Biology 1A Oct 8, 1998
Lecture 12 - Algae II
Page Contents :
Overview of Lecture:
Multicellularity has evolved many times in many ways.
Rhodophyta: the red algae.
Chlorophyta: the green algae.
Overview of Lab:
(A bullet indicates a handout.)
- Algal Morphology (cont'd).
I. Multicellularity has evolved many times in many ways.
A. Multicellularity has evolved many times.
II. Rhodophyta: the red algae.
1. The ancestors of animals & of fungi were unicellular.
B. How do you create a multicellular organism from a unicellular one?
2. The ancestors of the reds, greens, and chromists were all unicellular.
3. Each group developed multicellularity independently of the others.
1. Cellular division
C. Multicellularity in algae.
2. Cellular cohesion
1. colony - loose association of few to 1,000 of cells
D. Introduction to meristems
2. coenocytes - multinucleate tubes
3. filaments - chains of cells (end-to-end)
a. unbranched filaments
4. membranes - flat sheet of cells; one to two cells cells thick
b. branched filaments
5. parenchyma - "blocks" of cells with divisions in three directions
1. Some cells remain meristematic - retain ability to divide.
2. apical meristems
3. basal meristems
4. intercalary meristems
A. What are the red algae?
III. Chromista: haptophytes, diatoms, and kelps.
1. Over 4000 species
B. Distinguishing traits
2. Principal seaweeds of tropical marine waters
3. Live at greatest depths of any algae
1. cell wall - celloluse & mucilaginous substances (alginates)
C. Economic importance
2. flagellae - none
a. chlorophylls a & d
i. water-soluble pigments
ii. found only in reds and cyanobacteria
iii. phycoerythrin - red pigment; absorbs blue light
iv. phycocyanin - bluish pigment
4. photosynthate - floridean starch
5. life cycles
a. isomorphic alternation of generations
b. complex triphasic life history - two diploid phases
1. Porphyra - nori; vital to Japanese sushi industry; used as wrap or in soups
2. Gracilaria - source of agar for culturing
3. Gelidium - source of alginates for chocolate syrup, mayonnaise
4. Chondrus crispus (Irish "moss") - carageenan, emulsifier in pudding
5. some encrusted by calcium carbonate - create many tropical reefs and beaches
A. Distinguishing traits
IV. Chlorophyta: the green algae.
1. cell wall
a. cellulosic compounds
b. usually contains other compounds; variable between groups
a. in most groups, present only in the gametes
b. two dissimilar flagellae; attached laterally
a. chlorophyll a & c
4. photosynthate - laminarin, mannitol, oils
b. fucoxanthin - golden-brown carotenoid
a. Major groups: Haptophytes, Diatoms, Brown algae
b. Several non-photosynthetic groups: e.g. Oomycota
c. Most of the rest are lumped together as chrysophytes
1. unicellular phytoplankton
2. coccoliths - CaCO3 plates secreted from Golgi apparatus
3. important fossil group
1. What are the diatoms?
D. Brown algae
a. unicellular or colonial
2. Diatoms have a rigid frustule
b. no flagellae
c. most are diploid
d. phytoplankton - most important source of food in aquatic ecosystems
a. located inside the cell membrane
3. diatomaceous earth
b. made of crystalline silica
c. minute pores may be involved in locomotion
d. pennate or centric - defines the two major diatom groups
e. two halves like a petri dish or box
a. dead diatoms accumulate on bottom of ocean, and are pressed into rock
b. mined for economic uses
1. What are the brown algae?
a. About 1000 species
2. Example of complex morphology: Macrocystis
b. Principal seaweeds of cool and temperate waters
c. kelps versus rockweeds
d. Most have alternation of generations, usually heteromorphic
e. Often have complex morphology
a. holdfast - attaches to substrate
3. Variations in morphology:
c. blade - main organ of photosynthesis
d. float - keeps blades near the surface
a. Fucus (rockweed) - receptacles, conceptacles; brown with a diploid life cycle
4. Importance of kelps
b. Nereocystis (bull kelp)
a. kelp forests
b. economic uses
A. What are the green algae?
1. 65,000 species, large percentage are freshwater desmids
B. Distinguishing traits
2. Perhaps the most diverse group of algae morphologically
1. cell wall - cellulose & cellulosic compounds
a. 2, 4, many, or absent
b. number and symmetry of attachment distinguishes major groups
a. chlorophylls a & b (same as in plants)
b. carotenoids & xanthophylls
a. starch (same as in plants)
5. other characteristics
b. stored in organelles called pyrenoids
a. sexual reproduction - all three kinds found
b. life cycles - all three kinds found
c. morphology - unicells, colonies, filaments, membranes, etc.
|alginates|| || ||
||diatomaceous earth|| || ||
|antheridium|| || ||
||epitheca|| || ||
|apical meristem|| || ||
||filament|| || ||
|basal meristem|| || ||
||float|| || ||
|blade|| || ||
||floridean starch|| || ||
|calcium carbonate|| || ||
||frustule|| || ||
|carageenan|| || ||
||fucoxanthin|| || ||
|cellular cohesion|| || ||
||holdfast|| || ||
|cellulose|| || ||
||hypotheca|| || ||
|chlorophyll b|| || ||
||intercalary meristem|| || ||
|chlorophyll c|| || ||
||intertidal|| || ||
|chlorophyll d|| || ||
||kelp|| || ||
|coccolith|| || ||
||laminarin|| || ||
|coenocyte|| || ||
||mannitol|| || ||
|colony|| || ||
||mastigonemes|| || ||
|conceptacle|| || ||
||membrane|| || ||
||triphasic life history|
|costae|| || ||
||meristem|| || ||
- How many times has multicellularity evolved? Which algal groups have multicellular species?
- What must happen to produce a multicellular organism? How do meristems help solve this problem?
- How did fungi become multicellular? Is this kind of multicellularity found in other groups?
- How are colonies different from other kinds of multicellularity?
- What are the similarities between coenocytes and filaments? What are the differences?
- Explain the connection between meristems and indeterminate growth.
- What is the only multicellular group to completely lack meristems?
- Which group of seaweeds is most common in cool and temperate oceans? in tropical oceans?
- Why are red algae able to survive at greater depths than other algae?
- How is the life cycle of a red alga different from the typical alternation of generations?
- Why was the discovery of this life cycle important?
- What are some economic uses of red algae? of brown algae? of diatoms?
- Compare and contrast the cell wall composition of the six major algal groups. Do the same for flagellae, pigments, and photosynthates.
- Which group of algae contains chlorophyll d? chlorophyll b? mannitol? starch? floridean starch?
- What are the three major groups of phytoplankton? How are they important? How are they similar? How are they different from each other?
- Distinguish between kelps and rockweeds.Which would you expect to have larger floats and why?
- Diagram and label the parts of a typical kelp. Explain how each part functions.
- Describe the intertidal zone. How are alginates important to the survival of algae that live there?
- Draw and explain the structure of a typical flagellated chromist cell.
- What is a coccolith? What controversy started when coccoliths were first discovered?
- How was this controversy resolved?
- What kind of sexual life history do diatoms have? When is meiosis initiated and why?
- Diagram and explain the structure of a typical diatom frustule. What is it made of? How is its structure relevant to diatom asexual reproduction?
- What is diatomaceous earth? How is it formed? How can it be used economically?
© 1998 Brian R. Speer. These pages for the personal use of students and teachers; any commercial use or publication is strictly prohibited.