BIO153H5 Lecture Notes - Lecture 14: Burgess Shale, Central Canal, Triploblasty
Document Summary
Topics: fossil record evolution of complexity evolution of the coelom. While there is great diversity of body plans, there are also many constraints on the engineering of animals. Advantages of being multicellular: tissue differentiation division of labour, more complex functions larger body size possible. Surface area - volume ratio small animals: gases, nutrients, wastes move by diffusion larger animals need organ systems to pump gases, nutrients, wastes in/out. Habitat challenges: marine animals are isotonic; freshwater animals must eliminate water (leaks in osmotically) terrestrial animals: lack of buoyancy; protection of gametes and zygote. Locomotion challenges: sessile / slow animals tend to have radial symmetry. 1 fast animals need to be bilaterally symmetrical; cephalization is part of this trend. Common attributes of all animals: multicellular no cell walls heterotrophs motile embryo goes through blastula stage (blastula = hollow ball of cells) Animals are monophyletic members of the opisthokont lineage (along with fungi)