2.2 Communities and Ecosystems

Transcription

1 2.2 Communities and Ecosystems

2 A community = all the biotic (living) components of a habitat. Tropical Rainforest is a community of plants, animals, bacteria, and fungi Sloths are famous for their green coloration, a result of the algae that live in their hair and help provide camouflage

3 An Ecosystem = the community AND the physical environment it interacts with. Ecosystems may be of varying sizes from a drop of water to an entire forest.

4 There are 3 key ecological concepts that are vital to your understanding of how everything else works: Respiration Photosynthesis Productivity

5 Respiration Is the conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy

6 Respiration All living things must respire to get energy to stay alive Respiration involves breaking down food, often in the form of glucose, to release energy which is used in living processes. Much of the energy produced in respiration is heat energy which is released(dissipated) into the environment. This increases the entropy of the system while the organism maintains a relatively high level of organization (low entropy)

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8 Respiration

9 Photosynthesis Is the process by which green plants make their own food from water and carbon dioxide using energy from sunlight

10 Photosynthesis A transformation of light energy into chemical energy (glucose) Glucose is then the starting point for the plant to make every other molecule that it needs Photosynthesis produces the raw material for producing biomass

11 Photosynthesis Green plants contain chloroplasts with the green pigment chlorophyll In the chloroplasts the energy from sun is used to split water and combine the hydrogen to carbon dioxide to create the glucose The oxygen split from the water molecule is the waste product oxygen

12 Photosynthesis All plants respire In the sunlight plants respire and photosynthesize In the dark they only respire

13 Compensation Point when all CO2 that plants produce in respiration is used up in photosynthesis, the rates of the two processes are equal and there is no net release of either O2 of CO2. This ususally occurs at dawn or dusk when light intensity is not too high. *The plant is neither adding biomass nor using it up to stay alive. It is just maintaining itself

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17 Photosynthesis

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20 Food Chains, Trophic Levels and Food Webs

21 Food Chains Food chain = the flow of energy from one organism to the next Shows the feeding relationships between species in an ecosystem Arrows show the direction of energy flow

22 Trophic Levels Trophic Level = feeding level in a food chain.

23 Primary Producers (PP) Two types of producers. Most producers are Autotrophs (green plants) make their own food from CO 2 and H 2 O using sunlight (PHOTOSYNTHESIS!)

24 Primary Producers (PP) Supply nutrients to soil Bind soil, stop soil erosion Provide energy for all other trophic levels Habitat for other organisms

25 Other Producers Two types of producers. Chemosynthetic organisms Make their own food from simple compounds. Do not require sunlight. Often are bacteria found in deep oceans

26 Primary Consumers (PC) Heterotrophs (feed on other organisms) Herbivores (consume PP) Populations controlled by negative feedback They also disperse seeds Plants herbivores

27 Primary Consumers (PC)

28 Secondary Consumers (SC) Heterotrophs (feed on other organisms) Carnivores and Omnivores Consume herbivores and other carnivores, sometimes eat primary producers

29 Secondary Consumers (SC) Pollinate flowers Remove old and diseased animals from population

30 Secondary Consumers (SC)

31 Tertiary Consumers (TC) Heterotrophs (feed on other organisms) Top Carnivores and Omnivores Consume herbivores and other carnivores, sometimes eat primary producers

32 Tertiary Consumers (TC) Remove old and diseased animals from population

33 Decomposers Get their energy from dead organisms Bacteria and fungi Secrete enzymes that break down the organic matter in dead organisms

34 Decomposers Crucial role in the ecosystem!! They are tiny but important! Break down dead organisms Control the spread of disease Release nutrients back into the cycle

35 Detritivores Get their energy from detritus Detritus = decomposing organic material (dead organisms, feces, or parts of an organism) Ex: crabs, worms, beetles, mites

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38 Detritivores Crucial role in the ecosystem!! Break down dead organisms Release nutrients back into the cycle Control the spread of disease

39 Food Webs In ecosystems, there are many food chains that are interconnected. Limits of food chains only show each organism eating one other organism. In reality, organisms eat many other species as food! Food webs = complex network of interrelated food chains in an ecosystem

40 Food Webs Arrows point towards the direction of energy flow (arrow goes into the organism that is eating it) Show the complex feeding relationships that trophic pyramids and food chains cant show. (ex. A grizzly bear is a top predator but also eats plants)

41 Food Webs Read and annotate Arctic Food Web article. Create a food web using only the animals mentioned in the article. Use the cut outs and a large whiteboard to draw arrows between the organisms. After you have made the food web, color code each organism as: Tertiary consumer Secondary consumer Primary consumer Primary producer Decomposers Detritivores

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43 3 types of ecological pyramids

44 Your challenge: Design a poster that contains all 3 ecological pyramids They must have explanations that are easy to understand Visuals Units of measure Advantages and disadvantages of each Everyone in the group must be able to explain these pyramids Use your textbook pages The internet/videos My PPT on the class website

45 Ecological Pyramids- include pyramid of numbers, biomass, and productivity and are quantitative models and are usually measured for a given area and time. They allow easy examination of energy transfers and losses They display what feeds on what and what organisms exist at different trophic levels Demonstrate that ecosystems are systems in balance

46 Pyramid of numbers Constructed by counting the number of organisms at each trophic level. Samples from an area are used and the results multiplied to represent the whole.

47 Pyramid of numbers The length of each bar gives a measure of the relative numbers Pyramids have producers at the bottom, usually in the greatest number. The bottom usually has many individuals in the producer, but some may have a large single plant or tree as a producer so the base is one individual which supports many consumers.

48 Pyramid of numbers Advantages: A simple easy method of giving an overview and is good for comparing changes in a population numbers over different times or seasons Disadvantages: All organisms are included regardless of their size, therefore a pyramid based on an oak tree would have a narrow base and get larger as it goes up the trophic levels. Does not allow for juveniles or immature forms Numbers can be too great to represent accurately

49 Pyramid of biomass Biomass is the quantity of dry organic material in an organism, It can also be measured for a population, a particular trophic level, or an ecosystem In a pyramid of biomass, it is the dry material of all organisms at that trophic level. (mass of each individual x # of individuals) Units of biomass = mass = _g_ area m 2 (land) g m -2 g/m 3 for volumes of water shown like this g m -3 Units can be energy content = J (joules)

50 Pyramid of biomass More likely to be pyramid shaped Exceptions include oceanic ecosystems producers are phytoplankton. Phytoplankton reproduce fast but are present in small amounts at one time. Remember that a pyramid only represents a certain time (e.g. winter)

51 Pyramid of numbers 15.0 g 8.0 g Draw a pyramid of biomass with calculations from the pyramid of numbers. You are solving for an area on land measured out by meters. Your answers should have gm g 0.8 g Average mass of organism X Number of organisms

52 Pyramid of Biomass Advantages: takes account of the size of organisms, so it overcomes some problems of pyramid of numbers Disadvantages: difficult to measure accurately because sampling involves killing of organisms Seasonal variation leads to inverted pyramids (e.g. less phytoplankton in winter) Some animals have a lot of bone or shell which can distort the results (e.g. a turtle s shell has a large mass, but cannot be eaten for energy) Like pyramid of numbers it is a snapshot in time and place.

53 Pyramid of biomass

54 Pyramid of productivity Most accurate way to model an ecosystem Shows the flow of energy through each trophic level usually over a years time Shows the energy or biomass being generated and available as food to the next trophic level

55 Pyramid of productivity Units are measured in: energy per area per time energy joules area m 2 time year It is saying, how much energy (J) is produced in 1 m 2, over a 1 year period. SHOULD be written as J m -2 yr -1 1 m 2

56 Pyramid of Productivity Always pyramid shaped in healthy ecosystems as they must follow the second law of thermodynamics

57 Pyramid of productivity Shows how much energy is transferred from one trophic level to another. This is the energy pyramid you have been used to seeing! In the pyramid There are 10,000 J of energy produced by plants living in 1 m 2, per year 10 J m -2 y J m -2 y -1 1,000 J m -2 y -1 10,000 J m -2 y -1 1,000,000 J m -2 y -1

58 Pyramid of productivity 10% of energy goes to the herbivores = 1, % J m -2 y -1 Solve for this pyramid. Not all transfers are exactly 10%. Use the above formula to solve for the missing boxes. The transfer for the producers to the herbivores has been done. 5 % 10 % 1,000 J m -2 y -1 10,000 J m -2 y -1 J m -2 y -1 1,000,000 J m -2 y -1

59 2 super markets cannot be compared by just looking at the cereal on the shelves. The rate at which goods are being stocked and sold needs to be known. Both may have well stocked shelves but the rate of removal of goods from a major city shop may be considerably more than from a village shop.

60 Pyramid of biomass represent the just the stock on the shelf at a given time, whereas pyramids of productivity show the rate at which that stock is being removed by customers and restocked by employees.

61 Pyramid of productivity Advantages: Most accurate system, shows the actual energy transferred and allows for the rate of production Allows for comparison of ecosystems based on relative energy flows Pyramids are never inverted Energy from solar radiation can be added Disadvantages: Data is difficult to collect as rate of biomass production over time must be measured Many species feed at more than one trophic level (true for all pyramids) so assigning them to on trophic level is difficult

62 Construct the 3 pyramids on graph paper Page 74

63 2.2 Consequences of Ecological Pyramids

64 How the structure of the ecological pyramid affects the ecosystem The structure of ecological pyramids has consequences that can be seen in the way an ecosystem functions.

65 1. Concentration of toxic substances in the food chain If a chemical in the environment breaks down slowly, or does not break down at all, it will accumulate in organisms. POPs = persistent organic pollutants Common chemicals: pesticides, heavy metals like Mercury Two ways chemicals can accumulate: Bioaccumulation Biomagnification

66 Bioaccumulation Bioaccumulation = when a chemical builds up in a single organism over time What types of organisms would be most at risk for bioaccumulation? Animals that eat more, are larger, and have longer lifespans As the fish get older, and eat more, they will build up more chemicals in their bodies.

67 Bioaccumulation How does it happen? The chemical accumulates because it does not break down easily The chemical gets stored in fat cells of organisms.

68 Biomagnification Biomagnification = the tendency of toxins to concentrate in organisms at higher trophic levels.

69 Biomagnification Concentration of the chemical at lower trophic levels may not have much effect But, as you go up the trophic pyramid, the highest levels will have very high amounts of the chemical

70 Biomagnification How does it happen? Pollutants get into the producers (through water or air) Small herbivores eat many producers, and may also get the chemical through water. Carnivores eat many herbivores, and get even more of the chemical in their bodies. They take in so much of the chemical that it causes disease or death.

71 Video on Biomagnification of DDT

72 What other historical events have resulted in biomagnification? Class discussion (Minamata Bay, Bhopal Disaster, etc)

73 Difference between Bioaccumulation and Biomagnification Same organism has toxin build up in its body over time Bioaccumulation Amount of toxin increases in higher trophic levels Biomagnification

74 Bioaccumulation or biomagnification?

75 Bioaccumulation or biomagnification? In the polar bear? In the ecosystem? In the seal?

76 2. Food chains have a limited length Food chains cannot go on forever. Eventually the energy available runs out. WHY? Only 10% of available energy makes it to the next trophic level.

77 2. Food Chains have a Limited Length The 90% of energy that is lost as heat what was it used for? Respiration to keep the organism alive Herbivores destroying plants as they trample it Plant material that can t be eaten (e.g. only eat the leaves of trees, not the wood) Energy to move

78 2. Food Chains have a limited length How many trophic levels can a food chain have? Terrestrial: 4 levels Aquatic: 5 levels 1

79 2. Food Chains have a Limited Length Why do aquatic ecosystems have more trophic levels than terrestrial ecosystems? Aquatic organisms don t have to use as much energy to MOVE and MAINTAIN their bodies They have the water holding them up!

80 3. Top Carnivores are Vulnerable Highest level is most susceptible to changes in ecosystem Top carnivores require more territory Ex. Clouded leopards in Borneo rainforests # of leopards declining due to deforestation for palm oil (destroying territory and prey) Top carnivores have a limited diet, and need to eat lots of food to survive If a source of food is destroyed, has a larger effect There are few top carnivores to begin with Small populations are more at risk