Download Organisms and Experiments

Organisms and Experiments
Name
Illustration
Comments and common experiments
This is a tiny beetle, easily reared in flour and with a short life
cycle of only 7-12 weeks.
Experiments: population growth; competition; genetics.
Tribolium
flour beetle
Easily found in damp leaf litter.
Experiments: taxis (behavioural response)/food choice
typically using choice chambers.
Woodlice
various species
Daphnia
water fleas
Easily purchased from pet shops where they are used as fish
food.
Experiments: examining factors affecting feeding rate or heart
rate e.g. nicotine.
Lemna
duck weed
Common plants on slow moving water and ponds. Easily
reared in the laboratory in small containers e.g. Petri dishes or
old 35mm film containers. Capable of rapid growth.
Experiments: examining factors affecting population growth
such as competition, space, availability of a range of different
nutrients and toxicity testing.
Seeds
various species
Experiments: examining factors that affect the distribution of
seeds by air or animals or factors affecting the germination of
seeds such as salinity, inhibitors etc.
Artemia
brine shrimp
Brine shrimp are easily reared in laboratory conditions. Eggs
can be obtained from most aquarium shops where they are
used as fish food.
Experiments: see the British Ecological Society guide.
Hydra
Hydra is a little bit harder to keep in a lab.
Experiments: examination of factors that affect their feeding
behaviour and growth. Hydra will feed on Daphnia and brine
shrimp.
Hydra eating brine shrimp
Arabidopsis
thaliana
thale cress
This tiny plant, a rapid-cycling Brassica (cabbage) can
complete its entire life cycle in just six weeks. It is used
extensively as a model organism by biologists and the entire
base sequence of its genome has been established.
Experiments: a very large number of experiments is possible.
A good starting point would be to look at the Science & Plants
for Schools (SAPS) website for further guidance.
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Organisms and Experiments
Name
Saccharomyces
cerevisiae
yeast
Illustration
Comments and common experiments
Yeast has been used since ancient times in baking and
brewing. It is one of the most intensively studied
eukaryotic model organisms. It can be grown in a sugar
solution where it grows rapidly producing ethanol and
CO2.
Experiments: examining the effect of pH, temperature,
different types/concentrations of sugar on growth.
Lumbricus
terrestris
earthworm
Locust
Fly larvae
Earthworms can be easily obtained by digging in damp fertile
soil.
Experiments: the dorsal blood vessel can easily be seen under
a binocular microscope and the contraction rate measured in
various conditions.
Locusts can be obtained from most pet shops.
Experiments: often used to examine the ventilation rate in
different gas environments.
Easily purchased from most fishing shops in large numbers.
Experiments: the larvae’s sensitivity/response to light,
temperature, food, etc. This would fit in well with the A2
topic that deals with forensics.
Fruit
various species
Experiments: fruit produce a hormone called ethylene that is a
gas. This hormone has several effects including that of
ripening fruit. Pectinase enzyme breaks down fruit cell walls
in ripening. Damage to fruit causes browning as phenolic
compounds are released. See the Science & Plants for Schools
(SAPS) website for more details.
Drosophila
fruit fly
Drosophila has been the standard experimental organism for
geneticists for a long time. They can be obtained from
suppliers although they can be expensive. However, they can
also be found around any over-ripe fruit in the wild.
Experiments: genetic experiments would be the most obvious
although there are others. However, care would have to be
taken to make sure the experiment fits the A-level
specification.
Homo sapiens
Humans
In theory, readily available; however, it is not always easy to
obtain enough of them for a suitable sample size. There are
usually ethical issues to be considered here: generally people
are not enthusiastic about giving up limbs or fingers for the
sake of improving your A-level practical, unlike plants which
rarely protest.
Experiments: common experiments include looking at the
effect of exercise on breathing rate, factors affecting reaction
time, eyes and perception.
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