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Transcript
Ecosystems and the Environment Unit 10 Ecosystems: What is an Ecosystem? And Energy Flow in Ecosystems Chapter 16.1 and 16.2 Benagh 2013 Interactions of Organisms and Their Environments • We are part of the environment along with all of Earth’s other organisms. • Ecology: the study of the interactions of living organisms with one another and with their physical environment. Benagh 2013 Ecology • Habitat: The place where a particular population of a species lives – The range of tolerance an organism possesses determines where it can live. • Community: the many different species that live together in a habitat • Ecosystem: a community and the physical aspects of its habitat (soil, water, weather) • Abiotic Factors: the physical aspects of a habitat • Biotic Factors: the organisms in a habitat Benagh 2013 Diverse Communities in Ecosystems • Biodiversity: the variety of organisms, their genetic differences, and the communities and ecosystems in which they occur. • Biodiversity can be impacted by limiting factors, which can control the number of organisms in an ecosystem. Examples: nutrients, water, shelter, etc. Benagh 2013 Change of Ecosystems Over Time • The physical boundaries between ecosystems are not always obvious. • Additionally, ecosystems do not remain static (the same). • For example a volcano, a receding glacier, or fire can destroy vegetation and create new habitat. – The first organisms to live in these newly formed habitats are often small, fast-growing plants called pioneer species. Benagh 2013 Succession • Once new species start moving into this newly formed habitat, they go through process called succession. • Ecological Succession: a somewhat regular progression of species replacement • Primary Succession: succession that occurs where life has not existed before – Volcanic island • Secondary Succession: succession that occurs in areas where there has been previous growth – Abandoned field Benagh 2013 Glacier Bay: An Example of Succession • An example of primary succession is a receding glacier because land is continually being exposed as the face of the glacier moves back. • The soil is poor in nitrogen at first. • Pioneer species (the first species to colonize a new area) move in. • Alder seeds blow in, their roots fix nitrogen (make it usable for plants) and add nutrients to the soil. – Nitrogen Fixation: the process by which gaseous nitrogen is converted into ammonia, a compound that organisms can use to make amino acids Benagh 2013 Glacier Bay: An Example of Succession • New trees are able to move in. • Eventually, the area is filled with dense thickets of trees. • The ecosystem has finally become a climax community: a community that has reached a steady state through ecological succession. Benagh 2013 Primary Energy Source • Everything that we do requires energy, and this energy flows from organism to organism. • Most life on Earth depends on photosynthetic organisms. • Primary Productivity: the rate at which organic material is produced by photosynthetic organisms in an ecosystem. – This determines the amount of energy available in an ecosystem. • Producers: organisms that capture energy in photosynthesis including plants, algae, and some bacteria • Consumers: organisms that consume plants of other organisms to obtain the energy necessary to build their molecules. Benagh 2013 Trophic Levels • Trophic Level: one of the steps in a food chain or pyramid. • First Level (lowest level): producers which perform photosynthesis and sometimes absorb nitrogen gas with the help of nitrogen-fixing bacteria. • Second Level: Herbivores, which eat primary producers. Use microorganisms to help digest plant materials in their guts. • Third Level: Secondary consumers; animals that eat other animals. • Fourth Level: Tertiary Consumers; carnivores that eat other carnivores • Detritivores: organisms that obtain their energy from the organic wastes produced at all trophic levels. – Decomposers: Bacteria and fungi are decomposers because they cause decay. – Decay is very important because it allows for the recycling of nutrients. Benagh 2013 Aquatic Food Chains • Food Chain: the path of energy through trophic levels. Benagh 2013 Aquatic Food Web • Food Web: a complicated, interconnected group of food chains. – In most ecosystems, energy does not follow simple straight paths seen in simplified food chains. Benagh 2013 Energy Transfer • During every transfer of energy within an ecosystem, energy is lost as heat. • Thus, the amount of useful energy decreases and energy passes through an ecosystem. • This is why there are more producers and primary consumers than secondary and tertiary consumers. • Only about 10% of energy is passed up trophic levels. • Sometimes energy is not the only thing transferred between trophic levels: – Biological Magnification: the accumulation of increasingly large amounts of toxic substances within each successive link of the food chain. Benagh 2013 The Pyramid of Energy • Ecologists often illustrate the flow of energy through an ecosystem using an energy pyramid. • Energy Pyramid: a diagram in which each Trophic level is represented by blocks stacked one another. – The width of the block indicates how much energy is stored at each trophic level. – Only about 1/10 of the energy in a trophic level is found in the next trophic level, so it takes a pyramid shape. Benagh 2013 Limitations of Trophic Levels • Most ecosystems only involve three or four trophic levels because too much energy is lost to support more. • Biomass may sometimes be a better indicator of energy than organism number. – Biomass: the dry weigh of tissue an other organic matter found in a specific ecosystem. Each higher level contains only 10% of the biomass found in the trophic level below it. Benagh 2013 04/03/13 DOL: For each statement below, identify the relevant ecological term. 1. The LIVING part of an ecosystem. 2. The type of succession that occurs where life has not existed before. 3. Organisms that capture energy in photosynthesis including plants, algae, and some bacteria. 4. Organisms that cause decay. 5. The amount of energy that passes to the next trophic level. Cycling of Materials in Ecosystems Chapter 16.3 Benagh 2013 Biogeochemical Cycles • Nature does not throw away raw materials! • The physical parts of the ecosystems cycle constantly in various nutrient cycles! • Carbon atoms are passed from one organism to another. – Producers are eaten by herbivores, which are eaten by carnivores, which are eaten by top carnivores, which eventually die and are decayed by decomposers. Eventually their carbon atoms become part the soil to feed the producers and start the process over! • The four biogeochemical cycles we will talk about are the water, carbon, phosphorus, and nitrogen cycles. • Biogeochemical cycle: the circulation of substances through living organisms from or to the environment. – Substances cycle between living and non-living reservoirs. Benagh 2013 • Of all nonliving components of an ecosystem, water has the greatest impact on the inhabitants: • Precipitation (rain and snow) • Ground water (water stored under ground) • Ultimately the water cycle is caused by heating by the sun leading to evaporation. The Water Cycle Benagh 2013 • Living Components: • Water is taken up by the roots of plants. • Water moves back into the atmosphere by evaporating from leaves in transpiration (which is also ultimately caused by the sun). • Water is very important to aquatic ecosystems such as lakes, rivers, oceans, estuaries, and wetlands. The Water Cycle Benagh 2013 The Carbon Cycle • Carbon cycles between the nonliving environment and living organisms. • The nutrient cycling of carbon is very closely related to the cycling of Oxygen (O2). • Carbon dioxide (CO2) in the air/water is used by plants, algae, or bacteria in photosynthesis to make new organic nutrients (sugars). Carbon atoms can return to the pool of CO2 in the air and water in three ways: 1. 2. 3. Respiration Combustion Erosion Benagh 2013 The Carbon Cycle 1. Respiration: Oxygen (O2) is used to oxidize organic molecules in cellular respiration and CO2 is released as a byproduct. Benagh 2013 2. Combustion: Carbon returns to the atmosphere through burning. – – – The Carbon Cycle Carbon in wood can stay there for many years, and is released when the wood is burned. In fossil fuels (oil, natural gas, coal) the carbon has been stored underground for millions of years! Burning releases CO2 which is necessary for plant growth but can potentially cause global warming if too much carbon is released! Benagh 2013 The Carbon Cycle 3. Erosion: Marine organisms use carbon dioxide dissolved in the sea water to make calcium carbonate shells. – Shells of dead organisms eventually form sediments such as limestone. – As limestone is exposed and erodes, carbon is again available to different organisms. Benagh 2013 The Phosphorus Cycle • Phosphorus is an essential part of our bodies. – Essential for ATP and DNA creation. • Phosphorous is usually stored in soil and rock as calcium phosphate. • It dissolves in water to form phosphate ions, PO43-. • This phosphate is absorbed by the roots of plants and used to build organic molecules. • Animals eat the plants and reuse the organic phosphorus. • Excessive amounts of nutrients such as phosphorus entering waterways causes too many algae to grow and hurts the aquatic system. Benagh 2013 The Nitrogen Cycle Benagh 2013 • The atmosphere is 78 percent nitrogen gas, N2. • In spite of how much nitrogen is around us, most organisms cannot use it in that form because of the strong bonds between the two N atoms. • Some bacteria can break the bond and make ammonia, NH3 in a process called Nitrogen Fixation. •Nitrogen Fixation: the process by which gaseous nitrogen is converted into ammonia, a compound that organisms can use to make amino acids. •Nitrogen fixation is performed by bacteria that live in the soil and root nodules (swellings) of plants like alder trees. The Four Stages of the Nitrogen Cycle 1. Assimilation: the absorption and incorporation of nitrogen into organic compounds by plants. 2. Ammonification: the production of ammonia (NH3) by bacteria during the decay of organic matter. 3. Nitrification: the production of nitrate from ammonia. 4. Denitrification: the conversion of nitrate to nitrogen gas. Benagh 2013 04/05/13 DOL: For each statement below, identify the relevant biogeochemical cycle. 1. Includes the process of combustion 2. Includes the processes of transpiration. 3. The main reservoir (storage area) for this nutrient is the atmosphere, but most organisms cannot utilize it in this form. 4. Usually stored in soil and rocks. 5. Includes the process of assimilation, or incorporation into our proteins. The Environment Chapter 18 Benagh 2013 Acid Rain • Coal-burning power plants make smoke with lots of sulfur, because the coal contained lots of sulfur. • Sulfur introduced into the atmosphere combines with water vapor to form sulfuric acid. • Sulfuric acid carried back to Earth’s surface in precipitation (rain or snow) is called Acid Rain. • Lowering the pH of water (making it more acidic) can cause death of organisms such as lake animals, tree root fungi, and plant death. Benagh 2013 The Ozone Layer • Remember, we need that protective layer of Ozone (O3) created by early photosynthetic cyanobacteria. • The Ozone layer protects us from dangerous Ultraviolet (UV) light. • In 1985, Scientists noticed that there was an Ozone hole over Antarctica. Every year, the hole gets worse, allowing more UV light to get to Earth’s surface. • Increased exposure to UV light can cause skin cancer, cataracts, etc. Benagh 2013 Ozone Destruction • The ozone is being destroyed primarily by a class of chemicals called Chlorofluorocarbons (CFCs). CFCs are normally stable. • CFCs are used as coolants in refrigerators and air conditions, as propellants in aerosol spray cans, and foaming agents in plastic-foam creation. • It turns out, high in the atmosphere where we find the ozone layer, CFCs are not so stable. • They lose a chlorine atom, which enters into a series of reactions that destroy the Ozone (O3) and turn it into regular Oxygen (O2). • CFCS are now banned as aerosol can propellants in the U.S. Benagh 2013 Global Temperature • Since the 1950s, the global temperatures have been increasing. • In Earth’s history, there have been many periods of Global Warming, which are often followed by periods of cold. • Scientists hypothesize that human activity may be significantly contributing to the modern global warming we see today. Benagh 2013 The Greenhouse Effect • Our planet would be cold except that we have a layer of Greenhouse Gases containing water vapor, carbon dioxide (CO2), methane, and nitrous oxide keeping it warm because the bonds between these atoms absorbs solar energy as heat radiates from earth. This is called the Greenhouse Effect. – Greenhouse Effect: heat is trapped within the atmosphere of the Earth in the same way that glass traps heat in a greenhouse. • Due to the burning of fossil fuels, we have increased the carbon dioxide in the atmosphere. Benagh 2013 Global Warming • The figure below shows the average change in global temperature since 1960 compared to the concentration of carbon dioxide in the atmosphere. • There is a strong correlation between the two, which has convinced many scientists that temperature and carbon dioxide levels are related. • However, correlation is not causation. Benagh 2013 Chemical Pollution • The environment can not absorb any amount of pollution. Too much pollution can cause problems in ecosystems and to humans. • Chemical pollution is a major environmental problem. • Examples of chemical pollution: – Oil spills – Toxic materials – Carcinogenic (cancer-causing) materials – Agricultural chemicals such as pesticides (which are often toxic) Benagh 2013 • Modern agriculture often introduces large amounts of chemicals, including: pesticides, herbicides, and fertilizers. • Molecules of chlorinated hydrocarbons including the pesticides DDT, chlordane, lindane, and dieldrin are slow to break down in the environment. • These chemicals are also stored in the fat of animals. • As these molecules move up trophic levels, they become increasingly concentrated. Types of Chemical Pollution Benagh 2013 • Biological Magnification: the accumulation of increasingly large amounts of toxic substances within each successive link of the food chain. • In birds, DDT causes eggs to be thin, and fragile—these eggs often break. • This was the worst in predatory birds because they are high in the food chain and occupy a high trophic level. • As such, the numbers of predatory birds dwindled. • In 1972 the use of DDT was restricted in the U.S. Benagh 2013 Types of Chemical Pollution Loss of Resources • We are damaging ecosystems in many ways, including consuming or destroying resources that we cannot replace. • There are three kinds of nonrenewable resources being consumed or destroyed far too quickly: 1. Extinction of Species: we have destroyed 50% of the worlds rainforest in 50 years, taking many species with them. 10% of well known species are endangered, and there are likely many more unknown species at risk. 2. Loss of Topsoil: fertile soil for agriculture is being depleted because of poor land management that washes away rich topsoil (the fertile part of soil that allows plants to grow) 3. Groundwater Pollution and Depletion Benagh 2013 3. Ground-Water Pollution and Depletion • Finally, we cannot replace ground water. • Much of our water is stored underground in aquifers (rock reservoirs for water). • Water seeps into aquifers too slowly to replace, and we are removing too much of the water. • In the U.S., most areas are not concerned with conserving ground water—we waste water on lawns, washing cars, and flushing toilets. Benagh 2013 Growth of Human Population • Birth rates are high across the world, and death rates are decreasing. This leads to an increase in population size. • Population growth is fastest in the developing countries of Asia, Africa, and Latin America. • We reached 6 billion in 1999. There are now 7 billion people on the planet. • There are concerns that we may be reaching our carrying capacity. Benagh 2013 04/09/13 DOL: For each statement below, identify the environmental problem described. 1. Sulfur in the atmosphere leads to lowered pH of water. 2. The breakdown of this atmospheric structure is caused by CFCs and can lead to increased rates of skin cancer. 3. Human-caused increase of Earth’s average temperature caused by the excessive release of greenhouse gases. 4. The accumulation of increasingly large amounts of toxic substances within each successive link of the food chain. 5. Size of human population. 04/11/2013 Journal Entry In the journal section of your binder, address the following questions in paragraph form. At the end of 5 minutes, you should have written 4-5 complete sentences. 1. What is symbiosis? 2. What was the relationship described in the video? 3. How has each species changed to help the other species? How Organisms Interact in Communities and how Competition Shapes Communities Chapter 17.1 and 17.2 Evolution in Communities • Ecosystem’s inhabitants are a web of interactions between organisms. • Some interactions among species are the result of a long evolutionary history where the organisms adjust to one another. • Natural selection has often matched characteristics of flowers to a pollinator. • Coevolution: back-and-forth evolutionary adjustments between interacting members of a community. Predators and Prey Coevolve • Predation: the act of one organism killing another for food. – Lions eating zebras • Parasitism: one organism feeds on and usually lives on or in another, typically larger organism. Parasites do not usually kill their prey (known as their host). – External parasites: feed on the host’s outside • Lice, fleas on dogs – Internal parasites: live entirely within the host’ body • Hookworm Plant Defenses Against Herbivores • Predation is also a problem for plants, which are rooted to the ground. • Plants have thorns, spines, prickles, and chemical compounds that discourage herbivores. • Secondary Compounds: defensive chemicals found in plants; often the primary means of defense. • Certain herbivores can feed on and be protected by the chemicals. Symbiotic Species • Symbiosis: two or more species living together in a close, long-term association. • Can be: – Beneficial to both organisms – Benefit one organism and leave the other harmed or unaffected • Parasitism: one type of symbiotic relationship that is detrimental to the host organism. Mutualism and Commensalism • Mutualism: a symbiotic relationship in which both participating species benefit. – Ants and Aphids: aphids suck sap from plants which they alter and secrete— ants use this as food and “milk” the aphids. The ants protect the aphids, so they are both helped by the relationship. • Commensalism: a symbiotic relationship in which one species benefits and the other is neither harmed nor helped. – Clown Fish and Sea Anemones: anemones have stinging tentacles, but the clown fish can live among the tentacles for protection. Anemones are not harmed by the relationship. Competition • Competition: the biological interaction when two species use the same resource. – Examples: food, nesting sites, living space, light, mineral nutrients, and water. – Competition occurs for resources in short supply. • Niche: the functional role of a particular species in a ecosystem. – How and organism lives—the job it performs in the ecosystem. – A niche may be describe in terms of space utilization, food consumption, temperature range, requirements for moisture or mating, etc. Size of a Species’ Niche • Fundamental Niche: the entire range of resource opportunities an organism is potentially able to occupy within an ecosystem. • Example: The Cape May Warbler’s niche includes the temperature it prefers (northeastern U.S. and Canada), when it nests (Summer), favorite foods (Small insects), where in the tree it finds food (tips of tree branches). Dividing Resources Among Species • Realized Niche: the part of the fundamental niche actually occupied by a species. • So, the realized niche of the Cape May warbler is only a small portion of its fundamental niche. • Five species of warblers feed on spruce trees at the same time, but each one feeds on different parts of the tree. Competition and Limitations of Resources • Shortage is the rule in nature, meaning that species are almost sure to compete with one another. • Darwin noted that competition should be greatest between similar organisms. • Competitive Exclusion: elimination of a competing species when two species are competing—the species that uses the resource more efficiently will eliminate the other. When Can Competitors Coexist? • Competitive exclusion is not always the outcome when organisms compete for limited resources. • If species avoid competing, they may coexist. • Gause forced several species into competition. In one case, one species won out (competitive exclusion) but in the other, both species found a way to coexist. Predation and Competition • Predation reduces the effects of competition. • Pain examined how sea stars (which eat clams and mussels) affect the numbers of species in intertidal communities. • He found that when sea stars were not present, there were less numbers of other species. Star fish reduce competition and therefore promote biodiversity. – Biodiversity: the variety of living organisms present in a community. Biodiversity and Productivity • The greater the number of species a plot of land has, the more plant material the plot can make. • The more species are found in an area, the greater the productivity. • Additionally, a more diverse ecosystem recovers more fully from disasters such as droughts. Growth Patterns in Real Populations • Exponential Growth Patterns are best to describe faster growing organisms such as: – Many plants – Insects Exponential Growth Curve: Also called a j-curve • Logistic Growth Model is best to describe slower growing organisms such as: – Bears – Elephants – Humans • Density-Independent Factors: environmental conditions – Weather – Climate Logistic Growth Model: Also Also called called a an j-curve s-curve Rapidly Growing Populations • r-strategists: grow exponentially when environmental conditions allow them to reproduce. – Results in temporarily large populations. • When environmental conditions are good, the population grows rapidly. When conditions are poor, the population size drops quickly. • Generally r-strategists: – Have a short life span – Reproduce early – Many small offspring – Offspring mature with little parental care Slowly Growing Populations • K-strategists: organisms that grow slowly with small population sizes and a population density usually near the carrying capacity (K) of their environment. • Generally K-strategists: – Have a long life – Mature slowly – Have few young – Provide extensive care for young 04/11/13 DOL: For each statement below, identify the statement as true or false. If the statement is false, correct it to make it true. 1. Symbiosis includes only positive relationships. 2. In amensalism, both species benefit. 3. In commensalism, neither species benefits. 4. A niche is the functional role of a particular species in a ecosystem. 5. An r-strategist will probably live longer than a K-strategist. 04/15/13 Journal Entry • In the journal section of your binder, address the following questions in paragraph form. At the end of 5 minutes, you should have written 4-5 complete sentences. 1. What is a biome? 2. What determines the vegetation in a biome? 3. Identify any biomes that you know along with their defining characteristic? 4. What biome do you think we live in here in Dallas? Major Biological Communities Chapter 17.3 Benagh 2013 Climate, Temperature, and Moisture • Climate: the prevailing weather conditions in any given area. • The two most important elements of climate are temperature and moisture: – Temperature: most organisms are adapted to living within a particular range of temperatures and will not thrive if temperatures are colder or warmer. – Moisture: All organisms require water. On land, water is sometimes scarce, so patterns of rainfall often determine an area’s life-forms. The warmer the air, the more moisture the air can hold. Benagh 2013 Climate, Temperature, and Moisture Benagh 2013 Major Biological Communities • Very similar communities occur in places with similar climates and geographies. • Biome: a major biological community that occurs over a large area of land. Benagh 2013 Major Biological Communities • Temperature and precipitation are extremely important to determining where biomes occur. • In general, temperature and available moisture decrease as latitude (distance from the equator increases). • Temperature and moisture also decrease as elevation (height above sea level increases. Benagh 2013 Terrestrial Biomes • Tropical Rain Forest: As much as 450 cm rain/year, little seasonal differences (warm all year). Contain the most biodiversity of all biomes, have a high primary productivity even though they have infertile soils. • Savannas: Great dry grasslands in tropical areas with little precipitation (90-150 cm) with a long dry season and wider fluctuation in temperature. Contain few trees and have an open landscape. Benagh 2013 Terrestrial Biomes • Taiga: Cold, wet climates with coniferous forests. Long, cold winters, most precipitation in summer. Many large mammals such as elk, moose, and dear, wolves, bears, lynxes, and wolverines live here. • Tundra: Between the Taiga and the permanent ice of the north pole is the Tundra. Covers 1/5 of the Earth’s surface. Low annual precipitation (less than 25 cm), with low available water because it is frozen in permafrost (permanent ice). Foxes, lemmings, owls, caribou. Benagh 2013 Texas Terrestrial Biomes • Deserts: Less than 25 cm precipitation, sparse vegetation, found in interior of continents. • Temperate Grasslands: Moderate climates half-way between equator and poles often are grasslands. Highly productive with deep, fertile soil. Bison in U.S. were once found here. • Temperate Deciduous Forests: Mild climates, plentiful rain, with trees that shed their leaves. Warm summers, cold winters, 75-250 cm precipitation. Cover much of eastern U.S. Deer, bears, beavers, raccoons. • Temperate Evergreen Forests: Drier weather leads to evergreen forests. Benagh 2013 Aquatic Communities • Freshwater (lakes, ponds, streams, and rivers) are very rare; only about 2% of the Earth’s surface. Ponds and lakes have three zones: – Littoral Zone: Shallow zone near the shore; insects, amphibians, fish – Limnetic Zone: Away from the shore, but close to the surface; algae, zooplankton, fish – Profundal Zone: Deep-water zone with less light; bacteria, worms— decomposers • Wetlands: swamps, marshes, and bogs, store water, diverse organisms. Benagh 2013 Marine Communities • ¾ of the Earth’s surface is ocean, with 3 types of marine communities. • Shallow Ocean Waters: many species live here, and this includes intertidal zones, coral reefs, and cool coastal zones with many nutrients. • Surface of the Ocean Sea: Plankton drift here and fishes, whales, and jellyfish feed on these plankton, which do 40% of photosynthesis on Earth. • Ocean Depths: In the deepest waters, there is no light, and bizarre invertebrates and fishes live here, such as squids and angler fishes. There is great biodiversity here. Benagh 2013 Diatoms • Diatoms: photosynthetic, unicellular protists with unique double shells. • Their shells are made of silica and have unique markings. • Diatoms are abundant in lakes and oceans and are important producers in the food chains, and do a lot of photosynthesis. Benagh 2013 04/15/13 DOL: For each of the statements below, identify the biome. 1. Dry and found in interior of continents. 2. Forests in areas with seasons where the leaves fall. 3. Cold desert, covered in permafrost. 4. Warm and wet with dense vegetation and poor soil. 5. Grasslands such as those found in Texas.