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Topic 4 - Ecology

Topic 4 - Ecology. 4.1 Communities and Ecosystems. 4.1.1 Define: (1) Ecology—the study of relationships between living organisms and between organisms and their environment. Ecosystem—a community and its abiotic environment.

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Topic 4 - Ecology

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  1. Topic 4 - Ecology

  2. 4.1 Communities and Ecosystems 4.1.1 Define: (1) 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. Species—a group of organisms which can interbreed and produce fertile offspring. Habitat—the environment in which a species normally lives or the location of a living organism.

  3. 4.1 Communities and Ecosystems 4.1.2 Explain how the biosphere consists of interdependent and interrelated ecosystems. (3) Biosphere – the thin layer of ecosystems that cover the earth (all of them!)

  4. 4.1 Communities and Ecosystems Interdependence Example: Many ecosystems depend on oxygen from the rain forests, or from algae in the ocean Interrelationship Example: Rising temperatures in the poles resulting in melting of the ice would have great effects on coastal ecosystems all over the world

  5. 4.1 Communities and Ecosystems 4.1.3 Define: (1) autotroph (producer) – organisms that use an external energy source to produce organic matter from inorganic raw materials Examples: trees, plants, algae, blue-green bacteria

  6. 4.1 Communities and Ecosystems heterotroph (consumer) – organisms that use the energy in organic matter, obtained from other organisms Three Types: • consumers • detritivore • saprotroph

  7. 4.1 Communities and Ecosystems • consumers – feed on other living things • detritivore – feed on dead organic matter by ingesting it • saprotroph (decomposer) – feed on dead organic material by secreting digestive enzymes into it and absorbing the products

  8. 4.1 Communities and Ecosystems 4.1.4 Describe what is meant by a food chain giving three examples, each with at least three linkages (four organisms). (2) A food chain is a sequence of relationships between trophic levels where each member feeds on the previous one.

  9. 4.1 Communities and Ecosystems 4.1.5 Describe what is meant by a food web. (2) A food web is a a diagram that shows the feeding relationships in a community. The arrows indicate the direction of energy flow.

  10. 4.1 Communities and Ecosystems 4.1.6 Define trophic level. (1) A trophic level is where an organism is positioned on a food web. Producer Primary consumer Secondary consumer Tertiary consumer

  11. 4.1 Communities and Ecosystems 4.1.7 Deduce the trophic level of organisms in a food chain and a food web. (3) • The student should be able to place an organism at the level of producer, primary consumer, secondary consumer etc, as the terms herbivore and carnivore are not always applicable.

  12. 4.1 Communities and Ecosystems 4.1.8 Construct a food web containing up to 10 organisms, given appropriate information. (3)

  13. 4.1 Communities and Ecosystems 4.1.9 State that light is the initial energy source for almost all communities. (1) • xref- 2.8.2- Photosynthesis • Reference to communities that start with chemical energy is not required. Such as deep sea ocean vents.

  14. 4.1 Communities and Ecosystems 4.1.10 Explain the energy flow in a food chain. (3) • Energy losses between trophic levels include material not consumed or material not assimilated, and heat loss through cell respiration.

  15. 4.1 Communities and Ecosystems 4.1.11 State that when energy transformations take place, including those in living organisms, the process is never 100% efficient, commonly being 10–20%. (1)

  16. 4.1 Communities and Ecosystems 4.1.12 Explain what is meant by a pyramid of energy and the reasons for its shape. (3) • 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 J/m2/yr.

  17. 4.1 Communities and Ecosystems

  18. 4.1 Communities and Ecosystems

  19. 4.1 Communities and Ecosystems 4.1.13 Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled. (3) Energy enters as light and usually leaves as heat. Nutrients do not usually enter an ecosystem and must be used again and again. Nutrients such as Carbon dioxide, Nitrogen, and Phosphorus

  20. 4.1 Communities and Ecosystems 4.1.14 Draw the carbon cycle to show the processes involved. (1) • The details of the carbon cycle should include the interaction of living organisms and the biosphere through the processes of photosynthesis, respiration, fossilization and combustion. Recall of specific quantitative data is not required.

  21. 4.1 Communities and Ecosystems 4.1.15 Explain the role of saprotrophic bacteria and fungi (decomposers) in recycling nutrients. (3) The digestive enzymes secreted by saprophytes breaks down the organic molecules in dead material releasing the nutrients that were ‘locked up’

  22. 4.2 Populations 4.2.1 Outline how population size can be affected by natality, immigration, mortality and emigration. (2)

  23. 4.2 Populations • Natality – offspring are produced and added to the population • Mortality – individuals die and are lost from the population • Immigration – individuals move into the area from somewhere else and add to the population • Emigration – indivuals move out of the area and are lost from the population

  24. 4.2 Populations 4.2.2 Draw a graph showing the sigmoid (S-shaped) population growth curve. (1)

  25. 4.2 Populations 4.2.3 Explain reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases. (3)

  26. 4.2 Populations Exponential Phase Population increases exponentially because the natality rate is higher than the mortality rate. This is because there is an abundance of food, and disease and predators are rare.

  27. 4.2 Populations Transitional Phase Difference between natality and mortality rates are not as great, but natality is still higher so population continues to grow, but at a slower rate. Food is no longer as abundant due to the increase in the population size. May also be increase predation and disease.

  28. 4.2 Populations Plateau Phase Natality and mortality are equal so the population size stays constant. Limiting Factors: shortage of food or other resources increase in predators more diseases or parasites If a population is limited, then it has reached its carrying capacity

  29. 4.2 Populations 4.2.4 Define carrying capacity. (1) The maximum population size that can be supported by the environment

  30. 4.2 Populations 4.2.5 List three factors which set limits to population increase. (1) Limiting Factors: shortage of food or other resources increase in predators more diseases or parasites

  31. 4.2 Populations 4.2.6 Define random sample. (1) In a random sample, every individual in a population has an equal chance of being selected.

  32. 4.2 Populations 4.2.7 Describe one technique used to estimate the population size of an animal species based on a capture-mark-release-recapture method. (2) • Various mark and recapture methods exist. • Knowledge of the Lincoln index (which involves one mark, release and recapture cycle) is required.

  33. 4.2 Populations population size = where . . . • n1= number of individuals initially caught, marked and released • n2 = total number of individuals caught in the second sample • n3 = number of marked individuals in the second sample

  34. 4.2 Populations 4.2.8 Describe one method of random sampling used to compare the population numbers of two plant species, based on quadrant methods. (2)

  35. 4.2 Populations Random sampling of plant species usually involves counting numbers in small, randomly located, squares within the total area. These squares are usually marked with frames called quadrats.

  36. 4.2 Populations 1. mark out gridlines along two edges of the area

  37. 4.2 Populations 1. mark out gridlines along two edges of the area 2. use a calculator or tables to generate two random numbers to be used as co-ordinates. Place a quadrat at the co-ordinates such as 14, 31

  38. 4.2 Populations 2. use a calculator or tables to generate two random numbers to be used as co-ordinates. Place a quadrat at the co-ordinates 3. count how many individuals are inside the quadrat. Repeat 2 and 3 as many times as possible

  39. 4.2 Populations 3. count how many individuals are inside the quadrat. Repeat 2 and 3 as many times as possible 4. Measure the total size of the area occupied by the population, in square meters

  40. 4.2 Populations 4. Measure the total size of the area occupied by the population, in square meters 5. calculate the mean number of plants per quadrat. Then calculate the population size using the following equation:

  41. 4.2 Populations

  42. 4.2 Populations 4.2.9 Calculate the mean of a set of values. (2) mean = sum of values / number of values 5 3 6 7 2 4 6 8 9 10 7 14 18 6 3 5+3+6+7+2+4+6+8+9+10+7+14+18+6+3= 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 108 / 15 = sum of values number of values 108 7.2

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