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I. Diagnostic Characters of the Green Algae.

How many are there? about 500 genera with 8000 species.
How old are they?  400 to 500 million years old with some at 600 myo.
Where are green algae found?
90 %of species in freshwater habitats
10 % marine species are predominantly tropical species; many are here in Hawai'i.
How are their cells organized? One to multinucleate organization.
What pigments do they possess?
Chlorophyll a and Chlorophyll b
Certain tropical genera possess siphonoxanthin & siphonein.
How is the chloroplast constructed?
Thylakoids in stacks of 3 to 6 forming grana. 
Chloroplast is enclosed by double unit membrane.
What storage product is made?  Starch
Cell wall features?
Cellulose fibrils embedded in an amorphous matrix of polysaccharide.
The polysaccharides are of at least two types: pectic substances or xylan-mannan polymers.
Cell and thallus complexity?
Many species of unicells exist as free living adults.
There are also multicellular complex thalli.
These macrophtyes typically have swimming unicells as life-history components (gametes or spores).
Check out this diversity

II. Simplest cell construction.

Chlamydomonas

III. Developmental lineages and comparative life history strategies.

Single cells to multiple cells with increasing complexity (Order Volvocales) with primitive life history.

Chlamydomonas
Pandorina
Gonium
Eudorina
Volvox

All of these genera reproduce via the Zygotic Meiosis Life History

Increasingly complex multicell thalli and modified morpology of gamete but with primitive life history (Order Coleochaetales).

Coleochaete

Increasingly complex adult morphologies and intermediate life history (Order Ulvales).

Ulva
Enteromorpha

These genera reproduce via the Sporic Meiosis Life History.

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

Codium
Halimeda

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.  Is it the only very conservative character?

V.   hotlinks.gif (5957 bytes)

Green algae, UC Berkeley Coleochaete, UC Berkeley
California green algae Spirogyra reproduction
What is watermelon snow? Green algae detoxify pesticides
What is Marimo in Japan ? Dry Tortugas National Park
Phycology links  

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