Skip to content
Studia will be closed for Christmas and NYE.
Learn more
  • About
  • Academy
    • Studia School
    • Studia Tutoring
    • Studia Consultation
    Ready to elevate your education?
    Contact us
  • Workshop
  • Care
  • E-Shop
  • Resources
  • Blog
  • Home
  • About
  • Studia School
  • Studia Tutoring
  • Studia Consultation
  • Studia Workshop
  • Studia Care
  • Shop
  • Resources
  • Blog
Platform
Fe-mail Fe-phone Fe-map-pin Fe-instagram
Platform
Back
  • IGCSE Edexcel
  • Biology
  • 4. Ecology & The Environment

Biology

  • IGCSE Edexcel
  • Revision Notes

4. Ecology & The Environment


4.1 The Organism in the Environment>4.2 Feeding Relationships>4.3 Cycles within Ecosystems>4.4 Human Influences on the Environment>

1. The Nature & Variety of Living Organisms

1.1 Characteristics of Living Organisms >

2. Structure & Function in Living Organisms

2.1 Level of Organization >2.2 Cell Structure >2.3 Biological Molecules >2.4 Movement of Substances Into and Out of Cells >2.5 Nutrition (in Plants) >2.6 Nutrition (in Human) >2.7 Respiration >2.8 Gas Exchange (in Plants) >2.9 Gas Exchange (in Human) >2.10 Transport (in Plants) >2.11 Transport (in Human) >2.12 Excretion (in Plants) >2.13 Excretion (in Human) >2.14 Coordination and Response (in Plants) >2.15 Coordination and Response (in Human) >

3. Reproduction & Inheritance

3.1 Reproduction (in Plants) >3.2 Reproduction (in Human) >3.3 Inheritance >

5. Use of Biological Resources

5.1 Food Production >5.2 Selective Breeding >5.3 Genetic Modification (Genetic Engineering) >5.4 Cloning >

4.2 Feeding Relationships

4.2.1 Understand the names given to different trophic levels, including producers, primary, secondary and tertiary consumers and decomposers

Trophic levels:

  • Describes the feeding relationships between different organisms
  • Energy flows from one trophic level to another
  • Eventually all energy is transferred to the environment
  • Some energy is lost to the environment during transfer between trophic levels
  • Starts with energy flowing from the sun to the producers (first trophic level) in the form of light
  • Organisms can be classified at different trophic levels in the same food web
  • They may eat primary, secondary or tertiary consumers

4.2.2 Understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer

Food chain:

  • Represents feeding interactions within a community
  • Arrows represent transfer or energy from one organism to another

Food web:

  • Network of connected food chains in an ecosystem
  • Show interdependence on different species
  • Interdependence is when species depend on each other for resources
    • Changes in the population of one species can affect the population of others
  • Animals generally rely on multiple food sources
  • E.g. if the earthworm population gets wiped out, the population of grass would increase significantly
    • The population of frogs and mice would significantly decrease as they don’t have other food sources to rely on
    • The population of sparrows would not be affect as much due to the presence of caterpillar
    • This ensures that some of their population survives

Pyramid of numbers:

  • The width of the box represents the number of organisms at each trophic level
  • The size of the box depends on the species population and size of the organism
    • One large producer can contain enough energy to support a large population of smaller primary consumers such as insects
  • All pyramids should follow the order of trophic levels in the food chain
    • Producers at the bottom and tertiary consumers at the top
    • It does not have to look like the traditional pyramid shape

Pyramid of biomass:

  • The width of the box represents the dry biomass (without water) of each organism
  • The size of the box will always be decreasing
    • Biomass of organisms will always be decreasing as you go up the food chain
    • Some of the food consumed at the next trophic level is excreted as waste
  • Better way to represent interdependence in the food chain

Pyramids of energy:

  • Represents the amount of energy in the biomass of organisms at each trophic level
  • Will always have a very wide base as producers contain the most amount of energy
  • As you go up the food chain, the amount of energy at each trophic level decreases
    • Only around 10% of it is passed on

4.2.3 Understand the transfer of substances and energy along a food chain

Transfer of energy:

  • Energy from the sun is absorbed by producers converted into chemical energy through photosynthesis 
  • The glucose produced is used for the biomass of producers
  • Primary consumers eat producers and break down the biomass through digestion 
    • Chemical energy released is used for the maintenance or increase of their own biomass
  • Secondary consumers eat primary consumers where the biomass is broken down through digestion
    • Chemical energy released is used for the maintenance or increase of their own biomass
  • Chemical energy is transferred throughout the trophic levels by to consumption

4.2.4 Understand why only about 10% of energy is transferred from one trophic level to the next

Loss of energy:

  • Energy is passed on to different trophic levels through consumption
  • Not all energy absorbed or consumed is used for making biomass
  • Some energy is lost to the environment through:
    • Metabolic waste excreted by the organism e.g. urine
    • Movement requiring energy
    • Heat produced to maintain body temperature
    • Undigested waste products that are removed from the body e.g. faeces
  • Only energy converted into biomass can be passed onto the next trophic level
    • Parts of an organism that is consumed will contribute to the transfer of energy
    • Energy in parts of organisms not consumed will degrade 
    • The energy will be lost to the surroundings
Previous4.1 The Organism in the Environment
Next4.3 Cycles within Ecosystems

Start Your Success Story Today

  • enquiries@studiaacademy.com
  • (+852) 5487 8448
  • 1201B, Tower 1, Admiralty Center,

    18 Harcourt Road, Admiralty, Hong Kong
  • studiaacademy
  • studiaeshop
  • About Studia
  • Getting to Studia
  • Studia School
  • Studia Tutoring
  • Studia Consultation
  • Studia Workshop
  • Studia Care
  • Studia Shop
  • Studia Resources
  • Studia Blog
  • Studia Platform

© 2025 Studia Academy. All rights reserved.

  • Terms of Use
  • Privacy Policy

Contact Studia

Please fill out the form below, and we’ll get back to you as soon as possible.