Category: 05. Algae

Algal cells are eukaryotic and contain three types of double-membrane-bound organelles: the nucleus, the chloroplast, and the mitochondrion. In most algal cells there is only a single nucleus, although some cells are multinucleate. In addition, some algae are siphonaceous, meaning the many nuclei are not separated by cell walls. The nucleus contains most of the genetic material, or deoxyribonucleic acid (DNA),…

Some algae can be harmful to humans. A few species produce toxins that may be concentrated in shellfish and finfish, which are thereby rendered unsafe or poisonous for human consumption. The dinoflagellates (class Dinophyceae) are the most notorious producers of toxins. Paralytic shellfish poisoning is caused by the neurotoxin saxitoxin or any of at least 12 related compounds, often produced by the dinoflagellates Alexandrium tamarense and Gymnodinium catenatum. Diarrheic shellfish poisoning is caused by…

Algae form organic food molecules from carbon dioxide and water through the process of photosynthesis, in which they capture energy from sunlight. Similar to land plants, algae are at the base of the food chain, and, given that plants are virtually absent from the oceans, the existence of nearly all marine life—including whales, seals, fishes, turtles, shrimps, lobsters, clams, octopuses, sea stars, and worms—ultimately depends upon algae. In addition to making organic molecules, algae produce oxygen as…

Algae are almost ubiquitous throughout the world and can be categorized ecologically by their habitats. Planktonic algae are microscopic and grow suspended in the water, whereas neustonic algae grow on the water surface and can be micro- or macroscopic. Cryophilic algae occur in snow and ice (see red snow); thermophilic algae live in hot springs; edaphic algae live on or in soil; epizoic algae…

The size range of the algae spans seven orders of magnitude. Many algae consist of only one cell, while the largest have millions of cells. In large, macroscopic algae, groups of cells are specialized for specific functions, such as anchorage, transport, photosynthesis, and reproduction; such specialization indicates a measure of complexity and evolutionary advancement. The algae…

Algae, singular alga, members of a group of predominantly aquatic photosynthetic organisms of the kingdom Protista. Algae have many types of life cycles, and they range in size from microscopic Micromonas species to giant kelps that reach 60 metres (200 feet) in length. Their photosynthetic pigments are more varied than those of plants, and their cells have features not found among plants and animals. In…

Algae are defined as a group of predominantly aquatic, photosynthetic, and nucleus-bearing organisms that lack the true roots, stems, leaves, and specialized multicellular reproductive structures of plants. Their photosynthetic pigments are also more varied than those of plants, and their cells have features not found among plants and animals.