1.1 Characteristics of Life: A* understanding for iGCSE Biology

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The iGCSE specification says that all living organisms share the following basic characteristics and then lists 8 bullet points.  This seems unnecessarily unhelpful because every student in the whole word learns MRS GREN for the 7 characteristics of life…

Make sure you understand the exact meaning of each of the following terms:

  • Movement
  • Respiration
  • Sensitivity
  • Growth
  • Reproduction
  • Excretion
  • Nutrition

Not all organisms Move from place to place of course and lots of things move that are not alive.  So that doesn’t make me think that this is a good way to start the whole study of Biology.  It is true that all living things, without exception, Respire.  “Respiration is a series of chemical reactions that happens inside cells in which food molecules are oxidised to release energy for the cell” – good definition that….   Sensitivity means the ability to detect and respond to changes in the environment.  Mammals do this through their nervous and hormonal systems, plants through plant growth substances such as auxin.  Growth either involves a cell getting larger or in multicellular organisms, the two processes of cell division and cell specialisation.  All living things have the potential to Reproduce, to create new individuals of their species.  Excretion is the removal of waste molecules (e.g. carbon dioxide, urea) that have been made inside cells.  Nutrition means either obtaining food molecules by eating another organism or if you are a plant, and I guess none of you are,  by making your own food molecules through photosynthesis.

The people who wrote the specification have added “they control their internal conditions” to the list.  This is actually a better characteristic of life than many above as it is a universal feature of all life.  The term for this process is Homeostasis – the ability to regulate and control the internal environment.

It is a shame that two of the best ways to decide whether something is alive have been left off the list.  All living things on earth are made of cells.  Some organisms are unicellular (Paramecium for example) but many are made of many cells.  And all living organisms have the molecule DNA as their genetic material.  If you get a question on this in the exam, it’s probably better to talk about the 8 characteristics of life the examiner likes… That’s exams for you!

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