Next Generation Curriculum-embedded Science Performance Task
Grade/ Course
Task Name
Task Summary
NGSS PE (s)
NGSS DCI(s)
NGSS Practices
CT Science
Standards
Middle School/ Life Science
THE LINKAGE OF DIFFUSION AND HUMAN BODY SYSTEMS
In this performance task students will use demonstrations of osmosis and
diffusion experiments to observe the movement of water, sugars and starches
across artificial and natural membrane systems. Students will develop
schematic drawings to model and explain the movement of molecules across
the cell membrane as an essential component of cell function. Students will use
their understanding of simple membrane functions at the cellular level,
combined with online & literature research to write a paper on the topic,
”Importance of Diffusion in the human body”. In their paper student groups will
use arguments, supported by their schematic drawing models, and evidence
from their research and experimental findings to explain how cell-based organ
systems depend on diffusion as an important part of their normal functioning.
MS-LS1-2. Develop and use a model to describe the function of a cell as a whole
and ways parts of cells contribute to the function.
MS-LS1-3. Use argument supported by evidence for how the body is a system of
interacting subsystems composed of groups of cells.
for particular body functions.
(MS-LS1-1)Within cells, special structures are responsible for
particular functions, and the cell membrane forms the boundary that controls
what enters and leaves the cell.
(MS-LS1-2) In multicellular organisms, the body is a system of
multiple interacting subsystems. These subsystems are
groups of cells that work together to form tissues and
organs that are specialized
2. Developing and using models. A simulation is one type of model that can be
used to understand complex systems and generates predictions.
6. Developing explanations. Students need to develop an explanation of how
cell-based organ systems depend on osmosis and diffusion as an important part
of their normal functioning.
7.Use an oral and written argument supported by evidence to support or refute
an explanation or a model for a phenomenon. (MS-LS1-3)
Use an oral and written argument supported by empirical evidence and
scientific reasoning to support or refute an explanation or a model for a
phenomenon or a solution to a problem. (MS-LS1-4)
7.2 — Many organisms, including humans, have specialized organ systems that
interact with each other to maintain dynamic internal balance.
GRADE-LEVEL CONCEPT 7.2.a.
The cell is filled with a fluid called cytoplasm; cells contain discrete membraneenclosed structures called organelles that perform specific functions that
support the life of the organism. The structure of the organelle is related to its
function. The entire cell is surrounded by the plasma membrane that controls
the flow of materials into and out of the cell.
DRAFT
GRADE-LEVEL CONCEPT 7.2.b.
1. Systems consist of parts that interact with and influence each other. Parts of
a system work together to make the whole entity work. Similarly, each part of
an animal body has a specific job to do, and all the different parts work
together to support life.
CCSS.ELA-LITERACY.RST.6-8.1
Cite specific textual evidence to support analysis of science and technical texts.
CCSS.ELA-LITERACY.RST.6-8.2
Determine the central ideas or conclusions of a text; provide an accurate
summary of the text distinct from prior knowledge or opinions.
CCSS/Literacy in
Science &
Technology
Skill Objective
Addressed
Context and
Alignment
Task
Characteristics
CCSS.ELA-LITERACY.RST.6-8.3
Follow precisely a multistep procedure when carrying out experiments, taking
measurements, or performing technical tasks.
CCSS.ELA-LITERACY.RST.6-8.7
Integrate quantitative or technical information expressed in words in a text
with a version of that information expressed visually (e.g., in a flowchart,
diagram, model, graph, or table).
NGSS practices as listed above
This task is embedded into middle school life science unit after students have
completed their learning of human body systems.
The task includes three main activities
1. Anticipation Guide
Watching a video on “osmosis experiment” to engage students in the
inquiry followed by student’s coming up with their notices and
wonders. The video will get student’s excited and increase their
curiosity about the topic and also get them thinking about the
phenomenon (5 min). Each group will then share their wonders with
the rest of the class to further increase the inquiry about the topic.
Students will then read an article on “Diffusion and human body” to
understand the process of diffusion and osmosis and how these
processes relate to the functions of human organ system at the cellular
level.
This article will also allow teachers to assess the students on CCSS, RST.
6-8.1,8.2.
2. Hands on diffusion/osmosis experiment using dialysis tubing and two
solutions to observe the movement of water, sugars and starches
across artificial membrane systems, and later on students will use the
results of their experiment to draw a schematic model.
This assignment will help teachers to assess CCSS, RST,6-8.3 , 8.7.
3. Research on the phenomenon of diffusion and osmosis with respect to
different body processes, (absorption, gas exchange, and filtration etc.)
4. Write a paper on the topic , “Importance of Diffusion in human body
DRAFT
systems”
Task Materials
This performance task requires the use of the following materials
Test tubes, beakers, stirrers, dialysis tubing, ties, molasses, starch, Lugol’s
iodine, water, and computers/ reading materials.
Student Learning Objectives
What do students need to understand about the function of cell membranes with respect to the organ
systems
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Process of osmosis and diffusion
Role of cell membranes in the organ system
Role of osmosis and diffusion in the functions of organ system
Developing a schematic model for the phenomenon of osmosis and diffusion.
Use the schematic model to explain how a single cell contributes to the functioning of the organ
system.
Task Administration Overview
Session 1
Session 2
Overall Assessment Structure
Introduction/Anticipation- Introduce students to the
concept of Diffusion and Osmosis by showing a you
tube video. The video shows the effect of placing two
different eggs in hypo and hypertonic solutions
demonstrating the process of osmosis. Students will
fill in the chart on I notice/ I wonder after watching
the video and share their wonders with the class.
Then students will read an article on “Diffusion and
human body” to reinforce the concepts and
vocabulary related to the topic, and also use the skill
on “citing textual evidence “/ “author’s purpose” to
show their understanding. (ccss)
Performing an experiment on diffusion/osmosis to
observe the movement of water, sugars and starches
across the artificial cell membrane, (dialysis tubing).
Students will analyze the results of the experiment to
answer the questions at the end of the experiment.
Then students will show their understanding by
drawing a schematic model on how diffusion works in
the body processes.
DRAFT
NGSS Connection
Getting the background
knowledge to develop a
model of the concept on
processes of osmosis and
diffusion through cell
membranes.
Designing the schematic
models of the processes
of diffusion and osmosis
in the human body organ
systems.
Session 3
Provide students with time and access to the internet
to perform their research about the movement of
molecules across cell membranes in various organ
systems. Students will be provided with a resource of
websites and some guiding questions to help them
focus their research.
Students will now use their schematic drawing as well
as the resources from their reading, experiment and
research to write a paper on the topic
“Importance of Diffusion in the human body
systems.”
The paper should have five paragraphs with an
introduction, three paragraphs for the body, and
finally a conclusion. Students should cite the sources
of their research at the end of the paper.
DRAFT
Use argument supported
by evidence in their
presentations to explain
how the processes of
diffusion and osmosis
work in different organ
systems.
Student materials for Session 1 Performance Task MS: (LS)
Anticipation Guide
https://www.youtube.com/watch?v=SSS3EtKAzYc
After watching this small clip from you tube complete the following chart along
with your team.
We Notice
We Wonder
DRAFT
Diffusion and Human body
Read closely the article on Diffusion and Human body, highlight or underline any important information
relevant to the topic, and answer the questions at the end. Cite the evidence from your reading to justify
your answers. (CCSS.ELA-LITERACY.RST.6-8.1), (CCSS.ELA-LITERACY.RST.6-8.2)
1) The Cell Membrane
The cell is the basic functional unit of all living things. If one is to understand what is happening
within an organism, it is necessary to study what is happening to the individual cells within the
organism .The cell membrane, sometimes referred to as the plasma membrane, is a phospholipid
bilayer that creates a definite boundary between the inside of the cell and the outside of the cell. The
structure of cell membrane allows it to easily regulate the materials that enter and exit the cell .
Because the cell membrane allows certain materials to pass through it, and keeps other materials out
of it, it is referred to as a semi-permeable or selectively permeable membrane. Much like the security
guard at a government center, movement into and out of the cell is highly regulated.
2) Diffusion
Water, carbon dioxide, and oxygen are a few substances that are able to pass through the cell
membrane without any help from the proteins embedded in the membrane. These materials can
simply pass through the membrane without the use of energy and they will do so in an attempt to
reach an equal solute concentration inside and outside of the cell. This process is called diffusion,
when substances move from a region of high concentration to a region of low concentration. The
"goal" of diffusion is to reach a state of equilibrium. This does not mean that movement of
molecules stops once equilibrium is reached. Equilibrium is a state of balance, where for every
molecule of a substance that moves into a cell, another one moves out of the cell . To visualize
diffusion, imagine two rooms that are connected by one door. If the door connecting the two rooms is
closed and everyone is crammed into only one of the rooms, as soon as the door opens, people will
begin to walk into the other room to spread out. Most likely, they will not all move into the newly
opened room. Instead, they will spread out until every area of the two rooms has roughly the same
density (or concentration) of people. People will still be able to walk around and mingle, but they will
likely readjust so that every part of the room is equally comfortable at all times. Diffusion is an easy
concept to model. Simply place a drop of food coloring into a glass of water (being careful to make
sure that the fluid in the glass is completely still). The food coloring will slowly spread out in the
water until it is evenly mixed throughout.
3) Diffusion In the Human Body
Within the body, diffusion is vital to the functioning of the cardiovascular system and other body
systems as well. When oxygen is inhaled into the lungs, it ends up at high concentration in the alveoli,
the round sacs at the end of the bronchioles. Because blood that is flowing through your lungs is
deoxygenated, there is a higher concentration of oxygen inside the alveoli than in the blood. In an
attempt to reach equilibrium, the oxygen simply diffuses into the blood across the cells at the
alveolar/capillary boundary. Similarly, the blood circulating through the capillaries in your lungs
contains high amounts of carbon dioxide that has been picked up as a waste product from cellular
respiration. The concentration of carbon dioxide in the blood is much higher than it is in the alveoli,
DRAFT
and the carbon dioxide moves into the alveolar gas through simple diffusion; it is then exhaled out of
the body 7. In regards to cells, simple diffusion is only possible if the material is able to permeate the
membrane.
4) Examples of Diffusion
Below are examples of diffusion in the body across concentration gradients.
Place
Particles that move
From
To
Gut
Digested food particles Gut cavity
Blood in capillary of villus
in small intestine
Lungs
Oxygen
Alveolar air space
Blood circulating around the
lungs
Lungs
Carbon Dioxide
Blood circulating
Alveolar air space
around the lungs
Remember: Particles continue to move from a high to a low concentration until all the particles
are evenly and randomly distributed.
5) Osmosis
Osmosis is simply a special type of diffusion. It occurs when water molecules pass through
a partially permeable membrane. Some membranes in plant and animal cells allow certain
particles to pass through them but not others. They are partially permeable membranes.
During osmosis, more water molecules pass from the pure water into the dilute solution than
pass back the other way. This is because there is a higher concentration of water molecules in
the pure water than in the solution. This results in more water molecules diffusing across the
concentration gradient from the water to the solution. Eventually, the level on the more
concentrated side of the membrane will rise, while that on the less concentrated side falls.
6) Osmosis is the overall movement of water from a dilute solution to a more
concentrated solution through a partially permeable membrane. This is still like diffusion,
as the water is moving from a higher concentration of water to a lower concentration of
water. When the concentration of water is the same on both sides of the membrane, the
movement of water will be the same in both directions. At this point, the net exchange of
water is zero, and the system is in equilibrium. If red blood cells are placed in pure water,
water enters them by osmosis and the red blood cells swell up and burst.
DRAFT
Name: _____________________
Date: ______________
1. What is this article about?
_____________________________________________________________________________________
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_____________________________________________________________________________________
2. What is the author communicating about in the first paragraph? Why is this information important?
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3. What does the word semipermeable mean? How is this word related to the cell?
_____________________________________________________________________________________
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_____________________________________________________________________________________
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4. In paragraph 2, the author uses an example to visualize diffusion. Does this example help you to
understand what diffusion is? How?
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DRAFT
5.What is the relationship of diffusion and human body? Explain with the help of citing textual evidence
from the article.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
6. How is osmosis similar and different from diffusion? Use textual evidence to support your answer.
_____________________________________________________________________________________
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_____________________________________________________________________________________
_____________________________________________________________________________________
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7. Explain with the help of textual evidence how diffusion takes place in the alveoli and capillaries?
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
DRAFT
Osmosis & Diffusion Lab – Dialysis Tubing
Background
The movement of molecules through a cell membrane is termed osmosis or diffusion. Such movement
is principally possible because nutritive molecules are smaller than membrane micro pores. If the
molecules are too large, no molecular transfer, or diffusion occurs.
Thus, some membranes may transmit selectively and are termed semi-permeable membranes. In the
following experiment, cellophane dialysis tubing serves as an excellent representation of the cell
membrane. The enclosed tube may, for the purpose of this experiment, be considered a single living cell
in greatly enlarged form.
Materials
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Glucose Solution
Starch Solution
Iodine Solution
Glucose Test Strips
Dialysis Tubing
String,
400 ml Beaker,
10 mL Graduated Cylinder,
Scissors,
Ruler
Procedure
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Measure and cut 20 cm of dialysis tubing.
Place this tubing in a beaker and cover it with water. Allow it to soak for about five minutes.
Remove the tubing from the water and rub one of the ends between your thumb and
pointer finger to open. Once open, submerge it in water again for about thirty seconds.
Tie one end of the tubing in an overhand knot
Measure 5 ml of starch solution using the 10 ml graduated cylinder and pour it into the
tube.
Thoroughly rinse the graduated cylinder, shake dry, and measure 5 ml of glucose solution.
Pour this into the tubing as well.
Tie the second end of the tubing in an overhand knot and rinse it under the faucet. Set your
“cell” on a clean surface.
Fill the 400 ml beaker ¾ full with tap water. Add 10 drops of Iodine solution and stir well.
(Iodine will turn blue-black in the presence of starch).
Test the solution in the beaker for the presence of glucose by dipping a glucose test strip
into it. After 30 seconds, compare the color on the strip to the color chart on the side of the
bottle. Complete the Initial Status information on your data table.
Place the artificial cell (the sealed tubing with solutions) into the beaker of solution and
allow it to remain undisturbed for 15-20 minutes.
Remove the tubing from the beaker and record your observations in the data table for final
status of the solution and the bag.
Retest the solution in the beaker and in the bag with a new glucose test strip and record this
data in your table.
DRAFT
Data
Name ________________________________
Materials
Bag
Initial
Contents
Initial Solution
Color
Final Solution
Color
Initial
Presence of
Glucose
Final Presence
of Glucose
Glucose &
Starch
Beaker
H2O + I
Analysis of Results
Answer the following questions on a separate sheet of paper
1.
2.
3.
4.
5.
6.
7.
(a) Describe the test results, which show the presence of starch. (b) Can the starch molecules
pass through a dialysis membrane? Which results support this conclusion?
Is the membrane selectively permeable? Explain.
Describe and account for any changes that occurred in beaker. Be sure to specify the direction
of movement for each molecule.
Describe and account for any changes that occurred in the bag. Be sure to specify the direction
of movement for each molecule.
For each of the following questions, explain your answers using your results. a) Which molecules
pass through the membrane? b) What molecules were unable to pass through the membrane?
Can you relate the results of this experiment with digestion or absorption?
Draw and label a schematic model to show the movement of four molecules from the bag into
the beaker and vice versa?
DRAFT