Chlorophyta

Outline

Introduction

a.k.a. chlorophytes, green algae

most diverse algal group

most closely resemble "plants"

Cells

Chloroplasts:

chlorophylls a + b + carotenoids (e.g., b-carotene)

thylakoids in stacks of 2 to 6

2 membranes

one to many pyrenoids (also with rubisco)

reserve polysaccharide = starch, deposited inside chloroplast

come in a wide variety of shapes

Cell covering

scales: only in Prasinophyceae

cell wall: cellulose with hemicellulose and pectins in amorphous component

Cytokinesis

new cell wall may have a complex of microtubules associated with it

phycoplast: parallel to new cell wall

phragmoplast: parallel to spindle apparatus microtubules

new cell wall may be made through furrowing or by means of a cell plate

Flagella (whiplash)

There are differences in the orientation of the flagella, the basal bodies and the microtubules that anchor the flagella. These differences are used to assing class.

class	cell covering	mitosis	microtubule organization in cytokinesis	basal body orientation	habitat	life cycle
Prasinophyceae	organic scales or naked	closed	variable	variable	variable	haplontic (usually)
Chlorophyceae	cellulose cell wall	closed	phycoplast	[opposite, with cruciate microtubular roots]	freshwater	haplontic, with zygospore (dormant zygote)
Ulvophyceae	cellulose cell wall	closed	none	[opposite, with cruciate microtubular roots]	marine	diplohaplontic
Charophyceae	cellulose cell wall	open	phragmoplast	[parallel, with unilateral microtubular roots]	freshwater	haplontic, with zygospore (dormant zygote)

characteristics in green are characteristics shared with "green plants"

Prasinophyceae

similar to ancestral chlorophytes

probably an artificial class

highly variable

Chlorophyceae

Diversity -- 3 evolutionary lines

motile

unicellular, e.g., Chlamydomonas

colonial, e.g., Volvox

non-motile

unicellular, e.g., Chlorella

colonial -- often as coenobia, e.g., Scenedesmus, Pediastrum, Hydrodictyon

Filamentous (and parenchymatous) chlorophyceans:

Fritscheriella -- terrestrial with rhizoids

Ulvophyceae

Diversity -- 3 evolutionary lines

Filamentous -- e.g., Cladophora

Flat sheets -- e.g., Ulva

Siphonous (coenocytic) -- e.g., Caulerpa -- has leaf-like and root-like structures

Charophyceae

Diversity

Filamentous algae

e.g., Spirogyra -- reproduction through conjugation, zygospore

Desmids -- made of 2 half-cells

e.g., Cosmarium -- reproduction through conjugation, zygospore

Stoneworts

e.g., Chara, Nitella -- macroalgae with complex reproductive structures

Coleochaetales

filamentous or discoid, e.g., Coleocheate

most closely related to green plants (mosses, ferns, vascular plants, etc.)

Vocabulary

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