Option G - Ecology and conservation

G.1 The ecology of species

G.1.1 3 Explain the factors that affect the distribution of plant species including temperature, water, light, soil pH, salinity and mineral nutrients.

G.1.2 3 Explain the factors that affect the distribution of animal species including temperature, water, breeding sites, food supply and territory.

G.1.3 3 Analyse the significance of the difference between two sets of data using the Students’ t-test given the appropriate formula and tables.

The t-test can be used to compare two sets of data and measure the amount of overlap. The factors of concern are:

t =                        s²₁ + s²₂

n₁ n₂

x = mean

s = standard deviation

n = number of entries in a set of data

s² = variance

|x ₁ - x ₂| = the positive difference between the two means

Read also notes for 4.5.10 and 4.5.11

Large values of t indicates little overlap and almost certainly a difference between two sets of data. In contrast, a small value of t indicates a lot of overlap and probably no difference. A probability of 0.05 is regarded as significant and a critical value read off from a table.

The t-test should only be used on normally distributed data. Ideally with large samples (> 30 measurements per set of data) and the value of t should be compared with the critical value at T degrees of freedom. For example sizes < 30 the value of t is only approximate and the degrees of freedom is n_{1 +} n₂ – 2. If t 8 critical value then it is possible to reject the null hypothesis.

G.1.4 3 Explain what is meant by the niche concept, in terms of an organism’s spatial habitat, its feeding activities and interactions with other organisms.

Niche is an often misunderstood term. It has been said that whereas ‘habitat’ is an organism’s address, ‘niche’ represents its profession.

G.2 The ecology of communities

G.2.1 3 Explain the following interactions between species, giving two examples of each: competition, herbivory, predation, parasitism and mutualism.

Mutualism is here two members of different species benefit and neither suffers. Examples include, rumen bacteria/protozoa, lichens, and Chlorella/Chlorohydra. There are many others. The other interactions specified are obvious.

Gross production – respiration = net production.

G.2.5 3 Explain the differences in photosynthetic efficiency between tropical forests, temperate forests, deserts and polar ecosystems.

G.3. The ecology of ecosystems

Include ground level ozone as well as the effect of UV light in the stratosphere.

G.3.3 3 Explain the effects of living organisms on the abiotic environment with reference to the changes occurring during primary succession to climax communities including soil development, accumulation of minerals, reduced erosion, altered river flows, and increased rainfall.

G.4 Biodiversity and conservation

G.4.2 2 Outline the factors that caused the extinction of two named animals and one named plant species.

Choose examples other than dinosaurs; some more recent examples: (e.g., Everglades Kite, rainforest species, island species, animals at top of food chains and… the Dodo).

G.4.3 2 Compare the relative biodiversity of biomes including tropical rainforest, temperate forest, desert and tundra.

G.4.4 2 Calculate the index of diversity using the Simpson formula and outline its significance.

D = N(N – 1)

ª n(n – 1)

N = total number of organisms

n = number of individuals per species

It is a measure of species richness. A high value of D suggests a stable and ancient site and low D values could suggest pollution, recent colonisation or agricultural management. It is normally used in studies of vegetation but can also be applied to comparisons of animal (or even all species) diversity.

G.4.5 3 Explain the use of biotic indices and indicator species in monitoring environmental change.

G.4.6 3 Discuss reasons for the conservation of biodiversity including ethical, ecological, economic and aesthetic arguments, using rainforests as an example.

G.4.7 3 Explain the advantages of conservation of endangered species in situ (terrestrial and aquatic nature reserves).

G.4.8 3 Discuss the management of nature reserves including control of alien species, restoration of degraded areas, promotion of recovery of threatened species and control of exploitation by humans.

G.4.9 3 Explain the use of ex situ conservation measures including captive breeding of animals, botanic gardens and seed banks.

G.4.10 3 Discuss the types of action that can take place at national level including data collection, monitoring and legislation.

G.4.11 3 Discuss the importance of surveys of biodiversity, environmental monitoring and environmental impact assessment.

G.4.12 3 Discuss the role of international agencies and measures in conservation including IUCN, the Rio Convention on Biodiversity, CITES, WWF and Red data books.

G-5 Microbial ecology (4h)

G.5.1 1 State that all chemical elements that occur in organisms are part of biogeochemical cycles and that these cycles involve water, land and the atmosphere.

G.5.2 3 Explain that all such cycles summarise the movement of elements through the biological components of ecosystems (food chains) to form complex organic molecules and subsequently into simpler inorganic forms which can be used again.

G.5.3 3 Explain that chemoautotrophs can oxidise inorganic substances as a direct energy source to synthesise ATT.

G.5.4 1 State that chemoautotrophy is found only among bacteria.

G.5.5 1 State that electron donors (substrates) include hydrogen sulfide, ammonia, nitrite ions and sulfur and that electron acceptors (oxidising agents) include oxygen, sulfate ions and nitrate ions (cross reference 9.1.1 and C.5.1).

G.5.6 2 Draw a nitrogen cycle including the process of nitrogen fixation (free-living, symbiotic and industrial), denitrification, nitrification, feeding, excretion, root absorption, and putrefaction (ammonification).

G.5.7 2 Outline the roles of Rhizobium, Azotobacter, Nitrosomonas, Nitrobacter. and Pseadomonas denitrificans.

G.5.8 2 Describe the conditions that favour denitrification and nitrification.

G.5.9 3 Discuss the actions taken by farmers/gardeners to increase the nitrogen fertility of the soil including fertilisers, ploughing/digging and crop rotation (use of legumes).

G.5.10 2 Outline the consequences of releasing raw sewage and nitrate fertiliser into rivers including eutrophication, algal blooms, deoxygenation, increase in biochemical oxygen demand (BOD), and subsequent recovery.

Names of specific organisms are not expected.

G.5.11 3 Analyse quantitative data on biogeochemical cycles.

G.6.1 2 Describe the role of atmospheric ozone in absorbing ultra violet (UV) radiation.

G.6.2 2 Outline the effects of UV radiation on living tissues and biological productivity.

G.6.3 2 Outline the chemical effect that chlorine has on the ozone layer.

G.6.4 3 Discuss methods of reducing the manufacture and release of ozone-depleting substances including recycling refrigerants, reduction of gas-blown plastics and CFC propellants.

G.6.5 2 Outline the origin, formation, and the biological consequences of acid precipitation on plants and animals.

G.6.6 3 Discuss ways to reduce emissions of gases that promote acid precipitation including flue-gas (emissions resulting from the burning materials) and fuel desulfurisation (removal of sulfur), and the use of alternative energy sources.

G.6.7 3 Discuss the advantages and disadvantages of the use of renewable energy sources in various parts of the world including solar, hydroelectric, tidal, geothermal, wind and oceans (tidal, currents and temperature differentials).

G.6.8 1 State that biomass can be used as a source of fuels such as methane and ethanol.

G.6.9 3 Explain the principles involved in the generation of methane from biomass, including the conditions needed, organisms involved and the basic chemical reactions.

G.6.10 2 Outline the damage caused to marine ecosystem by the overexploitation of fish.

G.6.11 3 Discuss international measures that would promote the conservation of fish.