Chapter 32 Overview of Animal Diversity Features of Animals Animal structure o Multicellular eukaryotes o Cells with no cell walls Supported and joined by extracellular proteins especially collagen o Most with specialized nerve and muscle cells Unique to animals Organized into tissue usually Animals are ingestive heterotrophs o Some parasites are absorptive o Difference in fungi absorptive heterotroph Life cycle o Diploid except for sperm and egg 13 6a o Embryonic development Most animals have similar genes that control development including the Hox genes Fertilization zygote cleavage process blastula gastrulation Gastrulation Forms the gastrula with blastopore and archenteron cavity Creates germ layers origins of major tissues o Larval stage before adulthood in most animals Larva differs in form function and often habitat from the adult Metamorphosis to adult form Snake has no larval stage Larval stage is the main way of dispersal in aquatic environments sea snail Larva can survive the winter and utilize better resources than the adult butterfly and caterpillar Not competing for the same resources frogs and tadpoles Animal Origin and Fossil History 28 3 One common ancestor of all animals Chanoflagellates are the closest protist group to animals 32 3 o Small no cell walls to fossil record o Evidence is collar cells and genes Pre cambrian animals Ediacaran biota about 565 mya 32 4 o Earliest known animal fossils o Soft bodied sponges jelly fish like Paleozoic Era Cambrian Explosion about 535mya 32 5 o Dramatic animal diversification o Almost all major phyla and more o First mineralized skeletons and shells Later Paleozoic era o Vertebrate fish dominate the seas o Arthropods invade land o Much later vertebrates invade land amphibians o First amniotes ancestors of reptiles and mammals Mesozoic Era Dinosaurs pterosaurs and aquatic reptiles Origin of birds and mammals Cretaceous extinction Cenozoic Era Diversification of modern groups Animal Body Plans Most animals are symmetric Radial symmetry cnidarians o Meets the world at 360 degrees o Associated with sessile or planktonic life Bilateral symmetry o Meets the world head on o Associated with active search for food or escape o Usually with head concentration of sensory organs at the anterior cephalization Most animals have tissue layers Diploblastic o With 2 germ layers formed in gastrula stage o Cnidaria porifera ctenophores o Layer lining the body cavity and on the outside o Ectoderm outer covering and nerves o Endoderm digestive tract and internal organs Triploblastic o With 3 germ layers o Mesoderm develops between the ectoderm and endoderm Produces muscles and enoskeleton Body Cavity Fluid filled space between the body wall and gut Cushions internal organs Allows independent movement and expansion of gut Can act as hydrostatic skeleton o Something for muscles to push against Most body cavities are true coeloms o Completely lined with mesoderm o Gut supported and has muscles Some pseudocoelom o Mo mesoderm between cavity and gut Acoelomates have no body cavity Developmental patterns Protostome development o Blastopore of gastrula becomes adult mouth o Coelom forms from a split in solid mesoderm mass 32 9 o Spiral cleavage Daughter cells oblique to parent cells o Cleavage is determinate Early embryonic cells fated to become certain body parts Lose any cells others can t take the lost cell s place leads to deformation or death Deuterstome Development o Blastopore of gastrula becomes adult anus second opening becomes mouth o Coelom forms from fold of archenteron o Radial cleavage Daughter cells perpendicular to parent cells o Cleavage is indeterminate Any early cell can become a complete organism Animal Phylogeny Relationships still debated Approximately 36 phyla Newer DNA analyses change older trees Use Fig 32 11 Major Clades 1 common ancestor of metazoans animals Sponges porifera form a basal taxon for animals o No true tissues Eumetazoans most have true tissues o Diploblastic ctenophore and cnidarian are basal Most eumetazoans are bialterian o Bilateral symmetry and triploblastic Deuterostome includes chordates and Echinodermata o Most other phyla are protostomes Lophotrchozoans are most diverse o Some have trochophor larva Mollusca and annelida o Some have a lophophore feeding structure Brachipoda and ectoprocta Ecdysozoans o With exoskeleton they shed as they grow Ecdysis shedding the exoskeleton Nematode and arthropoda and others