animal life encyclopedia

[...]... “Cladistic Analyses of the Animal Kingdom.” Biological Journal of the Linnaean Society 57 (1996): 385–410 Zrzavý, Jan S., et al “Phylogeny of the Metazoa Based on Morphological and 18S Ribosomal DNA Evidence.” Cladistics 14 (1998): 249–285 Per Sundberg, PhD 14 Grzimek’s Animal Life Encyclopedia ••••• Reproduction, development, and life history Ontogeny and phylogeny All animals must reproduce, passing... (diversification) of animal forms Some researchers have suggested that the absence or lack of metazoan life in the early fossils is due to the simple fact that the first animals were small organisms lacking structures (like shells) that fossilized well Some findings support the view that the first animals were microscopic; however, as has already been mentioned, there were also large animals in this period... existed before the Cambrian explosion but did not leave fossil evidence until later Some researchers have proposed that a more complicated life style, more complex interactions among animals, and especially the advent of predation were a strong Grzimek’s Animal Life Encyclopedia Vol 2: Protostomes Evolution and systematics selective force for developing such features as shells as antipredation devices... the details of metazoan phylogeny, all analyses make a clear differentiation between the lower and diploblastic anGrzimek’s Animal Life Encyclopedia Evolution and systematics imals on the one hand and the triploblastic animals on the other Some time after the radiate phyla evolved, animals with bilateral symmetry (a body axis with a clear front end and back end) and a third germ layer (the mesoderm) appeared... of plants and animals existed about 1.6 billion years ago, which is long after the first appearance of eukaryotes and long before any definite fossil records of metazoans The Ediacaran fauna (600–570 mya) contains the first evidence of the existence of many modern phyla This evidence, Grzimek’s Animal Life Encyclopedia however, is largely a matter of trace fossils, which result from animals moving... adult animal, with many tissues, organs, and systems in their proper places, all functioning in a coordinated manner, are referred to as the animal s ontogeny Clearly, the ontogeny of an animal is critical to determining what kind of creature the animal is and what it can become Thus, it should be no surprise that specific ontogenetic patterns tend to be characteristic of particular groups of animals... phylum of animals must also have a distinctive ontogenetic pattern So, taking it one step further, we can reason that an animal s ontogeny (the developmental history of the individual), correlates with its phylogeny (the evolutionary history of the phylum) Some nineteenth-century naturalists and biologists were so struck by this relationship that they argued that an aniGrzimek’s Animal Life Encyclopedia. .. XNR Productions, Madison, WI Laura Exner Tanya Buckingham Cory Johnson Jon Daugherity Paula Robbins Grzimek’s Animal Life Encyclopedia Andy Grosvold xvii This page intentionally left blank ••••• Topic overviews What is a protostome? Evolution and systematics Reproduction, development, and life history Ecology Symbiosis Behavior Protostomes and humans This page intentionally left blank ••••• What is... characters outlined by Grobben; however, it is rare to find more Grzimek’s Animal Life Encyclopedia A land snail crawling on grass (Photo by JLM Visuals Reproduced by permission.) 5 What is a protostome? Vol 2: Protostomes Resources Books Brusca, R C., and G J Brusca Invertebrates, 2nd ed New York: Sinauer Associates, 2003 Nielsen, C Animal Evolution: Interrelationships of the Living Phyla, 2nd ed New York:... months In any event, however, the protists are the first eukaryotic organisms, and the forerunners of the multicellular animals known as metazoans One example of protists is phylum Ciliophora, the ciliates, which are very common in benthic (sea bottom) and plankGrzimek’s Animal Life Encyclopedia Dorsal reconstruction of a crustacean (Waptia fieldensis) from the Middle Cambrian Burgess Shale of British .