Chrysophyta Diagram: Algae Classification Quiz and Flashcards

Study Notes

Characterized by a wide range of differentiation in basic taxonomic features, leading some authors to treat some of its six classes as separate divisions.
Classes Chrysophyceae and Bacillariophyceae are represented in this article.

Pigment system composed of chlorophyll A and C, and large amounts of carotenoids and xanthophylls, giving a yellow-green appearance.
Reserve food material is Chrysolaminarine, oil, and fats.
Cell wall is composed mainly of cellulose, with two overlapping H-shaped parts in many genera.
Algae can be unicellular, filamentous, or siphonious, with motile forms having two unequal flagella.
Asexual reproduction occurs by the formation of zoospores, either simple or compound, with simple zoospores having two apical unequal flagella.
Sexual reproduction is Isogamous, anisogamous, or oogamous.

A siphonous branched alga that inhabits freshwater, marine, and moist soil habitats.
Coenocytic structure of filaments is obvious, with septa absent except for those separating reproductive structures from the main filaments.
Vegetative reproduction occurs by fragmentation.
Asexual reproduction occurs by the formation of zoospores in zoosporangia, which arise at the tip of a filament following a septum formation.
Sexual reproduction is oogamous, involving the production of antheridia and oogonia.

Members are unicellular or colonial forms, with a pigment system dominated by carotenes and xanthophylls, especially fucoxanthin, resulting in a golden brown color.
Reserve food materials are chrysolaminarine, oil, and fats.
Cell wall is chemically composed of silicon.
Motile gametes have a single anterior flagellum.
Diatoms are diploid in their vegetative phase, with meiosis occurring only during gamete formation.
Rigid cell wall, referred to as frustules, is composed of two overlapping halves: the upper epitheca and the lower hypotheca.
Frustules have markings used in taxonomy, and some pennate diatoms have a fissure known as the raphe.

Diatoms are abundant in all waters, both fresh and marine, and form an important element of the plankton flora of the sea.
They are also found on damp soil, rocky walls, dry cliffs, and bark of trees, and some species have been reported from hot springs.
Some diatoms occur as epiphytes growing on other algae or water plants, and many occur as fossils, forming large deposits known as diatomaceous earth.

Cell division occurs by an increase in volume of the frustule, followed by a mitotic division of the nucleus, resulting in the formation of two protoplasts.
Each daughter protoplast has a half old wall and secretes a new half wall, which fits inside the original old half wall.
The process of cell division usually takes place during the night, and after repeated divisions, the size of the diatom attains its minimal size, forming an auxospore that restores the original size.
Auxospore formation is the result of a sexual process, which may be autogamous, isogamous, anisogamous, or oogamous.

As food, diatoms are abundant in water and form the food chain of aquatic animals, including fish and whales.
As industrial or commercial value, diatoms are used in:
- Filters of sugar refineries
- Metal polishes
- Manufacture of dynamite
- Insulators in pipes, boilers
- Manufacture of glass, porcelain, paints
- Toothpaste and face powder
- Reducing danger of explosion in wall mines
- Manufacturing light and heat-resistant bricks
In biology, diatoms are used to:
- Test the efficacy of high-power microscopes
- Study the liver oil accumulated in fish livers, which is reported to be the condensates of diatoms
- Originate from fossilized diatoms, which form oil during photosynthesis