Interrelationships of Organisms with each other and with their Environment

1. Interrelationships of Organisms with each other and with their Environment

2. The Ecosystem Ecological terms Biome A large, easily recognizable, community unit established by complex interactions of climate, or physical and biotic factors. Habitat A well-defined region with a particular set of environmental conditions

4. Levels of Organization in Ecology Ecosystem a regions communities and their physical surroundings Population a group of interacting and potentially interbreeding organisms Community group of interacting populations

5. The Ecosystem Habitat specific locality where an organism lives Niche describes the �place� of an organism in its environment and the �profession� of an organism No two different species can occupy the same niche

6. The Ecosystem Biotic factors factors of the environment of an organism due to the presence of other living organisms with which it comes into regular contact Abiotic factors physical and chemical factors affecting an organisms

7. Populations and Communities

9. Lag phase: very slow growth with a small number of individuals Exponential phase: grows at an ever increasing rate, provided no factors limits growth since more individuals are available for reproduction

10. Stationary phase: the size of the population stabilizes at a particular level since certain factors now limit further population growth Carrying capacity is the limit to the number of individuals an area can support

11. Death phase: the population decreases because the high population causes the carrying capacity of the environment to decline

12. Logistic Growth in the Real World (restricted growth)

13. population decline and extinctiongrowth = birth rate � death rateif death rate too high -> extinction 99% extinctEffect of human beings!

14. Human population: basic facts

15. The 5 countries with the largest total population

16. Control of Human Populations Human beings are the top organism in many food chains, they have little fear of predators.

18. With advances in food production, technology, etc., the human population has grown virtually unchecked in recent times. The Malthusian principle (1798) states that with the world's food supply to increase arithmetically, the human population would increase geometrically, famine would be inevitable.

19. Carrying capacity: food, space, physical and biological factors

20. Law of the Minimum, is a law developed in agricultural science formulated by Justus von Liebig. It states that growth is controlled not by the total of resources available, but by the scarcest resource

21. Interspecific competition: Paramecium George Gause P. caudatum goes extinct Strong competitors, use the same resource (yeast) Competitive exclusion

22. Potential Outcomes of Competition One species will become extinct Species may coexist because each uses the habitat in different enough ways to survive (microhabitat specialization) Species may evolve differences in niche, reducing competition

23. Predation predators often exert strong control over prey populations as prey become more common, they are more easily preyed upon and vice versa

24. Predator will not eat all prey: Protective mechanism of prey Hide in refuges Prey switching when prey population density is low

26. Example of Population Regulation

29. Primary Producers They are photosynthetic organisms which manufacture organic substances using light, water and CO2. Gross primary product is the rate at which photosynthetic organisms (primary producers) produce organic food per unit area, per unit time. Net primary productivity is the food which is stored (about 80%) and is available to the next link in the food chain, i.e. the primary consumers.

30. Energy flow Input of solar radiation into the biological system Food chain Producers Consumers primary consumers, secondary consumers, scavengers (detritus feeder), Decomposers

31. The type of primary producers varies from habitat to habitat. Chemosynthetic bacteria are also primary producers because they do provide energy for ecosystems, although their energy contribution is very small compared with photosynthesis.

32. Consumers Primary consumers are herbivores. 30% of the energy is absorbed, others being lost as urine and faeces. Most of this 30% is lost as heat, with less than 1% incorporated into the body of primary consumers and so made available to the secondary consumers - the carnivores. Carnivores incorporate twice as much energy as herbivores into their bodies because their protein-rich diet is much more easily digested. Parasites and scavengers are also consumers.

33. Decomposers and Detritivores Decomposers then release valuable nutrients like carbon, nitrogen which may then be recycled. Organic chemicals in faeces, urine & wastes are also decomposed by decomposers. Detritivores are a group of animals which feed on detritus - organic debris (small fragments) from decomposing plants and animals. Differences between detritivores & decomposers: Detritivores are usually larger and have internal digestion rather than external digestion, e.g. earthworms, maggots, sea cucumbers.

35. Energy loss along the food chain heat energy of respiration Products of excretion and egestion Death and decay of organisms Results?

37. Ecological Pyramid Pyramid of energy shows energy flows through the trophic levels of a community Pyramid of numbers shows the number of organisms at each trophic level in a community Pyramid of biomass shows the mass or organisms at each trophic level

38. Pyramid of Energy - most accurate An energy of pyramid overcomes the disadvantages of the other forms of ecological pyramid. Here the horizontal bar is drawn in proportional to the total energy utilized at each trophic level. The total productivity of the primary producers of a given area (m2) can be measured for a given period (1 year). From this, the proportion of it utilized by the primary consumer can be calculated, and so on up the food chain. DRAWBACK: to get the necessary data can be very complex and difficult.

39. Ecological Pyramids - easy and simple method Pyramid Of Numbers - size of block represents number of organisms at that trophic level The use of pyramids of numbers has drawbacks: 1. All organisms are counted regardless of their sizes. Both an oak tree and an aphid are counted as an individual. 2. The young which eats less is also counted as one. 3. The number of individuals are so great that it is impossible to represent on the same scale as other species in the food chain.

40. Some different shaped pyramids: Oak tree ?? sphid ?? ladybird This bulges in the middle. Sycamore?? caterpillar ?? protozoan parasites(of the caterpillar) This is an inverted pyramid.

41. Pyramid Of BIOMASS by estimating the total mass of organisms at each trophic level by measuring the dry mass of a sample of organisms. The relative biomass is represented by bars of proportionate length.

42. Drawbacks: 1 It is impossible to measure the biomass of all individuals in a population. The small sample taken is not representative. 2 The time at which a sample taken may affect the result. For example: Figures for a deciduous tree in summer and winter, the standing crop gives no indication of total productivity. A young tree with many years of growth has no offspring if no seeds are produced; whereas a small diatom may have produced many times the tree�s biomass in the same period of time.

43. A diatom may have produced many times the tree's biomass in the same period of time BUT GIVES AN INVERTED PYRAMID OF BIOMASS: In oceans at certain times of the year zooplankton biomass exceeds phytoplankton biomass, although over the year as a whole the reverse is true.

45. Food web Shows the feeding relationships of a community more fully than do food chains Consists of interconnected food chains.

46. 2006

49. Past paper 2006 Q. 12

50. 2006, Paper I, Q.12 (a)

51. 2006, Paper I, Q.12 (a) Concept for mark award Title (�) Labelling of axes �, �) Unit (�) Good use of scale (�) Bar chart for each pollutant correctly plotted (1,1) Key (�)

52. 2006, Paper I, Q.12 (b) Concept for mark award Correct feeding sequence (2) C ? E ?D? A (1)

53. 2006, Paper I, Q.12 (c) Levels of both pollutants increases along the food chain (1) Due to bioaccumulation effects (1) Both pollutants cannot be easily degraded / excreted (1), thus they stay in the body of organisms Organisms at each trophic level feed on a large number of organisms in the preceding trophic level (1) (any 2 of the last three point)

54. 2006, Paper I, Q.12

55. 2006, Paper I, Q.12 (ii) For A, the RQ of both pollutant is greater than 1, for D, the RQ of mercury also exceeds 1, the survival of these organisms is threatened by the pollutants in the conservation area (1) The survival of B and E is not threatened as the RQ of the pollutants are below 1 (1) If A and D die, organisms at the lower trophic levels will increase in number (1), thus upsetting ecological balance This would cause a change in the community composition in the conservation area (1) / biodiversity in the area decreases as a result of the removal of A and D.

56. The Cycling of Nutrients Energy exists in many forms, only some of them can be utilized by living organisms. In an ecosystem, energy is obtained as light and this is converted to chemical energy which passes along the food chain. Energy is lost as 'heat' to the environment AND CANNOT BE RE-USED (or recycled) BY ORGANISMS.

57. Minerals, however, can be recycled in two components: 1. A geographical component - rock & deposits in oceans and atmosphere 2. A biological component - organisms which convert one form of the mineral to another and so recycle it. It includes producers, consumers and decomposers.

59. The Carbon Cycle Plants absorb atmospheric CO2 to form living materials of plants by photosynthesis. Living materials are then transferred to bodies of other organisms in the food chain. Then through respiration and decomposition, CO2 is formed again. Thus there is a continuous recycling of CARBON between the atmosphere and living organisms, atmospheric CO2 being relatively constant.

62. The Nitrogen Cycle 1. nitrogen-fixing bacteria in root nodules of leguminous plants: N2 ?? NO3- (free nitrogen-fixing bacteria & nitrogen-fixing blue-green bacteria could perform the same activity) For the synthesis of proteins from carbohydrates in plant cells 2. putrefying bacteria: proteins ?? NH3 3. nitrifying bacteria: NH3 ?? NO2- ?? NO3- (nitrification to release energy - chemosynthesis) 4. denitrifying bacteria: NO3 - ?? N2 (under anaerobic conditions - farmers dig up their soils to avoid this)

63. Concept map exercise

64. H.W. Ch. 11, P. 293, Q.7, Q. 11 Hand in next Monday

68. Interdependence of organisms Symbiosis Mutualism both organisms are benefited. Commensalism one of the two organisms benefits, while the other neither loses nor gains.

69. Interdependence of organisms Antagonism Parasitism The host is harmed by the parasite, but is usually not killed by it. Predation one species (the predator) attacks and kills another species (the prey). Competition when two types of organisms live together in the same habitat require the same materials from the environment, their presence strongly affect one another.

70. Succession Change in the species found in a community over time Primary succession is the progressive colonisation of a previously unoccupied area. Secondary succession begins in a area which has been previously colonised. The end point is known as a climax community.

71. Communities change over time: Succession Many communities show predictable changes in species composition over time species alter their environment in ways that may reduce their own success Stages of succession primary (on newly formed land) secondary (reestablishment after destruction)

72. Species composition changes continually species diversity increases and then levels off productivity increases with stage proportion of nutrients bound up in biomass increases until most is in biomass of plants

73. Wetland ecology (Mai Po) http://online.wwf.org.hk/booking/en/info.html?type=ST#17

74. Sampling Methods It is virtually impossible to identify and count every organism in a habitat. For this reason only small sections of the habitat are usually studied in detail to represent the whole area. Sampling techniques are used:

75. Quadrats a sturdily built wooden frame, can be folded for easy transport and storage

76. Quadrats - When placed on the ground, the species present within the frame are identified and their abundance recorded - Sampling could be random or systematic

77. Line Transect - useful where a transition of flora and/or fauna occurs - a string or tape is stretched out along the ground in a straight line; record the organisms touching or covering the line all along its length or at regular intervals - Profile transect: when there is appreciable height change along the transect and thus affecting the distribution of its species

78. Belt Transect It is a strip, usually a metre wide, marked by putting a second line parallel to the other. The species between the lines are carefully recorded, working a metre at a time.

79. Point Frames - for grassland field study of dense vegetation

80. Collecting Methods Collecting all organisms within a habitat is normally impractical and therefore small areas are selected. Remember to return all material to its original position after searching & collecting sufficient specimens. Some collecting apparatus for general use are listed below:

81. 1. specimen tube 2. screwed-topped jars 3. polythene bags 4. forceps 5. paint brush 6. bulb pipette 7. pooter

82. 8. widger 9. sieve 10. hand lens 11. enamel dish 12. beating tray 13. light traps 14. Tullgren funnel 15. Baermann funnel 16. mammal traps 17. pitfall traps 18. netting

83. Estimating Population Size The exact methods used for estimation depend not only the nature of the habitat but also on the organisms involved, e.g. animals - population ; plants - percentage cover

84. Using Quadrats - By sampling an area using quadrats and counting the number of individuals within each quadrat, it is possible to estimate the total number of individuals within the area confined to plants and sessile, or very slow-moving animals; fast-moving animals are disturbed and run away

85. Class exercise Design an experiment to estimate the no. of students in TWGSS. Assuming you don�t know about the class size, no. of classes and the students are wandering about in the campus.

86. procedure Set some traps to capture the students Count the no. of students captured Tag the students and release them Sometimes later, set the traps again Count the no. of students captured and no. of captured students having the tag

87. Capture-recapture Techniques - useful for mobile animals which can be marked - capture, marked, released, randomly recaptured and marked individuals recorded

88. Assumption There is no. change in the population in-between the 2 captures Tagging will not affect the chance of being caught

89. Capture-recapture Techniques Factors affecting the accuracy of the estimation: deaths, migration, individuals become more liable to predation, etc. Examples: arthropods marked on their backs with non-toxic paint, fish have tags attached to opercula, mammals have tags clipped to their ears, birds have their legs ringed

90. Abundance Scales The population size may be fairly accurately determined by making some form of frequency assessment. These are subjective and involve an experimenter making some estimate of the number of individuals in a given area, or the % cover of a particular species. This is especially useful where individuals are very numerous, e.g. barnacles on a rocky shore, or where it is difficult to distinguish individuals, e.g. grass plants in a meadow.

91. The assessments are usually made on an abundance scale of 5 categories: Abundance, Common, Frequent, Occasional, Rare.

92. S.7 Mock 09-10 5. (a) Describe the main features of an ecological succession. (5 marks) (b) Daisies are small flowering plants. Describe how you would estimate the number of daisies growing in a playing field. (6 marks) (c) Describe how you would use the mark-release-recapture technique to estimate the number of small mammals in an area of woodland. (4 marks) (d) In fishponds, ammonium ions are produced by the fish. Bio-filters may be used to remove these ions from the water. The microorganisms in the bio-filter can convert the ammonium ions to nitrate thus increasing the nitrate content in water. However, some nitrates will be changed to nitrogen gas. Describe how microorganisms produce (i) nitrates (3 marks) (ii) nitrogen gas. (2 marks) Total: 20 marks

93. (b) 1 Use of quadrats; 2 Grid created / co-ordinates; 3 Random; 4 From calculator / random number tables / random number generator; 5 Count number in each quadrat; 6 Obtain average; 7 Multiply by area of field; 6 max