Examining Marine Green Algal Cells
Duration
3 class periods (2 for collection and activity, 1 for mini observatory extension)
Theme
Marine algal cells are easily viewed using a compound microscope and show similar
characteristics to terrestrial plant cells.
Objectives
Students will:
 Examine the organelles of marine green algal cells.
 Gain experience using microscopes and proper microscope technique.
 Use the Ocean Networks Canada Data Plotting Utility to investigate the
relationship between primary production (estimated using chlorophyll-a) and
solar radiation.
Vocabulary
Eukaryote: Any organism whose cells contain a nucleus and other structures
(organelles) enclosed within membranes.
Cell membrane: A selectively permeable, biological membrane that separates the
interior of a cell from the outside environment.
Nucleus: A membrane-enclosed organelle found in eukaryotic cells containing most of
the cell’s genetic material.
Cytoplasm: The gel-like substance enclosed within the cell membrane. Also includes
the cell’s organelles.
Cell wall: A tough, flexible layer located outside the cell membrane that provides
support and protection to the cell as well as acting as a filtering mechanism.
Vacuole: A membrane-bound organelle resembling an enclosed compartment.
Responsible for maintaining turgor pressure (osmotic water flow into plant cells).
Chloroplast: The organelle responsible for conducting photosynthesis. Contains
chlorophyll.
Multinucleate: A cell with more than one nucleus.
Uninucleate: A cell with only one nucleus.
1
PLOs Addressed (Activity + Extensions)
Grade(s)
Curriculum
Organizer
Prescribed Learning Outcomes
8, 9, 10
Processes of Science
A1 Demonstrate safe procedures.
A3 Represent and interpret information in graphic form.
A4 (Grade 8 A5) Demonstrate scientific literacy.
A5 (Grade 8 A6) Demonstrate ethical, responsible, cooperative behaviour.
A6 (Grade 8 A7) Describe the relationship between scientific principles and
technology.
A7 (Grade 8 A8) Demonstrate competence in the use of technologies specific to
investigative procedures and research.
8
Life Science:
Cells and Systems
B1 Demonstrate knowledge of the characteristics of living things.
B2 Relate the main features and properties of cells to their functions.
8
Physical Science:
C2 Explain the properties of visible light.
Optics
10
Life Science:
Sustainability of
Ecosystems
B1 Explain the interaction of abiotic and biotic factors within an ecosystem.
B3 Explain various ways in which natural populations are altered or kept in
equilibrium.
Background
Cells are the smallest units of life, containing the basic components necessary for all life
functions. All organisms are composed of cells but there is a great diversity in cellular
structure. Despite differences between plant, animal, and bacterial cells, there are some
common characteristics.
All eukaryotic cells contain a cell membrane, a nucleus, and cytoplasm.
Figure 1. Simplified animal cell.
Among the green algae there are few cellular differences to land plants. The green algae
are evolutionarily important as they are the descendants of the organisms that gave rise
to terrestrial plants.
2
Both plants and the green algae share common characteristics. They all have cell
walls, a large vacuole, and the presence of chloroplasts. In this activity students will
be able to identify these characteristics using a microscope.
Figure 2. Simplified plant cell.
The green algae differ from land plants in that they have a thin cell wall with no
secondary thickening (i.e., woody tissues). Marine algal cells can be either
multinucleate or uninucleate. These features will be evident when viewing the green
algae under a compound microscope.
Materials
1 x bucket
Live marine green algal specimens (e.g., Ulva sp., Cladophora sp., Codium fragile,
Acrosiphonia sp.), enough for a class (e.g., 1 specimen per 3–4 students)
Class set of compound microscopes (each capable of 10X and 40X magnification)
1 x ruler
Procedure
Activity 1
1.
2.
3.
4.
Travel with students to a local dock or rocky intertidal zone.
Collect local species of green algae.
Bring samples back to the classroom in a bucket of seawater.
Optional: Read the poem, The Microscope, by Maxine Kumin (see Extensions
section).
5. Using the information in the “Background” and “Vocabulary” sections, introduce
cells to the students and draw labeled diagrams of simplified animal and plant
cells.
6. Make water mount slides of sections of marine green algae samples.
3
7. View green algal cells under 10X and then 40X magnification.
8. Draw and label cell structure.
9. Estimate size of cells using a ruler and the field of view of the microscope:
10. Compare and contrast the differences in cell structure between the different
marine algal species collected.
Questions:






Identify the structures that differentiate a marine algal cell from an animal cell.
o Marine algal cells (like plants) have a cell wall (animal cells only have a
cell membrane), chloroplasts (for photosynthesis), and a large vacuole
(animal cells have one or more smaller vacuoles).
Identify the structures that differentiate a marine algal cell from a terrestrial
plant cell.
o Marine green algal cells have thinner cell walls than terrestrial plants and
are more commonly multinucleate than terrestrial plant cells.
Why do different species have different arrangements of organelles?
o E.g., Cladophora sp. has a spiral network of chloroplasts due to the
genus’ peculiar growth pattern influenced by turgor pressure in the cells.
Why are the cells so small? Why aren’t they larger?
o As a cell grows, its surface area/volume ratio decreases (i.e. the surface
area does not increase as much as the volume). At some point in a cell’s
growth this ratio becomes so small that its surface area is too small to
allow the passage of enough raw materials to sustain activities within the
entire volume. At this point the cell cannot get larger.
Discuss the limitations of techniques and instruments (e.g., compound
microscopes) to the study of cell structure.
o See below.
Examine scanning electron microscope images of cells (you can find good
examples here) and discuss the advantages (and disadvantages) to this type of
microscopy.
o A good overview of the advantages and disadvantages of optical and
electron microscopes can be found here.
Fieldtrip Safety
While students are collecting algae on the beach or dock they should be wearing
lifejackets at all times. Docks can be slippery and the students will be reaching over the
dock to collect samples.
At a beach, the intertidal zone can be a dangerous area, especially before and after
storms. Students and teachers should watch for rogue waves that may catch students
off guard. Always have at least one student on guard to watch for unexpected waves or
swells.
4
Activity 2
1. Log into the Ocean Networks Canada Data Plotting Utility using the Username
and Password provided to you.
2. If your page does not immediately display the Arctic Observatory (see name in
upper left of page), from the green menu bar at the top, select a mini
observatory by clicking on “Tools”, select “Network Preference: […]”, and choose
“Switch to Arctic Observatory”.
3. Make sure you are operating the Data Plotting Utility by clicking on “Plotting
Utility” on the green menu bar.
4. On the sidebar on the left, click the “+” next to “Cambridge Bay” to expand the
menu, click the “+” next to “Underwater Network”, then the “+” next to “Water
Quality Monitor”.
5. From the list of water quality parameters measured by the various sensors
onboard the mini observatory, click on “Chlorophyll”. A graph should now display
on the screen.
6. Staying in the sidebar, click the “+” next to “Shore Station”, then the “+” next to
“Meteorological Station A”, followed by the “+” next to “Meteorological Station”.
7. From the list parameters measured, click on “Solar Radiation”. Two graphs
should now display on screen.
8. Overlay the plots by right-clicking on one of the plotted parameters in the
sidebar (e.g. “Solar Radiation”) and selecting “Add to Plot 1 Right Y Axis”, where
Plot 1 is Chlorophyll and Plot 2 is Solar Radiation.
9. Towards the top of the screen, underneath the green menu options, find the
section titled, “Time Period Selection”. In the “Date From (UTC)” box, enter “01Jan-2014”; in the “Date To (UTC)” box, enter “18-Jul-2014”. Click the “Plot”
button under “Refresh Plot(s)”. You should now see a graph that looks like the
one below (“Chlorophyll” in blue, “Solar Radiation” in red):
Questions:
1. How does chlorophyll vary with solar radiation during the time period we’ve
chosen? Why does this relationship exist?
 Chlorophyll concentration generally increases as solar radiation increases.
 Early in the year, sunlight (solar radiation) is a limiting factor on algal
growth and chlorophyll concentrations are low. As we move from winter
into spring and then summer, sunlight increases and is no longer limiting
algal growth. As growth of algae increases, so too does chlorophyll
concentration.
5
2. What other abiotic factor(s) might influence the growth of marine algae and
therefore the production of chlorophyll?
 Nutrient availability (e.g., nitrate and phosphate), temperature, and
salinity are other possible factors affecting marine algal growth.
3. What change in chlorophyll concentration would you expect during the winter
months? You can test your prediction by entering different dates in the “Date
From (UTC)” and “Date To (UTC)” boxes. Alternatively, you can show all the data
available for the chosen sensors: Immediately to right of the “Date From (UTC)”
box is the “Time Presets” section; choose “All Available” from the drop-down
menu, then click the “Plot” button next to it.
 Chlorophyll concentrations decrease in the winter due to lower solar
radiation—reduced dramatically due to ice cover and Cambridge Bay’s
northern latitude.
4. To visually inspect the differences in algal growth between seasons, click on
“SeaTube” listed in the green menu options towards the top of the screen. On
the sidebar on the left, click the “+” next to “Cambridge Bay”, click the “+” next
to “Underwater Network”, then the “+” next to “2014”. Choose a date within the
range used to plot the graphs (January 1–July 18, 2014), then click on a month
to select it, followed by a date, and then a time: a camera recording for this time
period made from the mini observatory will then be displayed. By looking at
recordings from different months and days, you should be able to see differences
in algal growth at different times. For example:
January 1, 2014
6
July 18, 2014
5. Does a relationship exist between chlorophyll and oxygen? Why do you think so?
How would you illustrate this using the Data Plotting Utility?
 Yes, a relationship exists between chlorophyll and oxygen. Chlorophyll

concentrations are an indicator of marine algal growth. As marine algae
are photosynthetic organisms, they produce oxygen: therefore, more
algal growth (higher chlorophyll concentrations) leads to more oxygen
production; low algal growth (low chlorophyll concentrations) leads to
less oxygen production. Thus, chlorophyll and oxygen are positively
correlated.
Use the Data Plotting Utility to produce graphs for chlorophyll and
oxygen, as for chlorophyll and solar radiation. For example:
6. How would you investigate the chlorophyll, solar radiation, and oxygen data for
today?
 Use the Data Plotting Utility to produce graphs for chlorophyll, solar
radiation, oxygen, and restrict the date range for today’s date, or use the
drop down menu under “Time Presets” and choose “Last 10 Minutes”,
“Last 2 Hours”, or “Last 24 hours”. For example:
7
Extensions
The Microscope (by Maxine Kumin)
Anton Leeuwenhoek was Dutch.
He sold pincushions, cloth, and such.
The waiting townsfolk fumed and fussed
As Anton’s dry goods gathered dust.
He worked, instead of tending store,
At grinding special lenses for
A microscope. Some of the things
He looked at were: mosquitoes’ wings,
the hairs of sheep, the legs of lice,
the skin of people, dogs, and mice;
ox eyes, spiders’ spinning gear,
fishes’ scales, a little smear
of his own blood, and best of all,
the unknown, busy, very small
bugs that swim and bump and hop
inside a simple water drop.
Impossible! Most Dutchmen said.
This Anton’s crazy in the head!
We ought to ship him off to Spain!
He says he’s seen a housefly’s brain!
He says the water that we drink
Is full of bugs! He’s mad, we think!
They called him dumkopf, which means dope.
That’s how we got the microscope.
8
Questions:
1. Why do you think the poem was written in this way? (I.e., why/how does the
author use dramatic irony?)
2. How would you explain what you would have seen under the first microscope?
3. What is the author alluding to with things “that swim and bump and hop”?
Further Questions
Grade 8



What characteristics do marine algae share with other living things?
The marine algae you looked at were collected from shallow water. Would you
expect to find algae in deep ocean water? Why?
What wavelengths of light are important for photosynthesis in marine algae?
How deep do each of these wavelengths penetrate into deep ocean water?
Grade 10

How might changes in abiotic factors (e.g., changes in ocean current patterns,
extreme weather, water contamination), impact marine algal populations? How
might impacts to these populations affect other living things, including humans?
Additional Activities



Ocean News Teacher’s Guide, “Exploring the Fluid Frontier”, Part A: Pages 8–14
feature activities investigating the properties of visible light, the behavior of light
in water, and adaptations of marine organisms to low ambient light levels:
http://oceanlink.info/ONews/OceanNewsReader/TG1a.pdf
Ocean News Teacher’s Guide, “Exploring the Fluid Frontier”, Part B: Pages 45
and 47–50 feature activities investigating the use of satellites to monitor ocean
chlorophyll concentrations:
http://oceanlink.info/ONews/OceanNewsReader/TG1b.pdf
Ocean News Teacher’s Guide, “Marine Biodiversity”: Pages 173–175 looks at the
use of seaweed and seaweed derivatives by humans:
http://oceanlink.info/ONews/OceanNewsReader/TG5.pdf
Resources




Druehl, L. (2001). Pacific Seaweeds. Harbour Publishing.
Raven, P., Johnson, G.B., Mason, K.A., Losos, J.B., Singer, S.S. (2014). Biology.
McGraw-Hill Education.
This activity is a good refresher on how to wet mount slides and estimate cell
size under a microscope: http://www.radford.edu/jkell/CellsizeEx3.pdf
Video resources discussing why plants appear green:
o http://youtu.be/aAQYpra4aUs
o http://youtu.be/545rqaOJQD8
9