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I. Diagnostic Characters of the Brown Algae.

How many are there? about 265 genera with about 2000 species.
How old are they?  probably not more than 200 million years old with some at 65 myo.
Where are brown algae found?
1 % of species in freshwater habitats.
99 % are marine species.
In tropical areas, a few brown algal species can produce substantial biomass.
How are their cells organized? Uninucleate organization throughout all cells.
What pigments do they possess?
Chlorophyll a, Chlorophyll c and Fucoxanthin.
How is the chloroplast constructed?
Thylakoids in stacks of 3 to 6 forming grana. 
Chloroplast is enclosed by double unit membrane.
Chloroplast enclosed by an additional two layer membrane system (Chloroplastic Endoplasmic Reticulum or CER).
This additional membrane system in continuous w/ ER of cell.
What storage product is made? 
Laminarin, a beta 1,3 linked glucan polymer.
Mannitol, a sugar alcohol.
Cell wall features?
Cellulose fibrils embedded in an amorphous matrix of polysaccharide.
The polysaccharide is predominantly alginate.
Cell and thallus complexity? 
NO unicells exist as free living adults.
All are multicellular complex thalli.
These macrophtyes typically have swimming unicells as life-history components (male gametes or spores).
Check out this diversity

II. Simplest cell construction.

Ectocarpus filaments and production of motile cells via plurilocular structures.

III. Developmental lineages and comparative life history strategies.

Simple to increasingly complex (Order Ectocarpales) with intermediate life history.

Ectocarpus
Hincksia

All of these genera reproduce via the Sporic Meiosis Life History.

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

Dictyota
Dictyopteris

All of these genera reproduce via the Sporic Meiosis Life History

Most complex adult morphology (Order Fucales) and most advanced life history

Sargassum
Turbinaria

All of these genera reproduce via the Gametic Meiosis Life History

IV. Recap major themes

Increasing complexity shown in adult morphologies and life history strategies.

Gamete type is extremely conservative character.

Most advanced orders possess modified male gametes.

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Brown Algae, UC Berkeley What's the Sargasso Sea?
California brown algae, Sonoma State University Kelp Tank Exhibit, Monterey Bay Aquarium's Kelp Cam

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