Purpose:Observe the process of osmosis in plants and relate to biotic elements of the oceans.

Background:

Water is a critical element of the body, and adequate hydration is a must to allow the body to function. Up to 75% of the body's weight is made up of water. Most of the water is found within the cells of the body (intracellular space). The rest is found in what is referred to as the extracellular space, which consists of the blood vessels (intravascular space) and the spaces between cells (interstitial space).

Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in. The body is very dynamic and always changing. This is especially true with water in the body. We lose water routinely when we: breathe, sweat, or urinate. In a normal day, a person has to drink a significant amount of water to replace this routine loss. The body lives within a very narrow range of normal parameters, and signs and symptoms of dehydration will occur quickly if the water is not replenished. Complications from dehydration include crams, vomiting, nausea, heart palpitations, kidney failure, coma, and shock.

Water molecules move across membranes through a process called osmosis. Water moves across a a membrane to higher levels of salt concentration to reach equilibrium. Animals and plants that live in the ocean usually have a high salt content within their cells in order to avoid dehydration. On the other hand animals and plant that are not adapted to salt water may have a low salt content, and thus become dehydrated when placed in salt water.
Question:
Why can’t many land and freshwater plants live in the ocean?

Why can’t many saltwater plants live in fresh water?

There are freshwater fish and saltwater fish, and few of them can live in bothenvironments: why is this so?

Procedures:
Day 1

  1. Mix a strong salt water solution in a beaker with 100 ml of water (If the solution is 10% salt…, how much salt should you add to 100 ml of water?( ______)
  2. Fill a second beaker with 100 ml fresh water
  3. Gather two pealed pieces of carrotand twopieces of celery.
  4. Test the crispness of your vegetables by trying to bend them.
  5. Weigh each vegetable and record in the table on the following page.
  6. Place vegetables in beakers and observe next class. Write a hypothesis.

Identify the following elements of this experiment:

Independent Variable:______

Dependent Variable: ______

Control Group: ______

Constants (3-5): ______

Hypothesis (in Salt Water): ______

Rationale:

Hypothesis (in Fresh Water): ______

_Rationale:______

Day 2

  1. Again test the flexibility and weight of each vegetable. Record in chart.
  2. Extension – place vegetables from salt water back in to the fresh water. Observe at the end of the class period. Is there a change?
    Data Chart Carrot:

Solution: / Day 1 Description / Day 1
Weight in grams / Day 2 Description / Day 2
Weight in grams / Difference in weight / Gain or Lose H20
Salt Water
Fresh Water

Data Chart Celery:

Solution / Day 1 Description / Day 1
Weight in grams / Day 2 Description / Day 2
Weight in grams / Difference in weight / Gain or Lose H20
Salt Water
Fresh Water

Class Data -Carrot

Group: / 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / Average
Salt Water: Difference in weight
Fresh Water: Difference in weight

Class Data –Celery

Group: / 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / Average
Salt Water:
Difference in weight
Fresh Water: Difference in weight

Graph class averages on the graph paper on the next page.

Describe the overall observed changes from day 1 to day 2:

How do animals and plants in the ocean avoid dehydration?

What would happen if you placed a freshwater plant in an ocean environment?

My conclusion is that molecules of water diffuse from an area of ______concentration to an area of ______concentration. When the vegetables soaked in salt water, the water traveled from the ______into the ______; the vegetables mass ______by ______g. The reverse happened when the vegetables were soaked in fresh water. In that case, the water flowed from the ______into the ______; the vegetable’s mass ______by ______g. Hence, the water tends to leave the inside of the organism, unless it has a ______salt level than its environment.

Graph – don’t forget title, axis values, axis titles, and the bar graph!