2020-10-10
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The plant kingdom is made up of multicellular, photosynthetic eukaryotes. These multicellular organisms contain specialized cells that perform different tasks.
Marine algae (seaweeds and phytoplankton) are a loose group of some of the simplest organisms that contain chlorophyll (like plants) but include members of both the Empires Prokaryota (Kingdom Bacteria – e.g., cyanobacteria) and Eukaryota (Kingdoms Chromista, Plantae and Protozoa…). Marine algae though are abundant throughout the ocean and can either float freely or cling to substrate such as rocks and reefs. The majority of seaweeds are classified as red algae (~6,000 species). There are also brown algae (~2,000 species) and green algae (~8,000 species). None of the algae species are known to be poisonous, and many species are harvested for human consumption.
Phytoplankton
Phytoplankton are microalgae that form an essential component of the marine food chain. These single-celled plants provide nourishment to many marine species and they also play an important role in regulating the amount of carbon in the atmosphere. There are two main types of the larger phytoplankton species: Diatoms and Dinoflagellates. Smaller phytoplankton categorized as nanoplankton and picoplankton.
Diatoms
The cell walls of diatoms are made of silica formed into their characteristic “pillbox” shape. Diatoms are composed of two valves or frustules, one on top of the other, within which the living matter of the diatom is found. Diatoms are either found singly where each individual lives in a single box, or found in chains. Diatoms reproduce by dividing in half. One half is attached to the top valve, the other is attached to the bottom valve. Once the division takes place, each half creates a new valve to form another whole. The new valve is secreted in the old valve, therefore the average size of each diatom is reduced with every new generation. It is thought that there are as many as 100,000 species of diatoms currently inhabiting the earth, and they occur in both fresh and saltwater.
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Dinoflagellates
Dinoflagellates are the other primary form of large phytoplankton with about 2,000 species. Unlike diatoms, dinoflagellates are mobile through the use of a flagella. Also unlike diatoms, they do not have an external skeleton made of silica, however they are protected by cellulose. dinoflagellate - Ceratocorys sp.Dinoflagellates are typically solitary and do not form chains like diatoms. Like the diatom they reproduce through fission. Once divided, each half retains half of the original cellulose armor and replaces the missing half to form a new whole. Some dinoflagellates can produce toxins that are released into seawater. When there are large blooms, a phenomenon known as red tide occurs. In some cases increased levels of dinoflagellate toxin may cause other marine life to die. The symbiotic algae found in many corals, or zooxanthellae, are actually a non-mobile species of dinoflagellate. Dinoflagellates have strong bioluminescence and have been a source of fascination for sailors and other mariners as their ships pass through waves which become lit up by these organisms at night.
Algae
Algae are photosynthetic eukaryotes that are either unicellular, colonial, or multicellular. Algae with at least some multicellular members are grouped into two main Empires or Domains (Prokaryota and Eukaryota) and then further down into multiple Kingdoms (e.g., Plantae), Supergroups, Divisions, etc. mainly in the Eukaryota Domain: Phylum Rhodophyta (red algae), Class Phaeophycea (brown algae) and Phyla Chlorophyta and Charophyta (green algae). Red and brown algae species are most commonly marine; green algae are found in abundance in both marine and fresh water.
Phylum Rhodophyta (Red Algae)
Red algae grow as single-celled plants or plants that grow as filaments, branched plants, broad flat plates, and ruffled plants. They come in a variety of sizes, but most red algae are small. All species attach to substrate such as rock or coral and sometimes to an animal shell or even another algae species.
Giant Kelp, Macrocystis pyrifera - Channel IslandsClass Phaeophycea (Brown Algae)
Brown algae contain the largest and most complex algae plants. Pacific kelp are a brown algae species. There are no unicellular or colonial forms of brown algae. Brown algae stores food reserves as a substance called laminarin, similar to a lesser known species of gold algae in the Class Chrysophyceae. Brown and gold algae also have in common the presence of flagellated cells of both sperm and motile spores. Brown algae are commonly found attached to the substrate in cool, shallow waters near the shore in temperate and subpolar regions. Some forms of brown algae have developed adaptations to survive life on the coast where they may be pounded by surf or submerged then exposed with the tide. Large brown algae are used as shelter for some bottom-dwelling animals. They also provide serve as substrate for other algae that grow as epiphytes, or plants that grow on other plants.
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Exercise 47. Read and translate the following words and word combinations from Russian into English.
Фитопланктон, диатомовые водоросли, динофлагелляты, водоросли, хлорофилл, цианобактерии, свободно плавающие, субстрат, морские водоросли, ядовитый, нанопланктон, пикопланктон, кремнезем, биолюминесценция, донные животные,растительный эктопаразит.
Exercise 47.Give the definition to the following terms: аlgae, dinoflagellates, phytoplankton, diatoms.
Exercise 40.Look through the text to find out more information about:
- the plant kingdom is made up of multicellular, photosynthetic eukaryotes;
- none of the algae species are known to be poisonous;
- phytoplankton are microalgae;
- the symbiotic algae found in many corals;
- b rown algae contain the largest and most complex algae plants.
