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1.  What you can do
2.  Water
3.  Ecology
4.  Amphibians
5.  Environmental Issues
6.  Keystone species
7.  Get Wet!-
     Field Study Ideas

8.  The Zoo Experience
9.  Frogs & Friends
10. Case Studies
11. Resources
12. Glossary

Wetland Curriculum Resource
Unit 2. Water - Answers and Notes for Educators

2.1 Too Salty For Me

  1. See diagrams in "Background for Educators".
  2. Fish are adapted in the following ways:
    • they are constantly drinking water to replenish water that is lost by osmosis
    • the urine that is excreted is very concentrated
    • they possess organs in their gills that remove salt from their blood
  3. Amphibians reduce the water lost in their urine. When proteins breakdown in amphibians, ammonia is formed. Ammonia is toxic and requires large amounts of water to be diluted. To compensate for this, amphibians convert the toxic ammonia in the urine to urea, which is less toxic and requires less water to dilute.

2.3 Self A'Steam

  1. Evaporation. Heat must be present.
  2. Condensation. It occurs between the 2 cookie sheets. Cool conditions must be present.
  3. The bag acts to cool the moist air, causing the water vapour contained in it to condense, resulting in the formation of water droplets.
  4. Water is constantly lost through evaporation in nature. It enters the atmosphere as water vapour, but eventually cools and returns to the earth's surface as precipitation, just as the water in the experiment did.

2.4 I'll Drink To That

  1. The first process is evaporation and then condensation.
  2. Water moves from the earth's surface to the air by evaporation then it condenses and falls back to the earth as rain or snow.
  3. When water evaporates, it leaves behind solid substances. The condensed water is clean, and there is no harm in drinking it.

2.5 Bigger Than the Both of Us

  1. Water contracts until it almost reaches its freezing point. As it cools from 4 deg. C to 0 deg. C, water expands. This unusual physical property is known as the anomalous expansion of water. Because of this unusual behaviour, water is most dense at 4 deg. C. At this point, it has the greatest mass for a given volume. Then, as it cools below 4 deg. C and freezes, it becomes less and less dense. Ice is less dense than water, which explains why it floats. The anomalous expansion of water is vital to aquatic organisms. Because of it, water freezes from the surface down, instead of from the bottom up. The frozen water at the top protects the water from freezing below. The water temperature below the ice remains above 0 deg. C.
  2. This is the point where the water is contracting.
  3. There is a reproductive advantage because the ground thaws from the top down. The wood frog can remain near the surface and it is the first amphibian to "wake up" and move into temporary ponds to breed and lay eggs.

2.6 Raindrops

  1. The marbles will accumulate in the lowest area at the base of the hill because of the actions of gravity.
  2. When rain falls on a slope, it will tend to flow downward and accumulate in the lowest area and a wetland is formed.
  3. Rain falling on a parking lot or other hard surface, like compact soil, hits the surface and flows away very quickly. This often creates forceful run-offs, even small streams that can cause erosion. When rain falls on the forest floor the plants, their roots and so on, create a slower run-off, allowing the water to filter slowly into the groundwater and allowing it to be taken up by the plants.
  4. In the springtime, amphibians use temporary ponds and puddles for breeding.

2.7 Cool Change

  1. High temperatures increase respiratory rate and more oxygen will be used.
  2. Temperature can affect the dissolved oxygen content in water. The controls will eliminate that possibility.
  3. As water temperatures increase, oxygen is used up at a faster rate.
  4. Because of the large numbers, the oxygen supply could be used up totally. Amphibians feel the greatest stress just before dawn, because during the night, plants are taking in oxygen for respiration, thus decreasing oxygen levels at an even quicker rate.
  5. Amphibians require less oxygen in the winter. Their metabolic rate decreases when they hibernate, and therefore they consume less oxygen.

2.8 Just A Pinch

  1. The plants and the algae are the producers.
  2. Decomposers such as bacteria and microscopic fungi found in the pond water make up the invisible organisms.
  3. The control helps us determine which changes are a result of the addition of fertilizer and which are simply changes that would have occurred even if fertilizer had not been added.
  4. Answers will vary, but increased productivity (a larger biomass) will normally be observed. The pond water introduces a wide range of organisms (rotifers, protozoans, desmids, crustaceans, diatoms, etc.) into the mini-ponds (i.e. the jars). Eggs and spores of many organisms may be present on the snails and plants. The added nutrients will spawn increased plant growth which in turn, provides more food to sustain a larger snail population.
  5. Sewage contains many nutrients, including carbon, nitrogen, and phosphorus. When these nutrients are released into an aquatic ecosystem, they cause accelerated growth just as the fertilizer did in the mini-ponds.
  6. We try to prevent excess nutrient and fertilizers from wetlands because these will artificially increase the nutrient levels resulting in increased primary production (i.e. production of algae, plants, etc.). A large quantity of oxygen is used to achieve this high level of production and, as the plant life is increased, sunlight is blocked out, oxygen reduced and followed by a large die off of the plant life. This die-off then increases oxygen demand for the decaying process and the cycle continues. For further information about more problems with fertilizers see 5. Environmental Issues, Chemical Contaminants.

2.9 Sally Mander's Favourite Place

  1. South facing shorelines are warmer than north facing ones, (up to 10 deg. warmer). Amphibians seek warmer waters to call, bask, or lay their eggs.


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