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Chapter 4: Ecosystems: Components, Energy Flow, Matter Cycling EQ’s: What language (vocabulary) is used by ecologists to classify the various aspects of the ecosystems they study? 4-1 The Nature of Ecology Definitions: Ecology is the study of how organisms (biotic) interact with each other and their environment (abiotic). Abiotic factors include: sunlight, temperature, precipitation, wind, fire, soil, etc.). Organisms are individual living things. Organisms that reproduce with each other under natural conditions are called species. 1 Eukaryotic organisms have a membrane bound nucleus and complex organelles. Almost all organisms have eukaryotic cells. Prokaryotic: no distinct nucleus and lack most organelles (bacteria and the bluegreen algae. Asexual reproduction: no exchange of genetic information and therefore little genetic variation. 2 Sexual reproduction: combine sex cells to exchange genetic information and create genetic diversity in the offspring. 3 A population consists of all the individuals of the same species that occupy a specific area of the environment (habitat). A community consists of all the interacting populations in a given location. All the communities interacting communities along with the abiotic components in a given area constitute an ecosystem and all the ecosystems together make up the biosphere (see Fig:4.2; page 66). 4 4-2 Earth’s Life-Support Systems EQ’s: 1- How do tolerances levels and limiting factors help structure ecosystems? The Earth has several layers or spheres upon which life depends: Atmosphere: layer of air Hydrosphere: layer of water Lithosphere: layer of rock Biosphere: layer of life 5 High quality energy flows through the Earth’s systems from the sun. Matter, however, is recycled by living things. Photosynthesis is the process by which plants capture solar energy and use it to transform water and carbon dioxide into a carbohydrates. light 6CO2 + 6H2O --------------- C6H12O6 + 6O2 The sun’s energy also powers the cycling of matter that drives climate and weather systems across the planet. Assignment #1: Review Questions page 93; #’s 2, 3, 4, 5, 6 4-3 Ecosystem Concepts and Components The terrestrial (land) portion of the biosphere is divided into different biomes based upon climate and the forms of life adapted to it. Examples include: rain forests, deserts, deciduous forests, grasslands, tundra, etc. 7 The aquatic ecosystems are divided into freshwater (ponds, lakes, streams) and marine (coral reefs, coastlines, oceans, estuaries). Climate refers to the long-term weather patterns that influence the type of life that lives in an area. In reality ecosystems/biomes rarely have distinct boundaries and are rarely selfsustaining. Ecosystems merge in transition zones known as ecotones. ----------------------------5th-------------------- 8 Living things are distributed within ecosystems based upon the law of tolerance. Each population has a range of conditions (both physical and chemical) it can withstand (See Fig:4-14; page: 73). 9 For a population to exist within an ecosystem the physical and chemical conditions must fall within that species’ range of tolerance. Often one factor (limiting factor) tends to be the most important in determining the size of a population within an ecosystem. Assignment #2: Review Questions: 8, 9, 10, 11 (all parts) ----------------------2nd—6th --------------------- 10 4-4: Energy Flow in Ecosystems EQ: 1- How does the flow of energy contribute to the structure of ecosystems? Energy flows through an ecosystem only in one-way. The sequence of organisms through which energy flows is called a food chain. What information do food chains fail to convey? (2 things). 11 Food webs show a more realistic view of energy flow because organisms typically do not feed on a single species (Fig. 4-19). Living organisms are classified as either producers (autotrophs) capable of making their own food and consumers (heterotrophs) that cannot. Heterotrophs are further classified as herbivores (plant eaters), carnivores (meat eaters), omnivores (eat both), scavengers (feed on dead organisms), and decomposers (fungi and bacteria). 12 Both autotrophs and heterotrophs breakdown the carbohydrates produced during photosynthesis in a process known as aerobic respiration. C6H12O6+6O2---6CO2+6H2O+energy (ATP) As energy flows through an ecosystem much of it is lost. Most ecosystems have an ecological efficiency of 10%--20%. This loss of energy between trophic (feeding) levels is often illustrated using a pyramid of energy (See Figs. 4-20; 4-21). 13 As a result of this loss of energy most energy pyramids are limited to 5 or 6 trophic levels. Use the information provided in Figure 4-21 to perform the following calculations. How much of the Sun’s energy do the producers capture? _______ kcal 1. What percentage of that is transferred to the herbivore level (energy efficiency)? Energy out X 100 Energy In 2. What percentage is lost as metabolic heat? 3. What percentage of what the herbivores capture is passed on to the carnivores? 14 4. Of the original amount of heat captured by the producers (20,810 kcal) what percentage is passed on to the top carnivores? 5. So why are there typically so few top predators in a given ecosystem? Biodiversity (a renewable resource) measures the different forms of life and lifesustaining processes found in ecosystems. There are several types: Genetic diversity: genetic make-up Species diversity: number of different species in a given habitat Ecological diversity: diversity of biological communities 15 Functional diversity: diversity of biological and chemical processes needed for survival. 4-5 Primary Productivity The rate an ecosystem’s primary producers convert solar energy into biomass is called gross primary productivity (GPP). Some of this biomass is used to stay alive, grow, and reproduce (etc.). What remains is called net primary productivity (NPP). The NPP ultimately limits the number of consumers in a given ecosystem. It has been estimated that humans use or waste approximately 27% of the planet’s total NPP. 16 See Figure 4-25 to answer the following questions 1. What three ecosystems have the greatest NPP? 2. How many times greater is the NPP of a rain forest compared to a temperate Grassland? A temperate forest compared to a savanna? 17 Agricultural land compared to the open ocean? Estuaries compared to extreme desert? 4-7 How Do Ecologist’s Learn About Ecosystems EQ: What advantages and disadvantages are associated with the methods scientists use to study ecosystems? Field Research involves going into nature to observe and measure what is going on in ecosystems. Disadvantages include cost (travel, food, etc.) and the difficulty associated with trying to control variables. Laboratory research uses models that allow greater control of variables. The 18 major disadvantage is knowing if the model behaves like the real thing. Systems analysis involves the use of complex mathematical models and computer simulations to mimic the natural world. Today most ecological research is done using a combination of all three approaches. Assignment #3 Review Questions: 12, 13 (all terms), 14, 17. Textbook Review Assignment 19