Hypertonic to Hypotonic Flow - Osmosis! Let's Go!

Sixth graders have completed a lab on osmosis using gummy bears as a model of the cell.  The masses of three gummy bears were determined.  One was placed in an empty cup as a control.  One was placed in 250ml of water, and the final one was placed in 250ml of water in which a sugar cube had been added. 

Osmosis is the diffusion of water from an area of greater concentration to lesser concentration.   The bears that had been placed in sucrose water and tap water increased in mass after 72 hours by an average of 9 grams and 11 grams respectively.  The masses of the control bears stayed the same.

Students concluded that the bears were hypotonic to the water and therefore the water from the cup diffused through the outer membrane of the bears through osmosis into the gummy bear. 

Qualitative data was recorded as well.  Bears became soft, slimy and more fragile. 

Cellular Respiration

Transpiration of oxygen and water out of the stomata of leaves was evident in the plants found in the outdoor classroom this week.  Sixth graders placed a plastic bag around a leaf and left it for 24 hours.  When they returned to check on the project, most students found between 2.5 and 5 ml of water in their bag. This process proved that cellular respiration had taken place in the cells of the chosen plant.  

In cellular respiration, the mitochondria in cells convert small glucose molecules into energy, carbon dioxide, and water. This process is the other half of the energy cycle. Photosynthesis and cellular respiration are the two processes in the energy cycle. 

Students also completed a chromatography investigation where they took leaves from some of the green plants and placed them in alcohol.  After allowing the chlorophyll to break down, they placed a filter into the solution to separate the chlorophyll from the other colors in the leaf.  The fall leaf colors have been in the leaves throughout the growing season, we have not been able to see them because of the chlorophyll.  When plants start to go dormant for the winter, the chlorophyll breaks down and the other colors begin to show. 

Students were able to study the leaves at both the macro and micro scale by using the digital microscope with an ipad. 

How Do Cells Function?

How do you explain the ways cells contribute to the function of living organisms?  In an effort to promote the basic understanding of the role of cells in body systems and how those systems work to support the life functions of the organism, students have been completing experiments and modeling the cell organelle functions. 

Students placed raw eggs into five different solutions to see if the solution would pass through the barrier of the shells to affect the circumference of the egg.  Both quantitative and qualitative data were taken over a five day period to record changes in the egg.  Students inferred that the process of osmosis allowed some of the substances to pass through the shell and increase the size of the egg.   Students included a control egg that was not placed into any solution.  This was offered as evidence that it was the solutions that were affecting the egg size.  Constant variables that should stay the same were also identified to make sure that the experiment was a fair test.

Students then moved to the outdoor classroom to make cell models out of materials found outside.  The cell membrane was represented with a plastic bag and the cytoplasm that the materials were placed into was made of corn syrup.  Students then explained which biotic factors they chose to represent the organelles and why they were chosen.

Life Comes From Life!

Sixth graders have been studying cells and cell theory in Science.  They have created models, group diagrams, and microscope slides of real specimens from the outdoor classroom wetland.

The conclusions they have drawn support the cell theory.

All organisms are made up of cells.  Some are multicellular and some are unicellular. The cells allow the organisms to carry out the functions of life. All cells come from existing cells.

In Technology class, students are looking at the cells from the macro scale.  They are collaborating with google shared documents over the systems of the body and preparing presentations to share with classmates.  

How Does Your Ape Index Compare to Michael Phelps?

 

An ape index is a measure of the ratio of a person's arm span relative to their height. A typical ratio is 1.0   People with a ratio greater than 1.0 have a greater arm span than height.  A ratio less than one indicates a person who is taller than the distance between their outstretched arms.

While learning about the international system of measurements used by scientists, students found the ratio for everyone in the sixth grade class. The data was collected, (in centimeters of course), charted, and analyzed.  Student ratios fell in the range of .96 to 1.02. 

Michael Phelps, world-class swimmer and winner of 23 Olympic medals, has an index of 1.06.  His arm span is 12 cm. longer than his height. 

Nitrogen Cycle Animations

            The nitrogen cycle is the third ecological cycle the sixth graders have learned about this year.   They have completed a project in which they demonstrated the cycle in an animation. To make the project more "place based", students drew a picture of the tallgrass prairie which included wildflowers and forbs for their slide background. These prairie plants have bacteria in their roots that aid in nitrogen fixation.  The only other way that nitrogen can be converted into a usable form is through lightning. 

             After inserting their picture into powerpoint, they used the drawing  and animation tools to demonstrate the cycle. Nitrogen gas, N₂ is changed into a nitrate, NO_3, by the bacteria.  The plant is then able to utilize the nitrogen to grow and develop.  Animals receive nitrogen by eating the plants or other animals that have eaten the plants.  All living things must depend on this conversion to receive nitrogen even the though 78% of the atmosphere is made up of this gas. When the organisms die and return nitrates back to soil, it is converted to nitrogen gas by bacteria and released back into the atmosphere.

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Sixth Graders Stand and Deliver Illustrated Talks

Students presented illustrated talks on the Kansas or flyway bird they have researched this past month. This product represents the last step in the paraphrasing process that students have been practicing.  Students delivered their speeches without presenter notes, they were able to talk about their birds from memory over the things they have learned about it during this project. Most of the students included an uploaded jpeg of their drawing and sound files to enhance their presentations.  Each student was peer reviewed by all the members of his or her class according to the assessment rubric.  Videos can be accessed through Google classroom.