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BIOLOGY FORM 4 CHAPTER 8 - DYNAMIC ECOSYSTEM PART 3

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BIOLOGY FORM 4 CHAPTER 8 - DYNAMIC ECOSYSTEM PART 3

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BIOLOGY FORM 4 CHAPTER 8 - DYNAMIC ECOSYSTEM PART 3

  1. 1. DYNAMIC ECOSYSTEM PART 3 Part 2
  2. 2. How are populations measured?
  3. 3. Population Density:  is the number of individuals in a given area or volume
  4. 4. How can the population density be found? Impossible to count every organism in a population
  5. 5. How is the problem solved? ESTIMATE!! How is an estimate done? The size of a population is estimated by taking random samples
  6. 6. Methods of estimating population size OBJECTIVE METHODS  Quadrats  Capture-Recapture [Mark-release]
  7. 7. What are ‘Quadrats’?
  8. 8. A Quadrat is:  a metal or wooden frame which forms a square of known area such as 1m2
  9. 9. Various sizes of quadrats
  10. 10. 0.05  0.5 m quadrat Smaller quadrats are used when….. Zone is narrow.
  11. 11. Quadrats can be used to sample the flora
  12. 12. Can quadrats be used to sample fauna? Slow moving / sessile Topshells Limpets Barnacles
  13. 13. Fast moving animals BUT NOT:
  14. 14. How many quadrats? Explain why it would be useless to take more than 7 quadrats.
  15. 15. Quadrats provide calculation of three aspects of species distribution: 1) Species density 2) Species frequency 3) Species cover
  16. 16. Species Density:  the number of individuals of a given species in a given area
  17. 17. 2) Frequency:  a measure of the probability of finding a given species with any one throw of a quadrat in a given area  e.g. if a species occurs once every ten quadrats, its frequency is 10% [1/10 x 100]  is obtained by recording the presence or absence of a species in a quadrat
  18. 18. Frequency table Organism 1 2 3 4 5 6 7 8 9 10 Total Frequency %Frequency Quadrat throw thrownquadratsofNo organismcontainingquadratsofNo Frequency . .  If percentage is required multiply frequency by 100
  19. 19. The bunchgrass species and the cattail species have:  an identical density of 7 plants per 36 m2.  but different frequency. Frequency of:  bunchgrass (4/36 = 11%)  cattail (7/36 = 19%) Frequency depends on spatial distribution:
  20. 20. Frequency depends on quadrat size: Frequency of:  bunchgrass (4/36 = 11%)  cattail (7/36 = 19%) Frequency of:  bunchgrass (3/9 = 33%)  cattail (5/9 = 56%)
  21. 21. 3) Species Cover  a measure of the proportion of ground occupied by the species  buttercup is covering about 6 boxes out of 25: 6 100 24% 25  
  22. 22. Recording % Cover Quadrat with a grid.
  23. 23. Recording % Cover Subjective!! Better if done by ONE person.
  24. 24. Species cover can be more than 100% WHY?
  25. 25. Species cover can be more than 100% WHY? Overlap
  26. 26. RECAP Quadrat Sampling technique . Density - abundance, measured by actual count, per unit area. Counts are averaged when more than one sample is taken. A) Density = Total no of individuals of a species in all quadrats No. of quadrats x quadrat area = 5+6+4+2+7 / 5x 1m2 Quadrat 1 2 3 4 5 No. of individuals 5 6 4 2 7
  27. 27. Quadrat Sampling technique B) Percentage coverage = aerial coverage of all quadrats(m2) x 100% No. of quadrats x quadrat area = 9+8+8+7+8 X100 % / 5 X 1m2 Quadrat 1 2 3 4 5 Coverage (m2) 9 8 8 7 8
  28. 28. Quadrat Sampling technique  Frequency - the percentage of sample plots in which a species or target group appears.  C) Frequency = No. of quadrats containing the species = 3/5 No. of quadrats Quadrat 1 2 3 4 5 Frequency / / 0 / 0
  29. 29. Methods of estimating population size OBJECTIVE METHODS  Quadrats  Capture-Recapture [Mark-release]
  30. 30. Capture-Recapture Method How can fast moving animals be sampled? animals
  31. 31. Estimating numbers of mobile animals  Involves:  CAPTURE  marking  then capturing another sample of individuals Setting up traps to capture animals
  32. 32. Estimating numbers of mobile animals  Involves:  MARKING  then capturing another sample of individuals
  33. 33. Marking methods  Paint or dye, India ink  Color band  birds  Unique markings  Large mammals; keep photo record  Toe clipping  Reptiles, amphibians, rodents (NPS 2000) (Sutherland 1996)
  34. 34. Estimating numbers of mobile animals  Involves:  MARKING  then capturing another sample of individuals
  35. 35. This estimate of population size is:  called the Lincoln index Estimated total population = (No. of organisms in 1st sample) x (No. of organisms in 2nd sample) (No. of marked organisms recaptured)  relies on the following assumptions:
  36. 36. Assumptions: 1. Organism mix randomly within the population. 2. Sufficient time must elapse between capture and recapture to allow random mixing.
  37. 37. Assumptions: 3. It is applicable only to populations whose movement is restricted geographically. 4. Organisms disperse evenly within the geographical area of the population.
  38. 38. Assumptions: 5. Changes in population size as a result of immigration, emigration, births and deaths are negligible.
  39. 39. Assumptions: 5. Marking does not hinder the movement of the organisms or make them conspicuous to predators.
  40. 40. The photo below shows a student using another sampling technique. The photo below shows a student using another sampling technique. a) Name the piece of apparatus being used to sample plant density and diversity in the field. (1) Quadrat
  41. 41. The following photo shows three biology students during fieldwork in a woodland area. Explain why the sampling equipment shown in the diagram cannot be used for animals. (1) Animals move out of the quadrat and so cannot be counted.
  42. 42. Question: 1. The Humpback whale (Megaptera novaeangliae) used to be common in the western North Atlantic, with an estimated population of over 100 000. When commercial whaling began, the population was reduced and it is estimated that 90–95 % were killed. Populations are now increasing because the species was classified as ‘threatened’ and given special protection.
  43. 43. Question: a) Humpback whale populations are estimated from photographs taken from ships or aircraft. They have very distinctive natural markings so that individuals can be distinguished. The table shows the number of Humpback whales sighted in two consecutive years. Number photographed in year 1 1200 Number photographed in year 2 1157 Number of whales recognised in both sets of photographs 120
  44. 44. Question: (i) Use the Lincoln Index to calculate the population size of Humpback whales in year 2. Show your working. 1 2 Population size = m n n n  where n1= number seen in year 1 where n2= number seen in year 2 nm = number recognised in both years 1200 x 1157 = 11570 120
  45. 45. Question: (ii) Suggest three reasons why this figure may not be accurate. (3) 1. Individuals may not be recognised/be counted more than once; 2. Relative not absolute numbers/only an estimate; 3. Immigration/emigration from area; 4. qualified reason for not being seen e.g. underwater/diving/scared away by boats; 5. Births/deaths/caught by whalers; 6. May not mix randomly;
  46. 46. 2. The small black species of beetle shown in the drawing is common in the grass zone. It was decided to measure its population by using the mark -release-recapture method. Question: a) Suggest how this beetle might be marked before being released. (2) Using waterproof paint – mark a spot on underside of abdomen.
  47. 47. Pitfall traps were placed in the ground and left overnight. The following morning 18 beetles were captured. These were marked and released. The traps were emptied again after 1, 2 and 4 days. The results are shown in the diagrams. b) Present the results of this investigation in a suitable way. (3)
  48. 48. c) Use these results to calculate the beetle population. Show your working. (2) Day Number in second sample (marked) Total number in second sample 1 4 16 2 3 12 4 4 16 Total 11 44 18 x 44 = 72 11
  49. 49.  The study of the relationships between groups of organisms is called taxonomy, an ancient and venerable branch of classical biology.  Taxonomy is the art of classifying things into groups— established as a mainstream scientific field by Carolus Linnaeus (1707-1778).
  50. 50. Taxonomic group Plant example Animal example Kingdom Phylum Class Order Family Genus Species Common name Plant Tracheophyta Angiospermae Ranales Ranunculaceae Ranunculus acris Meadow buttercup Animal Annelida Oligocheata Terricolae Lumbricidae Lumbricus terrestris earthworm Animal Chordate Mammalia Primates hominidae Homo sapiens human
  51. 51. Other member (Panthera tigris)(Panthera tigris) Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Family: Felidae Genus: Panthera Species: P. tigris
  52. 52. Kingdom: Plantae (unranked): Angiosperms (unranked): Eudicots (unranked): Rosids Order: Malvales Family: Durionaceae Genus: Durio zibethinus
  53. 53. 1 . Has green colored body ......go to 2 Has purple colored body ..... go to 4 2 . Has 4 legs .....go to 3 Has 8 legs .......... Deerus octagis 3 . Has a tail ........ Deerus pestis Does not have a tail ..... Deerus mg 4 . Has a pointy hump ...... Deerus humpis Does not have a pointy hump.....go to 5 5 . Has ears .........Deerus purplinis Does not have ears ......Deerus deafus
  54. 54. 58 Example of Dichotomous Key 1a Tentacles present – Go to 2 1b Tentacles absent – Go to 3 2a Eight Tentacles – Octopus 2b More than 8 tentacles – 3 3a Tentacles hang down – go to 4 3b Tentacles upright–Sea Anemone 4a Balloon-shaped body–Jellyfish 4b Body NOT balloon-shaped - 5

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