Lesson 17. Identifying Homeostatic Relationships between Unicellular Organisms,
Multicellular Heterotrophic Organisms and Plants
Estimated Time: 5 days
Objective: Compare regulation in plants to regulation in humans
EQ: Do plants regulate or maintain homeostasis the same as unicellular and multicellular
heterotrophic organisms? Explain why or why not.
Bridge: We have taken a look at lot of different life processes and how they affect heterotrophic
organisms, like humans.
What about plants?
Do they have to regulate or maintain homeostasis like animals or even unicellular organisms?
Do they have a nervous system?
What about an endocrine system that releases hormones?
Mini Lesson:
Unicellular organisms do not have the same structures for maintaining homeostasis as
multicellular organisms but they use the same functions. For example, where fish use the
osmotic gradient to maintain water balance which evolved from whether they were in salt or
fresh water, a unicellular organism, like our paramecium, will use a specialized organelle called
a contractile vacuole, to gather up the excess water and spit it out of the cell through the cell
membrane. Unicellular organisms also do not have complex endocrine systems to help regulate
cellular communication or complex nervous systems for electrical impulses, but the nucleus and
cell membrane have structures built into them to code for, produce and receive hormones and the
cytoplasm will deliver electrical impulses since they don’t have to go very far.
But many plants are multicellular and some even larger and more complex than even a human or
our largest animals. In fact, the second largest organism in the world is a plant: a giant sequoia
found in Sierra Nevada, Californa. The largest is a fungus found in Oregon called Armillaria
ostoyae that spans 2200 acres (3.4 miles) and is approximately 8,000 years old.
But when I think of plants or fungus, I don’t think of them like I do animals, but they are still
living things so they must be able to find that balance.
Expectations for Work Period: You will be investigating the organization of plants and
comparing them to animals. In these comparisons, consider all of the life processes we have
looked at so far with regards to unicellular organisms and multicellular organisms, specifically
humans.
Work Period:
You will be split into groups. You will investigate the life process you have been assigned and
prepare a presentation for the class. Plants have even more variety than animals throughout
evolution, so look for things that are common between the plants to present to the class. (for
example, some plants have large flat leaves like trees in the rainforest while some plants that
have leaves that are very thin and prickly like a cactus…. What do those leaves have in
common).
Group Assignments:
circulation
nutrition
synthesis
digestion
regulation of water/solutes (think of diffusion/osmosis)
cellular respiration
excretion
respiration (like the respiratory system in people)
communication
When you present, you need to provide enough information for your classmates to be able to
discuss the following table:
Homeostasis in Different Organisms
Life
Unicellular
Process
Organisms
Structure Function
Circulation
Nutrition
Synthesis
Digestion
Regulation of
water/ solutes
Cellular
respiration
Excretion
Respiration
Communication
Animals
Structure
Plants
Function
Structure
Life
Process
Function
Notes to the Students: While you do this, you may notice that the processes in plants may have
the same function but a different process name is assigned to it or it may be the same process but
functions a little differently.
Use the Life Process column on the right to identify if that process has a different name (for
example, plants have internal water regulation and it is called the same but they have features
that control the interface between internal and external regulation and it has a different name,
same function).
If it is the same life process (for example, communication in plants is called the same thing as
communication in animals but it functions a little differently) then just fill in the name in the
right column to match the column on the left.
Note to teachers:
1. for the presentations, you can have the students do it any way that you want to…. Power
point, create a word or publisher document like a notes page/handout, SMART, posters,
etc…. but whichever way you do it, you will want to find a way to locate it all in the
same location so students can refer back to it for notes and filling out the chart. For
example, if your students all do powerpoint presentations, upload those powerpoints to a
common server they can all access. If they do posters, let the students do a gallery walk
after the presentation to help gather the information or set it up like a science fair where
they can go and gather the data while having a point person to answer questions (group
members can rotate through going around the room to get the information), etc. If its
posters, I usually take pictures of the posters and post the jpegs so they have a reference
later (like I do with the macromolecules once they build them back in lesson 5 of the
biochem unit).
2. When they get to nutrition and synthesis in plants, make SURE that they don’t just
substitute in photosynthesis for one of them because plants still synthesize other materials
AND they still undergo nutrition with pulling minerals and vitamins out of the soil. They
can report photosynthesis out in both of these categories, but add it as an additional life
process. That is one of the major points of this project, because photosynthesis is the
next set of lessons!
3. Same kind of idea for transpiration: plants use osmosis and the concept of turgor
pressure to maintain water balance in plants but this is as much for regulation as it is to
keep cell integrity in the vacuoles. The properties of water should also come into play
(specifically cohesion and capillary action) with the concept of transpiration. Make sure
this gets added to water regulation, not substituted for water regulation.
Summary: answer the EQ
Closing: Fungi are a not quite plants and not quite animals. Do you think that they perform
functions closer to that of plants or that of animals? Explain your answer.
SPED and ELL Modifications:
Students have to be able to find, sort, organize and process information about multiple
organisms and multiple life processes – thus this is a HUGE multi-stepped task for most special
needs and ELL students. With that in mind, be sure to group them with highly efficient students
who can help delegate tasks and sort information with them. Students should complete these
tasks using either an iPad, or netbook. These options can both make a poster and offer spell
check, and translation services for non-english speaking students. It would also be highly
beneficial to have one completed as a model so students could view exactly what is expected.
Ipad apps to make a poster:
 Phoster
 PosterMaker
Apps and Internet Activities:
Students will need basic search, and picture apps to help create a poster for this project.
For creating the posters Phoster
 PosterMaker
For Searching for information I recommend:
 YouTube
 Cell and Cell structure App: has a video feature they can watch plant and animal cells
Independent Practice: Reading and questions on fungi life processes.