Edexcel IGCSE Biology

Revision Notes

1.1.2 Living Organisms: Nutrition & Respiration


  • Organisms must obtain food to provide energy
    • Energy is necessary to carry out life processes e.g. movement, respiration and excretion

Nutrition in plants

  • Plants use sunlight, carbon dioxide and water to produce oxygen and glucose in the process of photosynthesis
  • Because plants create their own food for energy, they are described as being autotrophic

Nutrition in animals

  • Animals consume other living organisms in order to obtain the energy they require
  • They break down larger complex molecules into simpler molecules through the process of digestion
  • As animals obtain their food from a range of different sources, they are described as being heterotrophic

Autotrophs and Heterotrophs, IGCSE & GCSE Physics revision notes

Autotrophs make their own food whereas heterotrophs obtain it from a range of food sources

Exam Tip

Sometimes understanding the origin of a word can help us to remember the meaning, for example:

Autotroph comes from:

  • ‘auto’ = ‘self’
  • ‘trophic’ = ‘feeding’

Heterotroph comes from:

  • ‘hetero’ = ‘different’
  • ‘trophic’ = ‘feeding’


  • Respiration is a chemical reaction carried out in all living organisms
  • Energy is released from glucose either in the presence of oxygen (aerobic respiration) or the absence of oxygen (anaerobic respiration)
  • The reactions ultimately result in the production of carbon dioxide and water as waste products
  • Energy is transferred in the form of ATP

Word equation for aerobic respiration, IGCSE & GCSE Chemistry revision notes
The equation for aerobic respiration

Exam Tip

Make sure not to confuse respiration with gas exchange. Gas exchange involves getting oxygen into the cells and carbon dioxide out. Respiration uses the oxygen supplied from gas exchange to release energy in the form of ATP.

Author: Ruth

Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. With 10 years of teaching experience across the 3 key science disciplines, Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top