Syllabus Edition

First teaching 2023

First exams 2025

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Functions of Life (HL IB Biology)

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Cara Head

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Cara Head

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Functions of Life

  • Unicellular (single-celled) and multicellular (many cells) organisms must carry out the following functions to stay alive:
    • Metabolism - all the enzyme-catalysed reactions occurring in a cell, including cell respiration
    • Reproduction - the production of offspring. It may be sexual or asexual
    • Homeostasis - the ability to maintain and regulate internal conditions within tolerable limits, including temperature
    • Growth - the permanent increase in size
    • Response - (or sensitivity), the ability to respond to external or internal changes (stimuli) in their environment. Thus improving their chance of survival
    • Excretion - the disposal of metabolic waste products, including carbon dioxide from respiration
    • Nutrition - the acquisition of energy and nutrients for growth and development, either by, absorbing organic matter or by synthesising organic molecules (e.g. photosynthesis)

  • Unicellular organisms have adapted unique ways to carry out these functions compared to multicellular organisms
    • Mitochondria are present to provide energy through respiration
    • The cell membrane controls movement of materials in and out of the cell to maintain homeostasis
    • Ribosomes are present to produce proteins for growth and repair, in addition enzymes for vital cell functions
    • Vacuoles are used for digestion purposes and also to store waste substance
    • Cilia or flagella are used for movement of the organism in response to changes in the environment 

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Cara Head

Author: Cara Head

Expertise: Biology

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding