Combined Science Double Award - 9204 OxfordAQA

Energy Transferred In Ecosystems

Bayani Gaba-gaba

Stand in a wheat field on a bright afternoon and an enormous amount of energy is pouring onto every square metre around you. Almost none of it ends up in the grain. Ninety nine parts in a hundred bounce off, slip past or warm the soil, and of the fraction the crop does capture, most is spent again before anything reaches a cow, a sparrow or you. Ecosystems are not efficient machines. They leak at every joint.

This lesson follows that leak from end to end. You will find out why plants and algae hold on to only about one per cent of the light that reaches them, why roughly nine tenths of the biomass at any feeding level never makes it to the level above, and where the missing nine tenths actually goes. Then you will use the numbers: tracking one animal's whole yearly ledger from mouthful to growth, building a pyramid of biomass to scale, and reading one you are handed in an exam closely enough to say what it tells you about the ecosystem and what it cannot.

Manufura

  1. Radiation from the Sun is the source of energy for most communities of living organisms. Plants and algae transfer about 1 % of the incident energy from light for photosynthesis. This energy is stored in the substances that make up the cells of the plants.
  2. Only approximately 10 % of the biomass from each trophic level is transferred to the level above it because: some materials and energy are always lost in the organisms’ waste materials; respiration supplies all the energy needs for living processes, including movement. Much of this energy is eventually transferred to the surroundings. Construction of food webs and chains, and of pyramids of numbers, is not required. An understanding of pyramids of numbers is not required.
  3. The biomass at each stage can be drawn to scale and shown as a pyramid of biomass. Students should be able to interpret pyramids of biomass and construct them from appropriate information.

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Takardar Darasi

A lion is a heavy animal living in a landscape full of grass, yet a savannah supports only a handful of lions across many square kilometres. The grass is not in short supply. What is in short supply is the energy that survives the journey from the grass to the zebra and from the zebra to the lion. Every ecosystem you will ever be asked about is shaped by that shrinking supply, and the whole of this topic comes down to two numbers you must be able to use with confidence: about 1 per cent at the way in, and about 10 per cent at every step afterwards.

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Nazarin Darasi

Barka da kammala darasi akan Energy Transferred In Ecosystems. Yanzu da kuka bincika mahimman raayoyi da raayoyi, lokaci yayi da zaku gwada ilimin ku. Wannan sashe yana ba da ayyuka iri-iri Tambayoyin da aka tsara don ƙarfafa fahimtar ku da kuma taimaka muku auna fahimtar ku game da kayan.

Za ka gamu da haɗe-haɗen nau'ikan tambayoyi, ciki har da tambayoyin zaɓi da yawa, tambayoyin gajeren amsa, da tambayoyin rubutu. Kowace tambaya an ƙirƙira ta da kyau don auna fannoni daban-daban na iliminka da ƙwarewar tunani mai zurfi.

Yi wannan ɓangaren na kimantawa a matsayin wata dama don ƙarfafa fahimtarka kan batun kuma don gano duk wani yanki da kake buƙatar ƙarin karatu. Kada ka yanke ƙauna da duk wani ƙalubale da ka fuskanta; maimakon haka, ka kallesu a matsayin damar haɓaka da ingantawa.

  1. Approximately what percentage of the light energy reaching plants and algae is transferred for photosynthesis? A. 1% B. 10% C. 50% D. 90% Answer: A
  2. Approximately what percentage of the biomass at one trophic level is transferred to the trophic level above it? A. 1% B. 10% C. 50% D. 90% Answer: B
  3. Which process does NOT cause biomass to be lost between one trophic level and the next? A. Egestion of undigested food in faeces B. Excretion of urea in urine C. Respiration to supply energy for movement D. Absorption of digested food into the blood Answer: D
  4. In a pyramid of biomass the scale used is 1 cm to 300 g/m2. The producers have a biomass of 3000 g/m2. How long should the producer bar be? A. 1 cm B. 3 cm C. 10 cm D. 30 cm Answer: C
  5. Why do ecologists compare dry mass rather than the mass of the living organisms? A. Dry mass is quicker to measure than wet mass B. Water content varies between organisms, so wet mass is not a fair measure of the material present C. Water stores most of the energy in an organism D. Drying an organism increases the energy it contains Answer: B

Yi aikin wadannan tambayoyi a cikin manhaja

Yi aikin wadannan tambayoyi a cikin manhaja

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