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TAMU BIOL 112 - CH32

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Chapter 32 Overview of Animal DiversityFeatures of Animals- Animal structureo Multicellular eukaryoteso 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 heterotrophso Some parasites are absorptiveo Difference in fungi= absorptive heterotroph- Life cycleo 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 recordo Evidence is: collar cells and genesPre-cambrian animals- Ediacaran biota about 565 mya (32.4)o Earliest known animal fossilso Soft bodied sponges, jelly-fish likePaleozoic Era- Cambrian Explosion about 535mya (32.5)o Dramatic animal diversificationo Almost all major phyla and moreo First mineralized skeletons and shells- Later Paleozoic erao Vertebrate fish dominate the seaso Arthropods invade lando 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 extinctionCenozoic Era- Diversification of modern groupsAnimal Body PlansMost animals are symmetric- Radial symmetry= cnidarianso Meets the world at 360 degreeso Associated with sessile or planktonic life- Bilateral symmetryo Meets the world head ono Associated with active search for food or escapeo Usually with head= concentration of sensory organs at the anterior (cephalization)Most animals have tissue layers- Diploblastico With 2 germ layers (formed in gastrula stage)o Cnidaria, porifera, ctenophoreso Layer lining the body cavity and on the outsideo Ectoderm= outer covering and nerveso Endoderm= digestive tract and internal organs- Triploblastico With 3 germ layerso Mesoderm develops between the ectoderm and endoderm Produces muscles and enoskeletonBody Cavity- Fluid filled space between the body wall and gut- Cushions internal organs- Allows independent movement and expansion of gut- Can act as hydrostatic skeletono Something for muscles to push against- Most body cavities are true coelomso Completely lined with mesodermo Gut supported and has muscles- Some pseudocoelomo Mo mesoderm between cavity and gut- Acoelomates have no body cavityDevelopmental patterns- Protostome developmento Blastopore of gastrula becomes adult moutho Coelom forms from a split in solid mesoderm mass (32.9)o Spiral cleavage Daughter cells oblique to parent cellso 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 moutho Coelom forms from fold of archenterono Radial cleavage Daughter cells perpendicular to parent cellso Cleavage is indeterminate Any early cell can become a complete organismAnimal PhylogenyRelationships still debated- Approximately 36 phyla- Newer DNA analyses change older trees- Use Fig 32.11Major Clades- 1 common ancestor of metazoans (animals)- Sponges (porifera) form a basal taxon for animalso No true tissues- Eumetazoans-most have true tissueso Diploblastic ctenophore and cnidarian are basal- Most eumetazoans are bialteriano Bilateral symmetry and triploblastic- Deuterostome- includes chordates and Echinodermatao Most other phyla are protostomes- Lophotrchozoans are most diverseo Some have trochophor larva (Mollusca and annelida)o Some have a lophophore feeding structure Brachipoda and ectoprocta- Ecdysozoanso With exoskeleton they shed as they grow Ecdysis= shedding the exoskeleton Nematode and arthropoda and


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TAMU BIOL 112 - CH32

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