BIO325H5 Lecture Notes - Lecture 4: Pericardium, Heart, Ground Tissue
Document Summary
Makes sense to have an organ like a heart, one that must change shape to function, situated in its own inviolate space. The contraction of one chamber (e. g, atrium) is pressure-coupled to the distension of the other (e. g. , ventricle). Insect circulatory systems do not have to transport respiratory gases (oxygen and carbon dioxide), that is accomplished by the tracheal tubes. Lateral cracks are stopped when they reach a new fibre just as in composite material . Snipping" off these supporting fibreswith their incisors: some grasses use silica (in effect glass") as a defense. It forms plant cell walls, and can be a food for herbivores. But mammalian herbivores lack the enzymes to break acetyl linkageswhile micro-organisms dohave these enzymes: a large group of mammalian vertebrates evolved a symbiotic relationship with micro- organisms so as to benefit from their enzymatic capabilities: the ruminants. The rumen is the part of their gut housing the symbionts (protozoa, bacteria).
