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Topic 14B Invertebrates - 2

Topic 14B Invertebrates - 2. Further Advances in Body Plan Body Cavity Pseudocoelom Coelom Segmentation Jointed Appendages Exoskeleton Notochord and dorsal nerve cord. Nematoda. Rotifera. Roundworms: Pseudocoelomates. There are seven phyla

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Topic 14B Invertebrates - 2

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  1. Topic 14B Invertebrates - 2

  2. Further Advances in Body Plan • Body Cavity • Pseudocoelom • Coelom • Segmentation • Jointed Appendages • Exoskeleton • Notochord and dorsal nerve cord

  3. Nematoda Rotifera Roundworms: Pseudocoelomates • There are seven phyla • The pseudocoel serves as a hydrostatic skeleton • Gains rigidity from being filled with fluid under pressure • Therefore muscles can work against this “skeleton” • Lack a defined circulatory system Cilia aid in feeding and locomotion

  4. The evolution of an internal body cavity was important for three reasons Circulation Rapid passage of material Movement Muscle-driven body movement Organfunction Little deformation by surrounding muscles Roundworms: Pseudocoelomate Body

  5. Phylum Nematoda • Nematodes are bilaterally symmetrical, cylindrical, unsegmented worms • Covered by a thick, flexible cuticle • Mouth is equipped with piercing organs called stylets • Food passes through the mouth by the sucking action of the pharynx • Lack flagella or cilia • Reproduction is sexual

  6. Phylum Nematoda • Important as parasites of plants and animals • Trichinella sp. • Cause trichinosis • Acquired from pigs • Ascaris lumbricoides • Intestinal roundworm • Infects one out of every six people worldwide

  7. Pinworm

  8. Plant Parasitic Nematodes

  9. Gastropods • Snails and slugs Mollusks: • Bivalves • Clams, oysters and scallops • Cephalopods • Octopuses and squids

  10. The bulk of the animal kingdom consists of coelomates

  11. Mollusks • Only major phylum of coelomates without a segmented body • The second largest animal phylum, after Arthropods • The body consists of three distinct parts • Head-foot; Visceral mass; Mantle • Gills capture O2 from water and release CO2 • The radula is a rasping, tongue-like organ • Used to scrape algae off rocks

  12. Mollusks: • Important consumers • Filter feeders • Grazers • Carnivores • In many – a radula to scrape food

  13. Cephalopods, a type of mollusk • Only the nautilus retains external shell • Other cephalopods are streamlined, active swimmers • All move by jet propulsion • Water is forced out of mantle cavity through a funnel-shaped siphon • Have large brains relative to body size

  14. Cephalopods

  15. Cuttlefish Body Plan esophagus Figure 25.22Page 429 digestive gland kidney stomach brain arm jaw mantle reproductive organ internal shell siphon ink sac heart accessory heart tentacle radula anus gill

  16. Summary of body plans so far… • Important changes in body plan: • Multicellularity with tissue-like differentiation:Porifera • True tissues:Cnidaria • Bilateral symmetry:Platyhelminthes • Coelom:Mollusca(reduced or absent in some) • These helped animals adapt to different environments or exploit the same environment in a different manner

  17. Annelids: Phylum Annelida Polychaete Segmented, coelomate worms • Class Polychaeta -polychaetes • Class Hirudinea -leeches • Class Oligochaeta -earthworms leeches Earthworm

  18. Segmentation is the building of a body from a series of similar units It offers evolutionary flexibility Small change  different function - specialization Three characteristics Repeated segments Separate segments able to expand or contract independently Specialized segments Front segments contain the worm’s sensory organs Connections Materials and information pass through partitions in the segments Segmentation underlies the body organization of all complex coelomate animals incl. annelids

  19. Circulatory System • Mechanism for movement of nutrients, wastes, hormones, etc. • Evolutionary changes in circulatory systems • Open: circulation via sinuses, cavities in coelom, mixes with body fluids • Closed: • specialized vessels • Blood separate from body fluid • Quick/efficient

  20. Phylum Arthropoda The most successful of all animal groups Arthropods: Advent ofJointed Appendages • 2/3rd of all named species • 80% of all arthropods are insects • Scientists estimate that a quintillion insects are alive at any one time

  21. Phylum Arthropoda: • All have jointed appendages • Exoskeleton of chitin • protects • provides sites for muscle attachment • Brittle - limits arthropod body size Four lineages: • Trilobites (all extinct) • Chelicerates (spiders, mites, scorpions) • Crustaceans (crabs, shrimps, barnacles) • Uniramians (insects, centipedes, millipedes)

  22. Arthropod bodies are segmented • Most larval stages have many segments • These fuse into functional groups in the adult

  23. Jumping spider Bullfrog ant • Two main groups: • Chelicerates: lack jaws/mandibles: • mouthparts called chelicerae - foremost appendages of the body • Uniramians: have mandibles = mandibulates

  24. Chelicerates • Oldest group of arthropods • Include spiders, scorpions, horseshoe crabs • Originated in marine environments • Arachnids: all terrestrial

  25. Body Plan of a Spider eye brain heart digestive gland Malpighian tubule poison gland book lung ovary silk gland anus pedipalp mouth sperm receptacle spinners chelicera Figure 25.28Page 433

  26. Edible crab Sowbug • Three general types • Crustaceans • 1. Decapods • Crabs, shrimp, lobsters • 2. Pillbugs and sowbugs • Terrestrial crustaceans • 3. Barnacles • Sessile as adults

  27. Body of a lobster • Large, diverse group of primarily aquatic organisms • Differ from insects, but resemble millipedes and centipedes, in having legs on their abdomen and thorax • Head has two pairs of antenna, three pairs of food-handling appendages • Crustaceans Used for swimming and reproduction May be compound

  28. Mandibulates • Consist of a head region followed by numerous similar segments • Centipedes have one pair of legs on each segment • Millipedes and Centipedes • Millipedes have two pairs of legs on each segment Active carnivores - predators Sedentary herbivores scavengers

  29. Insects

  30. Grasshoppers Beetle Flea Honeybee Moth Dragonfly Mandibulates • The largest group of arthropods by far • ~ 1 million species identified • Insects

  31. Mandibulates Butterfly Mosquito • Have three body sections • 1. Head • With a pair of antennae and elaborate mouthparts • Insects Housefly • 2. Thorax • Three segments, each with a pair of legs • Wings are attached • 3. Abdomen • Up to 12 segments

  32. Insect

  33. Fig. 19.21

  34. In the coelomates there are two different developmental patterns In protostomes, the mouth develops from or near the blastopore The anus (if present) develops later from another region of the embryo In deuterostomes, the anus develops from or near the blastopore The mouth develops later from another region of the embryo 21.10 Protostomes andDeuterostomes

  35. Deuterostomes differ from protostomes in three other fundamental embryological features • 1. Cleavage pattern • In protostomes, the egg cleaves spirally • In deuterostomes, the egg cleaves radially • 2. Developmental fate of cells • In protostomes, the cells are committed even early on • In deuterostomes, the commitment occurs later • 3. Origination of coelom • In protostomes, it forms directly from the mesoderm • In deuterostomes, it forms indirectly via the archenteron

  36. Echinoderms have an endoskeleton composed of hard calcium-rich ossicles that are often fused They consist of about 6,000 living marine species Sand dollar Feather star Sea urchin Sea star Sea cucumber Echinoderms:The First Deuterostomes

  37. Echinoderms are bilaterally symmetrical as larvae But they become radially symmetrical as adults This could be an environmental adaptation Adults have a five-part body plan The key evolutionary innovation is the development of a water vascular system A fluid-filled system with a central ring canal and five radial canals Thousands of tiny, hollow tube feet extend from each radial canal

  38. Chordates are members of the phylum Chordata Lancelets Tunicate Chordates:Improving the Skeleton • Their nearest animal relations are the echinoderms • However, chordates employ a truly internal endoskeleton • Chordates are quite diverse

  39. Distinguishing features of chordates • 1. Notochord • A stiff, but flexible rod, that forms beneath the nerve cord • 2. Nerve cord • A single dorsal nerve to which other nerves are attached • 3. Pharyngeal slits • A series of slits behind the mouth into the pharynx • 4. Postanal tail • A tail that extends beyond the anus • All chordates have all four of these at some time in their life

  40. Fig. 21.41

  41. Fig. 21.42 A mouse embryo (at 11.5 days of development) Vertebrates • In their body plan, chordates are segmented • Segments are called somites Muscle somites

  42. With the exception of tunicates and lancelets, all chordates are vertebrates • Distinguishing features of vertebrates • 1. Backbone • A bony vertebral columnreplaces the notochord • 2. Head • Well-differentiated, with skull and brain • All vertebrates have an internal skeleton made of bone and cartilage against which the muscles work • This makes possible great size and movement

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