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First teaching 2014

Last exams 2024

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Functions of Life (DP IB Biology: SL)

Revision Note

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Catherine McCosker

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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)

Functions of Life: Paramecium & Chlorella

Paramecium

  • Paramecium are unicellular protozoans commonly found in freshwater. They range in size from 50 to 320 μm

Chlorella

  • Chlorella is a small (2 to 10 μm) unicellular green alga. They are abundant in freshwater and can be found in a symbiotic relationship with Paramecium
  • As Chlorella are living they carry out all the functions of life, although due to different structures, there are some differences to Paramecium

Comparison of the Functions of Life Between Paramecium and Chlorella

Functions of Life Table 1, downloadable IB Biology revision notesFunctions of Life Table 2, downloadable IB Biology revision notes

The functions of life in Paramecium 1, downloadable IB Biology revision notesThe functions of life in Paramecium 2, downloadable IB Biology revision notes

The functions of life in Paramecium

The functions of life in Chlorella, downloadable IB Biology revision notes

The functions of life in Chlorella

Examiner Tip

To remember the functions of life think of MR H GREN. Note the similarities in the functions of life between Paramecium and Chlorella.

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Catherine McCosker

Author: Catherine McCosker

Expertise: Biology

Cate has over 20 years’ experience teaching Biology to IGCSE, IB and A-level students in seven different countries across Asia, Europe, North America and the Middle East. This has given her a fine appreciation of different cultures, places and teaching methods. Cate has a keen interest in producing Biology revision resources that will help students engage with the subject.