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2.5 Investigating Ecosystems

2.5 Investigating Ecosystems. Review Zonation and Succession on your notes. Monitoring Abiotic Factors. Ecosystems can be roughly divided into:- Marine Freshwater and Terrestrial systems. Monitoring Abiotic Factors. Complete the diagram in your notes. MONITORING BIOTIC (LIVING) FACTORS.

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2.5 Investigating Ecosystems

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  1. 2.5 Investigating Ecosystems

  2. Review Zonation and Succession on your notes

  3. Monitoring Abiotic Factors • Ecosystems can be roughly divided into:- • Marine • Freshwater and • Terrestrial systems

  4. Monitoring Abiotic Factors • Complete the diagram in your notes

  5. MONITORING BIOTIC (LIVING) FACTORS • Once the abiotic conditions within an environmental gradient have been measured, we can begin to ask questions about the distribution of organisms within the study area • Which species are present • The size of a particular population of organisms • The productivity in a particular area • The diversity of a particular area

  6. MONITORING BIOTIC (LIVING) FACTORS • Complete the table in your notes

  7. COLLECTING DATA - Where? • When collecting environmental data, it is almost impossible to collect every possible data point • We use sampling methods to make estimations • These methods enable us to get a random sample from an entire ecosystem and then use extrapolation to make estimates and predictions • In order to avoid bias it is important that these methods are truly random. • Two methods used in ecology to determine where to collect a sample are quadrats and transects.

  8. Assumptions Made When Sampling • The sample is representative of the whole system • It is necessary to take enough samples so that an accurate representation is obtained • It is important to avoid bias when sampling

  9. Estimating Populations of Organisms • We estimate populations because it would take way too long to count every living thing in a given ecosystem. • We can estimate populations of plants or animals • Random Sampling: All organisms must have an equal chance of being captured.

  10. Common Sampling Methods • Abundance of Non-motile Organisms • Transects and Quadrants • Abundance of Motile Organism • Actual Count (very difficult if large system) • Lincoln Index • Capture – Mark - Recapture • Species Diversity • Simpson Diversity Index • For comparing 2 habitats or the change in one habitat over time

  11. Lincoln Index

  12. Measuring abundance of Mobile Organisms • If the organism is mobile we use a method called the capture-mark-recapture method • We then use this data to calculate the Lincoln Index

  13. How to Capture Motile Organisms • REMEMBER: IB Animal Experimentation Policy • Pitfall Traps • Small Mammal Traps • Tullgren Funnels (invertebrates) • Kick Net

  14. Estimating Populations of Animals • Lincoln index (capture-mark-release-recapture) n1 x n2 N = n3 • N = Total number of population • n1 = Number of animals first (mark all of them) • n2= Number of animals captured in second sample • n3= Number of marked animals in second sample Ex. 40 mice were caught, marked (tail tattoo) and released. Later, 10 mice were recaptured, 4 of which had tattoo marks.

  15. Lincoln Index

  16. Example • 50 snowshoe hares are captured in box traps, marked with ear tags and released. Two weeks later, 100 hares are captured and checked for ear tags. If 10 hares in the second catch are already marked (10%), provide an estimate of N • **Realize for accuracy that you would recapture multiple times and take an average**

  17. Lincoln Index Assumptions • The marked animals are not affected (neither in behavior nor life expectancy). • The marked animals are completely mixed in the population. • The probability of capturing a marked animal is the same as that of capturing any member of the population. • Sampling time intervals must be small in relation to the total time of experiment of organisms life span. • The population is closed (no immigration and emigration) • No births or deaths in the period between sampling.

  18. Some Possible Sources of Error • Emigration & Immigration • Natural disaster or disturbance between captures • Trap happy or trap shy individuals • Organisms did not have enough time to disperse back into ecosystem • Animals lost marks between recapture

  19. Quadrat Sampling

  20. Estimating Populations of Plants • Quadrat Estimation • Population Density- The number of plants within the given area of the quadrat (m2) • Percentage Coverage- How much of the area of a quadrat is covered by plants? • Frequency- How often does a plant occur in each quadrat? • Acacia senegalensis was present in 47 of 92 quadrats, for a frequency of 51%

  21. Square Quadrat Method • N = (Mean # per quadrat) (total area) Area of each quadrat • This estimates the population size in an area • Ex. If you count an average of 10 live oak trees per square hectare in a given area, and there are 100 square hectares in your area, then • N = (10 X 100 hectare2) / 1 hectare2 = 1000 trees in the 100 hectare2

  22. In addition to population size we can measure… • Density = # of individuals per unit area • Good measure of overall numbers • Frequency = the proportion of quadrats sampled that contain your species • Assessment of patchiness of distribution • % Cover = space within the quadrat occupied by each species • Distinguishes the larger and smaller species

  23. Grid Quadrate • Measures percent frequency – the % of quadrats in which the species is found • OR • Measures percent coverage –the % of area within a quadrat covered by a single species • NOTE: When you are looking at one species at a time • If not using a 10 x 10, you must turn into a percentage (squares covered/total # of squares)

  24. Percent Frequency

  25. http://www.slideshare.net/nirmalajosephine1/biology-form-4-chapter-8-dynamic-ecosystem-part-3-42839437

  26. Percent Coverage Percent Coverage 1 m • Find the percent coverage • Count full squares • Now combine pieces to make full squares • Calculate percentage coverage 18 22 14 24 24 14 2 1 15 4 3 15 1 m 23 17 21 12 19 20 13 17 12 18 13 5 6 16 10 11 8 9 22 7 23 20 19 12 16 21

  27. Calculate Population Density What is the population density of species x ? What is the population density of species Y? What is the population density of species Z? Quadrat 1= 0.5m2

  28. Calculate Percentage Coverage What is the percentage of plant coverage in this quadrat? Quadrat 1= 0.5m2

  29. Percentage Frequency Quadrat 1 What is the frequency of species X? What about species V? Quadrat 2 Quadrat 3

  30. How choose quadrat size? • Think about the size of the organism. • Think about the area of the system. • The smaller the quadrat the more accurate, however the smaller the sample size • Larger quadrats increase inaccuracy but allow for broader sample of an area

  31. Measuring Biomass • Get a sample of the organisms, dry them out completely in a dehydrating oven (to remove all water!), find the mass and extrapolate : • If you collect 10 plants, dry them out and find their average dry biomass to be 20g, what would the biomass of a population of 2500 plants be? • 50,000g • Remember – biomass can be used to create pyramids of biomass when looking at energy transfers and is needed for many productivity calculations!

  32. Transets

  33. Transects • A TRANSECT - A line, strip or profile of vegetation which has been selected for study. measure any of these abiotic and/or biotic components of an ecosystem along an environmental gradient

  34. Transect • In order to complete a transect, a piece of string or measuring tape is laid out along the selected gradient.

  35. Line Transects • A measured line is randomly placed across the area in the direction of an environmental gradient • All species touching the line are recorded along the whole length of the line or at specific points along the line • Measures presence or absence of species

  36. Belt Transects • Transect line is laid out and a quadrant is placed at each survey interval • Samples are identified and abundance is estimated • Slow moving animals (limpets, barnacles, snails) are collected, identified then released • For plants an percent coverage is estimated

  37. Belt Transects • Data collection should be completed by one individual as estimates can vary person to person

  38. Transect • These can either be sampled continuously or as an interrupted transect where samples are taken at regular, fixed distances along the line.

  39. Transect • To measure changes in space i.e. zonation, this technique should be completed within a short space of time to avoid any daily cycles • For studies of long term change i.e. succession, the transect should be repeated at the same time of day and at regular intervals over a suitable time period depending on what is being studied or assessed.

  40. Kite Diagrams • Used to illustrate changes in species over space or time along an environmental gradient. • The width of each ‘kite’ represents the percentage cover or abundance of that species.

  41. Simpson Index

  42. Species Diversity • The two main factors taken into account when measuring species diversity • 1. Richness • A measure of the number of different species present in a particular area. • The more species present in a sample, the 'richer' the sample. • Takes no account of the number of individuals of each species present. It gives as much weight to those species which have very few individuals as to those which have many individuals. http://www.countrysideinfo.co.uk/simpsons.htm

  43. Species Diversity • The two main factors taken into account when measuring species diversity • 2. Relative Abundance • The relative number of individuals of each species present http://www.countrysideinfo.co.uk/simpsons.htm

  44. How Can We Know Diversity? Use the Simpsons diversity index below D = ____________N (N-1)_______________ n1(n1−1) + n2(n2 −1) + n3(n3 −1) +…nk(nk −1) D = Diversity N = Total number of organisms of all species n = number of individuals of a particular species ***The higher the D value the more diverse the sample is!!!!!

  45. Example Data Calculations

  46. How can changes in these populations be measured? • Necessary because populations may change over time through processes like succession • But also because human activities may impact a population and we want to know how • Impacts include  toxins from mining, landfills, eutrophication, effluent, oil spills, overexploitation

  47. Analyzing Simpson’s Index • Used to compare 2 different ecosystems or to monitor an ecosystem over time • D values have no units and are used as comparison to each other • High D Value Indicates: • Stable and ancient site • More diversity • Healthy habitat • Low D Value Indicates: • Dominance by one species • Environmental stress • Pollution, colonization, agriculture

  48. How to Capture Motile Organisms REMEMBER: IB Animal Experimentation Policy • Pitfall Traps • Small Mammal Traps • Tullgren Funnels (invertebrates) • Kick Net

  49. Classification

  50. What is classification? • Science of grouping organisms based on their physical characteristics.

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