PowerLecture: Chapter 25 Part I Animal Evolution – The Invertebrates

Characteristics of Animals Multicelled Aerobic heterotrophic eukaryotes Most reproduce sexually

Animal Origins Originated during Precambrian (1.2 billion - 670 million years ago)

Radial Symmetry radial symmetry Fig. 25-5a, p.406

Bilateral Symmetry dorsal posterior ventral anterior Fig. 25-5b, p.406

Animal Tissues Ectoderm Endoderm Mesoderm

The Gut - 2 types Saclike gut Complete digestive system One opening for taking in food and expelling waste Complete digestive system 2 Openings; mouth and anus

Body Cavities - Acoelomate epidermis gut cavity no body cavity; region between gut and body wall packed with organs Fig. 25-6, p.406

Body Cavities - Pseudocoel epidermis gut cavity unlined body cavity (pseudocoel) around gut Fig. 25-6, p.406

lined body cavity (coelom) Body Cavities - Coelom gut cavity lined body cavity (coelom) peritoneum Fig. 25-6, p.406

Segmentation Repeating series of body units Units may or may not be similar Insects - segments may be fused

Segmentation Fig. 25-8c, p.407

Segmentation Fig. 25-8a, p.407

Fig. 25-7, p.407 sponges cnidarians flatworms annelids mollusks roundworms arthropods echinoderms chordates coelom reduced coelom reduced coelom lost pseudocoel molting PROTOSTOMES mouth from blastopore radial ancestry, two germ layers DEUTEROSOMES anus from blastopore bilateral, coelomate ancestry, three germ layers true tissues multicelled body Fig. 25-7, p.407

Deuterostomes Protostomes Fig. 25-2a, p.404

p.408

Choanoflagellates Protozoans most closely related to animals Resemble collar cells (stay tuned for more on this)

flagellated collar cell Animal Origins flagellated collar cell Fig. 25-4a, p.405

p.408

Sponges - Phylum Porifera No symmetry, tissues or organs Reproduce sexually Microscopic swimming larvae

Sponge Structure water out glasslike structural elements amoeboid cell pore central cavity semifluid matrix flattened surface cells water in flagellum microvilli nucleus Fig. 25-10, p.409

Fig. 25-9a, p.408

Fig. 25-9b, p.408

Fig. 25-9c, p.408

p.408

Phylum Placozoa One living species, Tricoplax adherens 2-layer body, 3 mm across Fig. 25-11, p.409

p.408

Cnidarian Diversity Scyphozoans Anthozoans Hydrozoans Jellyfish Sea anemones Corals Hydrozoans

Phylum Cnidaria Nerve net Hydrostatic skeleton Saclike gut nematocysts capsule’s lid at free surface of epidermal cell trigger barbed thread inside capsule nematocyst Fig. 25-13, p.410

mesoglea-filled bell tentacles Fig. 25-13b, p.410

outer epithelium (epidermis) inner epithelium (gastrodermis) Two Main Body Plans Polyp outer epithelium (epidermis) mesoglea (matrix) Medusa inner epithelium (gastrodermis) Fig. 25-12, p.410

Fig. 25-14a1, p.411

Fig. 25-14a2, p.411

Fig. 25-14b, p.411

Fig. 25-45a, p.431

Obelia Life Cycle (Hydrozoan) female medusa male medusa reproductive polyp sperm ovum feeding polyp zygote polyp forming planula Fig. 25-15a, p.411

Deuterostomes Protostomes

Flatworms: Phylum Platyhelminthes Acoelomate, bilateral, cephalized Most hermaphroditic

Three Classes Turbellarians (Turbellaria) Flukes (Trematoda) Tapeworms (Cestoda)

Planarian Organ Systems Digestive branching gut pharynx; protrudes onto food, then retracts into the body between feedings

Planarian Organ Systems Neuro-sensory rudimentary brain (pair of large ganglia in head) pair of nerve cords that have lateral branchings

Planarian Organ Systems Reproductive ovary testis oviduct genital pore

Planarian Organ Systems Excretory pair of highly branched tubules that adjust water and solute levels in body Fig. 25-16d, p.412

flame cell opening of tubule at body surface Fig. 25-16e, p.412

flame cell nucleus cilia fluid filters through membrane folds Fig. 25-16f, p.412

Fig. 25-17, p.413

Fig. 25-18, p.413 proglottids scolex a Larvae, each with inverted scolex of future tapeworm, become encysted in intermediate host tissues (e.g., skeletal muscle) b A human, a definitive host, eats infected, undercooked beef which is mainly skeletal muscle d Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts c Each sexually mature proglottid has female and male organs. Ripe proglottids containing fertilized eggs leave host in feces, which may contaminate water and vegetation. Fig. 25-18, p.413

proglottids scolex Fig. 25-18e, p.413

Deuterostomes Protostomes

Rotifers Bilateral Cephalized Crown of cilia at head Complete gut

Fig. 25-22a, p.416

one of two ciliated lobes at head end mouth modified pharynx; internal jawlike elements, salivary glands cluster of nerve cells gastric gland (esophagus behind it) proto-nephridium stomach intestine cloaca (this type is a chamber for digestive and excretory wastes) anus gland that secretes cementing substance for “toe” one of two “toes” Fig. 25-22b, p.416

Two Coelomate Lineages Protostomes Mollusks Annelids Arthropods Deuterostomes Echinoderms Chordates

Cleavage Patterns Protostome embryo (spiral cleavage) Deuterostome embryo (radial cleavage)

Deuterostomes Protostomes

Annelids: Phylum Annelida Segmented, coelomate worms Class Polychaeta Class Oligochaeta Class Hirudinea

Polychaetes Most marine Bristles extend from parapods on each segment “jaws” toothlike structures Most marine Bristles extend from parapods on each segment Head end is specialized pharynx (everted) antenna palp (food handling) tentacle eyes chemical-sensing pit parapod

Polychaetes Fig. 25-19a, p.414

Fig. 25-19b, p.414

Fig. 25-19c, p.414

Leeches - Class Hirudinea Predators and parasites Less obvious segmentation

before feeding Fig. 25-20a, p.414

after feeding Fig. 25-20b, p.414

Earthworm - An Oligochaete No parapodia, few bristles per segment Nerve cord Dorsal blood vessel Circular muscle Coelom Longitudinal muscle Nephridium Seta (retracted) Nerve cord Fig. 25-21, p.415

Earthworm Nephridium bladderlike storage region of nephridium nephridium’s thin loop reabsorbs some solutes, relinquishes them to blood blood vessels body wall funnel (coelomic fluid with waste enters here) external pore (fluid containing wastes discharged here) Fig. 25-21, p.415

Earthworm Circulatory System Hearts Fig. 25-21, p.415

Earthworm Digestive System Coelomic chambers Crop Gizzard Esophagus Pharynx Mouth Fig. 25-21, p.415

Earthworm Nervous System Brain Nerve cord Fig. 25-21, p.415

head end Fig. 25-21g, p.415

of outwardly similar body segments are bristles used in locomotion on both sides of outwardly similar body segments are bristles used in locomotion Fig. 25-21h, p.415

Old Genes, New Drugs Fig. 25-1, p.402

Old Genes, New Drugs p.403