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# ESS Topic 2.1 - Structures

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This presentation corresponds with Topic 2.1: Ecosystem Structures from the IBDP ESS-SL course.

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• Students should be able to place an organism at the level of producer, primary consumer, secondary consumer, and so on, as the terms herbivore and carnivore are not always applicable.
• Pyramids are graphical models of the quantitative differences that exist between the trophic levels of a single ecosystem. A pyramid of biomass represents the standing stock of each trophic level measured in units such as grams of biomass per square metre (g m–2). Biomass may also be measured in units of energy, such as J m–2. In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore the pyramids become narrower as one ascends. Pyramids of numbers can sometimes display different patterns, for example, when individuals at lower trophic levels are relatively large. Similarly, pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass present at a given time (there may be marked seasonal variations). Both pyramids of numbers and pyramids of biomass represent storages. Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain. For example, the turnover of two retail outlets cannot be compared by simply comparing the goods displayed on the shelves; the rates at which the shelves are being stocked and the goods sold also need to be known. Similarly, a business may have substantial assets but cash flow may be very limited. In the same way, pyramids of biomass simply represent the momentary stock, whereas pyramids of productivity show the rate at which that stock is being generated. Biomass, measured in units of mass or energy (for example, g m–2 or J m–2), should be distinguished from productivity measured in units of flow (for example, g m–2 yr–1 or J m–2 yr–1). A pyramid of energy may be represented either as the standing stock (biomass) measured in units of energy (J m–2) or as productivity measured in units of flow of energy (J m–2 yr–1), depending on the text consulted. As this is confusing, this syllabus avoids the term pyramid of energy.
• Pyramids are graphical models of the quantitative differences that exist between the trophic levels of a single ecosystem. A pyramid of biomass represents the standing stock of each trophic level measured in units such as grams of biomass per square metre (g m–2). Biomass may also be measured in units of energy, such as J m–2. In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore the pyramids become narrower as one ascends. Pyramids of numbers can sometimes display different patterns, for example, when individuals at lower trophic levels are relatively large. Similarly, pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass present at a given time (there may be marked seasonal variations). Both pyramids of numbers and pyramids of biomass represent storages. Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain. For example, the turnover of two retail outlets cannot be compared by simply comparing the goods displayed on the shelves; the rates at which the shelves are being stocked and the goods sold also need to be known. Similarly, a business may have substantial assets but cash flow may be very limited. In the same way, pyramids of biomass simply represent the momentary stock, whereas pyramids of productivity show the rate at which that stock is being generated. Biomass, measured in units of mass or energy (for example, g m–2 or J m–2), should be distinguished from productivity measured in units of flow (for example, g m–2 yr–1 or J m–2 yr–1). A pyramid of energy may be represented either as the standing stock (biomass) measured in units of energy (J m–2) or as productivity measured in units of flow of energy (J m–2 yr–1), depending on the text consulted. As this is confusing, this syllabus avoids the term pyramid of energy.
• Pyramids are graphical models of the quantitative differences that exist between the trophic levels of a single ecosystem. A pyramid of biomass represents the standing stock of each trophic level measured in units such as grams of biomass per square metre (g m–2). Biomass may also be measured in units of energy, such as J m–2. In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore the pyramids become narrower as one ascends. Pyramids of numbers can sometimes display different patterns, for example, when individuals at lower trophic levels are relatively large. Similarly, pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass present at a given time (there may be marked seasonal variations). Both pyramids of numbers and pyramids of biomass represent storages. Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain. For example, the turnover of two retail outlets cannot be compared by simply comparing the goods displayed on the shelves; the rates at which the shelves are being stocked and the goods sold also need to be known. Similarly, a business may have substantial assets but cash flow may be very limited. In the same way, pyramids of biomass simply represent the momentary stock, whereas pyramids of productivity show the rate at which that stock is being generated. Biomass, measured in units of mass or energy (for example, g m–2 or J m–2), should be distinguished from productivity measured in units of flow (for example, g m–2 yr–1 or J m–2 yr–1). A pyramid of energy may be represented either as the standing stock (biomass) measured in units of energy (J m–2) or as productivity measured in units of flow of energy (J m–2 yr–1), depending on the text consulted. As this is confusing, this syllabus avoids the term pyramid of energy.
• Pyramids are graphical models of the quantitative differences that exist between the trophic levels of a single ecosystem. A pyramid of biomass represents the standing stock of each trophic level measured in units such as grams of biomass per square metre (g m–2). Biomass may also be measured in units of energy, such as J m–2. In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore the pyramids become narrower as one ascends. Pyramids of numbers can sometimes display different patterns, for example, when individuals at lower trophic levels are relatively large. Similarly, pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass present at a given time (there may be marked seasonal variations). Both pyramids of numbers and pyramids of biomass represent storages. Pyramids of productivity refer to the flow of energy through a trophic level and invariably show a decrease along the food chain. For example, the turnover of two retail outlets cannot be compared by simply comparing the goods displayed on the shelves; the rates at which the shelves are being stocked and the goods sold also need to be known. Similarly, a business may have substantial assets but cash flow may be very limited. In the same way, pyramids of biomass simply represent the momentary stock, whereas pyramids of productivity show the rate at which that stock is being generated. Biomass, measured in units of mass or energy (for example, g m–2 or J m–2), should be distinguished from productivity measured in units of flow (for example, g m–2 yr–1 or J m–2 yr–1). A pyramid of energy may be represented either as the standing stock (biomass) measured in units of energy (J m–2) or as productivity measured in units of flow of energy (J m–2 yr–1), depending on the text consulted. As this is confusing, this syllabus avoids the term pyramid of energy.
• A pyramid of energy shows the flow of energy from one trophic level to the next in a community. The units of pyramids of energy are, therefore, energy per unit area per unit time, for example, kJ m–2 yr–1. In the graphic, the math is correct - make sure students understand that plants and other producers do not absorb/convert all the solar energy that falls on them.
• This should include concentration of non ‑ biodegradable toxins in food chains, limited length of food chains, and vulnerability of top carnivores. Definitions of the terms biomagnification, bioaccumulation and bioconcentration are not required. As the DDT moves up the trophic levels, its concentration remains fairly constant because it is a persistent (non-degrading) substance. However, its proportion/ratio to the total biomass at each trophic level increases as the biomass shrinks at each successive level.
• Include competition, parasitism, mutualism, predation and herbivory. Mutualism is an interaction in which both species derive benefit. Interactions should be understood in terms of the influences each species has on the population dynamics of others, and upon the carrying capacity of the others’ environment. Graphical representations of these influences should be interpreted. The graph on this page introduces students to the ideas presented in Topic 3.1 - Population Dynamics.
• This is the classic Lynx-Hare interaction showing several important points in ESS. Note the lab time between the changes in hare and lynx populations. 1. negative feedback (topic 1) 2. population interactions (topic 2) 3. carrying capacity (topic 3)
• ### ESS Topic 2.1 - Structures

1. 1. IBDP ESS-SL Topic 2.1 STRUCTURES Topic 2.1 STRUCTURES By Peter Stanley, International School of Tanganyika, 2008 Modified by Brad Kremer, International School of Tanganyika, 2011
2. 2. 2.1.1 Biotic vs. Abiotic <ul><li>“ Distinguish between biotic and abiotic (physical) components of an ecosystem.” (2) </li></ul><ul><li>Biotic (alive) </li></ul><ul><li>biotic components in an ecosystem include all living things AND their interactions </li></ul><ul><li>Abiotic (non living) </li></ul><ul><li>physical parts of an ecosystem </li></ul><ul><li>Where do these fit? </li></ul>predation altitude soil pH wind speed temperature humidity light intensity mutualism trees parasitism precipitation
3. 3. 2.1.2 Trophic levels <ul><li>Define trophic level. (1) </li></ul><ul><li>A trophic level is where an organism is positioned according to its feeding relationship to other organisms. </li></ul><ul><li>Each successively higher trophic level contains less energy and biomass than the trophic level immediately below it. </li></ul>Egyptian Cobra Grass Acacia Tree Shrub Field Mouse Weaver Bird Secretary Bird Tawny Eagle Serval Cat <ul><ul><li>Quaternary (4˚) consumer </li></ul></ul><ul><ul><li>Tertiary (3˚) consumer </li></ul></ul><ul><ul><li>Secondary (2˚) consumer </li></ul></ul><ul><ul><li>Primary (1˚) consumer </li></ul></ul><ul><ul><li>Producer </li></ul></ul>
4. 4. Quaternary consumers Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Primary consumers Herbivore Primary producers Producer A terrestrial food chain grass tree Eagle mouse cricket butterfly weaver termite 2.1.3 Trophic levels in chains and webs “ Identify and explain trophic levels in food chains and food webs selected from the local environment. ” (3) Click to try another web
5. 5. 2.1.4 Pyramids <ul><li>“ Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data.” (3) </li></ul><ul><li>Pyramids show the quantitative (number) difference between trophic levels of a single ecosystem. </li></ul><ul><li>We will explore 3 kinds of Pyramids used in ecology: </li></ul><ul><ul><li>Pyramids of numbers </li></ul></ul><ul><ul><li>Pyramids of biomass </li></ul></ul><ul><ul><li>Pyramids of productivity </li></ul></ul><ul><li>These type of pyramids tend to follow the 2nd law of thermodynamics (there is a tendency for numbers and biomass and energy to decrease along a food chain). </li></ul>storage movement
6. 6. 2.1.4.a Pyramids of Numbers <ul><li>Trophic levels usually found with more numbers of organisms at the bottom and fewer at the top... a pyramid of numbers. </li></ul><ul><li>When might it not be in the shape of a pyramid? (hint: just think #’s) </li></ul>1 tree , 1000 termites , 20 geckos , 1 crow 2˚ Consumer 1˚ Consumer 3˚ Consumer Producer
7. 7. 2.1.4.b Pyramids of Biomass <ul><li>Bio (life)... mass (~weight) </li></ul><ul><li>This is a measure of the stock (storage) of each trophic level at a specific moment (not over a long period of time). </li></ul><ul><li>The units used are: </li></ul><ul><ul><li>Mass => g / m 2 </li></ul></ul><ul><ul><ul><ul><li>or </li></ul></ul></ul></ul><ul><ul><li>Energy => J / m 2 </li></ul></ul><ul><li>When might the data result in a shape other then a pyramid? (hint: “at a specific moment in time”) </li></ul><ul><li>Need another hint? brrrrrrrrrrrrrrrr </li></ul>Winter or seasonal changes that significantly reduce the biomass for producers.
8. 8. 2.1.4.c Pyramids of Productivity also known as Energy Flow Pyramids Pyramids <ul><li>NOT “Energy Pyramids” which show a stock of energy at each trophic level at one moment. </li></ul><ul><li>Productivity/flow of energy </li></ul><ul><ul><li>flow of energy through a trophic level over time </li></ul></ul><ul><ul><li>units => g / m 2 /yr or J / m 2 / yr </li></ul></ul>
9. 9. <ul><li>Energy transformations are never 100% efficient. Feces, respiration and heat are all ways in which energy is used and not available for the next trophic level. </li></ul>Math Check! 2.1.4.c Energy Efficiency in Pyramids of Productivity Feces 100 J Growth (new biomass) 33 J Cellular respiration 67 J 200 J Plant material eaten by caterpillar
10. 10. 2.1.4.c Pyramids of Productivity 10% Rule 10% Rule <ul><li>Only 10% of the energy is taken in by the next tropic level! </li></ul>by Pearson Education
11. 11. 2.1.5 Effects of Pyramids <ul><li>“ Discuss how the pyramid structure affects the functioning of an ecosystem. ” (3) </li></ul><ul><li>Biomagnification of DDT in the food chain... the affects can be seen clearly in a pyramid. </li></ul>DDT 2˚ Consumer 1˚ Consumer 3˚ Consumer Producer
12. 12. 2.1.6 Definitions <ul><li>“ Define the terms species, population, habitat, niche, community and ecosystem with reference to local examples. ” (1) </li></ul><ul><li>Species: a group of organisms which can interbreed and produce fertile offspring. </li></ul><ul><li>Population—a group of organisms of the same species who live in the same area at the same time. </li></ul><ul><li>Habitat—the environment in which a species normally lives or the location of a living organism </li></ul><ul><li>Niche - a position/role taken by an organism in a community </li></ul><ul><li>Community—a group of populations living and interacting with each other in an area. </li></ul><ul><li>Ecosystem—a community and its abiotic environment. </li></ul><ul><li>Ecology—the study of relationships between living organisms and between organisms and their environment. </li></ul>
13. 13. 2.1.7 Population interactions <ul><li>Competition </li></ul><ul><li>competing for what? </li></ul><ul><li>Parasitism </li></ul><ul><li>parasite benefits, host is harmed </li></ul><ul><li>Mutualism </li></ul><ul><li>both species benefit (symbiotic) </li></ul><ul><li>Predation </li></ul><ul><li>hunting of prey by predators </li></ul><ul><li>Herbivory </li></ul><ul><li>consumers eating producers </li></ul>“ Describe and explain population interactions using examples of named species. ” (3) Using any reliable source in class to complete this list below:
14. 14. Predation