Introduction
This material acts as a study guide for unit A3 The characteristics of living things in Biology by Roberts, and unit A2 The characteristics of living things in The living world, also by Roberts. It is also a sort of index for the Humans as Organisms section of the syllabus, although this does not simply stick to these 7 processes.
Suggested teaching strategy
Units A1 How scientists work and A2 Studying biology of Biology
Unit A1 Studying biology of The living world could be read beforehand, but are not essential.
You could start with a brainstorming session about the difference between living organisms and non-living objects. This is likely to focus on human activities, e.g. eating, walking, sleeping, rather than universal concepts. As an all-round Biologist, I am rather keen to show the general application of this knowledge (hence the animals vs plants slant), although GCSE syllabuses concentrate mostly on humans.
There may be a problem in identifying names of processes rather than simple actions, if that is required.
This could then be followed by printed worksheets and instructions for their use.
As a matter of fact, I used to include the following, together with this graphic at an appropriate place on the (odd numbered) pages:
How to use these study guides
Read these sheets in conjunction with the textbook and pay attention in class so that you are able to fill in the gaps with the most appropriate words or information.
Do not leave sections uncompleted. If any section is not covered in class, it must be finished for homework. You are also expected to learn and understand the general topics they contain.
These sheets themselves constitute the homework, and will be collected in, marked and returned. You must also take the opportunity to correct and extend your answers at this stage. The sheets must be treated with respect, and filed in an accessible way so that they may be referred to and used for revision purposes.
Some pupils like the use of mnemonics to help them remember these processes.
Two common versions are : MRS GREN and MR GRIEF
Movement
Reproduction
Sensitivity
Growth
Respiration
Excretion
Nutrition
and
Movement
Reproduction
Growth
Respiration
Irritability
Excretion
Feeding
It would probably be fun to get a new slant on this; you could e-mail some of your classes' alternatives to me.
Possible problems
The main problems are likely to be misconceptions, mostly planted by parents or previous teachers?
Movement and sensitivity - These are not really apparent in green plants, and it may be useful if it is possible to refer to pot plants in the lab leaning over towards the light.
Growth - some examiners do not permit the notion that bacteria " grow " and will only allow mention of reproduction
Feeding - the idea that plants and animals both feed may take some convincing
Respiration - often confused with with breathing (a turbocharging process only found in active animals), but often (wrongly) seen as a different process in plants.
Practical activities
The observation experiments involving Elodea, and Mimosa are potentially OK, but they may suffer from availability problems, especially if you are starting this course in September, and they may also give the wrong ideas about plants - exceptions that prove the rule?
An alternative activity which I have used is the extremely flexible format "Mystery (Round?) Objects" practical:
A series of apparently inanimate round objects are examined (possibly using microscopes or hand lenses), then subjected to various treatments - immersed in liquids, etc, and then re-examined later for signs of life.
Practical Notes for teachers and technicians
The "Mystery objects" practical is a very simple one. Possibly it is best set up as a circus, with a variety of microscopes already set up with lettered specimens on slides, alongside containers of liquid.
- Brine shrimp eggs (Artemia salina) - supplied as source of food for Hydra, but often left over after they have been used. These may be recognised as "Sea monkeys", as marketed by an enterprising US company
.
These need to be sprinkled very sparingly on the surface of an artificial sea water solution (say 50 ml in a 100ml beaker), kept at room temperature and re-examined daily or weekly. Later on, they can be encouraged to congregate round a light source, showing movement, sensitivity, etc.
- Cress seeds - or mustard - or rape etc
These can be placed in a very shallow layer of (tap) water, kept at room temperature and re-examined daily or weekly. These will show growth (movement) and sensitivity to light and gravity
- Yeast - preferably of the old globular looking variety
These can be placed in a beaker of sugar solution, kept at room temperature and re-examined daily or weekly. Alternatively, they could be placed in a conical flask containing sugar solution, with a delivery tube leading into a test-tube containing water or limewater, to show respiration producing carbon dioxide. If the beaker overflows, it might be seen as growth! Another alternative is to measure the depth of deposit in the bottom of a measuring cylinder.
- Glass balls - such as sold for anti-bumping purposes (well, there need to be some non-living objects!)
These can be placed in a very shallow layer of (tap) water, kept at room temperature and re-examined daily or weekly. Please do not let me know if they show any of the characteristics of life, as I know thay can find their way to odd places!
This could be extended to include any interesting specimens, such as:
- Stick insect eggs
These need not be placed in a liquid, but could be placed in a small transparent container, e.g. universal indicator box, and re-examined regularly.
- Volvox
Being already in water, these can be left alone or placed in a very shallow layer of prepared artificial pond water, kept at cool room temperature and re-examined daily or weekly.
- Hydra - preferably the brown species.
These can be placed in a very shallow layer of prepared artificial pond water, kept at cool room temperature and re-examined daily or weekly. Some classes find their feeding behaviour interesting. If fed with Daphnia or brine shrimps (without the sea water) they may even increase in number, due to asexual reproduction!
- Dried peas
- Frozen peas, thawed
- Canned peas, drained
These can also be placed in a very shallow layer of (tap) water, kept at room temperature and re-examined daily or weekly. Only the former will germinate!
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