Shared Animal Characteristics

Multicellular Most have tissues and organs

Aerobic heterotrophsReproduce sexuallyDevelop from embryosMotileToday we will focus on invertebrates

No internal backboneCompare similarities and differences

through several basic features

Symmetry

Radial symmetry: body parts arranged around a central axis

Bilateral symmetry: have a front and back end and right and left side

Embryo Tissue Layers

Zygote develops into a mass of cellsPrimary tissue layers form

Simple radial animals have two layers Outer ectoderm Inner endoderm

Bilateral animals have a third layer, mesoderm in the middle

Pattern of Development

Protostome: first embryo opening becomes the mouth Examples: flatworms, molluscs, roundworms,

arthropods

Deuterostome: second embryo opening becomes the mouth Example: Echinoderms, chordates

Body cavity: Coelom

Cavity between the gut and the wall that is lined with tissue Cushions organs Helps organs grow and move independently

3 types of body cavities

Acoelomate: no body cavity Flatworms

Pseudocoelmate: false cavity Partially lined Roundworms

Coelomate: true cavityHigher animals

Animal Phylogenetic tree

Sponges: Phylum Porifera

No true tissuesNo germ layersAcoelomatesNo symmetrySessile adultAsexual and sexual reproductionSpicules: made of different substances; for protectionCollar cells (choanocytes)-flagellated, create water

currentsAmoebocytes-digestion, secretionEpidermal cells-cover surfaceOsculum: largest opening for water

Grantia slide

Jellyfish Phylum Cnidaria

Radial SymmetryTwo germ layersSimple tissuesAcoelomatesPolyp and/or medusa stageStinging cells—Cnidocytes with nematocysts

Fluid filled capsule with thread

Nerve net

Hydra-cnidarian example

Look at slides and live specimens

Roundworms: Phylum Nematoda

Bilateral symmetryThree germ layers Molt their cuticlePseudocoelomatesCephalization with brainComplete digestive system (2 openings)Many parasites

Roundworm examples

Ascaris: intestinal parasite, infects humansTrichinella: encysts in human muscles

causing trichinosisVinegar eels: live specimen

Three germ layersCoelomatesBilaterally symmetricalJointed appendagesExoskeleton with chitinSpecialized segmentsCephalization

Phylum Arthropoda

Arthropod Lineages

Trilobites (all extinct)Crustaceans (crabs, shrimps, barnacles) Chelicerates (spiders, mites, scorpions)Uniramians (insects, centipedes, millipedes)Today: dissect a crayfish

Wear goggles, gloves, and lab coatsCarosafe safety proceduresPut specimens in correct containers

No gloves or paper towels with tissue waste

No unauthorized dissections-please treat specimens with respect

Clean all dissection equipment at conclusion

Important Dissection Notes