10.1 Hunter–gatherers: human population numbers low and scattered. Little impact on the environment.
Domestication of some animals: semi-permanent dwellings and nomadic shepherds. More impact on the environment as accumulation of wastes in one spot whilst dwelling in that area, and possibly some felling of trees to make shelters.
Clearing of land to provide pastures for flocks, leading to more permanent residence in an area. Destruction of forests for pastures and dwellings. Overgrazing, loss of soil fertility and increasing erosion probable in some areas as the number of stock becomes a symbol of wealth.
Cultivation of the land for growing more food. People less dependent upon whims of nature for food. More permanent dwellings. Division of labour amongst population in an area and the start of permanent towns. Thus increased clearing for dwellings and farming. Increased waste accumulation in a particular place. With farming, industrial and scientific revolutions, there have been increases in populations, most gathered in large urban areas. Major areas of pollution are concentrated in spots related to specific activities – farming, mining, industry and dwelling. Most of these areas are close to some waterway and so the effects of human populations become spread, causing environmental damage far from the site of activity.
10.2 The inputs of light, organic matter and mineral salts are the same in a natural and an agricultural ecosystem but an agricultural system also has fertilisers and pesticides as well as requiring more water. Heat output is similar in both systems but agricultural systems have an increased organic matter and water output as well as outputting nutrients and soil particles
(from erosion). There is a lot more recycling of matter in a natural system than in an agricultural system (much organic matter is transported away to other areas; pesticides can kill many decomposer organisms). The natural ecosystem is more balanced since the amount of organic matter and water taken up by the system is approximately the same as that given out.
10.3 The types and number of inputs are more varied than in an agricultural system, and a large amount of waste, heat and carbon dioxide is generated. The amount of recycling is minimal.
10.4 There is decreased uptake of rainwater by plants, resulting in a raised water table which becomes saline due to leaching of mineral salts as the water passes through the soil and dissolves mineral salts. Since transpirational water loss by plants is also decreased, the water table also rises. Erosion increases without large plants such as trees to bind the soil with their roots. Soil along river flats becomes saline, causing plants to die and this also adds to erosion problems. River systems become more turbid as a result of the increased silt from erosion and salt from leaching of the soil, making the waterways inhospitable for many freshwater species.
10.5 Prevention of overgrazing; cultivation of soil-binding pastures; unrestricted movement of stock in large areas; contour ploughing; crop rotation; leaving stubble in soil between plantings; planting rows of trees between paddocks.
10.6 Wheatfield. The removal of trees from the slope leading down to the river means that there will be a decrease in transpirational water loss and thus leaching of the minerals in the soil and raising of the water table. The river flats are likely to become saline and result in death of the wheatfield. This will then be subject to erosion. The upper ploughed fields are contour ploughed, decreasing the likelihood of water erosion although wind erosion is still highly likely between plantings. The grassland probably has sufficient root binding to prevent both water and wind erosion provided it is not overgrazed and there are no hardened tracks due to stock movement.

10.7 They are deep and thus light does not penetrate; the water is only warm in the surface layers.
There is little mixing of water thus oxygen is low in the depths and nutrients accumulate at the bottom where producers cannot utilise them. Siltation from erosion of surrounding areas can build up and clog the feeding and respiratory surfaces of many animals.
10.8 They are the breeding grounds for many freshwater fish. Annual inundation with flood waters is necessary for the survival of many plant species surrounding wetlands. These trees provide food and shelter for a variety of species.
10.9 The large amount of water provided by irrigation percolates through the soil, dissolving mineral salts as it goes (many of which are provided by fertilisers). Thus the ground water becomes saltier and the water table is raised. As the surface waters evaporate they leave a high salt concentration in the surface soils. The raised water table leads to an increased output of water into river systems. Since the ground water has increased salinity, so too will the salinity of the river system be raised.
10.10 Eutrophication is a natural process whereby nutrients are built up in a body of water due to run off from adjoining land.
10.11 Increased use of fertilisers can raise the levels of nutrients in freshwater systems so that there is an imbalance between producers and consumers. Plant growth increases rapidly. Since carbon dioxide is more soluble in water than oxygen, much of the oxygen produced by photosynthesis is lost from the system. Thus at night there is inadequate oxygen for plant and animal respiration. Many organisms die, leading to an increase in decomposers which further deplete the oxygen supply, leading to more deaths of organisms.
10.12 Different species have different habitat requirements. The area left by fragmentation may be too small to support a particular species. The edges of the habitat fragment are subject to greater light and wind, making it inappropriate for other species to live there. The ability of the organism to utilise both the fragment of natural habitat and its surrounding pastoral land is another factor in its ability to survive. Thus some species will disappear from the area whilst others will flourish.
10.13 Variable answers e.g. a. Pink bloodwood gum; koala. b. Rose bush; sheep. c. Blackberry; rabbit.
10.14 a. Biological magnification: accumulation of a substance as it passes from one organism to another in the food chain. b. Biodegradable: a substance which is able to be broken down into other substances by decomposer organisms. c. Half-life: the time taken for half of a given quantity of the substance to be broken down into another substance. d. Herbicide: a chemical substance designed to kill or control the growth of an unwanted plant species. e. Insecticide: a chemical substance designed to kill insects. f. Pest: an organism which causes harm to humans or their resources.
10.15 Many pesticides are non-biodegradable, have a long half-life and thus are persistent for long periods of time, and display biological magnification, bringing about a wide range of symptoms in diverse organisms depending on their concentration. They are invariably broad spectrum, killing many more types of organisms than the actual pests they are controlling.
(Give examples such as the effects of 2,4,5-T and DDT on organisms which were not part of the pest eradication program.) Thus environmentalists are concerned with the destructive effects of pesticides on the environment, and health authorities are concerned with the effects of the pesticides on human health.

10.16 If the control organism destroys all of the pest, it too will die out. Further outbreaks of the pest, therefore, will not have a control agent present. If the population of both is small, an outbreak of the pest will result in a population increase of the control organisms and thus the ability to reduce the levels of the pest rapidly.
10.17 The control organism must be a predator, parasite or pathogen of the pest species only, it should not damage other plants and animals, and its numbers should dwindle as it reduces the pest.
10.18 It is a permanent management of target pests; there are no harmful environmental side effects; they are self-perpetuating, self-distributing and dependent; the risks are known before they are released into the environment and once established no further release of the organisms is required.
10.19 Variable answers e.g. a. Prickly pear by Cactoblastis cactoreum ; green vegetable bug by the parasitic wasp b.
Ascolcus basalis
Cane beetle by the cane toad; rabbits by myxomatosis.
10.20 Development of plant and animal species resistant to specific pests.
Release of sterilised male pest insects resulting in a subsequent decrease in population size.
Use of pheromone traps to lure and trap male insect pests.
Physical control, e.g. ploughing fields kills the pupae of some insect pests.
Spelling pastures or crop rotation.
Legislative control restricting the movement of plants or animals from areas infested with specific pests to pest-free areas.
10.21 A method which monitors the status of a pest and uses a variety of techniques to eliminate it at different stages of its development or population growth. The main advantage is that it creates a balance between human needs and environmental protection, by targeting different stages of the pest’s life cycle and so reducing damage by the pest to a tolerable level.
10.22 Variable answer, e.g.:
Pollutant
Organic wastes
Inorganic wastes – heavy metals
Possible harmful effects
May contain pathogenic bacteria; eutrophication.
Human death at high concentrations; heart, liver, lung, kidney and nervous system disorders; birth defects; kill soil organisms; decrease activity of aquatic organisms.
Major non-natural source
Untreated and partially treated sewage.
Industrial plants.
Detergents
Toxic substances
Sullage.
Some carcinogenic; cause birth defects.
Eutrophication.
Domestic pesticide treatment; industrial, effluents from factories that produce plastics, electrical insulators or hydraulic fluids.
10.23 A primary pollutant has a direct effect upon the atmosphere, whereas a secondary pollutant is formed as a result of the interaction between the waste and the atmosphere.
10.24 Photochemical smog is a secondary pollutant produced by chemical reactions between nitrogen oxides and hydrocarbons in the presence of sunlight.

10.25 a. nitrogen oxides: motor car engines; form acid rain which retards plant growth, is corrosive and causes eye and throat irritations. b. particulates: combustion of fossil fuels, motor car engines, incinerators, industries, road construction etc.; corrosive, causes eye, throat and nose irritations. c. carbon monoxide: combustion of fuels; displaces oxygen on haemoglobin reducing oxygen uptake which may be fatal, impaired nervous functions, heart disease. d. hydrocarbon vapours: motor car engines, solvents in paints and dry cleaning fluids; retards plant growth and brings about abnormal growth in buds and leaves; carcinogenic. e. sulfur dioxide: combustion of fossil fuels; smelting of mineral ores; form acid rain, corrosive, causing chest irritations and bronchitis.
10.26 A large amount of heat is generated in urban areas due to industrial and commercial activities and the transport of people from place to place. In central city areas there is a large amount of concrete and glass thus there is retention of reflected radiation. Thus overall there is an increase in temperature which can result in an increase in rainfall and decrease in winds. Since surfaces of houses, buildings and roadways result in an increased surface roughness relative to a natural environment, both eddying of winds and fogs increase. Movement and activities of people result in increased particulate matter in the atmosphere, allowing more matter on which water vapour may condense and thus increased rainfall. The higher temperatures in the urban areas may result in earlier flowering of some plants and increase in the number of certain birds.
10.27 Land pollution, which may result from disposal of wastes by industry, commerce and households, can have flow on effects to water and air. As water from rain moves through the land, it carries with it many toxic substances. These ultimately end up either in the ground water or seep into drainage channels and streams. Heavy rains may cause erosion of the land, carrying particulate matter into water ways. Wind erosion of the land results in the release of small particles of soil and pollutants into the air. Some chemical reactions may occur between pollutants in the soil, resulting in polluting vapours being released into the atmosphere. Some waste materials on land are burned, leading to air pollution.
10.28 Reduce the amount of waste, e.g. compost organic matter, recycle glass, plastics and metals.
Industrial waste should be treated to reduce it to a non-toxic, biodegradable status, or solidified and compacted and stored in special leak-proof containers until a means to degrade it to nontoxic status has been developed.
10.29 Ice age theory: an increase in particulate matter in the atmosphere will cause greater reflection of radiation back into space from the atmosphere, causing a reduction in temperatures at the earth’s surface.
Global warming theory: increased carbon dioxide from the combustion of fuels, and methane gas from domestic animals and sewage form a ‘blanket’ in the atmosphere, preventing the release at night of low wavelength infra-red radiation. Thus the atmosphere remains warmer, causing an increase in the temperature at the earth’s surface.
10.30 A ‘nuclear winter’ refers to the proposed decrease in surface temperatures resulting from increased particulate matter (as from a nuclear explosion) in the atmosphere.
10.31 The ozone layer absorbs much of the harmful high energy ultraviolet radiation. If the ozone layer is depleted, more of the radiation would impinge on the earth’s surface, animal tissues would be badly burned, there would be an increase in cancers, and all exposed bacteria, including those necessary for human survival, would be killed.
10.32 National Parks provide a means of conservation, thus maintaining species diversity whilst achieving recreational and educational use in a sustainable manner. Overuse for recreational purposes would lead to degradation of the environment (compaction of walking tracks would increase erosion, large numbers of people would create problems of waste disposal and possible pollution through seepage of impure water into the soil etc.).

10.33 The area under protection is very large and sparsely populated, and there are limited resources for adequate patrolling of the areas. The rewards for illicit trafficking of indigenous plants and animals are very great and the risks of being caught relatively small.
10.34 Few animals rely on one source of food. The greater the number of plant species, the greater the number of herbivores and thus the variety of carnivores. Thus the ecosystem has a greater chance of maintaining a balance under all abiotic conditions.
Biodiversity means genetic diversity both within species and among communities. Genetic diversity increases the chance that a species will survive if environmental conditions change, or a particular genetic strain is subject to parasitic or pathogenic attack.
The status of many species in the ecosystem is unknown. Thus their significance in maintaining a community, or being a possible source of food or pharmaceuticals for humans has not been assessed. Maintaining biodiversity could have very practical applications to human welfare in the future.
10.35 Most varieties of crop plants have been reduced to a few genetic strains, which have been developed for specific productivity. The wild strains from which these have been developed have virtually been eradicated. Thus if any of these strains become subject to a parasite or pathogen which can withstand present agricultural ‘treatments’, human staple food sources could become very scarce.
10.36 ‘Men of the Trees’ provide education programs and reafforestation of degraded land.
Individuals systematically exterminate feral animals which they sell for hides and pet food.
The Australian Government has quarantine regulations to reduce the spread of pests and feral species. There is legislation controlling the use of pesticides, irrigation, effluent and erosion.
‘Clean Up Australia’, ‘Waterwatch’ and ‘Landcare’ programs educate and provide practical means by which individuals can be involved in care of the environment.
10.37 Variable answer, e.g.:
Get up, have shower: make sure the shower is very quick to minimise water wastage; use minimum amount of soap so as not to cause eutrophication.
Have breakfast:
Make lunch:
Leave for school:
Etc. place all food scraps in a compost bin. pack lunch in a lunch box which can be reused; do not use plastic wrappers, etc. walk, ride a bike, share transport with nearby families, etc.