2.1 Food chains, webs and pyramids new.ppt
- 1. Energy in Ecosystems II IB syllabus: 2.1, AP syllabus Ch. 4
- 2. Syllabus Statements • The non-living, physical factors that influence the organisms and ecosystem—such as temperature, sunlight, pH, salinity, and precipitation—are termed abiotic factors. • An ecosystem is a community and the physical environment with which it interacts.
- 3. • The trophic level is the position that an organism occupies in a food chain, or the position of a group of organisms in a community that occupy the same position in food chains. • • Producers (autotrophs) are typically plants or algae that produce their own food using photosynthesis and form the first trophic level in a food chain. Exceptions include chemosynthetic organisms that produce food without sunlight. • Feeding relationships involve producers, consumers and decomposers. These can be modelled using food chains, food webs and ecological pyramids. • Ecological pyramids include pyramids of numbers, biomass and productivity and are quantitative models that are usually measured for a given area and time.
- 4. • 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 towards the apex. • Bioaccumulation is the build-up of persistent or non- biodegradable pollutants within an organism or trophic level because they cannot be broken down. • Biomagnification is the increase in concentration of persistent or nonbiodegradable pollutants along a food chain. • Toxins such as DDT and mercury accumulate along food chains due to the decrease of biomass and energy.
- 5. • Pyramids of numbers can sometimes display different patterns; for example, when individuals at lower trophic levels are relatively large (Inverted pyramids). • • A pyramid of biomass represents the standing stock or storage of each trophic level, measured in units such as grams of biomass per square metre (g m–2) or Joules per square metre (J m-2) (units of biomass or energy). • Pyramids of biomass can show greater quantities at higher trophic levels because they represent the biomass present at a fixed point in time, although seasonal variations may be marked. • Pyramids of productivity refer to the flow of energy through a trophic level, indicating the rate at which that stock/storage is being generated. • Pyramids of productivity for entire ecosystems over a year always show a decrease along the food chain.
- 6. vocabulary • Abiotic factor • Biomass • Biotic factor • Ecosystem • Standing crop • Trophic Level
- 7. Ecosystems • Are communities and their interactions with the abiotic environment
- 8. Ecosystem Components 2 parts –Abiotic – nonliving components (water, air, nutrients, solar energy) –Biotic – living components (plants, animals, microorganisms) Biota
- 9. Terrestrial Ecosystems Aquatic Life Zones • Sunlight • Temperature • Precipitation • Wind • Latitude (distance from equator) • Altitude (distance above sea level) • Fire frequency • Soil • Light penetration • Water currents • Dissolved nutrient concentrations (especially N and P) • Suspended solids • Salinity Significant abiotic factors
- 10. What abiotic factors effect this Aquatic food chain?
- 11. The abiotic influence • Species thrive in different physical conditions • Population has a range of tolerance for each factor • Optimum level best for most individuals • Highly tolerant species live in a variety of habitats with widely different conditions
- 12. Population Size Low High Temperature Zone of intolerance Zone of physiological stress Optimum range Zone of physiological stress Zone of intolerance No organisms Few organisms Lower limit of tolerance Abundance of organisms Few organisms No organisms Upper limit of tolerance The Law of Tolerance: The existence, abundance and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species
- 13. Abiotic factors may be Limiting Factors (2.6.1) • Limiting factor – one factor that regulates population growth more than other factors • Too much or too little of an abiotic factor may limit growth of a population • Determines K, carrying capacity of an area • Examples – Temperature, sunlight, dissolved oxygen (DO), nutrient availability
- 14. Techniques to measure abiotic factors • Terrestrial – Light intensity or insolation ( lux) – light meter; consider effect of vegetation, time of day… – Temperature (°C) – themometer; take at different heights, points, times of day, seasons… – Soil moisture (centibars) – tensiometer or wet mass dry mass of soil; consider depth of soil sample, surrounding vegetation, slope… • Aquatic (specify marine or fresh) – Salinity (ppt) – hydrometer; consider role of evaporation – Dissolved Oxygen (mg/L) – DO meter, Winkler titration; consider living organisms, water circulation, – pH – pH probe or litmus paper; consider rainfall input, soil and water buffering capacity – Turbidity (FTU) – Secchi disk or turbidity meter; consider water movement,
- 15. Techniques (2.2.2) • For any of them you should know the following 1. What apparatus is used for measurement and its units 2. How it would vary or be used to measure variation along an environmental gradient 3. Scientific concerns about its implementation 4. Evaluation of its effectiveness or limitations
- 16. Terminology and Roles of Biota • Producers (Autotrophs) – Through photosynthesis convert radiant to chemical energy (energy transformation) • Consumers (Heterotrophs) – Must consume other organisms to meet their energy needs – Herbivores, Carnivores, Omnivores, Scavengers, Detritivores • Decomposers – Break down organisms into simple organic molecules (recycling materials)
- 18. Food chains and Food webs • Food chain Sequence of organisms each of which is the source of food for the next • Feeding levels in the chain Trophic levels – First trophic level = producer – Second trophic level = consumer, herbivore – Third trophic level = consumer, carnivore – Highest trophic level = top carnivore – Arrows indicate direction of energy flow!!! – Decomposers are not included in food chains and webs • For complexity of real ecosystem need food web which shows that individuals may exist at multiple trophic levels in a system (omnivores)
- 19. Figure 53.10 Examples of terrestrial and marine food chains
- 20. Local examples Trophic Level Estuary system Everglades habitat Producer Turtle grass Phytoplankton Primary Consumer Grass shrimp Zooplankton Seconday Consumer Pin fish Blue gill Tertiary Consumer Spotted Sea trout Bass Quarternary Consumer Osprey Racoon 6th trophic level Aligator
- 22. Food Web • Summarizes the trophic relationships of a community through a diagram • Food chain web, once a given species enters the web at multiple trophic levels • Most consumers are not exclusive to one level (ex. we are omnivores)
- 23. Figure 53.11 An antarctic marine food web: Identify the trophic levels
- 24. Antarctic pelagic (open ocean) community found in seasonally productive Southern Ocean 1. Zooplankton: dominant herbivores in Antarctic are euphausids (krill) and herbivorous plankton called copepods 2. The zooplankton are eaten by carnivores including penguins, seals, fish, baleen whales 3. Carnivorous squid feeding on fish and zooplankton are important link in food web 4. Seals and toothed whales eat squid 5. During whaling years humans became top predators in the system 6. Entire food web depends on phytoplankton photosynthesizing microorganisms obtaining energy from the sun
- 26. Food Webs • Food webs are limited by the energy flowing through them and the matter recycling within them • Ecosystem is an energy machine and a matter processor 1. Autotrophs: make their own food (plants algae & photosynthetic prokaryotes) 2. Heterotrophs: directly or indirectly depend on photosynthetic output of primary producers
- 27. Producers • Transform energy into a usable form • Starting form may be light energy or inorganic chemicals • Turned into organic chemical energy • This is the form that is used at other trophic levels
- 28. Photoautotrophs
- 30. Consumers • Heterotrophs: get energy from organic matter consumed • Primary, Secondary & Tertiary consumers • Herbivores primary consumers, eat plant material e.g. – termites, deer • Carnivores other consumer levels, eat animal material e.g. eagles, wolves • Omnivores consumers eating both e.g. bears
- 31. Figure 53.0 Lion with kill in a grassland community
- 32. Decomposition • Decomposers obtain energy by breaking down glucose in the absence of oxygen • Anaerobic respiration or fermentation • End products = methane, ethyl alcohol, acetic acid, hydrogen sulfide • Matter recycling inorganic nutrients returned to producers
- 33. Mushroom Wood reduced to powder Long-horned beetle holes Bark beetle engraving Carpenter ant galleries Termite and carpenter ant work Dry rot fungus Detritus feeders Decomposers Time progression Powder broken down by decomposers into plant nutrients in soil Decomposition Process
- 34. Consumers or Decomposers • Detritivores = get their energy from detritus, nonliving organic material remains of dead organisms feces, fallen leaves, wood • May link producers to consumers – Dung beetles, earth worms • Saprotrophs = feed on dead organic material by secreting digestive enzymes into it and absorbing the digested products • Producers can reassimilate these raw materials – Fungi (mold, mushrooms), bacteria
- 35. Energy in living systems • Food chains, webs and pyramids, ultimately show energy flow • Obey the laws of thermodynamics • Obey systems laws – input, transfer, transformation, output
- 36. Thermodynamics Review Universal laws that govern all energy changes in the universe, from nuclear reactions to the buzzing of a bee. a) The 1st law: Energy can be transferred and transformed but not created or destroyed - Energy flow in the biological world is unidirectional: – Sun energy enters system and replaces energy lost from heat – Energy at one trophic level is always less than the previous level b) The 2nd law: Energy transformations proceed spontaneously to convert matter from a more ordered, less stable form, to a less ordered, more stable form - Energy lost as heat from each level - Energy at one level less than previous because of these lossed
- 37. Energy Flow in Communities • Energy unlike matter does not recycle through a community it flows • Energy comes from the sun • Converted by autotrophs into sugars • Amount of Light energy converted into chemical energy by autotrophs in a given time period Gross Primary Production GPP • The amount to pass on to consumers after plants have used their share Net Primary Production NPP • NPP = GPP - R
- 38. The Source of All energy on Earth is the …
- 39. Figure 3-10 Page 52 Energy emitted from sun (Kcal/cm 2 /min) 0 5 10 15 0.25 1 2 2.5 3 Wavelength (micrometers) Visible Light is The usable Energy
- 40. What is the sun? • 72% hydrogen, 28% helium • Temp and pressure high so H nuclei fuse to form He releasing energy • Fusion energy radiated as electromagnetic energy • Earth receives 1 billionth of the suns Energy • Most reflected away or absorbed by atmospheric chemicals
- 42. Energy to Earth • 30% solar energy reflected back into space by atmosphere, clouds, ice • 20% absorbed by clouds & atmosphere • 50% remaining – Warms troposphere and land – Evaporates and cycles water – Generates wind • < 0.1% captured by producers for photosynthesis • Energy eventually transformed to heat and trapped by atmosphere “Natural Greenhouse Effect” • Eventually reradiated into space
- 44. So if sunlight in = sunlight + heat out What state is the system in? Stable Equilibrium
- 45. Summary of solar radiation pathways • Incident radiation comes in, it is then… – Lost by reflection (ice caps) and absorption (soil, water bodies) – Converted from light to chemical energy (photosynthesis in producers) – Lost as chemical energy decreases through trophic levels – Through an ecosystem completely converted from light energy into heat – Reradiated as heat back to the atmosphere
- 46. Energy Flow II • Energy measured in joules or kilojoules per unit area per unit time • Energy conversion never 100% efficient • Some energy lost as heat • Of visible light reaching producers, only 1% is converted to chemical energy • Other levels are 10% efficient – only assimilate %10 of energy from previous level
- 47. Figure 54.1 An overview of ecosystem dynamics
- 48. Energy Flow and Food webs • Biomass = the total dry weight of all organisms in one trophic level • Usable energy degraded with each transfer – Loss as heat, waste, metabolism • % transferred = ecological efficiency ranges from 5-20% • More trophic levels = less energy available at high levels
- 50. If that loss happens at every trophic level think about how much energy is lost. Makes the lower trophic levels most efficient in terms of overall energy available in the system
- 51. Energy Flow through Producers • Producers convert light energy into chemical energy of organic molecules • Energy lost as cell respiration in producers then as heat elsewhere • When consumers eat producers energy passes on to them • In death organic matter passes to saprophytes & detritivores
- 52. Energy Flow through Consumers • Obtain energy by eating producers or other consumers • Energy transfer never above 20% efficient, usually between 10 – 20% • Food ingested has multiple fates 1. Large portion used in cell respiration for meeting energy requirements (LOSS) 2. Smaller portion is assimilated used for growth, repair, reproduction 3. Smallest portion, undigested material excreted as waste (LOSS)
- 53. Figure 54.10 Energy partitioning within a link of the food chain
- 54. Energy flow through Decomposers • Some food is not digested by consumers so lost as feces to detritivores & saprophytes • Energy eventually released by process of cell respiration or lost as heat
- 56. Construct and analyze energy flow diagrams for energy movement through ecosystems • Trophic level boxes are storages – biomass per area (g m-2) • Energy Flow in arrows – rate of energy transfer (g m-2 day-1)
- 57. Energy values in KJ m-2y-1 Often the size of the boxes and arrows is proportional to their amount
- 58. Using Pyramids to express ecosystem dynamics
- 59. Energy Input: 20,810 + 1,679,190 1,700,000 (100%) Energy Output Total Annual Energy Flow Metabolic heat, export Waste, remains 1,700,000 kilocalories Producers Herbivores Carnivores Top carnivores Decomposers, detritivores Energy Transfers 20,810 (1.2%) Incoming solar energy not harnessed 1,679,190 (98.8%) 4,245 3,368 13,197 720 383 2,265 90 21 272 5 16 Top carnivores Carnivores Herbivores Producers 5,060 Decomposers/detritivores 20,810 3,368 383 21 © 2004 Brooks/Cole – Thomson Learning
- 60. Pyramids • Graphic models of quantitative differences between trophic levels • By second law of thermodynamics energy decreases along food webs • Pyramids are thus narrower as one ascends – Pyramids of numbers may be different large individuals at low trophic levels – large forests – Pyramids of biomass may skew if larger organisms are at high trophic levels biomass present at point in time – open ocean
- 63. Losses in the pyramid • Energy is lost between each trophic level, so less remains for the next level – Respiration, Homeostasis, Movement, Heat • Mass is also lost at each level – Waste, shedding, …
- 64. Pyramids of Biomass • Represents the standing stock of each trophic level (in grams of biomass per unit area g / m2) • Represent storages along with pyramids of numbers
- 65. How do we get the biomass of a trophic level to make these pyramids? • Why can’t we measure the biomass of an entire trophic level? • Take quantitative samples – known area or volume • Measure the whole habitat size • Dry samples to remove water weight • Take Dry mass for sample then extrapolate to entire trophic level • Evaluation It is an estimate based on assumption that – all individuals at that trophic level are the same – The sample accurately represents the whole habitat
- 66. Abandoned Field Ocean Tertiary consumers Secondary consumers Primary consumers Producers © 2004 Brooks/Cole – Thomson Learning Pyramids of Biomass
- 67. Pyramids of Numbers • Needs sampling similar to Biomass and therefore has the same limitations • Also measures the storages
- 68. Grassland (summer) Temperate Forest (summer) Producers Primary consumers Secondary consumers Tertiary consumers Pyramids of Numbers © 2004 Brooks/Cole – Thomson Learning
- 69. Pyramids of productivity • Flow of energy through trophic levels • Energy decreases along the food chain – Lost as heat • Productivity pyramids ALWAYS decrease as they go higher – 1st and 2nd laws of thermodynamics • Shows rate at which stock is generated at each level • Productivity measured in units of flow (J / m2 yr or g / m2 yr )
- 70. Figure 54.11 An idealized pyramid of net production
- 71. Figure 54.14 Food energy available to the human population at different trophic levels Efficiency of trophic levels in relation to the total energy available decreases with higher numbers But efficiency of transfer always remains around that 10% rule
- 72. Take an Economic Analogy 1. If you look at the turnover of two retail outlets you can’t just look at the goods on the shelves • Rates of stocking shelves and selling goods must be known as well 2. A business may have substantial assets but cash flow may be limited 3. So our pyramids of Biomass and numbers are like the stock or the assets and our pyramids of Productivity are like our rate of generation or use of the stock
- 73. How does pyramid structure effect ecosystem function? 1. Limited length of food chains • Rarely more than 4 or 5 trophic levels • Not enough energy left after 4-5 transfers to support organisms feeding high up • Possible exception marine/aquatic systems b/c first few levels small and little structure 2. Vulnerability of top carnivores • Effected by changes at all lower levels • Small numbers to begin with • Effected by pollutants & toxins passed through system
- 74. Effects II: Biomagnification 1. Mostly Heavy metals & Pesticides • Insoluble in water, soluble in fats, • Resistant to biological and chemical degradation, not biodegradable 2. Accumulate in tissues of organisms 3. Amplify in food chains and webs 4. Sublethal effects in reproductive & immune systems 5. Long term health effects in humans include tumors, organ damage, …
- 75. Water 0.000002 ppm Phytoplankton 0.0025 ppm Zooplankton 0.123 ppm Rainbow smelt 1.04 ppm Lake trout 4.83 ppm Herring gull 124 ppm Herring gull eggs 124 ppm
- 78. • The insolation energy in an area of rainforest is 15,000,000 cal/ m2/day. This is the total amount of sun energy reaching the ground. The GPP of the producers in the area, large rainforest trees, is 0.0050 g/cm2/day and 25% of this productivity is consumed in respiration. By laboratory tests we found that 1 gram of rainforest tree contains 1,675 calories of energy. • A. What trophic level are the trees considered? (2 point) • B. Calculate the NPP of the system. (5 point) • C. Find the efficiency of photosynthesis. (5 point) • D. If a monkey population eats the fruit from the trees how many square meters of forest will each individual need to feed in if they require 400 calories each day?
- 79. Practice • Create a food web for the following FL organisms largemouth bass, panther, racoon, white tailed deer, bullfrog, shiner (small fish), water beetles, zooplankton, phytoplankton, marsh grass, rabbit, water moccasin, dragonfly, duckweed, egret, wood duck,
- 80. Human Blue whale Sperm whale Crabeater seal Killer whale Elephant seal Leopard seal Adélie penguins Petrel Fish Squid Carnivorous plankton Krill Phytoplankton Herbivorous zooplankton Emperor penguin Practice: Identify the trophic levels In the food web