marks the beginning of our evolutionary surveyof life on earth. Since this is a Botany course we will limitour labs to plants and plant-like organisms as well asorganisms that have been traditionally studied bybotanists. This week, we look at some of the oldest andstrangest groups of all:

To observe these groups, we will primarily use thecompound microscope, but unlike past labs, there will belittle sectioning of material. Many of the organisms intoday’s lab will be free-swimming or slightly moving, sostay alert.

For a review of using the microscopes, see:

As discussed in lecture, Cyanobacteria - also known as"Blue-Green Algae" are prokaryotes related tomembers of the Domain Bacteria.

All of the other groups of "Algae" are eukaryotes asdistinct from each other as the Kingdoms Plantae,Animalia & Fungi. One group, the Chlorophyta - or"Green Algae" are almost certainly the source groupfor land plants.

Consult your textbook during class for usefuldescriptions and good pictures of each group. The linksbelow provide a survey for material observed in lab.

Cyanobacteria

Bacillariophyta, Dinophyta & Euglenophyta

Rhodophyta & Phaeophyta

Chlorophyta

Here are some suggestions for mastering the groups

covered this week:

Draw a large picture of each organism in yournotebook (¼ to ½ page).

Carefully analyze the morphology of theorganism. Determine whether it is unicellular,colonial, filamentous, siphonaceous, ormulticellular - or a combination of theseconditions.

Consult your textbook and read about thegeneral life cycle represented by members ofthe organism's major group. Apply thisknowledge to identify the sexual and asexualphases of the life cycle if present. In particularanswer whether the organism has:

zygotic meiosisgametic meiosis

sporic meiosis

Are you looking at the haploid or diploid

Make sure you write down each organism's nameand major group.

bodies?

Where does meiosis and fertilizationoccur?

Be sure to label important features of theorganism, as well as other characteristics thatyou observe, including movement, color,different cell types, presence of pigments, etc.

download this lab in PDF format

Cyanobacteria or Blue-Green Algae are anextremely important group from an ecological,physiological and commercial point of view. Unlike mostother bacteria, cyanobacteria are photosyntheticaerobic organisms sometimes with considerablecomplexity. Because they are prokaryotes, the grouplacks chloroplasts and nuclei. You should observe andidentify the features that differentiate the followinggenera:

Anabaena:

Look for a “string-of-pearls” morphology. Observe anddraw vegetative cells & heterocysts. Colonies maylack a certain cell type, why? Heterocysts are importantbecause they are the site of nitrogen fixation. Don’tdiscard your slide yet.

Anabaena is not only free-living but also occurs insymbiosis with other organisms. In the Greenhouse,Anabaena can be collected from aerial roots of cycadswhere presumably they are photosynthetic andperforming a nitrogen fixing function. Make a thintransverse section of one of these roots and search forcyanobacteria. Record where within the tissues of thehost plant they are found and then “squash” thesection. Now search for individual filaments ofAnabaena. Compare the morphology of these colonieswith that of free-living (cultured) cells observed above.How are they different? Why?

Nostoc:

This organism is similar to Anabaena and occurs inrecognizable macroscopic and microscopic forms. First,observe the Nostoc “balls” on display, then take a sampleand observe the individual cells. What cell types do you

Anabaena

Nostoc

find?

Oscillatoria:

Look for the “hair-like” strands of this distinctivegenus. Without moving the slide, observe these strands. Notice that they are moving! How do they do this?

Stromatolite:

Stromatolites are fossils resulting from the activity ofcyanobacteria on soft sediments. They are comprised ofcountless layers of trapped particles laid down in duringor between periodic intervals of colony growth.Stromatolites are among the oldest fossils knownproviding evidence of life on Earth probably as long agoas 3.5 billion (3500 million) years.

Bacillariophyta, Dinophyta & Euglenophyta

Rhodophyta & Phaeophyta

Chlorophyta

Oscillatoria

These groups represent highly distinctive mostlyunicellular forms that are not closely related.

Bacillarophyta are better known by their informalname: "diatoms". Individual cells are free-living. Theyhave an outer cell wall built like a petri dish with twoglass (silica) valves.

In the mixed sample of diatoms present in lab,distinguish between pennate (elongate) and centric(radially symmetrical) forms. Draw an example of each.To understand what you are observing, it is useful todistinguish two viewpoints: girdle view (edge on) versusvalve view (looking at each valve straight-on). Do theseorganisms have flagellae? Are they moving? Diatomsmostly reproduce asexually by cell division. The twovalves separate during division with matching valvessynthesized inside the old. Since individual valves arehard and can't change in size, needless to say this createsa problem! What? Eventually, during sexualreproduction, both valves are shed and new larger onessynthesized de novo.

Synedra:

This is an interesting genus of colonial diatoms. Whichform of diatom - pinnate or centric - do these cellsrepresent? Are these diatoms alive? How do you know?Can you find both valve & girdle views of an individual?(Hint: look at the tips of filaments, they should lookdifferent in valve & girdle view).

The Dinophyta - also called "dinoflagellates" - are anexceedingly interesting group. Members of this groupare responsible for “red tides” frequently noted inecological/environmental literature. They are also

responsible for periodic mass kills of fish as well asneurological diseases sometimes seen in fishermen orswimmers in waters undergoing dinoflagellate "blooms".

Observe individuals from the mixed dinoflagellatemixture available in lab. Observe and draw what you see.In what way are forms different? Also look for flagellae- there are two. One flagellum extends outward fromone of the cell and is used for locomotion. The othervibrates within a groove in the cell wall running aroundthe cell's middle.

The Euglenophyta - or "euglenoids" are interestingorganisms that straddle the traditional plant/animalboundary. Some euglenoids are free-living heterotrophic"protozoans" whereas others are photosynthetic greenautotrophs. In recent years, research in this groupmakes it increasingly evident that like Chorophyta andgreen plants, euglenoids have incorporated aendosymbiotic cyanobacterium as a photosyntheticchloroplast.

Euglena:

This genus is a rapid swimmer. Observe the swimmingmotion of individual cells. Notice that some of theindividuals appear to change shape. This is because,unlike most algae and green plants, these organismshave do not have a rigid cell wall. Instead, they have aflexible proteinaceous outer covering called the pellicle. Look at individuals of Euglena to determine whetherthey are photosynthetic. How would you know? Observethe golden paramylon bodies within the cells. Theseare used for storage of metabolic products similar to, butdifferent from, the storage of starch in plants.

Cyanobacteria

Rhodophyta & Phaeophyta

Chlorophyta

Both of these groups are highly diverse, with unicellularand multicellular forms. Most conspicuous aremacroscopic and very plant-like seaweeds familiar toeveryone who has visited the marine shore. Take a lookat the mixed collection of tropical seaweeds available inlab. See if you can identify the major groups to whichthey belong by comparing the descriptions below.

The Rhodophyta - or "Red Algae" - are an extremelydiverse group inhabiting tropical and temperatesaltwater. The group is commercially important to manyhuman societies. Useful products from red algae include(among other things) agar, and nori for sushi.

The lifecycle of the Rhodophyta is one of the mostcomplex in the biological world. It consists of twosporophyte phases: carposporophyte andtetrasporophyte, and one gametophyte phase. Forexample, take a look in your textbook showing the lifecycle in the genus Polysiphonia. In what phase of the lifecycle does meiosis occur? What phase produces eggsand spermatia - the non-flagellated sperm?

In this course, we will not require you to learnthis life cycle in detail. However, we do ask thatyou understand its basic pattern including theterms emphasized above.

Polysiphonia:

What color is this genus? Why not green? Whatmorphology does it have? Polysiphonia is isomorphic,which means that the sporophyte and gametophytephases are vegetatively identical. Compare the life cyclein your text and draw what you see. Can you findreproductive organs: gametangia or sporangia? If so,what name can you apply to them? If no gametangia orsporangia are evident, can you tell what phase of the lifecycle you are observing anyway?

Calloglossa:

Now look at the organization of cells within the thallus ofCalloglossa. Draw what you see. How does this formdiffer from Polysiphonia?

Polysiphonia

Calloglossa

Th Phaeophyta - or "Brown Algae" include verylarge kelps as well as many smaller forms. The group isabundant in temperate saltwater and is also veryimportant in human diet and commerce. See your textfor an excellent introduction including life cycles ofrepresentative genera Laminaria and Fucus.

Ectocarpus:

Note the color and morphology of the genus Ectocarpus.Like Polysiphonia of the Red Algae, this genus hasvegetatively isomorphic sporophyte and gametophytegenerations. Can you find reproductive organs? Thisgenus has three types: unilocular sporangia,plurilocular sporangia, and pluriloculargametangia. Consult the life cycles in your text fordiagrams and definitions of each. Unfortunately,plurilocular gametangia and pleurilocular sporangia lookidentical.

On what phase of the life cycle would you expectplurilocular gametangia occur? On what phase of thelife cycle would both types of sporangia occur? In whatstructure does meiosis occur? Again, we do not requirethat you memorize this life cycle in detail. However, it isimportant to know what each structure does and inwhat phase of the life cycle it occurs: gametophyte orsporophyte.

Sphacelaria:

Now take a look at this genus consisting of a branchedthallus (body) of large cells. Draw what you see.

Cyanobacteria

Bacillariophyta, Dinophyta & Euglenophyta

Chlorophyta

Ectocarpus

Fucus

The Chorophyta - or "Green Algae" - are the mostdiverse group of algae both phylogenetically andmorphologically. Green algae are found many placesincluding freshwater, marine, soil and other terrestrialhabitats. It is interesting to note that members of thisgroup and higher plants have the same photosyntheticpigments: chlorophylls a & b. As a result, bothplants and Chlorophyta have the typical "green"appearance that we expect to see in plants. Thesegroups also share important metabolic & structuralcompounds including very important cellulose andstarch. Excellent paleontological, ultrastructural andbiochemical evidence indicate that that Chlorophyta andgreen plants are close relatives and that land plantsevolved from ancestors within the green algae.

There are three main classes of green algae:

ChlorophyceaeUlvophyceaeCharophyceae.

We will deal with members of the Chlorophyceae &Ulvophyceae today.

Members of the Chlorophyceae include a wide rangeof single-celled and colonial forms. All are characterizedby a distinctive type of cell division involving a structurecalled a phycoplast. Motile members of this group alsohave a distinctive pattern of microtubules associatedwith their flagella. Unfortunately both of features arebest seen with the electron microscope. See your text fordescriptions and photographs of these features.Although in lab, you will not be able to observe celldivision, it is useful to look at example morphologiesexhibited by members of the group to get a sense ofwhat they are like.

Volvocales:

Obtain a sample of the Volvocales mixture and look fordifferent genera under the compound microscope. Thisgroup is interesting because it displays a uniqueevolutionary pathway starting with independentunicells like that seen in the genus Chlamydomonas tocomplex globose multicellular colonies in Volvoxconsisiting of thousands of cells. Draw what you see.Where are the flagellae located? How are colonies ofcells organized? Is there evidence of differentiation ofcell function in colonies?

Chlamydomonas

Pandorina

Volvox

Hydrodictyon:

This genus is an example of a non-motile member ofthe Chlorophyceae. Individual cells are typically elongate- termed filamentous. Observe and draw the uniquecolony architecture of this alga. Compare what you seewith the description in your text.

Members of this group are primarily marine. They showa variety of intracellular organization ranging fromsingle cells to coenocytes as well as many differentkinds of multicellular body forms ranging fromfilamentous or parenchymatous colonies, to highlycomplex coenocytic individuals.

Cladophora:

Observe a sample of the genus Cladophora under thecompound microscope. This form consists of afilamentous colony of individual cells. Look for theinteresting net-like chloroplast within each cell. Drawwhat you see.

Ulva:

The life cycle of Ulva can be found in your text. Observeyoung examples of this this genus in culture as well asolder individual in the mixed sample of tropical seaweeds.Observe and draw how the colony is constructed. Whatis meant by the term parenchymatous as applied tothis form?

Bryopsis:

Now turn to the last - and strangest - member of theUlvophyceae we will look at today! The genus Bryopsis isa member of the marine siphonaceous green algae. Inthis group, "colonies" can be quite large but they arenot comprised of multiple cells! Instead the body iscoenocytic - undivided protoplasm in which areembedded thousands of nuclei somehow all workingtogether. As directed by your TA, take a sample ofBryopsis and draw what you see.

Cyanobacteria

Bacillariophyta, Dinophyta & Euglenophyta

Rhodophyta & Phaeophyta

Hydrodictyon

Ulva

001 Algae main002 Algae003 Algae004 Algae005 Algae