1.2-b) Energy conversion, transfer, and loss in food chains and food webs
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• Define ‘autotrophs’
• Autotrophs ➞ are organisms that can produce their own food (aka. producers) ✨ • They are normally green plants that produce thier own carbohydrates through photosynthesis (the conversion of light energy into chemical energy)
• Define ‘heterotrophs’
• Heterotrophs ➞ are animals that must meet its energy requirements by ingesting other organisms or organic matter derived originally from plants (aka. consumers) ⚡
• Define ‘Gross primary productivity’ (GPP)
• GROSS PRIMARY PRODUCTIVITY: ➞ is the rate at which autotrophs produce biomass in a given area and time period 🌱
• Define ‘Net primary productivity’ (NPP)
• Approximately half the GPP is used by plants for their own respiration ⚡ • The remainder is either stored or utilised by the plants for new biomass production and is available for consumption by heterotrophs 🔐 • NET PRIMARY PRODUCTIVITY ➞ is the actual quantity of energy available to next trophic level (after respiration) ⬆️
• Explain ‘ecological efficiency’
• Ecological efficiency ➞ is the percentage of biomass produced by one trophic level that is transferred and incorporated into biomass at the next trophic level.
• How can energy be lost when transferring through trophic levels?
• On average, only 10% of the energy that enters the trophic level is passed on to the next trophic level ⚡ • Energy is lost from the system through: ➞ Respiration ⚡ ➞ Movement 💨 ➞ Heat 🔥 ➞ Indigestible waste 💩 • An ecological efficiency of 10% limits most food chains to four or five links, which explains why the volume of biomass typically reduces at each trophic level 🤏
• Define an ‘ECTOTHERM’ and explain their role in energy transfer.
• ECTOTHERMS ➞ are organisms that cannot control their body temperatures. ↳ Their temperature is regulated by their surroundings (tend to be cold-blooded animals - i.e. reptiles, fish and amphibians) • Ectotherms ➞ are more ecologically efficient than endotherms, passing on up to 15% of residual energy to the next trophic level in comparison to approximately 7% by endotherms. ↳ Therefore, food chains containing several ectotherm species, particularly marine food chains, are often longer in length.
• Define an ‘ENDOTHERM’ and explain their role in energy transfer.
• ENDOTHERMS ➞ are organisms that must regulate their body temperatures. ↳ This requires a lot of energy so endotherms must consume more food so they have sufficient energy for thermoregulation (tend to be warm-blooded animals - i.e. mammals and birds) • Endotherms ➞ have a higher metabolic demand than ectotherms. ↳ This means that the energy being used to maintain body temperature cannot be used for biomass accumulation.