Ecological Communities What, Exactly, Andcal, Physical Event
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Ecological Communities Guiding Question: How do energy and nutrients move through LESSON 3 communities? • Explain the difference between a producer and a Reading Strategy As you read, generate a concept map consumer. using each of the boldface words highlighted in the lesson. • Explain the effect of inefficient energy transfer on Vocabulary primary producer, photosynthesis, community structure. chemosynthesis, consumer, cellular respiration, herbivore, • Describe how feeding relationships can have both carnivore, omnivore, detritivore, decomposer, trophic level, direct and indirect effects on community members. biomass, food chain, food web, keystone species LIFE REQUIRES ENERGY to organize matter into complex forms such as carbohydrates, to build and maintain cellular structures, to power interactions among species, and to power the geological forces that shape 5.3 LESSON PLAN PREVIEW our planet. Energy is somehow involved in nearly every biological, chemi- Differentiated Instruction cal, and physical event. So, where does all this energy come from? And Struggling students make a what, exactly, is energy? Venn diagram to compare and contrast producers and consumers. Producers and Consumers Inquiry Students model a Organisms are classified as either producers or consumers biomass pyramid. based on how they obtain energy and nutrients. Real World Students role-play a scenario to balance ecosys- Energy is the ability to do work. It is energy that changes the position, tem health and tourism needs. composition, or temperature of matter. The first law of thermodynam- 5.3 RESOURCES ics states that energy cannot be created or destroyed, only changed from Outdoors Lab, Life in a Drop of Pond one form to another. For example, solar energy is converted to thermal Water • Real Data Online • Real Data energy when absorbed by a sandy beach or a dark t-shirt. Just like matter, Math Worksheet • Lesson 5.3 Work- the total energy in the universe remains constant. However, unlike matter, sheets • Lesson 5.3 Assessment • energy is not recycled in the biosphere. It moves in a one-way stream, Chapter 5 Overview Presentation shaping communities in the process. GUIDING QUESTION Primary Production Energy cannot be created or destroyed, but it has to enter an ecosystem somehow. Organisms called autotrophs or FOCUS Ask volunteers to make a list of a few things they ate in primary producers, like the plant shown in Figure 18, capture energy the past week on the board. Point from the sun or from chemicals and store it in the bonds of sugars, mak- out that this food is either another ing energy available to the rest of the community. organism, or a combination of other organisms. If possible, identify the organisms that make up the foods in the lists. Use this list to launch a discussion on how matter and en- ergy moves through communities. FIGURE 18 Primary Producers Green plants, like this spring pea, can capture radiant energy from the sun and store it in the bonds of sugar molecules. Evolution and Community Ecology 141 Low energy, ▶ Energy From the Sun For nearly all of Earth’s ecological systems, the longer wavelength sun is the ultimate source of energy. The sun releases radiation from large 1 portions of the electromagnetic spectrum, shown in Figure 19. Earth’s Radio atmosphere filters much of this out, and we see only some of this radia- waves 10–2 tion as visible light. Some primary producers, such as green plants, algae, Microwaves and cyanobacteria, can turn light energy from the sun into chemical energy in a process called photosynthesis. Photosynthesis is the process 10–4 by which primary producers use sunlight to convert carbon dioxide and Infrared water into sugars, releasing oxygen along the way. Photosynthesis is a complex process, but the overall reaction can be summarized with the 10–6 Visible following equation: light Sun Ultraviolet 6CO2 + 6H2O + the sun’s energy → C6H12O6 (sugar) + 6O2 10–8 Wavelength (meters) Wavelength ▶ Energy From Chemicals Not all communities are powered by the sun’s energy. On the floor of the ocean, jets of water heated by magma under X-rays 10–10 Earth’s crust gush into the icy-cold depths. In one of the more amazing scientific discoveries of recent decades, scientists realized that these deep- 10–12 sea vents host entire communities of organisms. Deep-sea vents are deep Gamma enough underwater that they completely lack sunlight. Instead, primary rays producers such as bacteria use energy stored in the bonds of hydrogen –14 10 sulfide (H S) to convert carbon dioxide and water into sugars in a process High energy, 2 shorter called chemosynthesis. Chemosynthesis can be summarized as: wavelength 6CO2 + 6H2O + 3H2S → C6H12O6 (sugar) + 3H2SO4 FIGURE 19 Energy From the Sun The sun emits radiation from many portions of the electromagnetic Photosynthesis and chemosynthesis use different energy sources, but spectrum. All photosynthesis is each uses water and carbon dioxide to produce sugars. Energy from powered by just a small portion of the chemosynthesis supports many organisms including enormous clams and visible light that reaches Earth. tubeworms, and various species of mussels, shrimp, crabs, and fish. These ANSWERS organisms have adaptations that enable them to live in the extreme high- temperature, high-pressure conditions of deep-ocean vents. Reading Checkpoint The main difference is the source of energy. Reading What is the primary difference between photosynthesis and For photosynthesis, it is the sun. For Checkpoint chemosynthesis? chemosynthesis, it is energy stored in chemical bonds. Consumers Organisms that rely on other organisms for energy and nutrients are called heterotrophs, or consumers. Consumers, like those in Figure 20, make use of the chemical energy stored by photosynthesis or chemosynthesis in a process called cellular respiration. FIGURE 20 Consumers Most communities contain many kinds of consumers, including a variety of herbivores, carnivores, omnivores, detritivores, and decomposers. (a) Herbivore 142 Lesson 3 Cellular respiration is the process by which organisms use oxygen to release the chemical energy of sugars such as glucose, releasing carbon dioxide and water as a byproduct. The summary equation for cellular respiration is the exact opposite of that for photosynthesis: C6H12O6 (sugar) + 6O2 → 6CO2 + 6H2O + energy Cellular respiration does not only occur in consumers— primary producers also use cellular respiration to release energy and nutrients they themselves have stored. In fact, the term autotroph literally means “self feeder.” Heterotroph, on (b) Carnivore the other hand, means “other feeder.” ▶ Herbivores, Carnivores, and Omnivores Organisms that consume producers are known as primary consumers. Most primary consumers, such as deer and grasshoppers, eat plants and are called herbivores. Wolves that prey on deer are considered secondary consumers, as are rodents and birds that prey on grasshoppers. Tertiary consumers eat secondary con- sumers, and so on. Most secondary and tertiary consumers kill and eat other animals and are called carnivores. Animals that eat both plant and animal food are called omnivores. ▶ Detritivores and Decomposers Recall that nutrients, such as carbon, nitrogen, and phosphorus, are recycled in ecosystems. When animals eat plants, they break down plant tissues into their components. Then, the animals’ bodies use the nutrients to build their own tissues. What happens (c) Omnivore when animals die? How do nutrients re-enter the ecosys- tem? Luckily, ecosystems have recyclers called detritivores and decomposers. Detritivores, such as millipedes and soil insects, consume detritus—nonliving organic matter includ- ing leaf litter, waste products, and the dead bodies of other community members. Large detritivores, like vultures, are often called scavengers. Decomposers, such as fungi and bacteria, break down nonliving matter into simpler parts that can then be taken up and reused by primary producers. If it were not for detritivores and decomposers, (d) Detritivore nutrients would be lost to an ecosystem when organisms die. (e) Decomposer Evolution and Community Ecology 143 Real Data Energy Flow in Communities 2. Infer Use your answer to Question 1 to explain Energy transfer from one trophic level to another in a why most communities have only about three or community is only about 10% efficient. In addition to four trophic levels. affecting community structure, this inefficiency affects 3. Calculate How many units of energy would there our own “energy footprints.” need to be in the first trophic level to end up with 1. Calculate If 1000 units of energy are available at 1000 units of energy in the second? In the third? In the producer level of the energy pyramid, about the fourth? how many units are available for first-level con- 4. Apply Concepts Use your answer to Question 2 to sumers? Second-level consumers? Third-level explain why eating “down a food chain,” vegetables consumers? instead of meat for example, is more energy efficient. ANSWERS Energy and Biomass Real Data Inefficient energy transfer between organisms shapes the 1. First-level consumer: 100 units; structure of a community. second-level consumer: 10 units; third-level consumer: 1 unit As organisms feed on one another, matter and energy move through the 2. Very small amounts of energy are community’s trophic levels. An organism’s trophic level is its rank in a available to organisms at higher trophic levels feeding hierarchy. Primary producers always make up a community’s 3. 10,000