BIO 121 Lecture Notes - Lecture 14: Hydrostatic Skeleton, Chaetognatha, Annelid
10 Dec 2020
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Document Summary
Coral; calcium carbonate are the major structure of coral reefs. Up to a million year old; huge diversity; threatened by us. Previously, morphological traits were thought to mark relations. Segmentation in annelid worms was thought to be homologous to segmentation in arthropods. Increase body size through molting( shed old, make new) Nematode: larval stage goes through a round of molting. Unknown phylo position; early development similar to deuterostomes( might be homoplaseous) Ubiquitous in soil; freshwater and marine sediments; many parasites of plants and animals. No circular muscle to antagonize contraction of longitudinal muscles. Other worm phyla have circular and longitudinal muscles. Coelomic fluid transmits force to cuticle opposite to contracted side, to return. 4 molting stages, as body gets bigger to the straight position. One way gut, not muscular; material moves by contractions of pharanx in anterior. Many predators: prey on unicelled eukaryotes, other roundworm species. Many are anaerobic: derive energy through glycolosis; don"t have enzyme paths for aerobic respiration.
