BIO 1130 : Cambrian and Ordovician keywords.doc

• School: University of Ottawa
• Department: Biology
• Course: BIO 1130
• Professor: Jon Houseman

Document Summary

Acoelomates, which include the flatworm, fluke, tapeworm, and ribbon worm, exhibit bilateral symmetry and possess one internal space, the digestive cavity. An algal mat is a layer of usually filamentous algae on marine or fresh water soft bottoms. Algae and cyanobacteria are ubiquitous, often forming within the water column and settling to the bottom. In shallow environments, they are often dessiccated and revived with the next introduction of water and sunlight. Stromatolites can form in this way (see shark bay for a modern example). Any puddle of water can start the process - sunlight initiates the process and photosynthesis soon creates a green layer within the puddle. The puddle can dry up and leave a thin layer of "algal" mat and even leave mudcracks behind. Cyclicity involves the repeated process of wetting (rain), algal production, and redrying of the new deposit. This results in layer upon layer of algal mats and intervening thin layers of mud.