Biology: Diatoms

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the shape of an auxospore?

Oval

Spherical (correct)

Elipitical

Pyramidal

What is the ecological importance of diatoms in aquatic food chains?

They produce toxins that harm aquatic life

They are competitors with other aquatic plants

They are a food source for aquatic animals, including fish and whales (correct)

They are decomposers in aquatic ecosystems

What is the result of the division of an auxospore?

Cells with different valve morphology

Cells of maximum size for that particular species (correct)

Cells that are not viable

Cells of minimum size for that particular species

In which industry are diatoms used as filters?

Sugar refineries Signup and view all the answers

What is the role of diatoms in the formation of petroleum?

They are fossilized and form the basis of petroleum Signup and view all the answers

What is a unique feature of diatom cell walls?

They have a thick, rigid structure Signup and view all the answers

What is the main component of the cell wall in Chrysophyceae?

Cellulose Signup and view all the answers

What is the type of reproduction in which flagellated gametes of unequal size fuse?

Oogamous Signup and view all the answers

What is the name of the genus of siphonous branched algae that inhabits freshwater, marine habitats, and moist soils?

Vaucheria Signup and view all the answers

What is the type of zoospores that have two apical unequal flagella?

Simple zoospores Signup and view all the answers

What is the pigment system of Chrysophyceae composed of?

Chlorophyll A and C Signup and view all the answers

What is the reserve food material in Chrysophyceae?

Chrysolaminarine, oil, and fats Signup and view all the answers

What is the primary pigment system found in diatoms?

Carotenes and xanthophylls Signup and view all the answers

What is the composition of the cell wall in diatoms?

Silicon Signup and view all the answers

What is the function of the raphe in pennate diatoms?

It facilitates movement in the diatom Signup and view all the answers

What is the term used to describe the overlapping halves of the diatom frustule?

Epitheca and hypotheca Signup and view all the answers

What is the significance of diatoms in the ecosystem?

They are the primary producers of the aquatic ecosystem Signup and view all the answers

What is the term used to describe the deposits formed by fossilized diatoms?

Diatomaceous earth Signup and view all the answers

What is the ploidy level of diatoms in their vegetative phase?

Diploid Signup and view all the answers

What is the characteristic feature of the girdle in diatoms?

It is the area shared by parts of both valves Signup and view all the answers

Study Notes

Diatom Structure and Characteristics

Auxospores are spherical in shape and have different valve morphology than normal valves.
Division of auxospores produces cells of the maximum size for that particular species.
Cell wall is composed of silicon and is chemically rigid, referred to as frustules.
Frustules are composed of two overlapping halves: epitheca (upper) and hypotheca (lower).
The area shared by parts of both valves is called the girdle.
Some pennate diatoms have a fissure known as raphe on one or both valves.

Economic Importance

Diatoms are an important food source for aquatic animals, including fish and whales, and are known as "grass of the sea".
They have industrial value in filters of sugar refineries, metal polishes, dynamite manufacture, insulators, glass, porcelain, paints, toothpaste, and face powder.
They also have a role in the manufacture of light and heat resistant bricks, and in reducing the danger of explosion in wall mines.

Biology and Pigmentation

Diatoms are diploid in their vegetative phase, and meiosis occurs only during gamete formation.
The pigment system is dominated by carotenes and xanthophylls, particularly fucoxanthin, alongside chlorophyll a and c, resulting in a golden brown color.
Reserve food materials are chrysolaminarine, oil, and fats.
Motile gametes have a single anterior flagellum.

Classification and Habit

Diatoms are classified into two categories: Centrales and Pennales.
They are abundant in all waters, both fresh and marine, and form part of the plankton flora of the sea.
They can also be found in damp soil, rocky walls, dry cliffs, and the bark of trees, and some species occur as fossils, forming large deposits known as diatomaceous earth.

Reproduction

Cell division involves an increase in volume of the frustule, followed by mitotic division of the nucleus.
Asexual reproduction takes place through the formation of zoospores.
Sexual reproduction can be isogamous, anisogamous, or oogamous.

Chrysophyta

This group of algae is characterized by a wide range of differentiation in various taxonomic features.
Classes Chrysophyceae and Bacillariophyceae are represented in this group.
Class Chrysophaceae has a pigment system composed of chlorophyll A and C, and large amounts of carotenoids and xanthophylls, resulting in a yellow-green appearance.