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Biology Unit 4
Topic 5: On the wild side
17. Describe how to investigate the effects of
temperature on the development of organisms (eg
seedling growth rate, brine shrimp hatch rates).
You will need:
Brine shrimp egg cysts
2g sea salt for each treatment
100cm³ de-chlorinated water for each treatment
40cm³ beakers (one for each temperature to be tested)
Water baths or incubators (one for each temperature to be investigated)
Pair of forceps
Fine glass pipette
1. Decide on a range of temperatures from 5°C to 35°C to be tested.
2. Place 2g of sea salt into a 100cm³ beaker.
3. Add 100cm³ of de-chlorinated water and stir until the salt completely dissolves.
4. Label the beaker with sea salt and the temperature at which it will be incubated.
5. Place a tiny pinch of egg cysts onto a large sheet of white paper
6. Wet a piece of graph paper using a few drops of salt water. Dab the paper onto the white
sheet to pick up approximately 40 eggs. This will look like a tiny shake of pepper. Use a
magnifying glass to count the eggs. Cut the graph paper so that there are exactly 40 eggs.
7. Put the paper with the 40 eggs into the beaker (eggs-side down). After 3 minutes, use a pair
of forceps to gently remove the paper, making sure that all the egg cysts have washed off
into the water.
8. Repeat steps 2 to 7 for all the temperatures that are to be investigated.
9. If possible replicate the treatments.
10. Incubate the beakers at the appropriate temperatures, controlling exposure to light as far as
11. The next day count the number of hatched larvae in each of the beakers. To do this, place a
bright light next to the beaker. Any larvae will swim towards the light. Using a fine glass
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Biology Unit 4
pipette catch the brine shrimp and place them in a small beaker of salt water. Repeat the
counting daily for several days. Brine shrimps are very delicate and care must be taken when
12. Record the number of larvae that have successfully hatched at each temperature.