School Science/Care of living organisms

This page describes the care of living organisms in a school science laboratory, other than humans. For this, see human care.

Plants

The most common plant to be found in a school science lab is the geranium Pelargonium. They are very easy to grow and tolerate abuse well. They can be propagated from cuttings very easily. Take a section of geranium with one or two smallish leaves and leave in water for two to three weeks. When you see the roots growing, pot into sandy compost. Cuttings should be taken on a regular basis to replace old plants, which tend to become woody and unattractive after a couple of years laboratory abuse.

Geraniums are good for the following experiments:

• Testing leaves for starch
• Nail varnish impressions of stomata

Animals

Fish pond water

A good species of fish to keep is the goldfish as they can thrive in cold water. They come in a variety of fancy forms that are quite beautiful. Be careful that you don't keep fancy goldfish in the same tank as regular ones because ordinary goldfish can swim much faster than fancy ones and will kill them. Furthermore, ordinary goldfish have a bigger diet and are constantly digging food out of the gravel.

Water snails (Limnaea and others) can be purchased in the UK from a number of suppliers including Blades Biological. You can easily obtain snails from garden ponds and clean canals, or from many pet shops which stock fish. They help to keep a cold water fish tank clean and free of algae. They can be used to investigate respiration and the carbon cycle.

Stick insects

Stick insects come in a variety of species and by and large are very easy to keep. Beware some species of stick insect reproduce asexually and you will be overrun with little stick insects unless you remove the eggs. They typically live for about 18 months, and, depending on the species, feed on brambles or privet.

Woodlice

Start your own breeding tank: the best way to get woodlice at all times of the year (and no need to go searching under stones if ordered at the last minute). Use a large opaque plastic box with a lid; about 3-5cms of fine soil in the bottom; a couple of lumps of chalk; some clumps of damp cotton wool; a source of food, for example celery, potato, leaves.

According to which type and age range of woodlice you start with they should start breeding within a few weeks or months, although some can take up to two years to reach breeding age. If planning to be used for detailed investigation, only put one species in the tank, unless you want a selection of offspring.

Daphnia

Culture Daphnia (Water flea) or Cladoceran in an aerated aquarium filled with freshwater. Allow the water to stand for 24 hours to equilibrate dissolved gases.

Make a suspension of yeast in water, and pipette enough into the aquarium to just give the water a milky tinge. Introduce the Daphnia. When they clear the yeast from the tank, add a similar amount. If the tank is left in daylight, algae can grow on the sunlit side. This can be scraped off and broken up, and added to the diet of yeast. Be sure to change the water completely once a month.

One interesting, if slightly morbid way of cleaning 'green' tropical fish tanks of algae is to remove the fish into a second tank (being sure the second tank is well circulated and set at the appropriate parameters similar to that of the original tank) and add Daphnia to the algal soup. After a couple of weeks, when the Daphnia have eaten the algae, re-introduce the fish. This is also a good demonstration of a food chain in action.