Unformatted text preview: Algae
Types: Green, Brown, Red, Golden, Diatoms, and Dinoflagellates Key Points: Structure, Reproduction, Life Cycle, and Examples Overview Different types of algae are found on land, freshwater, and marine ecosystems They are the basis of most Food Webs Usually Single Celled Organisms that sometimes form larger colonies. May be ancient ancestors to most complex plants Structure
Algae can be unicellular or multicellular Algae the pigments xanthophylls, carotenes, thechlorophyll, Chlorophyll,and phycoerythrin Some Algae use flagella for locomotion Diatom's cell Wall are made of Silica. Other algae have cell walls made of glycoproteins and cellulose, where as some have no cell walls. ... Structure Green Algae: may be unicellular or multicellular in colonial forms. Uses chlorophyll. Has a cellulose cell walls, flagella, and nucleus bound organelles Brown Algae: marine organisms that form large, multicellular structures with cellulose cell walls and flagella. Contains xanthophylls, carotenes, and chlorophyll. Red Algae: multicellular,They have no flagella but do have cellulose cell walls and phycoerythrin pigments. Golden Algae: Cellulose cell wall with two flagella. Contains chlorophyll, xanthophyll, and carotene pigments. Dinoflagellates: Unicellular or Colonial with 2 flagella and cellulose cell wall. Produce toxic algal blooms causing "Red Tides." Diatoms: Have delicate silica cell walls in pen shapes or centric cyllinders that form "glass pill boxes. They also contain yellow-brown chloroplasts. Diatom Algae Structure Reproduction
-Algae reproduce in very diverse ways. -Algae can reproduce asexually, sexually, or even both. Asexual Reproduction Some multicellular algae, including Sargassum, reproduce asexually through fragmentation, in which fragments of the parent develop into new individuals. In a similar process called budding, special buds detach from multicellular algae and develop into new individuals, commonly found in Sphacelaria. Many algae produce special cells called spores that are capable of growing into new individuals. If these spores move about using flagella, they are known as zoospores. Sexual Reproduction The simplest form of sexual reproduction in algae is conjugation, in which two similar organisms combine, exchange genetic material, and then break apart. Spirogyra are known to use this method. Most multicellular algae undergo a more complex form of sexual reproduction involving the union of special reproductive cells, called gametes, to form a single cell, known as a zygote. Conjugation A Little Bit of Both Many algae use both sexual and asexual modes of reproduction. This is well demonstrated in the life cycle of the alga Chlamydomonas. The mature alga is a single haploid containing only one set of chromosomes. During asexual reproduction the cell undergoes mitosis, Four daughter cells are created that come from the enclosing parent cell as spores. The spores develop into mature haploid cells that are genetically identical to the parent cell. http://encarta.msn.com/en cyclopedia_761573848/Al gae.html#s20 ...
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