Lab 4: Algae
Today’s lab focuses on the evolution of multicellularity. One of the traits that systematists use to define plants is
multicellularity. Algae show varying levels of multicellularity, from single celled individuals to large multicellular organisms
with specialized organs.
PART 1
1. Each group will be assigned a collection of unknown slides to look at.
a. Do NOT remove the tape covering the slide labels.
2. Examine your slides and as a group, categorize each slide as one of the following growth patterns or
levels of multicellularity: (See page 467 and Fig.19-11)
a. Single celled
i. Where cell division is reproduction
b. Colonial
i. A loose collection of cells
ii. Some cells may have specialized structure/function
iii. See Fig19-18
c. Filamentous
i. A chain of cells held together in a straight line
ii. Some cells may have specialized structure/function
iii. See Fig19-19
d. Branched Filamentous
i. Filaments that fork and split.
ii. See Fig19-23
e. Membranous
i. A two dimensional sheet of cells.
ii. See Fig19-20
f. Parenchymatous
i. Structures formed from 3-dimensional masses of cells
ii. In Fig19-22(a) the “branches” appear filamentous, but the “stem” and reproductive organs (b and
c) are definitely 3-dimensional.
3. When your group has categorized all of your slides, write down your classifications and turn it in for a
preliminary grade.
PART 2
4. As a group, collect one image of each of your slides
a. Images must be clear enough that their growth pattern is obvious
5. Each image should have its own figure legend below it that includes the following information:
a. The growth pattern
b. The name of the organism (scientific AND common, if available)
c. The Division of algae this organism would be classified in (see Table 19-2 in the textbook)
d. A brief description of where you would most likely find this organism (fresh or salt water? Region
of the ocean? Region of the world?)
e. This legend should be written in paragraph form in complete sentences.
6. Collect all 6 of your images with their legends on a single page.
a. Place them in the order shown in #2
7. Submit your group’s page on Moodle by Sunday at 11pm.