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I. Diagnostic Characters of the Red Algae.

How many are there? about 600 genera with 5500 morphological species.
How old are they?  590 million years old for those with calcification.
Where are red algae found?
10 %of species in freshwater habitats.
90 % marine species with  tropical sites predominantly red algae.
In Hawai'i, about 70 % of our marine algal species are red algae.
These algae can produce substantial biomass and several species calcify (like corals).
How are their cells organized? One to multinucleate organization.
What pigments do they possess?
Chlorophyll a and phycobilins that are assembled into a phycobilisome.
Certain tropical genera possess ability to synthesize orange carotenoids that appear to protect plants from too much sun.
How is the chloroplast constructed?
Thylakoids do not stack at all; they form NO grana.
Chloroplast is enclosed by double unit membrane.
What storage product is made? 
Floridean starch with alpha 1,4 linked glucans. 
This starch lacks the amylose unbranched portion of "starch".
Cell wall features?
Cellulose fibrils embedded in an amorphous matrix of polysaccharide.
The polysaccharides are of at least two types: agar or carrageenan.
Cell and thallus complexity? 
A few species are unicells but show no sexual reproduction.
Unicells lack flagella; they can not swim.
There are multicellular complex thalli; the majority of them grow via apical cell division.
These macrophtyes typically have non-swimming unicells as life-history components (gametes or spores).

II. Simplest cell construction.

Porphyridium

There is no sexual reproduction cycle know for this alga.

III. Developmental lineages and a single life history strategy.

Simple to increasingly complex (Orders Bangiales and Nemaliales) with the intermediate life history strategies, the Sporic Meiosis pattern

Porphyra w/ a heteromorphic alternation of generations via the conchocelis phase.
Liagora typically with a heteromorphic alternation of generations via a microscopic phase.

These genera typically reproduce via the Sporic Meiosis Life History

Increasingly complex adult morphologies (Order Gigartinales) and intermediate life history

Gracilaria
Hypnea

All of these genera reproduce via the Sporic Meiosis Life History

Most complex adult morphology  (Order Ceramiales) and intermediate life history

Polysiphonia
Laurencia

All of these genera reproduce via the Sporic Meiosis Life History

IV. Recap major themes.

Increasing complexity shown in changes in adult morphologie.   Life history strategies have subtle distinctions among orders.

Gamete type is extremely conservative character with all sexually reproducing species having oogamy - a nonmotile "egg" and spherical (non-motile) males.

Is there any significance to the males being colorless?

V.  hotlinks.gif (5957 bytes)

Red Algae, UC Berkeley Porphyra culture as "nori"
California red algae, Sonoma State University Polysiphonia page
   

This page is maintained by Celia Smith and intended for use by undergraduates and graduates, Botany Dept, Univ Hawai'i at Manoa.