Category: 05. Algae

The classification of algae into taxonomic groups is based upon the same rules that are used for the classification of land plants, but the organization of groups of algae above the order level has changed substantially since 1960. Early morphological research using electron microscopes demonstrated differences in features, such as the flagellar apparatus, cell division process, and organelle structure…

Modern ultrastructural and molecular studies have provided important information that has led to a reassessment of the evolution of algae. In addition, the fossil record for some groups of algae has hindered evolutionary studies, and the realization that some algae are more closely related to protozoa or fungi than they are to other algae came late, producing confusion in evolutionary thought and delays…

Algae regenerate by sexual reproduction, involving male and female gametes (sex cells), by asexual reproduction, or by both ways. Asexual reproduction is the production of progeny without the union of cells or nuclear material. Many small algae reproduce asexually by ordinary cell division or by fragmentation, whereas larger algae reproduce by spores. Some red algae produce monospores (walled, nonflagellate, spherical cells) that are…

Not all algae have chloroplasts and photosynthesize. “Colourless” algae can obtain energy and food by oxidizing organic molecules, which they absorb from the environment or digest from engulfed particles. They are classified as algae, rather than fungi or protozoa, because in most other features they resemble photosynthetic algae. Algae that rely on ingestion and oxidation of organic molecules are referred…

As in land plants, the major carbohydrate storage product of the green algae is usually starch in the form of amylose or amylopectin. These starches are polysaccharides in which the monomer, or fundamental unit, is glucose. Green algal starch comprises more than 1,000 sugar molecules, joined by alpha linkages between the number 1 and number 4 carbon atoms. The cell walls of many, but not all, algae contain cellulose. Cellulose is formed…

Red wavelengths are absorbed in the first few metres of water. Blue wavelengths are more readily absorbed if the water contains average or abundant amounts of organic material. Thus, green wavelengths are often the most common light in deep water. Chlorophylls absorb red and blue wavelengths much more strongly than they absorb green wavelengths, which…

Photosynthesis is the process by which light energy is converted to chemical energy whereby carbon dioxide and water are converted into organic molecules. The process occurs in almost all algae, and in fact much of what is known about photosynthesis was first discovered by studying the green alga Chlorella. Photosynthesis comprises both light reactions and dark reactions (or Calvin cycle). During the dark reactions, carbon…

Cellular respiration in algae, as in all organisms, is the process by which food molecules are metabolized to obtain chemical energy for the cell. Most algae are aerobic (i.e., they live in the presence of oxygen), although a few Euglenophyceae can live anaerobically in environments without oxygen. The biochemical pathways for respiration in algae are similar to those of…

Mitosis, or the process of replication and division of the nucleus that results in the production of genetically identical daughter cells, is relatively similar among plants and animals, but the algae have a wide diversity of mitotic features that not only set the algae apart from plants and animals but also set certain algae apart from other algae. The…

A flagellum is structurally complex, containing more than 250 types of proteins. Each flagellum consists of an axoneme, or cylinder, with nine outer pairs of microtubules surrounding two central microtubules. The axoneme is surrounded by a membrane, sometimes beset by hairs or scales. The outer pairs of microtubules are connected to the axoneme by a protein called…