1. 1 The traditional metazoan phylogeny is being reevaluated using molecular data. (Remember the homology/analogy problem.) Therefore, key morphological characters used in traditional classification are not necessarily conservative Molecular systematics uses unique sequences within certain genes to identify clusters of related groups

2. 2 Molecular data has helped to clarify the relationship of different groups with the animals (metazoans) for example annelids and arthropods

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4. 4 Most taxonomists agree that the metazoan kingdom is monophyletic Three prominent hypotheses have been proposed for the origin of metazoans from single-celled protists

5. 5 1. The multinucleate hypothesis 2. The colonial flagellate hypothesis 3. The polyphyletic origin hypothesis Molecular systematics using rRNA sequences settles this argument in favor of the colonial flagellate hypothesis

7. 7 Scientists generally agree about the taxonomic classification of 36 animal phyla -They do disagree, however, about how these are interrelated Traditional reconstructions lump together phyla that share major features of body plan New reconstructions employ molecular comparisons of rRNA and other genes

8. 8 Both old and new phylogenies agree that: -Porifera belongs to paraozoa -Among the eumetazoans, Cnidaria and Ctenophora branch out before Bilateria -Bilateria are divided into two groups: protostomes and deuterostomes Modern phylogeny differs radically from traditional phylogeny in construction of the protostome lineage

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10. 10 Parazoans lack tissues, organs and a definite symmetry -However, they have complex multicellularity Posess choanocytes, spongin, mesohyl, spicules, osculum. Spicules found within the mesohyl. Sponges, phylum Porifera, are parazoans -Include marine and freshwater species -Larval sponges are free-swimming, but adults are anchored onto submerged objects

12. 12 Sponges use intracellular Digestion—mostly bacteria Sponge reproduction -Asexual = Fragmentation -Sexual = Egg and sperm -Larval sponges use cilia for swimming -Settle down on a substrate -Transform into adults

13. 13 Eumetazoans are animals with distinct tissues Embryos have distinct layers -Inner endoderm = Forms the gastrodermis -Outer ectoderm = Forms the epidermis and nervous system -Middle mesoderm (Only in bilateral animals, Ctnophora controversy) -Forms the muscles

14. 14 Eumetazoans also evolved true body symmetry -Radiata = Exhibit radial symmetry -Phylum Cnidaria -Phylum = Ctenophora -Bilateria = Exhibit radial symmetry -All other animals

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16. 16 Cnidarians are carnivores They have two basic body forms Polyps = Cylindrical and sessile Polyps = Cylindrical and sessile Medusae = Umbrella-shaped and free-living Medusae = Umbrella-shaped and free-living Gastrovascular cavity with extracellular digestion. Derived from gastrodermis

17.  Cnidarians have unique specialized cells on their epidermis called cnidocytes and nematocysts Cnidarians can reproduce sexually creating a ciliated swimming larvae called a planulae.  Can be poly, medusa, or both in life cycle.

18. 18 Hydrozoa (hydroids) Scyphozoa (jellyfish) Cubozoa (box jellyfish)box jellyfishAnthozoa (corals & anemones) Obelia Polyp & Med. Hydra Jellyfish Sex/asex Has an endosymbiotic relationship with a dinoflagellate

19. 19 A small phylum whose members are known as comb jellies, sea walnuts or sea gooseberries Structurally more complex than cnidarians 8 rows cilia Capture prey with a colloblast Contains strong adhesive material Triploblastic (probably). Recent molecular evidence has placed ctenophors at the base of the animal tree.

20. 20 The Bilateria are characterized by bilateral symmetry Allowed for high levels of specialization Allowed for high levels of specialization Bilaterians are traditionally classified by the condition of their coelom Acoelomates Acoelomates Pseudoceolomates Pseudoceolomates Coelomates CoelomatesTriploblastic

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22. 22 Modern protostome phylogeny distinguishes between two major clades that have evolved independently: -Spiralians: Grow by adding mass to an existing body -Ecdysozoans: Increase in size by molting their external skeletons

23. 23 Spiralians Grow by adding mass to an existing body Grow by adding mass to an existing body Two main groups Two main groups 1. Lophotrochozoa: mostly coelomates Include the phyla Brachiopoda, Mollusca and Annelida 2. Platyzoa: mostly acoelomates Include the phyla Platyhelminthes, and Micrognathozoa

24. 24 Ecdysozoans Increase in size by molting their external skeletons Increase in size by molting their external skeletons Two phyla have been particularly successful Two phyla have been particularly successful Nematoda (roundworms): pseudocoelomates Arthropoda: coelomates Insects, crustaceans, and others

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26. 26 The flatworms are soft-bodied animals Many species are parasitic Others are free-living Triploblastic Flame cells Move by ciliated epithelial cells Have developed musculature

27. 27 Flatworms lack a circulatory system -Flattened body shape and highly-branched gut utilize diffusion They have a simple nervous system -Eyespot can distinguish light from dark Most are hermaphroditic -Undergo sexual reproduction -Also have capacity for asexual regeneration

28. 28 Three classes: 1. Turbellaria: Free living flatworms. Dugesia. 2. Monogenea and Tematoda: Flukes. Endo and Ecto parasites Adaptions of endoparasites—epidermis, sensory Simple and complex life cycles Important pathogens—liver flukes, blood flukes 3. Cestodes: Tapeworms Tapeworms Intestinal parasite No digestive system. Scolex/neck/proglottids 4. All parasitic classes in Neodermata

29. 29 Nemerteans are often called ribbon worms or proboscis worms Are long animals that can stretch to several meters. Rhynchocoel Complete digestive system

30. 30 Nematodes are roundworms comprising many species with many sizes. Cuticle molts as it grows--Ectysozoa Found in marine, freshwater and soil habitats Some are parasites. Are bilaterally symmetrical and unsegmented Pharynx Important human parasites

31. 31 Rotifers are bilaterally symmetrical unsegmented pseudocoelomates They have complex internal organs They propel themselves through water by rapidly beating thick cilia at their heads -“Wheel animals” They gather food via a conspicuous organ called the corona

32.  Don’t forget quiz.  Read chapters for next week.