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Fig. 33-1. Overview: Life Without a Backbone. Invertebrates are animals that lack a backbone (ansence NOT a good character) They account for 95% of known animal species Is it a natural (monopyletic group)? i.e. clade or grade?. Fig. 33-2. Major groups. “Porifera” (grade). Calcarea
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Overview: Life Without a Backbone • Invertebrates are animals that lack a backbone (ansence NOT a good character) • They account for 95% of known animal species • Is it a natural (monopyletic group)? • i.e. clade or grade?
Fig. 33-2 Major groups “Porifera” (grade) Calcarea and Silicea ANCESTRAL PROTIST Cnidaria Lophotrochozoa Common ancestor of all animals Eumetazoa Ecdysozoa Bilateria Deuterostomia
Fig. 33-3-1 Placozoa (1 species) Calcarea and Silicea (5,500 species) 0.5 mm A sponge Cnidaria (10,000 species) A placozoan (LM) Ctenophora (100 species) A jelly Acoela (400 species) A ctenophore, or comb jelly 1.5 mm Acoel flatworms (LM) LOPHOTROCHOZOANS Rotifera (1,800 species) Platyhelminthes (20,000 species) A marine flatworm A rotifer (LM) Ectoprocta (4,500 species) Brachiopoda (335 species) Ectoprocts A brachiopod
Fig. 33-3-2 Cycliophora (1 species) Acanthocephala (1,100 species) 100 µm An acanthocephalan (LM) A cycliophoran (colorized SEM) Nemertea (900 species) Mollusca (93,000 species) An octopus Annelida (16,500 species) A ribbon worm A marine annelid ECDYSOZOA Loricifera (10 species) Priapula (16 species) 50 µm A loriciferan (LM) A priapulan
Fig. 33-3-3 Tardigrada (800 species) Onychophora (110 species) 100 µm Tardigrades (colorized SEM) An onychophoran Nematoda (25,000 species) Arthropoda (1,000,000 species) A roundworm A scorpion (an arachnid) DEUTEROSTOMIA Hemichordata (85 species) An acorn worm Echinodermata (7,000 species) Chordata (52,000 species) A sea urchin A tunicate
Fig. 33-3a porifera A sponge
Fig. 33-3b Cnidaria A jelly
Fig. 33-3c 0.5 mm A placozoan (LM)
Fig. 33-3d A ctenophore, or comb jelly
Fig. 33-3e 1.5 mm Acoel flatworms (LM)
Fig. 33-3f Lophotrochozoa A marine flatworm
Fig. 33-3g Lophotrochozoa A rotifer (LM)
Fig. 33-3h Lophotrochozoa Ectoprocts
Fig. 33-3i Lophotrochozoa A brachiopod
Fig. 33-3j Lophotrochozoa An acanthocephalan (LM)
Fig. 33-3k Lophotrochozoa 100 µm A cycliophoran (colorized SEM)
Fig. 33-3l Lophotrochozoa A ribbon worm
Fig. 33-3m Lophotrochozoa An octopus
Fig. 33-3n Lophotrochozoa A marine annelid
Fig. 33-3o Ecdysozoa 50 µm A loriciferan (LM)
Fig. 33-3p Ecdysozoa A priapulan
Fig. 33-3q Ecdysozoa 100 µm Tardigrades (colorized SEM)
Fig. 33-3s Ecdysozoa A roundworm
Fig. 33-3t Ecdysozoa A scorpion (an arachnid)
Fig. 33-3u Deuterostome An acorn worm
Fig. 33-3v Deuterostome A sea urchin
Fig. 33-3w Deuterostome A tunicate Closer!
Concept 33.1: Sponges are basal animals that lack true tissues • Sponges are sedentary animals from two phyla: Calcarea and Silicea • They live in both fresh and marine waters • Sponges lack true tissues and organs
Fig. 33-UN1 Calcarea and Silicea Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia
Sponges are suspension feeders, capturing food particles suspended in the water that pass through their body • Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food • Water is drawn through pores into a cavity and out through an opening
Fig. 33-4 Food particles in mucus Flagellum Choanocyte Collar Choanocyte Osculum Azure vase sponge (Callyspongia plicifera) Spongocoel Phagocytosis of food particles Amoebocyte Pore Spicules Epidermis Water flow Amoebocytes Mesohyl
Sponges consist of a noncellular mesohyl layer between two cell layers • Amoebocytes are found in the mesohyl and play roles in digestion and structure • Most sponges are hermaphrodites: Each individual functions as both male and female
Lophotrochozoans, a clade identified by molecular data, have the widest range of animal body forms • Bilaterian animals have bilateral symmetry and triploblastic development • The clade Bilateria contains Lophotrochozoa, Ecdysozoa, and Deuterostomia • Look at your tree!
Fig. 33-UN3 Calcarea and Silicea Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia
The clade Lophotrochozoawas identified by molecular data • Some develop a lophophore for feeding, others pass through a trochophore larval stage, and a few have neither feature • Lophotrochozoa includes the flatworms, molluscs, and many other important phyla
Flatworms • Members of phylum Platyhelminthes live in marine, freshwater, and damp terrestrial habitats • They are flattened dorsoventrally and have a gastrovascular cavity • Gas exchange takes place across the surface
Turbellarians • Turbellarians are nearly all free-living and mostly marine • The best-known turbellarians are commonly called planarians
Fig. 33-10 Pharynx Gastrovascular cavity Mouth Eyespots Ganglia Ventral nerve cords
Monogeneans and Trematodes • Monogeneans and trematodes live as parasites in or on other animals • They parasitize a wide range of hosts, and most have complex life cycles • Trematodes that parasitize humans spend part of their lives in snail hosts • Most monogeneans are parasites of fish
Blood fluke=schistomiasis Male Female Human host 1 mm Motile larva Ciliated larva Snail host
Tapeworms • Tapeworms are parasites of vertebrates and lack a digestive system • Tapeworms absorb nutrients from the host’s intestine • Fertilized eggs, produced by sexual reproduction, leave the host’s body in feces
Fig. 33-12 200 µm Proglottids with reproductive structures Hooks Sucker Scolex
Molluscs • Phylum Mollusca includes snails and slugs, oysters and clams, and octopuses and squids • Most molluscs are marine, though some inhabit fresh water and some are terrestrial • Molluscs are soft-bodied animals, but most are protected by a hard shell
Most molluscs have separate sexes with gonads located in the visceral mass • The life cycle of many molluscs includes a ciliated larval stage called a trochophore
Chitons • oval-shaped marine animals encased in an armor of eight dorsal plates
Gastropods • About three-quarters of all living species of molluscs are gastropods Video: Nudibranchs