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IB Biology Assessment Statements: Unit 7 option g
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IB Biology Assessment Statements: Unit 7 option g


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  • 1. Unit 5: Ecology and Evolution Lesson 5.1 Communities and Ecosystems
  • 2. 5.1 Communities and Ecosystems
    • Ecology—the study of relationships between living organisms and between organisms and their environment.
    • Ecosystem—a community and its abiotic environment.
    • Population—a group of organisms of the same species who live in the same area at the same time.
    • Community—a group of populations living and interacting with each other in an area.
    • Habitat—the environment in which a species normally lives or the location of a living organism.
    • Species—a group of organisms which can interbreed and produce fertile offspring.
  • 3. 5.1.2a Distinguish between autotroph and heterotroph.
    • autotroph (producer) – an organism that synthesizes its organic molecules from inorganic substances
    • Examples: trees, plants, algae, blue-green bacteria
  • 4. 5.1.2b Distinguish between autotroph and heterotroph. heterotroph (consumer) – an organism that obtains organic molecules from other organisms Three Types: consumers detritivore saprotroph
  • 5. 5.1.3 Distinguish between consumers, detritivores and saprotrophs .
    • Consumer - obtain nutrients from other living organisms
      • Decomposer – obtain nutrients from dead organic matter.
      • Detritivore - ingests organic matter and then breaks it down, eg. earthworms, vultures.
      • Saprotroph- secretes enzymes externally and then absorbs broken down products, eg. mushrooms, bacteria.
  • 6. 5.1.4 Describe what is meant by a food chain giving three examples, each with at least three linkages (four organisms).
    • Food chains illustrate feeding relationships between members of a community.
    • One food chain in this picture is: plankton -> fish -> seagull -> eagle
    • What other food chains do you observe in this picture?
  • 7. 5.1.5 Describe what is meant by a food web.
    • Food webs, like food chains, show the feeding relationships between community members. Food webs are non-linear and branching.
  • 8. 5.1.6 Define trophic level .
    • Trophic level- the level of the food chain at
      • which an organism is found. The hierarchal levels are shown below:
    • producer -> primary consumer -> secondary consumer -> tertiary consumer
  • 9. 5.1.7 Deduce the trophic level of organisms in a food chain and a food web.
    • Photosynthetic organisms are always producers. With each arrow, consumers move one generation away from the producer, eg. primary consumer, secondary consumer, tertiary consumer. When consumers (and producers) die they are decomposed, and their nutrients recycled.
  • 10. 5.1.8 Construct a food web containing up to 10 organisms, given appropriate information.
  • 11. 5.1.9 State that light is the initial energy source for almost all communities .
  • 12. 5.1.10 Explain the energy flow in a food chain.
    • Energy losses between trophic levels include material not consumed or material not assimilated, and heat loss through cell respiration.
  • 13. 5.1.11 State that energy transformations are never 100% efficient.
    • When energy transformations take place, including those in living organisms, the process is never 100% efficient. Commonly, it is between 10-20%.
  • 14. 5.1.12 Explain what is meant by a pyramid of energy and the reasons for its shape.
    • A pyramid of energy shows the flow of energy from one trophic level to the next in a community. The units of pyramids of energy are therefore energy per unit area per unit time, eg: Jm-2yr-1
  • 15. 5.1.13 Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled.
  • 16. 5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients.
    • During metabolism, living organisms build organic macromolecules in the form or polymers. Saprotrophs break down these polymers into monomers, so that they can be customized into new, specific polymers beneficial to the next organism which ingests them.
  • 17. Unit 5: Ecology and Evolution Lesson 5.2 The Greenhouse Effect.
  • 18. 5.2.1 Draw and label a diagram of the carbon cycle to show the processes involved .
  • 19. 5.2.2 Analyze the changes in concentration of atmospheric carbon dioxide using historical records.
  • 20. 5.2.3 Explain the relationship between rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced green house effect.
    • Greenhouse gases help retain atmospheric heat generated from solar radiation. As man made behaviors (deforestation, burning of fossil fuels) increase greenhouse gas levels, the warming effect is amplified beyond what occurs in the natural cycle.
  • 21. 5.2.4 Outline the Precautionary Principle
    • If an action is potentially catastrophic, the burden of proof falls upon the advocates of such action to prove that the catastrophe won’t occur before such action is implemented.
  • 22. 5.2.5 Evaluate the precautionary principle as a justification for strong action in response to threats posed by the enhanced greenhouse effect.
    • Consider whether the economic harm of measures taken now to limit global warming could be balanced against the potentially much greater harm for future generations of taking no action now?
    • What are your thoughts?
  • 23. 5.2.6 Outline the consequences of a global temperature rise on arctic ecosystems.
    • Melting of ice shelves, resulting in a global rise in sea level
    • Disruption arctic food chains with potential species extinction.
    • Release of carbon from organic matter in previously frozen soil.
  • 24. Unit 5: Ecology and Evolution Lesson 5.3 Populations
  • 25. 5.3.1 Outline how a population size can be affected by natality, immigration, mortality and emigration .
    • Natality- birth rate.
    • Mortality - death rate.
    • I mmigration - # members moving in.
    • Emigration- # members moving out.
      • Population change =
      • (natality + immigration) – (mortality + emigration)
  • 26. 5.3.2 Draw and label a graph showing the sigmoid (S-shaped) population growth curve.
  • 27. 5.3.3 Explain reasons for the exponential growth phase, the plateau phase and the transitional phase between the two.
    • Exponential phase :
    • Rapid increase in population growth.
    • Natality rate exceeds mortality rate.
    • Abundant resources available. (food, water, shelter)
    • Diseases and predators are rare .
  • 28.
    • Transitional phase :
    • Natality rate starts to fall and/or mortality rate starts to rise.
    • There is a decrease in the number of resources.
    • An increase in the number of predators and diseases.
    • Population still increasing but at a slower rate.
  • 29.
    • Plateau phase:
    • No more population growth, population size is constant. 
    • Natality rate is equal to mortality rate.
    • The population has reached the carrying capacity of the environment. 
    • The limited resources and the common predators and diseases keep the population numbers constant.  
  • 30. 5.3.4 List three factors which set limits to population increase.
  • 31. Option G: Ecology and conservation G1 Community ecology
  • 32. G 1.1 Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, salinity and mineral nutrients.
  • 33. G 1.2a Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory.
  • 34. G 1.2b Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory.
  • 35. G 1.3 Describe one method of random sampling, based on quadrat methods, that is used to compare the population size of two plant or two animal species.
  • 36. G 1.4 Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable
    • Distribution of Organisms:
      • quadrants are distributed equal distance from each other.
      • The species of interest are identified and counted.
      • The abiotic factor being investigated is measured.
      • Pattern of distribution is determined based upon data .
  • 37. G 1. 5 Explain what is meant by the niche concept, including an organism’s spatial habitat, its feeding activities and its interactions with other species.
    • Niche Concept :
    • What?: Organism’s role in the ecosystem
      • Who?: Interactions with other organisms
        • Competition
        • Predation
        • Mutualism
      • Where?: Spatial habitat is the area inhabited by the organism and how it affects it.
      • Why? Presence of organisms keep populations in check by their feeding activities .
  • 38. G 1.6 Outline the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism.
  • 39. Predation : A consumer (+) eats another consumer(-). Each population size affects the other. Competition: Two species rely on the same limited resource. (-,-)
  • 40. Mutualism : Both organisms benefit from the relationship. (+,+) Parasitism: Organism (+) that lives in or on another organism or host (-)
  • 41. G 1.7a Explain the principle of competitive exclusion.
    • The principle that when two species compete for the same critical resources within an environment
      • one of them will eventually outcompete and displace the other
        • the displaced species may become locally extinct, by either migration or death, or it may adapt to a sufficiently distinct niche within the environment so that it continues to coexist noncompetitively with the displacing species
  • 42. G 1.7a Explain the principle of competitive exclusion.
  • 43. G 1.8 Distinguish between fundamental and realized niches.
  • 44. growth rate Location in intertidal zone low high middle Chthamalus alone Balanus alone Fundamental Niche- where an organism is able to inhabit WITHOUT competition. Removal experiments – remove each species and see where the other grows Balanus fundamental niche Chthamalus fundamental niche
  • 45. growth rate Location in intertidal zone low high middle Realized Niche- where an organism is able to inhabit WITH competition. Where do they grow when allowed to compete? Balanus realized niche Chthamalus realized niche Balanus and Chthamalus
  • 46. G 1.9 Define biomass .
    • The total dry mass of organic matter in an ecosystem.
  • 47. G 1.10 Describe one method for the measurement of biomass of different trophic levels in an ecosystem.
  • 48. Option G: Ecology and conservation G2 Ecosystems and biomes
  • 49. G 2.1 Define gross production , net production and biomass
  • 50. G 2.2 Calculate values for gross production and net production using the equation: gross production – respiration = net production.
  • 51. G 2.3 Discuss the difficulties of classifying organisms into trophic levels.
  • 52. G 2.4 Explain the small biomass and low numbers of organisms in higher trophic levels.
  • 53. G 2.5 Construct a pyramid of energy, given appropriate information. RULE OF 10
  • 54. G 2.6 Distinguish between primary and secondary succession, using an example of each
    • Primary Succession
    • Secondary Succession
    Click for explanation
  • 55. G 2.7 Outline the changes in species diversity and production during primary succession.
  • 56. G 2.8 Explain the effects of living organisms on the abiotic environment, with reference to the changes occurring during primary succession .
  • 57. G 2.9 Distinguish between biome and biosphere .
  • 58. G 2.10 Explain how rainfall and temperature affect the distribution of biomes.
  • 59. G 2.11 Outline the characteristics of six major biomes.
  • 60. Option G: Ecology and conservation G3 Impacts of humans on ecosystems
  • 61. G 3.1 Calculate the Simpson diversity index for two local communities.
  • 62. G 3.2 Analyze the biodiversity of the two local communities using the Simpson index.
  • 63. G 3.3 Discuss reasons for the conservation of biodiversity using rainforests as an example
  • 64. G 3.4 List three examples of the introduction of alien species that have had significant impacts on ecosystems.
    • Purple loosestrife :
    • a highly aggressive plant invader of wetlands, can produce up to 2.7 million seeds per plant yearly, and spreads across approximately 480,000 additional hectares of wetlands each year. Ecosystem upset, since local fauna does not eat the plant.
  • 65.
    • The brown tree snake: an invasive originating in the South Pacific and Australia, has extirpated 10 of 13 native bird species, 6 of 12 native lizard species, and 2 of 3 bat species on the island of Guam.
  • 66.
    • The fungus, Ophiostoma ulmi , the pathogen that causes Dutch elm disease , and the  bark beetle , which carries the pathogen, were both introduced to the United States from Europe on infected wood. The combination of these two organisms has caused the destruction of millions of elm trees (EXTINCTION)
  • 67. G 3.5 Discuss the impacts of alien species on ecosystems.
  • 68. G 3.6 Outline one example of biological control of invasive species.
    • Sometimes introducing a natural enemy from the native range of the introduced pest can be effective.
    • Prickly pear cactus that invaded Australia from the Americas has been effectively controlled by introducing a moth from South America whose caterpillar feeds on the cactus.
    • Moth larva threatens native cactus species
  • 69. G 3.7 Define biomagnification .
    • Biomagnification is the process whereby the tissue concentrations of a contaminant increase as it passes up the food chain through two or more trophic levels
  • 70. G 3.8 Explain the cause and consequences of biomagnification, using a named example.
  • 71. G 3.9 Outline the effects of ultraviolet (UV) radiation on living tissues and biological productivity.
  • 72. G 3.10 Outline the effect of chlorofluorocarbons (CFCs) on the ozone layer.
  • 73. G 3.11 State that ozone in the stratosphere absorbs UV radiation.
  • 74. Option G: Ecology and conservation G4 Conservation of biodiversity
  • 75. G 4.1 Explain the use of biotic indices and indicator species in monitoring environmental change.
    • Indicator species are plants and animals that, by their presence, abundance, lack of abundance, or chemical composition, demonstrate some distinctive aspect of the character or quality of an environment.
    Studies in the United States show declines in spotted owls are matched by declines in other fragile species such as salamanders, frogs, some plants and other predators.
  • 76. G 4.2 Outline the factors that contributed to the extinction of one named animal species. Climate Change Retreating Glaciers/Warmer Temp. WOOLY MAMMOTH Loss of Habitat Forests outcompeted mammoth’s shrub food. Humans Inhabit newly exposed land in now favorable climate Over Hunting by humans
  • 77. G 4.3 Outline the biogeographical features of nature reserves that promote the conservation of diversity.
    • Determination of Size-
      • Single Large Site
        • Larger populations
    • Edge Effect
      • Smaller area on the “edge”
        • Higher risk of predators,
        • greater competition and
        • invasive species
    • Corridors
      • Connect isolated habitats.
        • Allows for travel between habitats.
  • 78. G 4.4 Discuss the role of active management techniques in conservation.
    • When humans intervene in the conservation of an area to restore areas and protect native species.
  • 79. G 4.5 Discuss the advantages of in situ conservation of endangered species (terrestrial and aquatic nature reserves).
  • 80. G 4.6 Outline the use of ex situ conservation measures, including captive breeding of animals, botanic gardens and seed banks.
  • 81. Option G: Ecology and conservation G5 Population ecology
  • 82. G 5.1 Distinguish between r-strategies and K-strategies .
  • 83. G 5.2 Discuss the environmental conditions that favor either r-strategies or K-strategies.
  • 84. G 5.3 Describe one technique used to estimate the population size of an animal species based on a capture–mark–release–recapture method.
  • 85. G 5.4 Describe the methods used to estimate the size of commercial fish stocks.
    • Study catches :
      • Species/Age/Length/Breeding Conditions
    • Information from Fishers :
      • Number and kinds of fish thrown back.
      • Tag and release
      • Perception of catch
    • Research Vessels :
      • Trawling assessing random samples.
      • Echolocation to monitor populations
  • 86. G 5.5 Outline the concept of maximum sustainable yield in the conservation of fish stocks . OVER FISHING CONSERVATION
  • 87. G 5.6 Discuss international measures that would promote the conservation of fish.