the available calories). Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 12 Practice FRQ 1.8- Describe the process of net primary productivity (NPP). Describe the relationship between primary productivity and biodiversity.  Instrumental Values of Ecosystems Provisions- Goods that humans can use directly. Regulating services- The service provided by natural systems that helps regulate environmental conditions. Support systems- The support services that natural ecosystems provide such as pollination, natural filters and pest control. Resilience- Resilience of an ecosystem ensures that it will continue to provide benefits to humans. This greatly depends on species diversity. Cultural services- Ecosystems provide cultural or aesthetic benefits to many people.  Energy Transfer Efficiency and Trophic Pyramids Biomass- The energy in an ecosystem is measured in terms of biomass. Standing crop- The amount of biomass present in an ecosystem at a particular time. Ecological efficiency- The proportion of consumed energy that can be passed from one trophic level to another. Trophic pyramid- The representation of the distribution of biomass among trophic levels. Objective/EKs/Skill  The ocean is the largest producer on the planet because of the amount of phytoplankton or algae. Only about 10% of the available energy from producers is available for the primary consumers. 10% of primary consumer’s calories 10% of 10% of producer’s secondary calories calories Fraction of sun’s energy Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 18  Tropical rainforest biomes are almost as productive as salt marsh estuaries when calculating the biomass per square meter. Biome Net Productivity 2500 2000 Grams Per Square Meter Per Year 1500 1000 500 0 Tropical Rainforest Deciduous Forest Boreal Forest Savanna Grassland Desert Biom e Type Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 19  Although energy appears to be “lost” from one trophic level to the next, the First Law of Thermodynamics or the Law of Conservation of Energy is maintained. First law of thermodynamics A physical law which states that energy can neither be created nor destroyed but can change from one form to another. Second law of thermodynamics The physical law stating that when energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes Some energy is wasted with death and decay, while other energy is used by organisms who are decomposers or detrivores. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 20  Food chains and food webs can become complicated. USGS Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 21  In ecosystems, energy is cycled through these niches: Autotrophs - produce food by photosynthesis Heterotrophs - consume autotrophs and other heterotrophs Decomposers - rearrange organic materials into nutrients for autotrophs The amount of energy available to support life is called the carrying capacity. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 22  Food chains represent the steps in transferring energy through the ecosystem. Arrows indicate the direction of flow of energy from prey to predator or plant to animal. Complex and integrated food chains are called food webs. The most common population in a community is called the dominant. The food web is built around organisms called critical biomass or keystone species. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 23  Energy transfer can be representations by trophic pyramids that compare the number of organisms in a population, or the weight (biomass) of organisms, or the productivity (energy calories). Biomass Pyramid Trophic Pyramid Numbers Pyramid Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 24  The amount of energy changes even though energy is never created or destroyed because: 1. Energy is converted into unusable forms such as heat. Warm-blooded animals are “expensive” in an ecosystem because they consume more calories to maintain body heat. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 25  2. Energy is converted for an organisms’ own respiration, metabolism, digestion and predation. USDA 3. Parts of an organism, such as bones and scales, do not provide calories. Advanced Environmental Science© by Carol Matthews and N. Kathryn Weatherhead published by Teaching Point 26 If one trophic level has 100,000 calories available, only 10,000 can potentially be transferred to the next trophic level. The more levels in the trophic pyramid the less energy is available in a usable form at the next higher level. Shorter food chains are more efficient, but they lack diversity. 27  Check your understanding 1. A zebra is an example of a. a secondary consumer b. a producer c. a detritivore d. a primary consumer e. a scavenger 2. The average efficiency of energy transfer between trophic levels is approximately a. 1% b. 4% c. 10% d. 40% e. 50% 3. The gross primary productivity of an ecosystem is a. the total amount of biomass b. the total energy captured by photosynthesis c. the energy captured after accounting for respiration d. the energy available to primary consumers e. the biomass of the producers 4. Ecosystem boundaries are a. based primarily on topographic features b. boundaries to nutrient flows c. never based on human created features d. are only used for ecosystems smaller than a few square hectares e. depend on many subjective factors  Practice FRQ 1.11 Describe one direct effect that a decline in the frog population would have on the food web. Identify an organism that is both a secondary and tertiary consumer