Animal Diversity (1 &) 2 Multicellular, eukaryotic, heterotrophic organisms that feed by INGESTION Body symmetry Radial symmetryBilateral symmetry Anterior Ventral Dorsal Posterior Tissue organization 2 tissue layers = Radially symmetric 3 tissue layers = Bilaterally symmetric Two tissue layers: Endoderm and Ectoderm Ectoderm Endoderm Gut Ectoderm Endoderm Gut Ex: Hydra Three tissue layers: Ectoderm, Mesoderm, Endoderm Ectoderm: External Layer Skin cells of epidermis Neurons of brain Mesoderm: Middle Layer Cardiac muscle, Skeletal muscle,Kidney cells, Red blood cells, Smooth muscle in gut Endoderm: Internal Layer Lung (Alveolar) cells Thyroid cells Pancreatic cells Body cavity Acoelomate Pseudocoelomate Eucoelomate Other characteristics: Openings into digestive tract: One opening or tube within a tube? Open vs. closed circulatory system Organs for gas exchange Organs for excretion Endoskeleton, exoskeleton, hydrostatic skeleton? Segmentation Porifera (i.e. sponges) Cnidaria (e.g. Hydra, sea anemones, jellyfish) 2 tissue layers Platyhelminthes (Flatworms) 3 tissue layers Acoelomate unsegmented No internal organs = must be flat to allow O2 and nutrients in via diffusion Most are parasitic Schistosomiasis is a disease caused by these guys. Tapeworm too. Annelida (Clamworms and earthworms) Segmentation! Organs! Theyre hydrostatic! Annelida (Clamworms and earthworms) Mollusca More than 85,000 species! Characteristics of most molluscs: Hard external shell for protection Mantle (excretes shell) Visceral mass Muscular foot for locomotion Snail radula! Ex: cuttlefish Adductor muscles are well- developed in scallops because theyre active swimmers. (Theyre also tasty) Basic bivalve anatomy Onwards! to Ecdysozoa = molting animals (Nematoda and Arthropoda) Body covering = cuticle = exoskeleton Nematoda Most abundant animal on Earth Pseudocoelomate Up to a million different species (only like 50k described) 15,000 species are described as parasitic Sheds proteinaceous cuticle LOTS of investment in reproductive organs Arthropoda Animals with exoskeleton, segmented body, and jointed appendages Exoskeleton is periodically shed Four subphyla: Cheliceriformes, Myriapoda, Crustacea, Hexapoda Exoskeleton is mainly chitin First organisms to fly unoccupied niche (air) allowed for massive radiation Cheliceriformes No antennae, no jaws Pincer-like appendages called chelicera used for grasping and fragmenting food Myriapoda Millipedes 2 pairs of legs per segment Detritivores Centipedes 1 pair of legs per segment Predators Crustacea Biramous (two-parted) limbs (even barnacles) Most are free-living aquatic animals Some (e.g. pill bugs) are terrestrial Some (e.g. barnacles) are sessile Ex: Crustacean claws branch into 2 segments Hexapoda: Six-legged arthropods External insect anatomy 3 distinct body units: head, thorax, and abdomen Insect head: Search for: compound eyes, ocelli, antennae, labrum, mouthparts Insect mouthparts: Mandible, maxilla, labium Chewing mouthparts (e.g. grasshopper) Evolution of mouthpart morphology A: Chewing B: Lapping (e.g. bee) C: Siphoning (e.g. moth) D: Sucking (e.g. mosquito) Arthropod respiration: Tracheal system No labs next week. Then only two more labs: - Animal Diversity 3 (chordates and starfish) - and then a final lab practical (no lecture for the last lab) I will post a study guide this week on thinkbiologically.com Dont forget to turn in your reports! Lots to do today! Have fun! Final notes: