Chrysophyta

Outline

Introduction

Taxonomy -- includes classes:
Chrysophyceae (golden-brown algae)

Xanthophyceae (yellow-green algae)

Bacillariophyceae (diatoms)

also, Phaeophyceae (brown algae)?

as well as the oomycetes and some protozoans (the Bicocoecids, in case you're interested, which include such genera as Cafeteria and Pseudobodo [no, I'm not making this up])

Properties of division Chrysophyta

chlorophylls a & c

fucoxanthin as accessory pigment

laminarin or chrysolaminarin as reserve material

thylakoids in sets of three

four chloroplast membranes (outer 2 = chloroplast ER)

cell walls optional

flagellated cells in some life stages (with whiplash and tinsel flagella)

...and tubular cristae in their mitochondria

The origins of chloroplasts and the endosymbiotic hypothesis

Chloroplasts of green plants and green algae
chloroplasts were once free-living relatives of cyanobacteria

evidence

Chloroplasts of chrysophytes

endosymbiosis of a eukaryotic alga

...explains why there are 4 membranes, etc.

Chrysophyceae -- golden-brown algae

Cells
walls -- siliceous scales or loricas

contractile vacuoles

Life cycle

haplontic

statocysts

Ecology

Mostly autotrophic, some mixotrophic

mostly in oligotrophic lakes (good P uptake)

Xanthophyceae -- yellow-green algae

Cells
walls -- cellulose, often in two parts

few flagellated (except as zoospores), mostly coccoid

filaments often coenocytic

Life cycle

diplontic

Vaucheria -- like Saprolegnia

Ecology

Mostly freshwater and terrestrial

Bacillariophyceae -- diatoms

Cells
only one tinsel flagellum

use fat as reserve material

siliceous cell wall = frustule

frustule = 2 valves + girdle bands

epivalve & hypovalve

Taxonomy

Pennales ("pennates")
bilateral symmetry

may have raphe

2 big chloroplasts

Centrales ("centrics")

radial symmetry

no raphe

central vacuole w/ many small chloroplasts

Life cycle -- diplontic

cued by decrease in cell size
Pennates -- isogamous

Centrics -- oogamous w/ flagellated sperm

zygote forms auxospore

resting spores & resting cells

Ecology

marine
importance

problems

endosymbiosis

freshwater

planktonic

growing on surfaces

Fossil diatoms

diatomaceous earth: of economic importance

paleontological studies -- past climate and lake status

Vocabulary

click here to go to Chrysophyta vocabulary


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