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Initially comparable seedlings receive the same light, water, mineral nutrients, temperature and suitable pH. Air flows to both at the same rate, but carbon dioxide is removed from the air supplied to one group. That group grows less. Which conclusion best uses this controlled comparison?
Under the tested conditions, carbon dioxide in the supplied air supported normal growth. Air is unnecessary because both seedlings obtain all of their food directly from soil. Extra mineral nutrients would replace both air and light in the seedling that grew less. This comparison proves the same growth response to carbon dioxide in every plant species. A growing population must be supplied from limited farmland. A farmer adds fertiliser to a nutrient-poor field, crop yield rises, and rain later carries fertiliser into a pond where algae grow rapidly. Which evaluation is complete?
Limited land and greater demand create production pressure; fertiliser can supply mineral nutrients and raise yield, but runoff can contaminate water and increase algal growth. Population growth does not increase food demand, although fertiliser may affect both crops and the pond. Fertiliser raised yield by killing insect pests, and the algal growth shows that pests reached the pond. Because fertiliser improved crop yield, it could not have been carried into the pond or affected algal growth. A pesticide reduces insect damage and a herbicide reduces weeds in a crop. Residues are later detected in prey animals and in predators that eat them. Which statement is correct?
The chemicals can reduce crop losses, but harmful residues can contaminate organisms and pass along a food chain when prey are eaten. The chemicals improve crops by supplying mineral nutrients, so their residues are additional food for predators. The chemicals must remain only on their target insects or weeds, so residues in other organisms are unrelated. Residues may enter prey, but harmful substances cannot be transferred from prey to a predator that eats them. Vegetation is cut and burned before a crop is planted. The first crop benefits from cleared land and ash, while nearby communities experience haze and heavy rain removes exposed soil. Which account is complete?
Slash-and-burn can make land available and ash can temporarily add minerals, but smoke haze can cause breathing difficulty and deforestation can increase soil erosion. Slash-and-burn cannot make land available or support any initial crop growth, so the crop observation is impossible. The haze is unrelated to breathing because smoke from burning vegetation cannot affect the respiratory system. Removing forest cover cannot affect erosion, so the exposed-soil loss must be unrelated to deforestation. Two matched greenhouse compartments begin with similar aphid populations and identical crop conditions. Ladybirds are introduced only into one compartment. After two weeks, that compartment has fewer aphids and less leaf damage, although some aphids remain. Which conclusion best explains the result?
Ladybirds are predators of the aphid prey; reducing the pest population can reduce crop damage without eliminating every aphid. The ladybirds improve the crop by feeding directly on its damaged leaves. It cannot be biological control unless the ladybirds eliminate every aphid. The aphids control the ladybirds by hunting and eating them. Which row correctly distinguishes improved varieties, intensive farming and agricultural uses of plant hormones?
Improved variety: selected useful plant or animal characteristics; intensive farming: substantial inputs for high output per unit area; plant hormones: weed control and regulation of growth or fruit ripening. Improved variety: the same crop given extra fertiliser; intensive farming: substantial inputs for high output per unit area; plant hormones: weed control and regulation of growth or fruit ripening. Improved variety: selected useful characteristics; intensive farming: leaving crops or animals unmanaged in the wild; plant hormones: weed control and regulation of growth or fruit ripening. Improved variety: selected useful characteristics; intensive farming: substantial inputs for high output per unit area; plant hormones: mineral fertilisers that feed plants directly.
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A watered plant with adequate nutrients is kept in darkness. Why is fertiliser not enough for normal growth?
Nutrients do not replace the light needed for photosynthesis. Fertiliser replaces light after one day. Plants obtain finished food from the fertiliser. Only water matters once nutrients are present. Why is there a need to improve world food production?
Only pesticide use creates demand for food. A growing population raises food demand while growing space is limited. Population growth does not affect food demand. Growing space is unlimited, so production need not improve. Which statement gives both a benefit and a cost of fertiliser use?
Fertiliser kills crop pests directly and cannot be carried into nearby water. Fertiliser reduces crop growth and always removes algae and water weeds from streams. Any crop benefit proves the method has no environmental cost. It can improve crop growth by supplying nutrients, but runoff can contaminate water and increase algae and water weeds. Which statement gives both a benefit and a cost of pesticide or herbicide use?
They feed crops and remain only on the target organism. They control only weeds and cannot enter soil or water. A production benefit makes food-chain transfer impossible. They reduce pest or weed losses, but contaminants can pass along food chains. Which evaluation of slash-and-burn is accurate?
It clears land, but haze harms breathing and deforestation increases soil erosion. Slash-and-burn gives no crop-production benefit and causes no environmental cost. It clears land while preventing both haze and erosion. Any improved yield proves the method is environmentally safe. A crop has poor mineral supply and heavy insect damage. Which matched response addresses both problems?
Use pesticide as the mineral nutrient and fertiliser as the insect killer. Use herbicide to feed the crop and fertiliser to kill insects. Use neither, because unlimited extra land will automatically solve both problems. Use an appropriate fertiliser for nutrients and a suitable pesticide to control the insect pest. How can biological control reduce the need for pesticides?
The pest prey hunt and remove their predators. It works only if every pest is eliminated permanently. Predators feed on pest prey and reduce the pest population that damages crops. It replaces one pesticide spray with another. Which statement about improving varieties for food production is correct?
An improved variety is simply any organism given extra fertiliser. Improved varieties are the same as introducing predators. Useful varieties of both plants and animals can be improved. Only crop varieties can be improved. A farmer chooses a plant variety that gives a higher usable yield in local conditions. Why can this improve food production?
The variety works because pest prey hunt predators. The variety has a useful characteristic that increases the amount of food produced under those conditions. It counts as an improved variety only because the farmer supplied more fertiliser. Only animal varieties can improve food production; plant varieties cannot. Fish are reared at high stocking density in managed enclosures, with controlled feeding and water quality, to produce more fish from the available space. Which method is this?
Intensive farming of farm animals. Biological control because fish must be predators. Improving a plant variety. Unmanaged farming in a natural area. Which statement about intensive farming is correct?
It is another name for plant hormones. It can be used for crops and farm animals to improve food production. Intensive farming can be used for crops only and never for farm animals. It means leaving all production conditions unmanaged. Plant hormones are applied so harvested fruit ripens at a controlled time. Which use is illustrated?
Regulating the ripening of fruits. Using hormones only to add mineral nutrients. Using hormones to kill insect pests. Using predators to control prey.
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