1. Evolution of the Animal Phyla
Chapter 19
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2. Outline Sponges Cnidarians Solid Worms Roundworms Mollusks Annelids
Arthropods
Echinoderms
Chordates
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3. General Features of Animals
All animals are multicellular heterotrophs.
Invertebrates account for 99% of all species.
Animal Kingdom includes about 36 phyla.
Most occur in the sea.
Three phyla dominate animal life on land.
Arthropoda (spiders and insects)
Mollusca (snails)
Chordata (vertebrates)
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4. General Features of Animals
Animal cells lack rigid cell walls and are usually quite flexible.
Members of the animal kingdom tend to move more rapidly and in more complex ways than members of other kingdoms.
Most animals reproduce sexually.
Embryonic Development
Morula
Blastula
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5. Phylogeny of Kingdom Animalia
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6. Kingdom Animalia has two subkingdoms:
Sponges
Kingdom Animalia has two subkingdoms:
Parazoa - lack definite symmetry and tissues organized into organs.
Dominated by sponges (Porifera).
Eumetazoa - have definite shape and and symmetry and highly specialized cells.
Sponges are simplest animals.
Bodies consist of masses of specialized cells embedded in gel-like matrix.
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7. Flagellated cells, choanocytes (collar cells) line body cavity.
Sponges
Phylum name, Porifera, refers to system of pores found in body of sponges.
Flagellated cells, choanocytes (collar cells) line body cavity.
Draws water into body.
Filter feeders
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9. Cnidaria (Jellyfish, hydra, coral) Capture prey with tentacles.
Cnidarians
Eumetazoans possess radial symmetrical with ectoderm and endoderm. Two phyla:
Cnidaria (Jellyfish, hydra, coral)
Capture prey with tentacles.
Cnidocytes (stinging cells)
Nematocyst (harpoon)
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10. Medusae - Free floating, gelatinous Polyps - Cylindrical
Cnidarians
Two body forms:
Medusae - Free floating, gelatinous
Polyps - Cylindrical
Ctenophora (comb jellies)
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12. Radial vs. Bilateral Symmetry
Radial Symmetry - Regular arrangement of parts around central axis.
Bilateral Symmetry - Right and left halves form mirror images.
Dorsal vs. Ventral
Anterior vs. Posterior
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13. Simplest of all bilaterally-symmetrical animals.
Solid Worms
Simplest of all bilaterally-symmetrical animals.
Ectoderm - Gives rise to outer covering and nervous system.
Mesoderm - Gives rise to digestive organs and intestines.
Endoderm - Gives rise to skeleton and muscles.
Lack internal cavity, except for digestive tract (acoelomate).
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14. Solid Worm Body Plan
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16. Excretory system consists of network of tubules running through body.
Solid Worms
Flatworms
Have incomplete gut and and cannot feed, digest, and excrete food simultaneously.
Excretory system consists of network of tubules running through body.
Lack circulatory system.
Simple nervous system.
Hermaphroditic
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17. Flatworm Anatomy
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18. Pseudocoelom vs. Coelom
Evolution of body cavity was key transition.
Circulation - Rapid passage of materials.
Movement - Muscle-driven movement.
Organ Function - Little deformation.
Acoelomates - No body cavity.
Pseudocoelomates - Possess pseudocoel.
Coelomates - Possess coelom (body cavity).
Open circulatory system
Closed circulatory system
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19. Bilaterally Symmetrical Body Plans
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20. Roundworms: Pseudocoelomates
Seven Phyla
Nematoda contains 12,000 recognized species (nematodes and roundworms).
Bilaterally symmetrical, cylindrical, unsegmented worms.
Covered by thick, flexible cuticle.
Lack flagella or cilia.
Reproduction is sexual.
Trichinella - Live in pig intestines.
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22. Endoderm, Mesoderm, Ectoderm Mollusks
Mollusks: Coelomates
Development of specialized tissues involved in primary induction in which one of three primary tissues interacts with one another.
Endoderm, Mesoderm, Ectoderm
Mollusks
Only major phylum of coelomates without segmented bodies.
Body composed of three parts:
Head-Foot, Visceral Mass, Mantle
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23. Gills capture oxygen from water and release carbon dioxide.
Mollusks: Coelomates
Mollusks
Gills capture oxygen from water and release carbon dioxide.
Radula - Rasping, tongue-like organ.
Three Major Classes
Gastropods
Bivalves
Cephalopods
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25. Key innovation to arise in coelomates was segmentation.
Annelids
Key innovation to arise in coelomates was segmentation.
Building of body from series of similar segments.
Small change in existing segment can produce new kind of segment with different function.
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26. Worm within a tube design. Three characteristics: Repeated Segments
Annelids
Worm within a tube design.
Three characteristics:
Repeated Segments
Specialized Segments
Connections
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28. All have jointed appendages. Rigid external skeleton (exoskeleton).
Arthropods
All have jointed appendages.
Rigid external skeleton (exoskeleton).
Protects animal and provides places for muscle attachment.
Brittle, thus there is a limit to arthropod body size due to exoskeleton thickness.
Estimates of a quintillion insects alive at any one time.
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30. Arthropods lacking jaws.
Chelicerates
Arthropods lacking jaws.
Mouthparts (chelicerae) evolved from appendages nearest anterior end.
Pediplaps
Arachnida is largest class.
57,000 named species including spiders, ticks, and scorpions.
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31. Chelicerates and Mandibulates
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32. Arthropods
Mandibulates have mandibles formed by appendages formed by other anterior appendages.
Crustaceans
Differ from insects, but resemble millipedes and centipedes as they have legs on their abdomen as well as thorax.
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33. Crustaceans
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34. Millipedes and Centipedes
Arthropods
Millipedes and Centipedes
Consist of head region followed by numerous similar segments. Centipedes have one pair of legs on each segment, and millipedes have two pairs of legs on each segment.
Insects
Largest group of arthropods.
Head, Thorax, Abdomen
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35. Protostomes and Deuterostomes
Mouth develops from or near blastopore. Anus (if present) develops from another region of embryo.
Dueterstomes
Anus forms from, or near, blastopore, and mouth forms subsequently on another part of blastopore.
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36. Protostomes and Deuterostomes
Deuterostomes differ from protostomes:
Cleavage Pattern
Spiral vs. Radial
Developmental fate of cells
Time of commitment
Origination of coelom
Mesoderm vs. Archenteron
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37. Embryonic Development in Protostomes and Deuterstomes
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38. Endoskeleton composed of hard, calcium-rich ossicles.
Echinoderms
First Dueterstomes
Endoskeleton composed of hard, calcium-rich ossicles.
Bilaterally symmetrical as larvae, but become radially symmetrical as adults.
Key evolution innovation was water vascular system.
Tube Feet
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40. Distinguished by four principle features: Notochord Nerve Cord
Chordates
Distinguished by four principle features:
Notochord
Nerve Cord
Pharyngeal Slits
Postnatal Tail
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42. Most endoskeletons made of bone. Bone formed in two stages:
Chordates
Vertebrates
Have internal skeleton made of bone or cartilage against which the muscles work.
Most endoskeletons made of bone.
Bone formed in two stages:
Matrix of collagen laid down.
Minerals impregnate fibers.
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43. Vertebrate Embryonic Development
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44. Review Sponges Cnidarians Solid Worms Roundworms Mollusks Annelids
Arthropods
Echinoderms
Chordates
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