Science Junction

 

Water What-ifs

Teacher Notes,
Lesson Extensions and
Alternative Assessment Ideas

Teacher Notes, Lesson Extensions and Alternative Assessment Ideas

Lesson 1-Does a change in temperature effect the growth and survival rate of aquatic plants?

1. Duckweed or elodea (anacharis) may be purchased from a pet supply store which specializes in aquariums or outdoor ponds.

    Lesson 2-How is the metabolic rate of clams effected by a change in temperature?

1. To make saltwater, add 35 grams of 1 Liter of aged tap water. Stir thoroughly and cap to store.

2. Clams may be purchased from a biological supply company or a local seafood market. Make sure the shells are not open when they are purchased. Store in the refrigerator until a few minutes before using.

3. Make sure the students wash their hands thoroughly with antibacterial soap after handling the clams.

4. Background Information-Thermal Pollution For many years water has been used as a coolant in industry, especially in power stations. It was never thought of as a problem, as nothing was actually added to the water. However, higher temperatures can cause enzymes and microbes to speed up, and can eventually kill them. Changes in temperature cause fish to migrate to regions where the water is at the best temperature for them, and can kill any species which cannot move away. Recently people have realized that only small changes in temperature are needed to have considerable environmental impact.

5. If degrees Fahrenheit thermometers are used, have the students use the following conversion chart to convert to degrees Celsius.

Lesson 3-What is the Optimal Temperature for the Hatching and Development of Brine Shrimp Eggs?

1. Brine shrimp eggs may be purchase from a scientific supply company or at a local pet supply store.

2. Brine shrimp culture should be made 24 hours in advance and can be kept indefinitely, if fresh salt water is added on a continual basis.

3. The common brine shrimp (artemia) are closely related to zooplankton such as Daphnia and are often used as live food for aquariums. The artemia life cycle begins by the hatching of dormant cysts which are encased embryos that are metabolically inactive. The cysts can remain dormant for many years as long as they are kept dry. When the cysts are placed in salt water, they are rehydrated and resume their development. After 15 or 20 hours at 25 degrees C (77 degrees F), the cysts burst and the embryo leaves the shell. For the first few hours, the embryo hangs beneath the cyst shell, still enclosed in the hatching membrane. The embryo will grow and progress through 15 molts before reaching adulthood in approximately 8 days. Adult artemia average about 8mm long, but can reach lengths of 20 mm under ideal conditions.

Other variables of importance are pH, light and oxygen. A pH of 7.5-8.5 is optimal, and can be lowered with muriatic acid (any type of acid may be used) or increased with baking soda. A minimum amount of light is necessary for hatching and is beneficial for increased adult growth. Two liter soda bottles with the tops cut off and filled with tap water make great hatching containers. To the bottle filled with water add 10 to 20 grams of salt without iodine and a pinch of sodium bicarbonate (baking soda). Test the pH to make sure in stays in a range of 7.5-8.5. Aeration is necessary and can be accomplished by a small air pump with a length of tubing long enough to reach the bottom of the bottle. Aeration should be light, as the eggs will not hatch if aeration is too brisk.

Feeding the brine shrimp is necessary if the culture is to be used for several days. A solution of baker's yeast and fish tank water to form a milky solution is an ideal food for the growing brine shrimp. The brine shrimp culture only needs a few drops of the yeast solution as they are not big eaters and overfeeding can foul the culture. The yeast solution can be placed in a dropper bottle and stored in the refrigerator.


Lesson Extensions

1. Allow the students to dissect the clams and identify the parts of the digestive system after finishing Lesson 2.

2. Use other filter feeders such as oysters or mussels and compare their metabolic rates to those of the clam.


Alternative Assessment Ideas

1. Have students assess the quality of several different water samples and determine how the numbers of plants and organisms will vary from sample to sample based on the temperature.

2. Set up several different aquatic ecosystems at different temperatures. Have the students keep a daily journal of the changes which take place over a period of time.



Water What-ifs Home | Temperature Lessons



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©1998 April J. Cleveland for Science Junction, NC State University.
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lessons/temp/tempteachernotes.htm
Last Modified: 7/27/00

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