1
1
Division: Chlorophyta (green algae)
~ 16,000 species ~ 90% freshwater
I. General Characteristics II. Distinguishing Classes III. Morphology IV. Classes in Detail
2
Hierarchical system of classification: Level: suffix: example: Domain Eukaryote Group Plantae Division -phyta Chlorophyta Class -phyceae Ulvophyceae Order -ales Ulvales Family -aceae Ulvaceae Genus Ulva species fenestrata
II. Algal taxonomy
3
DOMAIN 1.Bacteria- cyanobacteria (blue green algae)
2.Archae 3.Eukaryotes
Groups (Kingdom) 1. Alveolates- dinoflagellates 2. Stramenopiles- diatoms, heterokonyophyta 3. Rhizaria- unicellular amoeboids 4. Excavates- unicellular flagellates 5. Plantae- rhodophyta, chlorophyta, seagrasses 6. Amoebozoans- slimemolds 7. Fungi- heterotrophs with extracellular digestion 8. Choanoflagellates- unicellular 9. Animals- multicellular heterotrophs
“Algae”
4
Adapted from Sadava 2014
Glaucophytes
Rhodophyta
Chlorophytes
Charophytes
Land Plants
Plantae
Chl b, starch
2
5
Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophytes Charophyceae
Phylogenetics of Chlorophyta (morphological, molecular data)
Land plants
5 classes:
Chloroph
yta
Chl b, starch
Encasement of egg
Embryo, cuticle
6
I. General Green Characteristics:
1) Pigments: ?
2) Chloroplast structure?:
3) Storage product?
4) Flagella?
7
Chlorophyceae = freshwater Trebouxiophyceae = freshwater, soil and marine Ulvophyceae = marine macroalgae Prasinophyceae = primarily marine flagellates, some freshwater; modern representatives of earliest green algae Charophyceae = freshwater; all terrestrial plants are derived from Charophycean class
Classes:
8
1. How flagella are attached/constructed:
• basal bodies orientation • microtubule roots
2. Cell covering: • scales vs. cell wall
3. How cells divide: • aspects of mitosis and cytokinesis
II. Distinguishing among classes based on:
3
9
1. How flagella are attached/constructed: -basal bodies orientation -microtubule roots
anterior
swimming direction
Cell
Flagella
Basal Bodies
Microtubule roots
II. Distinguishing among classes based on:
10
Flagella- complex cellular projections used for movement - bundle of nine fused pairs of microtubule doublets surrounding two central single microtubules "9+2" Basal bodies- attachment site of the flagella - containing a microtubules 9 triplet configuration forming a hollow cylinder
Cell
Flagella
Basal Bodies
Microtubule roots
11
opposite parallel clockwise counterclockwise
Basal Bodies: ONE per flagellum, located at base of flagellum, anchoring into cell -pairs of basal bodies may be
5
Cell
Flagella
Basal Bodies
Microtubule roots
12
Microtubule roots: -under the cell membrane at point of attachment of basal bodies - may be cruciate or broadband Cell
Flagella
Basal Bodies
Microtubule roots
cruciate broad-band
4
13
2. Cell covering- scales vs. cell wall
II. Distinguishing among classes based on:
Scales are made of complex polysaccharides secreted from golgi
Cell wall = usually cellulose
prasinophyceae Chlorophyceae, trebouxiophyceae, Ulvophyceae, charophyceae
14
3. How cells divide: (aspects of mitosis and cytokinesis)
• open vs. closed mitotic spindle
• phycoplast vs. phragmoplast
• furrowing vs. cell plate formation in center of cell
closed
II. Distinguishing among classes based on:
Open -during Mt nuclear envelope breaks down
metacentric centrioles
15
Phragmoplast: double microtubules perpendicular to dividing plane -land plants
Phycoplast: microtubules parallel to dividing plane -rare in algae
3. How cells divide: (aspects of mitosis and cytokinesis)
• open vs. closed mitotic spindle
• phycoplast vs. phragmoplast
• furrowing vs. cell plate formation in center of cell
II. Distinguishing among classes based on:
furrowing furrowing
16
3. How cells divide: (aspects of mitosis and cytokinesis)
• open vs. closed mitotic spindle
• phycoplast vs. phragmoplast
• furrowing vs. cell plate formation in center of cell
II. Distinguishing among classes based on:
furrowing = most algae cell plate formation = a few algae and land plants
5
17
III. Morphology
Chlorophyta: easiest division to identify visually
• usually bright, grass-green color
18
III. Morphology
Chlorophyta: easiest division to identify visually
• usually bright, grass-green color Except -
Snow algae Dunaliella
Trentepohlia parasitic on Monterey Cypress
photo: M organ Bond
19
Charophyceans
Chlorophyceae Ulvophyceae Ulvophyceae
For classes: - any easy “rules” using external thallus morphology?
- Prasinophyceans are all unicells, but…
20
“napkin ring-shaped parietal”
“reticulate (net-like)”
Diversity in chloroplast shape: (unique to algae)
“cup-shaped parietal”
“axial (plate-like)”
“stellate (star-shaped)”
“multiple discoid”
“ribbon-like”
6
21
Some new terms:
Isogamy – sexual fusion between flagellated gametes that are similar in size and shape Anisogamy – sexual fusion between flagellated gametes of distinctly different sizes Oogamy – sexual fusion between a flagellated gamete (sperm) and non-flagellated gamete (egg) Sporophyte: diploid, 2n, multicellular release spores in alternation of generations Gametophyte: hapliod, 1n, multicellular release gametes in alternation of generations
Review:
22
Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae
Land plants
5 classes:
V. Classes in detail - Chlorophyte Diversity:
23
Class Charophyceae:
1. How flagella are attached/constructed:
• basal bodies orientation = parallel • microtubule roots = broad band
2. Cell covering: • scales vs. cell wall = wall
3. How cells divide: • spindle = open • microtubule organization = phragmoplast • division by = furrow or plate
24
Microtubule Roots: broadband Basal Bodies: parallel
Charophyceae
Cell
Flagella
Basal Bodies
Microtubule roots
7
25
Class Charophyceae:
most closely related to terrestrial plants
usually unicells or filaments, but sometimes colonies and more complex forms
freshwater
haplontic- 1N thallus, the zygote is the only diploid stage oogamous reproduction
dormant zygotes
Genera: Desmids, Chara
26
Algal Life Cycles Haplontic- 1N thallus, the zygote is the only diploid stage
N
Me
Mt
N
fuse
2N zygote
1N spores
grow
27
Class Charophyceae: Order Zygnematales Desmids
• 2 semi-cells that are mirror images, nucleus is in center
• asexual reproduction = mitosis
• sexual conjugation = pairing between cells
• movement through mucilage secretion
28
Class Charophyceae: Order Charales Genus Chara
Macroscopic Freshwater
Can be partially calcified
Central axis with whorls of branches at nodes Often smell of garlic
Food and nursery habitat for waterfowl
8
29
Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae
IV. Classes in detail - Chlorophyte Diversity:
Land plants
5 classes:
30
Class Prasinophyceae:
1. How flagella are attached/constructed:
• basal bodies orientation = variable • microtubule roots = variable
2. Cell covering: • scales vs. cell wall = scales
3. How cells actually divide: • spindle = open or closed • microtubule organization = phragmoplast or phycoplast • division by = furrow
31
Microtubule Roots: cruciate Basal Bodies: opposite
Some Prasinophyceans
Cell
Flagella
Basal Bodies
Microtubule roots
32
Class Prasinophyceae Genus Tetraselmis
modern representatives of ancestral green (most primitive)
unicellular flagellates
freshwater and marine
one plastid with one pyrenoid
mostly asexual
9
33
Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae
Land plants
5 classes:
V. Classes in detail - Chlorophyte Diversity:
34
Class Chlorophyceae:
1. How flagella are attached/constructed:
• basal bodies orientation = clockwise • microtubule roots = cruciate
2. Cell covering: • scales vs. cell wall = wall
3. How cells divide: • spindle = closed • microtubule organization = phycoplast • division by = furrowing
35
Microtubule Roots: cruciate Basal Bodies: clockwise
Chlorophyceae
Cell
Flagella
Basal Bodies
Microtubule roots
36
Class Chlorophyceae:
7000+ spp mostly freshwater
unicells, colonies, coenocytes, filaments,
haplontic life history- 1N thallus, the zygote is the only diploid stage, with “hypnozygote” = thick walled resting stage
isogamous, anisogamous, and oogamous species
Genera:
Chlamydomonas, Volvox, Dunaliella
10
37
• Cup-shaped chloroplast, orange eyespot
• Scientists sequenced and mapped genome in 2003
• Used as a model to determine how gene expression works
• Use mutations to determine where genes are on chromosomes
Order: Volvocales Genus: Chlamydomonas
38
Chlamydomonas life history:
Usually asexual
“palmelloid stage”
Mt
fluid conditions
moist but not wet conditions
39
Haplontic- Sexual reproduction in unfavorable conditions
Hypnozygote = resting stage
(1/2) (1/2) 40
Genus: Volvox
• Spherical colonies of 500 – 40,000 cells
• Each colony contains a large number of somatic cells and a small number of reproductive cells
• Zygotes are orange
11
41
Volvox life history
• Oogamous
• Gonidia = specialized cells that divide to become daughter colonies
• Zoospore = spore with flagella
• Endospore = surrounds zoospore
• Mesospore = initially surrounds endospore + zoospore
42
Genus: Dunaliella
• Common in salt ponds: have special ion pumps
• Packed with beta-carotene to protect from UV irradiance
• Commercial value (beta-carotene) = used for food coloring and in pharmaceuticals
43
Chlorophyceae Trebouxiophyceae Ulvophyceae Prasinophyceae Charophyceae
Land plants
5 classes:
V. Classes in detail - Chlorophyte Diversity:
44
Class Trebouxiophyceae:
1. How flagella are attached/constructed:
• basal bodies orientation = counterclockwise • microtubule roots = cruciate
2. Cell covering: • scales vs. cell wall = wall
3. How cells actually divide: • spindle = closed; metacentric • microtubule organization = phycoplast • division by = furrow
12
45
Microtubule Roots: cruciate Basal Bodies: counter- clockwise
Trebouxiophyceae
Cell
Flagella
Basal Bodies
Microtubule roots
46
Class Trebouxiophyceae:
mostly freshwater and terrestrial algae unicells, filaments, blades
Genera: Chlorella, Prasiola
47
Genus: Chlorella
- Unicellular - Endosymbiont in freshwater animals
- Single, cup-shaped chloroplast - Used by Melvin Calvin to investigate carbon fixation in plants (Calvin cycle) - Marketed as a dietary supplement
48
Genus: Prasiola
- Diplontic- 2N thallus, the gametes are the only haploid stage - Found in ultra-high intertidal (spray zone) in areas with high guano - “Nitrophilic”
- Thalli small (< 2cm), monostromatic blades - Individuals higher on shore produce asexual (2N) spores
- Individuals lower on shore produce gametes, oogamous