Trophic Levels & Food Chains (Edexcel GCSE Biology: Combined Science)

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Trophic Levels & Food Chains

Trophic levels

  • Trophic levels are used to describe the feeding relationships between organisms
  • The Sun is the source of energy for nearly all life on Earth
  • Energy flows from the Sun to the first trophic level (producers) in the form of light
  • Producers then convert light energy into chemical energy and it flows in this form from one consumer to the next
    • For example, plants (one type of producers) convert a small percentage of the light energy that falls on them into glucose, some of which is used immediately in respiration and some of which is stored as biomass
    • When a primary consumer (e.g. a herbivore such as a rabbit) feeds on a plant, the chemical energy stored in the plant's biomass is passed on to the primary consumer

  • Eventually, all energy is transferred to the environment – energy is passed on from one level to the next with some being used and lost at each stage
    • Energy is lost to the environment when heat energy is transferred from organisms to their surroundings

Trophic Levels Table

Energy table, IGCSE & GCSE Biology revision notes

  • Animals (known as consumers) can be at different trophic levels within the same food web as they may eat both primary, secondary and/or tertiary consumers

Food chains

  • A simple way to illustrate the feeding interactions between the organisms in a community is with a food chain
  • A food chain shows the transfer of energy from one organism to the next
  • The source of all energy in a food chain is light energy from the sun
  • The arrows in a food chain show the transfer of energy from one trophic level of the food chain to the next

Food chain, IGCSE & GCSE Biology revision notes

An example of a food chain (the sun is not included in food chains as it is not a living organism)

  • You need to know the terms given to each step in a food chain (the sun is not included in food chains as it is not a living organism):

    1. Producer: food chains always begin with a producer
    2. Primary consumer: producers are eaten by primary consumers (herbivores/omnivores)
    3. Secondary consumer: primary consumers are eaten by secondary consumers (carnivores/omnivores)
    4. Tertiary consumer: secondary consumers are eaten by tertiary consumers (carnivores/omnivores)

Food chain showing trophic levels, downloadable IGCSE & GCSE Biology revision notes

Trophic levels for a simple food chain

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Lára

Author: Lára

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.