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| Frage | Antworten |
| 5.1 what are producers? | photosynthetic organisms that manufacture substances using light energy, water and carbon dioxide |
| 5.1 what are consumers? 3 different types? | organisms that obtain their energy by feeding on other organisms primary - eat producers directly secondary - eat primary consumers tertiary - eat secondary consuumers |
| 5.1 what are the two main decomposer groups? | if fungi/bacteria = decomposer if animal e.g. earthworm = detritivores |
| 5.1 what are decomposers and what do they contribute to? | decomposers are a group of organisms that break down complex molecules in dead producers and consumers into simple components, releasing valuable minerals and elements in a form that can be absorbed by plants they contribute to recycling |
| 5.1 what is a trophic level? | each stage in a food chain |
| 5.1 what do the arrows on food chain diagrams represent? | the direction of energy flow |
| 5.1 what is a food web? what can be said about the feeding inter-relationships of organisms? | the linking of many food chains in a habitat to form a food web the feeding inter-relationships aren't fixed but change depending on time of year, age and population size of organsims |
| 5.2 why is most of the sun's energy not converted to organic matter by photosynthesis? | light may not fall on a chlorophyll molecule not all wavelengths of light absorbed and used for photosynthesis factors may limit rate of photosynthesis over 90% of sun's energy reflected back into space by clouds and dust/absorbed by atmosphere |
| 5.2 what is gross production? | total quantity of energy that plants in a community convert to organic matter |
| 5.2 what is net production? | rate at which the plants store energy =gross production - respiratory losses |
| 5.2 what are four reasons why there is a low energy transfer between each trophic level? | some of the organism not eaten some parts eaten but can't be digested so lost in faeces some energy lost in excretory materials energy lost as heat from respiration and to the environment from the body, also maintaining constant body temp |
| 5.2 what are three consequences of the inefficiency of energy transfer between trophic levels? | total amount of energy stored is less at each trophic level as you move up food chain total mass of organisms in particular place (biomass) less at higher trophic levels only four or five trophic levels in a food chain as not enough energy to support large enough breeding population at higher trophic levels |
| 5.2 how do you calculate energy transfer? | energy available after transfer divided by energy available before transfer x100% |
| 5.3 how is a pyramid of number drawn? | draw bars with lengths proportional to the numbers present at each trophiclevel |
| 5.3 what are two drawbacks of using a pyramid of number to describe a food chain? | no account taken of size e.g. one tree treated the same as small aphid #s may be so high can't represent them accurately on the same scale |
| 5.3 how is a pyramid of biomass made? what is biomass and units? | measure biomass of organisms at each trophic level biomass = total mass of plants/animals in a particular place gm-2 if area gm-3 if volume |
| 5.3 why may a pyramid of biomass be unreliable? possible way to overcome this? further problems? | unreliable due to varying amounts of water use dry mass have to kill organisms so have to use small sample which may not be representative |
| 5.3 what do pyramids of biomass and numbers both show? | show information about the organisms present at a particular time seasonal differences not apparent |
| 5.3 how is a pyramid of energy made? | measure energy stored in organisms |
| 5.3 how is data collected for a pyramid of energy? drawbacks? | hard to collect data and can be complex data collected in a given area for set period of time e.g. metre squared for a year |
| 5.3 why are pyramids of energy more reliable than pyramids of biomass? | same dry mass may store different amounts of energy e.g. 1g of fat vs 1g carbs |
| 5.3 what are the units of measurement for energy flow in pyramids of energy? | kJm-2year-1 |
| 5.4 what is an agricultural ecosystem made up of? | domesticated animals and plants used to produce food for humans |
| 5.4 what is the main aim of agriculture? | maximise the amount of energy that is transferred from the sun to humans by channeling the energy flowing through a food web into the human food chain and away from other food chains increases productivity |
| 5.4 what is productivity? | rate at which something is produced |
| 5.4 what is gross productivity? | rate at which plants assimilate chemical energy as a result of photosynthesis |
| 5.4 what two things are net productivity affected by? | area of ground covered by leaves of the crop efficiency of crop at carrying out photosynthesis |
| 5.4 explain the difference between natural and agricultural ecosystems in terms of energy input | to maintain agricultural ecosystem climax community prevented from forming so additional energy input to remove unwanted species etc additional energy comes from food (for farmers) or fossil fuels - for powering machine |
| 5.4 explain the difference between natural and agricultural ecosystems in terms of productivity | additional energy reduces effects of limiting factors on growth reduces competition for resources can grow more, fertilisers provide metals and ions, pesticides deal with unwanted pest overall productivity is higher |
| 5.4 draw up a comparison table for natural and agricultural ecosystems (seven points!) | (in natural) solar energy only lower productivity more species diversity more genetic diversity within species nutrients recycled naturally within system population controlled naturally e.g. climate, competition, predators natural climax community |
| 5.5 what are pest? | organism that competes with humans for food or space, may be a danger to health |
| 5.5 what are pesticides? | poisonous chemicals that kill pests. herbicides, insecticides, fungicides |
| 5.5 what four things should an effective pesticide be? | be specific - only toxic to pest be biodegradable - so once applied breaks down into harmless substances in soil. chemically stable so long shelf life be cost effective- development costs high, new pesticides only useful for a while before genetic resistance develops not accumulate - doesn't build up in specific areas/pass along food chain |
| 5.5 what is biological control? | controlling pests by using organisms that are either predators or parasites of the pest organism with the aim to control not eradicate |
| 5.5 what are two disadvantages of biological control? three advantages? | specific, doesn't become resistant, reproduces itself may become pest itself, doesn't act quickly as gap between when first introduced and organisms are reproducing |
| 5.5 what are three disadvantages of chemical control? | always affects non-target organisms as well must be reapplied at regular intervals making them expensive develop genetic resistance so new pesticides need to be developed |
| 5.5 what do integrated pest-control systems aim to do? | integrate all forms of control and decide acceptable level of pest |
| 5.5 what six things do integrated pest control systems involve? | use of biological agents if necessary and available using pesticides as last resort (pest pop out of control) removing pests mechanically e.g. hand picking regularly monitoring crop for signs of pest so early action can be taken manage environment so providing suitable habitats for natural predators choosing animal/plant varieties that suit local area and are as pest-resistant as possible |
| 5.5 explain how controlling pests affects productivity? | pests complete with crop for resources so less resources for crop these factors may become limiting and so reduce rate of photosynthesis and hence productivity growing crops in monoculture enables pests to spread rapidly pests of domesticated animals may cause diseases so animals don't grow properly decreasing productivity |
| 5.6 intensive rearing of domesticated livestock aims to? | produce max yield of meat, eggs and milk at lowest possible cost. converting smallest amount of food energy into greatest quantity of animal mass |
| 5.6 describe four ways 'factory farming' increases energy-conversion rate | movement restricted so less energy used in muscle contraction environment kept warm, reduces heat loss from body, less energy in maintaining high bod temp feeding controlled so animals receive optimum amount of food for max growth predators excluded so no energy loss to other organisms in food web |
| 5.6 what two other options are available other than factory farming? | hormones which increase growth rate selective breeding of animals - produces varieties more efficient at converting food eaten into body mass |
| 5.6 describe six features of intensive rearing of livestock | lower quality of food less space used, leaves more natural habitats disease- infections can spread easily use of fossil fuels, pollution, safety animal welfare - animals start acting aggressively over use of antibiotics to prevent disease = AR, resistance can be transferred to bacteria that cause human diseases |
| 5.6 what are three direct effects of intensive food production? | reduced species diversity b/c removal of hedges creation of monoculture over grazing (prevents regeneration of woodlands) |
| 5.6 what are two indirect effects of intensive food production? | absence of crop rotation pesticides and fertilisers |
| 5.6 what are four other conservation techniques? | plant hedges rather than fences maintain existing ponds organic rather than inorganic fertilisers crop rotation that includes nitrogen fixing crops |
| 5.6 what economic issue does intensive rearing present? | may force farmers to cut costs and supply cheap food just to stay in business |
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