Ecosystems Lecture Outline PDF

Because learning changes everything. ® Chapter 20 Ecosystems Lecture Outline Essentials of the Living World Seventh Edition George Johnson, Joel Bergh © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  20.1...

Because learning changes everything. ® Chapter 20 Ecosystems Lecture Outline Essentials of the Living World Seventh Edition George Johnson, Joel Bergh © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  20.1 Ecosystems 1 A community is the collection of organisms that live in a particular place. The place where a community lives is called the habitat. The combination of the community and habitat is called the ecosystem. © McGraw Hill, LLC 2  20.1 Ecosystems 2 The ecosystem is the most complex level of biological organization. The earth is a closed system with respect to chemicals but an open system in terms of energy. Organisms in ecosystems regulate the capture and expenditure of energy and the cycling of chemicals. © McGraw Hill, LLC 3  20.1 Ecosystems 3 You can think of the organisms in an ecosystem as chemical machines fueled by energy captured in photosynthesis. Producers first capture the energy. These are the autotrophs, such as plants, algae, and some bacteria. Consumers are the heterotrophs that obtain their energy- storing molecules by consuming other organisms. © McGraw Hill, LLC 4  20.1 Ecosystems 4 Ecologists assign every organism in an ecosystem to a trophic level. A trophic level is a feeding level composed of those organisms whose source of energy is the same number of consumption “steps” away from the sun. Food energy passes through an ecosystem from one trophic level to another. When the path is a simple linear progression, it is called a food chain. The chain ends with decomposers that break down dead organisms. © McGraw Hill, LLC 5  Figure 20.1: Trophic levels within an ecosystem Access the text alternative for slide images. © McGraw Hill, LLC 6  20.1 Ecosystems 5 Producers: The lowest trophic level of any ecosystem. Green plants occupy this role in most terrestrial ecosystems while algae do this in most aquatic ecosystems. Herbivores: Occupy the second trophic level and eat producers. They are the primary consumers. © McGraw Hill, LLC 7  20.1 Ecosystems 6 Carnivores: Occupy the third trophic level, eat herbivores, and are the secondary consumers. Some carnivores also eat plants, and are called omnivores. Detritivores are special consumers that eat dead organisms. Also known as scavengers. Decomposers are organisms that break down organic substances, making them available to other organisms. Bacteria and fungi are the principal decomposers in land ecosystems. © McGraw Hill, LLC 8  Figure 20.2: Members of the food chain (a) imagebroker/Alamy Stock Photo; (b) NPS photo; (c) Ron Crabtree/Getty Images; (d) aodaodaod/Getty Images; (e) Emmanuel LATTES/Alamy Stock Photo © McGraw Hill, LLC 9  20.1 Ecosystems 7 Primary productivity is the total amount of light energy converted by producers into organic compounds in a given area per unit of time. Net primary productivity is the total amount of energy fixed by photosynthesis per unit time minus that expended by photosynthetic organisms to fuel metabolic activities. Biomass is the total weight of all ecosystem organisms and increases as a result of the ecosystem’s net primary productivity. © McGraw Hill, LLC 10  20.1 Ecosystems 8 Much of the energy captured by producers is lost as energy passes through the ecosystem. 80% to 95% of the energy available at one trophic level is not transferred to the next. Figure 20.3 How heterotrophs use food energy © McGraw Hill, LLC 11  20.1 Ecosystems 9 Food chains usually consist of only three or four steps. So much energy is lost at each step that very little energy remains in the system after it has been incorporated into the bodies of organisms at four successive trophic levels. © McGraw Hill, LLC 12  20.1 Ecosystems 10 In most ecosystems, the path of energy is not linear because individuals often feed at several trophic levels. A food web describes this more complex path of energy flow. © McGraw Hill, LLC 13  Figure 20.4: A food web Access the text alternative for slide images. © McGraw Hill, LLC 14  20.2 Ecological Pyramids 1 There are generally far more individuals at the lower trophic levels than at the higher levels. Plants fix about 1% of the sun’s energy into their green parts. Consumers process into their own bodies only about 10% of the energy available in the organisms on which they feed. Similarly, the biomass of primary producers is usually greater than that of higher trophic levels. © McGraw Hill, LLC 15  Figure 20.5: Pyramid of Energy Access the text alternative for slide images. © McGraw Hill, LLC 16  20.2 Ecological Pyramids 2 The loss of energy that occurs at each trophic level places a limit on how many top-level carnivores a community can support. Top-level predators tend to be relatively large animals. Only 1/1,000th of the original energy captured by photosynthesis is available to a tertiary consumer. So top-level predators have no predators that subsist exclusively on them. © McGraw Hill, LLC 17  20.3 The Water Cycle 1 Unlike energy, the physical components of ecosystems are passed around and reused within ecosystems. This is termed cycling by ecologists. The paths of water, carbon, and soil nutrients as they pass from the environment to living organisms and back form closed biogeochemical cycles. © McGraw Hill, LLC 18  20.3 The Water Cycle 2 Of all the nonliving components of an ecosystem, water has the greatest influence on the living portion. Water cycles within an ecosystem in two ways. Environmental water cycle: Water vapor in the atmosphere condenses and falls to earth as precipitation. It reenters the atmosphere by evaporation from lakes, rivers, and oceans. Organismic water cycle: Water is taken up by plant roots. After passing through the plant, it evaporates from plant leaves via transpiration. © McGraw Hill, LLC 19  Figure 20.6: The water cycle Access the text alternative for slide images. © McGraw Hill, LLC 20  20.3 The Water Cycle 3 Deforestation breaks the water cycle. In especially dense forest ecosystems, such as tropical rain forests, 90% of the moisture in the atmosphere is taken up by plants and returned by transpiration. The vegetation is actually the primary source of local rainfall. When forests are cut down, water is not returned to the atmosphere. © McGraw Hill, LLC 21  20.3 The Water Cycle 4 In the United States, more than 96% of freshwater is in the form of groundwater. Groundwater occurs in permeable, saturated, underground layers of rock, sand, and gravel called aquifers. The increasing chemical pollution and use of groundwater is becoming a very serious problem. © McGraw Hill, LLC 22  20.4 The Carbon Cycle 1 The earth’s atmosphere contains plentiful carbon, present as CO2. The carbon cycles between the atmosphere and living organisms. Plants trap the carbon in organic molecules by photosynthesis. The carbon is returned to the atmosphere by respiration, combustion, and erosion. Some carbon is locked up for a long time as fossils. The burning of fossil fuels leads to some of this carbon being released back to the atmosphere. © McGraw Hill, LLC 23  20.4 The Carbon Cycle 2 Respiration: Organisms extract energy from organic molecules and give off carbon dioxide as a by-product. Combustion: When we burn wood or fossil fuels, carbon trapped long ago is released to the atmosphere. Erosion: When marine organisms die, their calcium carbonate shells are deposited, forming limestone. When limestone deposits become exposed and begin to erode, carbon is released back to the oceans. © McGraw Hill, LLC 24  Figure 20.8: The carbon cycle Access the text alternative for slide images. © McGraw Hill, LLC 25  20.5 The Nitrogen and Phosphorus Cycles 1 Most living organisms cannot use the main form of nitrogen in the atmosphere, N2 gas. The two nitrogen atoms of N2 are bound by a triple bond that is hard to break. Some bacteria can break this bond, and add the N to H atoms, forming ammonia (NH3). This process is called nitrogen fixation. © McGraw Hill, LLC 26  20.5 The Nitrogen and Phosphorus Cycles 2 Nitrogen fixation can only take place in the absence of oxygen. Nitrogen-fixing bacteria are found in cysts that admit no oxygen or within airtight nodules of certain plants, such as beans. The availability of fixed nitrogen in fields is very limited. Farmers supplement their fields by adding fertilizers. Industrial fixation of nitrogen now accounts for up to 30% of the nitrogen cycle. © McGraw Hill, LLC 27  Figure 20.9: The nitrogen cycle Access the text alternative for slide images. © McGraw Hill, LLC 28  20.5 The Nitrogen and Phosphorus Cycles 3 Phosphorous is another soil nutrient that is important to organisms because it is a key part of both ATP and DNA. Most of the phosphorous in ecosystems exists in soil or rock. Plants take up phosphorus from the soil or water. When organisms die, the phosphorus they contain is recycled back to the soil. If P-containing fertilizers or detergents pollute a lake, rapid uncontrolled blooms of algae result in a process called eutrophication. The excess algae soon die and then bacteria decomposing the algae use up the lake’s dissolved O2, killing other organisms. © McGraw Hill, LLC 29  Figure 20.10: The phosphorus cycle Access the text alternative for slide images. © McGraw Hill, LLC 30  20.6 The Sun and Atmospheric Circulation 1 The earth’s annual orbit around the sun and its daily rotation on its own axis are important in determining the world climate. The tropics are warmer than the temperate regions because the sun’s rays arrive almost perpendicular at regions near the equator. Because of the annual cycle and the inclination of the earth’s axis, all parts away from the equator experience a progression of seasons. © McGraw Hill, LLC 31  Figure 20.11: Latitude affects climate In this view of the earth, the southern hemisphere is tilted more towards the sun and is experiencing summer. Access the text alternative for slide images. © McGraw Hill, LLC 32  Figure 20.12: Air rises at the equator and then falls Access the text alternative for slide images. © McGraw Hill, LLC 33  20.7 Latitude and Elevation 1 Temperature varies with elevation, with higher elevations becoming progressively cooler. At any given latitude, air temperature falls about 6C for every 1,000-meter increase in elevation. © McGraw Hill, LLC 34  Figure 20.13: How latitude and elevation affect ecosystems Access the text alternative for slide images. © McGraw Hill, LLC 35  20.7 Latitude and Elevation 2 When a moving body of air encounters a mountain, it is forced upward. As it is cooled at higher elevation, rain is produced on the windward side of a mountain. As the air passes the peak and descends on the far side of the mountains, its moisture-holding capacity increases. The air dries the surrounding landscape, often producing a desert. This effect is often called a rain shadow. © McGraw Hill, LLC 36  Figure 20.14: The rain shadow effect Access the text alternative for slide images. © McGraw Hill, LLC 37  20.8 Ocean Ecosystems 1 The oceans have an average depth of more than 3 km and they are, for the most part, cold and dark. Photosynthetic organisms are confined to the upper few hundred meters because light does not penetrate any deeper. Almost all organisms that live below this level feed on organic debris that rains from above. © McGraw Hill, LLC 38  20.8 Ocean Ecosystems 2 There are three main types of ocean ecosystems: Shallow water. Open-sea surface. Deep-sea waters. Figure 20.15 Ocean ecosystems Access the text alternative for slide images. © McGraw Hill, LLC 39  20.8 Ocean Ecosystems 3 Shallow waters: The small area of water that occurs mostly along the shoreline and contains the most species. Part of this area consists of the intertidal zone, which is periodically exposed to air. (a) Stephen Frink/Getty Images Partly enclosed bodies of water, such as river mouths Figure 20.16a Shallow waters and coastal bays, have intermediate salinities and are called estuaries. © McGraw Hill, LLC 40  20.8 Ocean Ecosystems 4 Open-sea surface: Contains a lot of phytoplankton that drift with the current and perform 40% of all the photosynthesis that takes place on earth. (b) Jeff Hunter/Photographer’s Choice RF/Getty Images Also contains many fish. Figure 20.16b Open-sea surface © McGraw Hill, LLC 41  20.8 Ocean Ecosystems 5 Deep-sea waters: Contains very few organisms, but they are diverse. Many inhabitants are bioluminescent for the purpose of communication or predation. Many are specialized to a local area (that is, endemic). While some utilize energy falling to the ocean floor as debris from above, some deep-sea inhabitants are autotrophic. They derive energy from hydrothermal vent systems. © McGraw Hill, LLC 42  Figure 20.17: Deep-sea waters (a) Ron and Valerie Tay/age fotostock; (b) Kenneth L. Smith; (c) NOAA Okeanos Explorer Program, Galapagos Rift © McGraw Hill, LLC 43  20.9 Freshwater Ecosystems 1 Freshwater ecosystems include lakes, ponds, rivers, and wetlands. They are limited in area. All freshwater habitats are strongly connected to land habitats. Wetlands (marshes and swamps) constitute intermediate habitats. A large amount of organic and inorganic material continually enters bodies of freshwater from nearby land communities. © McGraw Hill, LLC 44  Figure 20.18: Freshwater organism John Mitchell/Science Source © McGraw Hill, LLC 45  20.9 Freshwater Ecosystems 2 Ponds and lakes have three zones in which organisms live, 1. Littoral (shallow “edge”). 2. Limnetic (open-water surface). 3. Profundal (deep-water). No light penetrates here. Figure 20.19a The three zones in ponds and lake Access the text alternative for slide images. © McGraw Hill, LLC 46  20.9 Freshwater Ecosystems 3 Lakes can be divided into two categories, based on their production of organic materials. Oligotrophic lakes have little scarce minerals and organic matter. Because they are deeper, they always have deep waters rich in oxygen. Eutrophic lakes have an abundant supply of minerals and organic matter. They have little oxygen at deep depths but are reinfused at overturns. © McGraw Hill, LLC 47  Figure 20.19: Oligotrophic and eutrophic lakes (b) Jeff R. Clow/Moment Open/Getty Images; (c) Martin Shields/Alamy Stock Photo Access the text alternative for slide images. © McGraw Hill, LLC 48  20.9 Freshwater Ecosystems 4 In temperate regions, large lakes undergo thermal stratification, a process in which water at 4C sinks below water that is either cooler or warmer. This is because water is most dense at 4°C. Overturns, when the deeper waters of the lake come to the surface and denser surface waters sink, occur in the spring and fall. This brings up fresh supplies of nutrients to the surface waters. © McGraw Hill, LLC 49  Figure 20.20: Spring and fall overturns in freshwater ponds or lakes Access the text alternative for slide images. © McGraw Hill, LLC 50  20.10 Land Ecosystems 1 A biome is a terrestrial ecosystem. Each biome is characterized by a particular climate and a defined group of organisms. A particular biome often looks similar, with many of the same creatures living there, wherever it occurs on the earth. The biomes differ remarkably from each other. There are seven major and seven minor biomes distributed throughout the earth. Biomes that normally occur at high latitudes also follow an altitudinal gradient along mountains. © McGraw Hill, LLC 51  Figure 20.21: Distribution of the earth’s biomes Felix Behnke/Cultura Creative RF/Alamy Stock Photo © McGraw Hill, LLC 52  20.10 Land Ecosystems 2 Tropical rain forests are the richest ecosystems on earth. Communites in these forests are very diverse and each type of organism is often represented by a Salparadis/Shutterstock few individuals. Figure 20.22 Tropical rain forest Access the text alternative for slide images. © McGraw Hill, LLC 53  20.10 Land Ecosystems 3 Savannas are grasslands that have widely spaced trees and seasonal rainfall. This biome is transitional between tropical rain forest and desert. David Min/Getty Images Figure 20.23 Savanna Access the text alternative for slide images. © McGraw Hill, LLC 54  20.10 Land Ecosystems 4 Deserts are dry places with sparse vegetation. Plants and animals may restrict their activity to favorable times of the year, when water is present. Comstock/Stockbyte/Getty Images Figure 20.24 Desert Access the text alternative for slide images. © McGraw Hill, LLC 55  20.10 Land Ecosystems 5 Grasslands (also called prairies) occur in temperate areas. Most of the original grasslands have been converted to use by agriculture. Finn O’Hara/Stockbyte/Getty Images Figure 20.25 Temperate grassland Access the text alternative for slide images. © McGraw Hill, LLC 56  20.10 Land Ecosystems 6 Deciduous forests are forests of trees that drop their leaves in the winter. Only remnants of the once great forests now remain. Bereczki Barna/Alamy Stock Photo Figure 20.26 Temperate deciduous forest Access the text alternative for slide images. © McGraw Hill, LLC 57  20.10 Land Ecosystems 7 The taiga is a great ring of coniferous trees that extends across vast areas of North America and Asia. Most of the trees occur in dense stands of one or Valerii_M/Shutterstock two species. Figure 20.27 Taiga Access the text alternative for slide images. © McGraw Hill, LLC 58  20.10 Land Ecosystems 8 Tundra is open, often boggy, grassland that occurs in the far north beyond the taiga. Permafrost, or permanent ice, usually exists within 1 meter of the surface. Cliff LeSergent/Alamy Stock Photo Figure 20.28 Tundra Access the text alternative for slide images. © McGraw Hill, LLC 59  20.10 Land Ecosystems 9 Chaparral consists of evergreen, often spiny shrubs and low trees. These communities occur in a “Mediterranean,” dry summer climate. Steven P. Lynch Figure 20.29 Chaparral Access the text alternative for slide images. © McGraw Hill, LLC 60  20.10 Land Ecosystems 10 Polar ice caps lie over the Arctic Ocean in the north and Antarctica in the south. This region receives almost no precipitation and fresh water is scarce. Frank Krahmer/Getty Images Figure 20.30 Polar ice Access the text alternative for slide images. © McGraw Hill, LLC 61  20.10 Land Ecosystems 11 Tropical monsoon forests occur at slightly higher altitudes than rainforest or where local climates are drier. H Lansdown/Alamy Stock Photo Rainfall is seasonal. Monsoon season brings rainfall from the oceans Figure 20.31 Tropical monsoon forest into the interior. Access the text alternative for slide images. © McGraw Hill, LLC 62