Option G

1. Option G Ecology and conservation

2. G. 2. 1 Define gross production , net production and biomass • Biomass- total dry mass or organic matter in organisms or ecosystems. • How it is done. • Gather living organisms in an ecosystem using random sampling. • Sort into trophic levels • Dry organism in an oven at 60-80 degrees Celsius • The mass for each trophic level is taken using a balance. • Dry and re-measure to make sure all of the water has been taken out. • Very destructive this is why a small sample is taken.

3. G. 2. 1 and G. 2.2 • Gross production – the total amount of organic matter produced by plants in an ecosystem. • Net production – amount of gross production in an ecosystem remaining after subtracting the amounted used by plants in respiration. • NP= GP – R • NP = Net production GP= gross production R=respiration

4. Question …. • Ecologists sometimes measure the gross production and net production of a species in an ecosystem. (a) Define the term gross production. (1) (b) Explain why the gross production of a species in an ecosystem is always higher than the net production. (2)

5. Answer … • total amount of energy / CO2 fixed by photosynthesis / plants / organic matter produced; 1 • (b) net production is gross production minus respiration;all species respire; 2

6. Question …. • The total solar energy received by a grassland is 5 × l05 kJ m–2 y–1. The net production of the grassland is 5 × 102 kJ m–2 y–1 and its gross production is 6 × l02 kJ m–2 y–1. The total energy passed on to primary consumers is 60 kJ m–2 y–1. Only 10% of this energy is passed on to the secondary consumers. (a) Calculate the energy lost by plant respiration.(2) (b) Construct a pyramid of energy for this grassland.

7. Answer Plant respiration = gross production – net production / 6 × 102 kJ m–2 y –1 – 5 × 102 kJ m –2 y –1;= 1 × 102 / 100 kJ m–2 y –1; 2Units required. (b)correct pyramid shape; Award [2 max] if there are units omitted. Award [2 max] if a bar is included forthe solar energy. Do not deduct marks if the areas of the bars are not proportionalto the values, although they should get smaller going up.[5]

8. G. 2. 3 Difficulties of classifying organisms into trophic levels. • Why is it hard to classify organisms into their trophic level and get biomass? • Occupy more than one trophic level. • Euglena – autotroph and heterotroph • Chimpanzee – eat main plants put also are top level consumers • Herring – 1st and 2nd level • Oysters – 1st and 2nd level

9. Question • Discuss, giving named examples, the difficulties of placing organisms in higher trophic levels. (5)

10. Answer • in food webs organisms often occupy two levels / eat at different trophic levels;some organisms eat prey from different trophic levels;not all feeding habits of all organisms are known;feeding habits may vary seasonally / during life cycle;eg chimpanzees feed on fruit, termites and monkeys / other examples;second example;as you move up the food chain, less energy is available / only 10–20% of energy ispassed to the next trophic level;broad diet to ensure adequate energy intake; [4]

11. G. 2.4 Small biomass and low numbers of organisms at higher trophic levels The energy content per gram of food decreases along the food chain. The total biomass of food available to the higher trophic levels are low. It can only support a few apex predators. High trophic levels contain small numbers of large organisms, with a low total biomass per unit area.

12. G.2.6 Distinguish between primary and secondary succession • Primary succession - an environment where living organisms have not previously existed. Land after volcanic eruption • Secondary succession – occurs in areas where an ecosystem is present, but is replaced by other ecosystems, because of an change in environmental conditions. Abandoned farmland, forest fire.

13. G. 2.7 Outline changes in species diversity and production during primary succession Initially low biodiversity, many producers small consumers. The amount of organic matter in the soil increases as organisms die. The soil becomes deeper helps bind minerals together. The soil structure improved to hold more water. Soil erosion reduced since roots are in place to hold soil in place. Amount of minerals recycled increases as soil can hold more minerals.

14. G.2.9 Distinguish between biome and biosphere Biome – type of ecosystem with similar temperature, rainfall and dominant flora and fauna. Biosphere – all of the biomes together makes up biosphere, this is where all life can be found on the planet.

15. G. 2. 11 how rainfall and temperature affect biome distribution.

16. G. 2.11 characteristics of six major biomes

17. G. 3. 1 Calculate the Simpson diversity index.

18. G. 3. 3 Discuss reasons for the conservation of biodiversity using the rainforest as an example Economic reasons • New commodities, new medicines, materials can be found • Ecotourism Ecological reasons • fix large amounts of CO2 and without increase greenhouse effect and greenhouse gases • Soil erosion, silt up river, flooding changes in weather patterns Ethical • Every species has the right to life • Cultural important to indigenous people Aestheitc • Beautiful species • Inspiration to writers, poets and painters.

19. G. 3. 4 list three examples of introduction of alien species that have had significant impacts on ecosystems. • Floating fern – takes over lakes, aquarium or pond plant. • 3 species of rats have introduced New Zealand during the 19th century. Causes extinction of native bird species. Big South Cape Island was rat-free until 1950 when the black rate came took over, attacked young birds in nest even adult birds. • Cain toads in australia

20. G. 3. 5 Discuss the impacts of alien species on ecosystems.

21. G. 3. 6 Outline one example of biological control of invasive species • Floating fern was introduced into lakes in tropic and subtropic. Doubles number of leaves every two weeks. Spreads over lake, preventing native species from growing. It has been controlled by introducing an alien species salviniaweevel.

22. G. 3. 7 Define biomagnification • The process by which chemical substances become more concentrated at each trophic level.

23. G. 3. 8 Explain the cause and consequences of biological control of invasive species. • Cane toads in Australia – brought in to eat insects attacking cane sugar, no predator, cane toads got out of control and become a highly invasive species.

24. G. 3. 9 Outline the effects of ultraviolet radiation on living tissues and biological productivity. • Increase mutation rates, causing damage to DNA • Cause increase in cancer • Cause severe sunburns, cataracts of eye • Reduced photosynthesis rates in plants and algae and so affects food chains

25. G. 3. 10 Outline the effect of chlorofluorocarbons (CFCs) on the ozone layer. • CFCs the main cause of ozone depletion. • UV light causes CFC s to disassociate and release atom of chlorine. • These chlorine atoms are highly reactive and cause ozone to convert to oxygen. • One chlorine atom can potentially cause the destruction of hundreds of thousands of ozone molecules.

26. G. 3. 11 State ….. That ozone in the stratosphere absorbs UV radiation.

27. G. 5. 1 distinguish between r-strategies and k-strategies • r-strategies – unstable environment – most successful are r-strategies. Only growing small body size. Mature early so reproduce at young age. Reproduce once. Produce many offspring. Give little to no parental care. Ex. Poppy, lemmings, herring • K-strategies- stable environment favored • Large animals, maturing late, reproduce more than once. Produce few offspring but care for young. • Ex. Tree, elephant, turtle

28. G. 5. 2 Discuss environmental conditions that favour either r-strategies or k-strategies

29. G. 5. 3 Describe one technique used to estimate the population size of an animal species based on capture, mark, release, recapture.

30. G. 5. 5 Outline the concepts of maximum sustainable yield in the conservation of fish stocks • Sustainable use of renewable resources means harvesting at a rate that avoids decline of the population. • Maximum sustainable yield – is the largest amount that can be harvested without a decline in stocks.

31. G. 5. 6 Discuss international measures that would promote the conservation of fish. • Monitoring of stocks and of reproduction rates. • Quotas for catches of species with low stocks. • Closed seasons in which fishing is not allowed, especially during the breeding season. • Exclusion zones in which fishing banned. • Moratoria on catching endangered species. • Minimum net sizes so that immature fish are not caught. • Banning of drift nets which catch many different scpies fish indiscriminately.

32. G. 5. 4 Describe the methods used to estimate the size of commercial fish stocks • Collecting data on fish caught. • Numbers and age of fish caught are analyzed. • Capture, mark, release, recapture, internal or external tagging. • Echo sounders