BIOL 153L General Biology II Lab
Black Hills State University
Lab 2: Diversity of Photosynthetic Organisms II
In Lab 1, you were introduced to photosynthetic cyanobacteria, flagellate protists, dinoflagellates,
and diatoms. Today, you will continue to explore photosynthetic organisms from the 'Tree of Life' –
but first, we make a small diversion to talk about the origin of the chloroplast organelle, the transition
from unicellular to multicellular forms of life, and confusion about the taxonomic term 'algae'.
THE CHLOROPLAST
The chloroplast is the organelle that is responsible for photosynthesis in eukaryotes, and it is now
recognized that these organelles originated as free-living photosynthetic prokaryotes that were eaten
by the eukaryotic, heterotrophic ancestors of true plants. Rather than being digested, however, these
prokaryotes were incorporated into the eukaryotic cells; mitochondria have a similar origin as
endosymbionts. Although the chloroplast appears to have evolved only once in the history of life, it
has undergone secondary capture on many occasions—for example, the consumption of a unicellular
eukaryotic green algae has enabled some mobile and carnivorous protists to become photosynthetic.
Such complicated origins of photosynthesis have been elucidated based on pigments, membrane
structures, and (most recently) DNA sequence analyses; see textbook, chapter 12, pp. 246-248.
Primary & Secondary Origins of the Chloroplast
Use the space below to sketch the history of the chloroplast presented by your instructor.
UNICELLULAR VS. MULTICELLULAR ORGANISMS
The simplest organisms are unicellular, meaning they are composed of one cell. Unicellular
organisms are small and tend to be short lived. Multicellular organisms are composed of multiple
cells that are specialized for specific tasks. They are larger—often very large!—and longer lived than
unicellular organisms. Unicellularity is the ancestral condition; over evolutionary time, multicellularity
has arisen in many groups. However, there is an intermediate stage where undifferentiated cells are
“stuck” together in filaments, sheets, or balls, but still function fairly independently. If this multicelled structure is ripped apart, the individual cells can still survive. These are considered colonies.
A colony is a basically a bunch of independent unicellular organisms that live together and function a
bit like a multicellular organism. As you can imagine, it is sometimes difficult—and contentious—to
decide if a living organism is colonial or multicellular. You will be confronting this issue with some of
the organisms studied in Labs 1 & 2 of BIOL 153L.
1
In Lab 1, you looked at the filamentous cyanobacteria Anabaena. Biologists disagree as to
whether Anabaena is multicellular. What is an argument that each filament is a multicellular organism? What is an argument that that each filament is a colony of individuals?
THE CONFUSING TERM 'ALGAE'
The placement of algae on the Tree of Life has been controversial – in fact, simply defining the term is
difficult! Traditionally, 'algae' has been applied to a wide range of aquatic photosynthetic organisms.
Biologists now agree that algae should only be used for eukaryotes (recall from Lab 1 that so-called
'blue-green algae' should be referenced as cyanobacteria, as they are photosynthetic prokaryotes.)
However, 'algae' is still used to reference photosynthetic eukaryotes of a wide range of evolutionary
histories, biological characteristics, and sizes (from one cell to millions, giant kelp for example grow
up to 60 meters in length). Thus, unicellular algae have often been categorized as protists; green algae
specifically have been categorized as plants; and multicellular brown algae and red algae have recently
been classified as protists or as plants. For these reasons, BIOL 153L will use a loose definition of
the term 'algae' – you can learn more about classification of algae (and roles of pigments, morphology,
and molecular data in the classification process) in your textbook (see chapter 15 and appendix A).
CONTINUE THE MARCH THROUGH THE TREE OF LIFE
Let's now continue our studies of photosynthetic organisms across the Tree of Life!
1. BROWN ALGAE are multicellular organisms that often resemble plants. However, despite their
appearance, they are more closely related to unicellular diatoms and dinoflagellates than they are to
true plants. Although brown algae can be found in freshwater, they are primarily found in temperate
and arctic marine regions. Some species, such as giant kelp, can grow to be 150 ft (45 m) long; such
brown algae form underwater 'forests' that provide food and shelter to marine animals. They are also
harvested by for food thickeners, and sometimes eaten as seaweed (e.g., kombu or kelp powder).
Examine Dictyota with a dissecting scope. Take a petri dish with a sample of this multicellular brown agae. Sketch Dictyota—be sure to indicate size and describe its color.
2
Make a wet mount of Dictyota and view with a compound light microscope. (Use a forceps or
probe to collect a small piece; press the cover slip down gently to fully flatten.) Draw to scale,
using field of view as a reference and noting the magnification. Label individual cells.
View herbarium sheets of brown algae. Draw the specimens below, making note of the
species names (and describing the specimens' color).
Sodium alginate, a product derived from brown algae, is the substance that thickens fast food
milkshakes. More recently, it has become a darling of molecular gastronomy (aka modernist cooking)
in a process called spherification. Spherification uses sodium alginate and calcium chloride. When
mixed with water, sodium alginate becomes thick but remains liquid—at low concentrations, it pours.
However, when sodium alginate is exposed to calcium chloride, it gels. If sodium alginate is dripped
into a calcium chloride solution, small balls form as the drops hit the solution. What makes this
process interesting is that sodium alginate can be mixed with small amounts of other liquids before
being dropped into calcium chloride. Modernist chefs turn crushed fruit, vegetables, or juice into
tasty caviar-shaped spheres; if you’ve selected fruity balls as a topping on a desert at Cherry Berry
Yogurt Bar in Spearfish, you’ve eaten food created by spherification.
Make alginate spheres at the station set up by your instructors. Following provided directions,
drop alginate solution into calcium carbonate – describe what happens in the space below!
3
2. RED ALGAE is usually (but not always) multicellular, occasionally present in freshwater, but
most common in tropical marine waters. Although red algae has the green chlorophyll A, reddish
phycobiliprotein pigments are usually more abundant. Recent molecular work suggests red algae are
related to green algae and belong in the 'true plant' lineage. Red algae are the deepest ocean dwelling
algae, are often covered in calcium carbonate, and are the best preserved algae in the fossil record.
They are also frequently utilized by humans: red algae is eaten as a vegetable (e.g., nori is used to
wrap sushi) or to produce thickeners/gels for processed foods and industrial products. Carrageenan
and agar are two of the best know substances extracted from red algae.
Examine Rhodymenia with a dissecting scope. Take a petri dish containing a sample of this
multicellular organism. Be sure to indicate size and provide a verbal description of color.
Make a wet mount of Rhodymenia and view with a compound light microscope. (Use a razor
blade to cut a small section; press the cover slip down gently to fully flatten.) Draw to scale,
using field of view as a reference and noting the magnification. Label individual cells.
View herbarium sheets of red algae. Draw the specimens below, making note of the species
names and describing color(s) of each.
4
Look at the display of commercial products containing carrageenan set up by your instructors.
What are examples of these products, and do you use any of them in daily life?
3. GREEN ALGAE share many features with land plants, including the presence of chlorophyll B
and storage of photosynthetic product as starch. As a result, green algae have long been classified as
plants rather than protists. Green algae range from flagellated unicellular organisms, to colonial balls
or filaments, to very plant-like multicelluar species; see chapter 15, pp. 345-346 for an overview.
Today we will look four very different types of green algae, as outlined below.
3a. Chlamydomonas is a unicellular flagellate green algae found in freshwater, ocean water, and soil—
even snow! It has two flagella (small and difficult to see), an eyespot (=stigma), and prominent
chloroplast. Make a wet-mount of Chlamydomonas; see chapter 15, pp. 345, 348-349.
Sketch Chlamydomonas. Be sure to label the chloroplast, nucleus and eyespot. Draw to scale,
using the field of view as a reference. Note the magnification.
3b. Volvox is a colonial green flagellate algae that is common in ponds. It is closely-related to
Chlamydomonas, but unlike its more solitary cousin, exists as colony of cells that live together in a
gelatinous matrix. Although individual cells coordinate movement with one another to move the
spherical colony toward light, Volvox is not considered truly multicellular.
Pick up a permanent slide (#230, Volvox sexual stages) or make a wet mount of live Volvox—
your instructor will tell you which to use, based on the health of the live culture. Note the small,
Chlamydomonas-shaped cells that cover the surface. These are the individual bi-flagellated cells that
move the colony; the larger, darker spheres are baby Volvox colonies. Eventually, they will break free
from the parent colony and swim away (see textbook, chapter 15, pp. 349-350).
If using prepared slides, watch the video Volvox2 to learn more about this organism's movements:
https://www.youtube.com/watch?v=He9FSeGRi3A
5
Sketch Volvox, labeling individual cells and juvenile spheroids. Draw to scale, using the field
of view as a reference. Note the magnification, and comment on this organism's movements.
Why is Volvox considered colonial and not multicellular?
3c. Spirogyra is a filamentous green algae that is common in freshwater. (It has such a cool name that
two '70s music bands share this name!) Each filament consists of multiple cylindrical cells joined
together end-to- end, and there are spirally arranged chloroplasts. Make a wet-mount of Spirogyra
(see textbook, chapter 15, p. 355), noting the spirally arranged chloroplasts. Spirogyra is quite
stringy and often clings to the vial. You may need to drag it rather than sucking it with the pipette—
it is large enough that you should be able to see a hair-like strand on your slide.
Sketch Spirogyra, labeling individual cells and chloroplasts. Draw to scale, using the field of
view as a reference. Note the magnification.
Compare Spirogyra to Spirulina from Lab 1. How are they similar? How are they different?
6
3d. Ulva, or Sea Lettuce, is a common marine algae. It looks a lot like a true plant—it can grow up to
1 foot tall and has specialized structures called holdfasts that anchor the plant and its leaf-like
thalli/blades. Ulva is frequently eaten as a vegetable. (See textbook, chapter 15, pp. 351-353.)
Examine Ulva germlings with a dissecting scope. Take a petri dish containing a sample of
this multicellular organism. Be sure to indicate size and provide a verbal description of color.
Make a wet mount of Ulva and view with a compound light microscope. (Use a forceps or
probe to collect a small piece; press the cover slip down gently to fully flatten). Draw to scale,
using field of view as a reference and noting the magnification. Label individual cells.
Before we move on from the algae, let's practice identification of some marine taxa! Watch Foraging
Seaweed: Harvesting a French Coastal Superfood (watch until 2:45) and proceed below...
https://www.youtube.com/watch?v=rqfPH2aawvM
The forager in the video shows the following seaweeds. Based on what you've learned in lab
so far, indicate whether these are brown, red, or green algae.
Kombu:
Giant Kelp:
Sea Spaghetti:
Fucus:
Sea Lettuce:
Gutweed:
Sea Pepper:
Dulse:
7
TRUE PLANTS (aka 'land plants') are the best known photosynthetic organisms. Photosynthetic
life originated in the ocean, and there were major hurdles to the transition into terrestrial habitats.
True plants had to develop mechanisms to protect against desiccation and UV radiation, structural
support, vascular systems to move water and food, and ways to disperse gametes and spores. Even
today, algae and cyanobacteria have a higher dependence on wet environments than true plants.
Nonetheless, the 'land plant' name is a bit of a misnomer because some true plants are aquatic or
marine (rooted in the soil substrate but suspended underwater for most or all of the life cycle). Labs
later in the semester will focus primarily on terrestrial land plants – today, we will give you just a
brief introduction to these diverse and ecologically + economically important organisms.
Display of land plant diversity.
Your instructor has assembled a small display of land plant diversity for you to review. Based on the
information provided, answer the following questions about adaptations of true plants to life on land.
Adaptations allowing mosses to live in terrestrial environments:
Adaptations allowing ferns to live in terrestrial environments:
Adaptations allowing conifers to live in terrestrial environments:
Adaptations allowing flowering plants to live in terrestrial environments:
Land plants that returned to water.
Some 'land plants' have returned to life in aquatic or marine habitats! For example, Cabomba (aka
fanwort) is a flowering plant that grows in freshwater. Cabomba has roots and must anchor itself in a
substrate; it doesn’t just float in the water column. (Some green algae, such as Chara, look similar to
Cabomba—however, green algae do not flower or have roots.) Cabomba grows densely and can
become a nuisance weed; thus, its importation is prohibited in some states. Cabomba generates a lot
of oxygen and is often used in freshwater aquaria. Look for bubbles that are forming along the leaves
in the Cabomba display set up by your instructor.
8
Sketch Cabomba – be sure to show the bubbles!
FUNGI are eukaryotic, non-photosynethetic organisms that include both single and multi-cellular
species. Because many fungi, such as mushrooms, look like plants and are non-mobile, fungi have
historically been classified as plants; moreover, some fungi form close symbiotic relationships with
green algae and/or cyanobacteria, and thus functionally may be regarded as photosynthetic.
Fungi are sometimes called absorptive heterotrophs because they secrete substances that dissolve
their food—and this food can be just about anything (e.g., living and dead plants and animals, glass,
petroleum, paint, rocks, etc.). Fungi have enormous ecological impacts—they, along with bacteria,
are the primary decomposers on earth. Fungi are composed of filaments called hyphae. They grow
from the tips of hyphae, and hyphae will mass together to form a mycelial mat. So-called “fruiting
bodies,” such as mushroom caps, are formed by many hyphae together. Interestingly, molecular data
indicate that fungi are more closely allied to animals than they are to plants! Fungal cell walls are
made of chitin, the substance found in arthropod exoskeletons, rather than cellulose, which is found in
plant cell walls. Fungal infections are extremely difficult to treat—substances that kill fungi are often
toxic to animal cells as well (see textbook, chapter 14).
Because of historical classification of fungi with plants, as well as their close association with certain
photosynthetic organisms, today's lab provides an overview of major fungal groups (Zygomecetes,
Ascomycetes, Basidiomycetes). Watch the video below to learn more about fungal diversity.
https://www.youtube.com/watch?v=b5rluxtABGA&t=59s
4.1 Zygomycetes are a group of filamentous fungi that mostly reproduces asexually. Most members
of this group live on decaying organic matter in the soil, while a few are parasites. Black bread mold,
Rhizopus, is probably the best known zygomycete. The black fuzz represents spore-producing
sporangia. Extensive mycelia occur throughout the bread, absorbing the nutrients. Because of this,
moldy bread should not be consumed, even if the surface mold is scraped away— the interior is likely
still full of fungal hyphae, which may contain toxins or carcinogens.
Observe images of black bread mold: go online and type “black bread mold.” Describe and/or
draw what you see.
9
Examine prepared slide 252 (Rhizopus nigrigans sporangia, zygotes w.m.). Hyphae grow
throughout the food source, absorbing nutrients. Stalked sporangiophores erupt from the surface—
at their base they have root-like rhizoids and at their tips they have spore-producing sporangia.
Young sporangia are white, and mature sporangia are black due to the grey spores (see your textbook,
chapter 14, Fig. 14-15, p. 289).
Sketch Rhizopus—label hyphae/mycelium, rhizoid, sporangiophore, and sporangium. (If you
can’t see any of these structures, indicate where you think it should be. )
4.2. Ascomycetes, which can be unicellular (such as yeasts) or filamentous, are a large group of
ecologically and economically important fungi. They are sometimes called 'sac fungi' because they
often produce sexual spores in the sac-like ascus structure. This group includes prized Morel and
truffles, the yeasts that produce bread and beer, and molds that make Brie, blue cheese and soy sauce.
Medically, the antibiotic Penicillin (from Penicillium) revolutionized the treatment of bacterial
infections, while Ciclosporin (from Tolypocladium) is an important immunosuppressor drug.
Unfortunately, this group also has members that cause serious economic and health damage. For
example, non-native ascomycete fungi nearly eliminated American Elm (Dutch Elm Disease) and
American Chestnut (Chestnut Blight) in North America. Ergot infected rye causes “St. Anthony’s
Fire” (hallucinations and a burning sensation), and Aspergillus flavus infected peanuts produce highly
carcinogenic aflatoxin. Athlete’s foot, jock itch, ring worm, and yeast infections such as thrush, are
also caused by ascomycetes (see textbook, chapter 14, pp. 291-295; ).
Observe Penicillium on lemon. Describe and/or draw what you see.
Examine prepared slide 218 (Penicillium conidia w.m.). Penicillium is an asexual fungus that
produces asexual fungal spores outside a sporangium –these spores are called conidia and are formed
at the tips of branched hyphae called conidiophores. Filtrates collected from Penicillium ushered in
the antibiotic age (sulfa drugs were already available but not as safe or effective). Penicillin saved the
lives of many soldiers during World War II, and became available for civilian use in 1945 (see
textbook, chapter 14, pp. 294-295).
10
Sketch Penicillum—label conidia and conidiophores. You will probably need to use 400X
magnification and gently focus up and down to see these.
Penicillium does not produce antibiotics specifically for humans! It makes it for itself. Why
do you think it produces antibiotic substances?
Examine preserved Peziza. The “fruiting body” of Peziza is cup-shaped, and is often reddish
orange with a rubbery texture. It is commonly found on rotting wood or dung. The cup is lined with
a fertile layer called the hymenium. Within the hymenium the asci (aka sacs) are packed together;
ascospores form within the asci. (See chapter 14, pp. 291-292; Fig. 14-19 shows an example life
cycle). Due to time constraints, we will only look at external views of Ascomycetes fruiting bodies.
Sketch a Peziza cup—label the hymenium (which is the location of asci and ascospore).
Peziza cups are found on the surface of soil or rotting organic materials. Where is the main
body of this fungus found?
11
4.3. Basidiomycetes include some of the most familiar fungi—mushrooms, toadstools, shelf fungi,
and puffballs. Less familiar rusts and smuts, which are plant pathogens, are also part of this group.
Basidiomycetes are characterized by microscopic, club-shaped structures called basidia that produce
basidospores. The familiar members have a macroscopic fruiting structure called the basidiocarp.
(See textbook, chapter 14, pp. 295-301; figure 14-25 shows an example life cycle.)
Identify mushroom structures. The familiar mushroom is characterized by a cap (aka pileus), stalk
(aka stipe), and ring (aka annulus). Immature button mushrooms are enveloped with a veil – the ring
is a remnant of the veil. The mushroom represents a fruiting body—it is connected to an underground
mycelial mat. Spore-producing basidia are found on the underside of the cap in the gills or pores.
Sketch the dried, mature mushroom—label cap, stalk, ring, and gills or pores. Draw an
arrow showing the location of basidia.
Introduction to Coprinus. Coprinus, or the shaggy mane mushroom, has gills that liquefy into black
ink as they mature. Watch the video below to see decomposition of mature Coprinus comatus:
https://www.youtube.com/watch?v=pJ4viO_j92Q
Now let's look at Coprinus under the microscope to see its internal structures more clearly. Examine
prepared slide #212 (Coprinus pileus c.s.) that has been set out by your instructor.
Sketch the cross section at 40X, 100X, and 400x—be sure to indicate magnification and show
field of view! Label cap, gills, stalk, basidium, basidiospores, and hyphae (these may not be
visible at all magnifications).
12
5. LICHENS are a type of photosynthetic fungi... sort of. A lichen is a symbiotic relationship
between a fungus and a cyanobacteria or green alga—multiple photosynthetic organisms may
exist in the same lichen. Although the lichen cyanobacteria and green algae can generally live without
the fungus, the reverse is not true. Lichen fungi grown in a lab without their symbiont become a
shapeless blob, but if their photosynthetic partner(s) is added to the culture, they develop their
characteristic lichen shape. Lichen shape and size varies substantially across species. Some form
thin, hard crusts on rocks, tree trunks, and soils (crustose lichens); others are somewhat leaf-like and
lobed (foliose lichens) or highly branched and three-dimensional in shape (fruticose lichens). Old
Man’s Beard (Usnea) is a common fruticose lichen that grows on conifer branches in the Black Hills.
Lichens are often the first organism to colonize habitats following major ecological disturbance. They
are also sensitive to pollution and their presence (or absence) may be an indicator of air quality.
View the permanent slide 263 of a lichen thallus. A thallus is the main body of a lichen. As a
result of the staining process, photosynthetic components of the lichen are not green in these slides;
they are the roundish structures in the middle of the thallus. Fungal cells are at the surface of the
lichen, as well as looping through the photosynthetic cells (see chapter 14, pp. 306-312).
Draw lichen thallus to scale, using field of view as reference and noting magnification.
Now view movies and lichen specimens but first inspect questions below!
Video #1: Lichen Diversity, Harvard Museum of Natural History (2:34) outlines some of the major
lichen types: http://youtu.be/YHBcW7Qhhpc
Video #2: Lichens provide important ecological and historical information to researchers. In the
video Studying Lichens, Harvard Museum of Natural History (3:24), see the creative method this
Harvard University scientist is using to study lichens: http://youtu.be/Wqg7AeDDYus
1. Describe and/or draw the main lichen types mentioned in the video and viewed in lab.
13
2. How do cyanobacteria/algae benefit from the symbiotic relationship that is a lichen? How
does the fungus benefit? One of these organisms benefits more—which one? Explain.
3. How did the researcher measure lichens she was studying? Is this repeatable? Explain.
4. If you were to research lichens in the same location as the Harvard researcher, what could
you test? State this in the form of a question, hypothesis, or prediction.
14