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Protists II (draft1)

Protists II (draft1) - Protista II In laboratory I you were...

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In laboratory I, you were introduced to animal-like protists (Protozoans), and these organisms were defined by their mobility and heterotrophic nutrition strategy. In this lab we will continue to survey this diverse group of organisms and further examine distinctive characteristics specific to plant-like protistans. Plant like protists or algae (singular alga ) encompass several different autotrophic groups of usually relatively simple living organisms that have the ability to capture light energy through photosynthesis, converting inorganic substances into simple sugars. Many taxonomists have traditionally regarded green photosynthetic protistans as simple plants (Viridiplantae), and indeed some chlorophytes are closely related to the higher plants. Others appear to represent different protist groups, alongside other organisms that are traditionally considered more animal-like (that is, protozoans). Thus algae do not represent a single evolutionary direction or line, but a level of organization that may have developed several times in the early history of life on earth (polyphyla). Algae range from single-celled, colonial to multi- cellular organisms, some with fairly complex forms. While many green algaes share many characteristics with plants, they all lack plant organs: leaves, roots, flowers, and other organ structures that characteristic of higher plants. Algaes are usually found in damp places or bodies of water and thus are common in terrestrial as well as aquatic environments. However, terrestrial algae are usually rather inconspicuous and far more common in moist, tropical regions than dry ones, because algae lack vascular tissues and other adaptations to live on land. Some algaes can live in non-moist environments by developing symbiotic relationships with fungi (lichens). The algae are the dominating primary producers in aquatic ecosystems, on unstable substrates (muds and sands) and in intertidal marine habitats. Algae are commonly exploited as foodstuffs, food additives, toothpastes, etc. Protista II The body portion of an algae is called a thallus. The thallus of an algae is usually haploid and the variety may define specific groups. There are four types of thalli, based on the following body structures: 1. UNICELLULAR ALGAE - A Structure that consists of a single cell, most are aquatic organisms, and form the phytoplankton, a population of photosynthetic organisms the forms the foundation of the food chain. They produce half of the worlds carbohydrates and are among the major producers of oxygen in the atmosphere. 2. COLONIAL ALGAE - Have a structure that consists of groups of cells acting in a coordinated manner. Some of these cells become specialized. This division of labor allows colonial algae to move, feed, and reproduce efficiently.
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