I. Diversity of Form Among the Chlorophyta

Chlorophyta Homework

I. Diversity of Form Among the Chlorophyta

Examine the micrographs available on the course website showing selected genera of green algae. For each representative genus you should determine insofar as possible the:

1. growth form

2. presence or absence of nucleus and chloroplast(s)

3. number and shape of chloroplast(s)

4. number of nuclei per cell

5. any particular wall characteristics

6. visible pigmentation

7. storage material (if possible to tell)

8. anything that can be seen of reproduction

Please don’t forget that you have Google image available to you on-line!

Volvocales
Chlamydomonas
Volvox
Coleochaetales
Coleochaete
Oedogoniolales
Oedogonium / Chlorococcales

Ankistrodesmus

Hydrodictyon

Pediastrum
Scenedesmus

II. Diversity of Form Among the Chlorophyta—Class Zygnemaphyceae

From our course website or the internet, observe and sketch these:

Chlorococcales (outgroup)
Chlorella
Zygnematales
Mougeotia
Spirogyra
Zygnema / Desmidiales
Closterium
Euastrum
Netrium
Cosmarium
Micrasterias
Staurastrum
Mesotaenium

Notes (WARNINGS!):

Sketching (biological illustration) is not only an important skill for a biologist, but is also a potentially lucrative career path. Pasting electronic images from the internet (with citations) will result in 50% score reduction on each image; without citations you earn course failure and referral to judicial for plagiarism and expulsion!

If you pull out pages from this handout or add pages to this handout, you must staple the pages of this assignment, in order and in the very-upper-left corner, before handing this assignment in for grading. Paper clips and folded-corners are not acceptable alternatives! (5points deduction).

Make and label a quick sketch of the green algae micrographs to help distinguish them. Labels are how you get points! 4 points each. Think cell structure; these are eukaryotes so they have organelles for you to label! How are the cells organized?

Chlamydomonas / Volvox(enlarge one or a few cells also)
Coleochaete / Oedogonium
Ankistrodesmus / Scenedesmus
Pediastrum / Hydrodictyon

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Using the website resources, make a quick sketch of the Zygnemaphyceae to help distinguish them. Label 4 cell parts includingthe chloroplast and any colors observed.4 points each

Maybe use a green color pencil to notice and remind you where chloroplasts are (and are not!). The pyrenoid is structure inside of a chloroplast, so they are NOT independent organelles! Be sure to label chloroplast, nucleus, cell wall, cell membrane, cytosol, etc. / Closterium / Cosmarium
Euastrum / Mesotaenium / Micrasterias
Mougeotia / Netrium / Spirogyra

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Staurastrum(seek additional views on Google Image for 3rd dimension) / Zygnema / The Zygnemaphyceae is a class of green algae which demonstrates evolutionary trends from unicellular to filamentous organization. Interestingly the morphology of each cell and the chloroplasts in the filamentous genera are remarkably similar to those of the free-living unicellular species

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III. Observing the Results of Evolution in the Zygnemaphyceae

Examine the diagrams you have made of each genus of onlyZygnemaphyceae (page 3, and above) and think about the characteristics that distinguish them. Construct a dichotomous key using the characteristics of the teningroup genera you have observed. Your key needs to be truly dichotomous (no trichotomies!) and clearly and accurately distinguishing the 10ingroup genera! Make sure the characters are clearly described: “spherical” (3D) is different from “discoid” (flattened sphere) or “circular.” An alga’s shape or its chloroplast shape cannot key out as “circular” in one step and “pointed/lobed” in another step! So “discoid” alone is not a selector; “discoid cell shape” or “discoid chloroplast” or “discoid thylakoids” are all much better! If your key is attached as a typed/printed item, add a title and use leader-tabs for the numbered steps! [hint: make a photocopy of page 3 and 4, cut apart the sketches along the rectangular frames, and separate groups and subgroups until all are distinguished from the others]. See page 7 for more help. The algae on page 2 are NOT part of this key!

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Algae Vocabulary

Genome

diploid: having two sets of chromosomes, two genomes

haploid: having one set of chromosomes, a single genome

meiosis: reduction division producing haploid from diploid

syngamy: union of haploid gametes to produce diploid

Life Cycle

diplohaplontic (sporic): separate multicellular haploid and diploid phases

diplontic (gametic): spore becomes gamete; vegetative body is diploid

gametophyte: the haplophase of a diplohaplontic life cycle

haplontic (zygotic): zygote becomes sporocyte; vegetative body is haploid

sporophyte: the diplophase of a diplohaplontic life cycle

Gametes

gamete: a hapoid sexual cell which unites during syngamy with its mate

amoeboid: wall-less cells with pseudopod properties like Amoeba

anisogamous: motile gametes: small male, large female Chlamydomonas braunii

conjugation: gametic fusion without any motile phase involving lateral fusions

isogamous: motile gametes identical (+/-) Chlamydomonas reinhardtii

oogamous: motile male gamete, sessile female gamete Chlamydomonas coccifera

spermatozoid: the motile male gamete in oogamous species

heterothallic: mating types are on separate thalli

homothallic: thallus produces both mating types

antheridium: a cell producing sperm cells

oogonium: a cell producing eggs

hypnozygote: a zygotic resting cell

zygote: the diploid product of syngamy

Cell structures

phragmoplast: assembly of microtubules peripheral and parallel to the spindle

phycoplast: assembly of microtubules perpendicular to the spindle

cell plate: coalescing vesicles of wall material to form new wall between daughter cells

furrowing: a pinching off of the cell between daughters, centripetal wall growth

eyespot = stigma: an area of chloroplast loaded with carotenoid pigments just opposite the photoreceptor

photoreceptor: a pigment, commonly rhodopsin, in cell membrane used for phototaxis

phototaxis: movement toward or away from light

chloroplasts: have the usual double outer membrane but no endoplasmic reticulum envelope. The thylakoids are lamellate with a varying number in each granum. Thylakoids contain chlorophylls a and b and use lutein, zeaxanthin, volaxanthin, etc. as antenna pigments. The usual products of photosynthesis include starch ( 1,4 glucan) and oils. The chloroplast genome consists of several circles of naked DNA

pyrenoid: an accumulation of ribulose bis phosphate carboxylase oxygenase (RuBisCO) and often associated with starch grains

Flagella

biflagellate: with 2 flagella

flagellum: an elongate projection from a cell with an axoneme of 9 peripheral doublet microtubules and 2 central microtubules

heterokont: flagella different

isokont: flagella identical

quadriflagellate: with 4 flagella

stephanokont: many flagella in ring at end of cell

Forms

coccoid: unicellular non-motile cells, not always rounded

filamentous: chains of cells, branched or unbranched

flagellate: a motile cell by virtue of flagella

heteromorphic: haploid and diploid vegetative phases are morphologically different

holdfast = hapteron: a disc-like or root-like appendage involved with attachment

isomorphic: haploid and diploid vegetative phases are morphologically similar

monad: a solitary flagellate cell

palmelloid = tetrasporal: cells in clumps held inside a mucilage sheath

rhizoid: a root-like filament of cells usually involved with attachment

sarcinoid: cells in packets

siphonocladus: filament of coenocytic cells

siphonous: coenocytic cell usually with large vacuole

stolon: a creeping section of the visible part of a thallus

thallose: sheets or parenchymatous

thallus: a relatively undifferentiated plant body without leaf, stem, and roots

unicellular: single-celled uninucleate

Asexual Reproduction:

aplanospores: reproductive cells look flagellated (eyespots, contractile vac) but are not

autospores: non-motile asexual reproductive cells, like vegetative cell

coenobium: endospores form colony and are released as a unit

planospores: a motile zoospore

zoospore: a flagellated spore

Habit

Benthic: living attached to a substrate

Epilithic: living attached to a rock

Epiphytic: living attached to a plant

Epizoic: living attached to an animal

Eutrophic: waters with excessive nutrients

Oligotrophic: waters with depleted nutrients

Pelagic: floating at or near the water's surface

Planktonic: living freely suspended in water

Producer: involved in primary production = photosynthesis

Terrestrial: living on land

Division Chlorophyta Taxonomy: 500 genera, 8000 species!

Class Chlorophyceae

Order Volvocales: unicellular/colonial

Order Chlorococcales: coccoid

Order Chaetophorales: branching filaments

Order Oedogoniales: branched/unbranched weird sex

Class Ulvophyceae

Order Codiolales unbranched filaments

Order Ulvales: thallose

Class Cladophorophyceae

Order Cladophorales, Siphonocladales, Acrosiphonales: siphonocladous

Class Bryopsidophyceae

Order Bryopsidales: siphonous

Order Halimedales: thalloid

Class Dasycladophyceae

Order Dasycladales: siphonous

Class Trentepohliophyceae

Order Trentepohliales: branched filaments

Class Zygnematophyceae

Order: Zygnematales: coccoid to unbranched filaments, special cytology

Order Desmidiales: unicellular with semicells

Class Klebsormidiophyceae

Order Klebsormidiales: sarcinoid, filamentous

Order Coleochaetales: pseudoparenchymatous

Class Charophyceae

Order Charales: unique vegetative structure and reproduction

Further notes on constructing a key:

The first dichotomous step of a key, should use a particular feature divide the ingroup into two major subgroups. For this key there is a huge hint on page 1!

The first part of this dichotomy (1a) should refer the one subgroup to step 2, which will then use dichotomies 2 through n to distinguish the members of this one subgroup.

The second part of this dichotomy (1b) should refer the other subgroup to step n+1, which will then use dichotomies n+1 through n+x to distinguish the members of this second subgroup.

After drafting it, be sure to test your key to be sure that it actually works to unambiguously and accurately distinguish and identify each of your ingroup species!

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