AQA GCSE Biology

Revision Notes

2.1 Principles of Organisation

Organisation: Principles

Levels of organisation, IGCSE & GCSE Biology revision notes

Multicellular organisms have many levels of organisation

  • Cells are the basic building blocks of all living organisms
  • Unicellular organisms are made from one cell, whereas multicellular organisms are made up of collections of cells
  • In complex multicellular organisms, cells are specialised to carry out particular functions. These specialised cells form tissues, which form organs in organ systems
  • In humans, the digestive system (provides the body with nutrients) and the respiratory system (provides the body with oxygen and removes carbon dioxide) are examples of organ systems that provide dissolved materials that need to be moved quickly around the body in the blood by the circulatory system

Organisation table

Organisation table, downloadable IGCSE & GCSE Biology revision notes

The Stomach

  • We can illustrate different levels of organisation by looking at the stomach:
    • The role of the stomach is to start protein digestion
    • To do this, the stomach produces proteases like pepsin, which digests proteins into amino acids.
    • Acid produced by glandular tissue in the stomach aids protein digestion; it helps proteins unravel so that enzymes can break the bonds holding the amino acids together. It also inhibits many microorganisms that may be present in food, reducing the chance of infection
  • The stomach is one of a number of organs that make up the digestive system
  • The role of the digestive system is to break down large insoluble molecules into smaller, soluble food molecules to provide the body with nutrients

 

The Stomach, downloadable IGCSE & GCSE Biology revision notes

 

Three types of tissue found in the stomach are muscular, epithelial and glandular. These tissues work together to allow the stomach to carry out its role

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Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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