1.2-b) Energy conversion, transfer, and loss in food chains and food webs

Question 1

• Define ‘autotrophs’

Answer 1

• 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)

Question 2

• Define ‘heterotrophs’

Answer 2

• Heterotrophs
  ➞ are animals that must meet its energy requirements by ingesting other organisms or organic matter derived originally from plants (aka. consumers) ⚡

Question 3

• Define ‘Gross primary productivity’ (GPP)

Answer 3

• GROSS PRIMARY PRODUCTIVITY:
  ➞ is the rate at which autotrophs produce biomass in a given area and time period 🌱

Question 4

• Define ‘Net primary productivity’ (NPP)

Answer 4

• 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) ⬆️

Question 5

• Explain ‘ecological efficiency’

Answer 5

• Ecological efficiency
  ➞ is the percentage of biomass produced by one trophic level that is transferred and incorporated into biomass at the next trophic level.

Question 6

• How can energy be lost when transferring through trophic levels?

Answer 6

1. On average, only 10% of the energy that enters the trophic level is passed on to the next trophic level ⚡
2. Energy is lost from the system through:
   ➞ Respiration ⚡
   ➞ Movement 💨
   ➞ Heat 🔥
   ➞ Indigestible waste 💩
3. 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 🤏

Question 7

• Define an ‘ECTOTHERM’ and explain their role in energy transfer.

Answer 7

• 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.

Question 8

• Define an ‘ENDOTHERM’ and explain their role in energy transfer.

Answer 8

• 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.