Photosynthesis

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(No Transcript)
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Outline

• Evolution of Animals
• Multicellularity
• Sponges
• True Tissues
• Cnidarians and Comb Jellies
• Hydra
• Obelia
• Bilateral Symmetry
• Flatworms
• Roundworms
• Body Cavities
• Acoelomates
• Psuedocoelomates
• Eucoelomates

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Evolution of Animals

• All animals are multicellular heterotrophic
  organisms that must take in preformed food
• Classification Criteria
• Level of organization
• Cellular, tissue, organ
• Body Plan
• Sac, tube-within-a-tube
• Segmentation
• Segmentation leads to specialization

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Evolution of Animals

• Classification Criteria, cont
• Symmetry
• Radial - Two identical halves
• Bilateral - Definite right and left halves
• Type of Coelom
• Pseudocoelom
• Coelom
• Early Developmental Pattern
• Protostome - First embryonic opening becomes the
  mouth
• Dueterostome - Second embryonic opening becomes
  the mouth

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AnimalsMulticellular, Heterotrophic Eukaryotes
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Traditional Phylogenetic Tree of Animals
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Multicellularity

• Sponges
• Only level of animal to have cellular
  organization
• Saclike bodies perforated by many pores
• Beating of flagella produces water currents that
  flow through pores into central cavity and out
  osculum
• Sessile filter feeders
• Asexual reproduction by fragmentation or budding

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Simple Sponge Anatomy
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True Tissue Layers

• Total of three possible germ layers
• Ectoderm
• Endoderm, and
• Mesoderm
• phlya Ctenophora and Cnidaria develop only
  ectoderm and endoderm
• Diploblasts
• Radially symmetrical

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Comb Jellies

• Small, transparent, and often luminescent
• Most of body composed of mesoglea
• Largest animals propelled by beating of cilia
• Capture prey with tentacles

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Comb Jelly Compared to Cnidarian
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Cnidarians

• Tubular animals that most often reside in shallow
  marine waters
• Polyp and medusa body forms
• Specialized stinging cells (cnidocytes)
• Fluid-filled capsule, nematocyst
• Two-layered body sac
• Outer layer - Protective epidermis
• Inner layer - Gastrovascular cavity
• Nerve net found throughout body

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Cnidarian Diversity
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Hydra

• Freshwater cnidarian
• Small tubular poly body about one-quarter inch in
  length
• Gastrovascular cavity is central cavity
• Tentacles can respond to stimuli
• Can reproduce sexually and asexually

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Anatomy of Hydra
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Obelia

• A colony of polyps enclosed by a hard, chitinous
  covering
• Feeding polyps
• Extend beyond covering
• Have nematocyst-bearing tentacles
• Reproductive polyps
• Budding of new polyps
• Also has sexual reproduction (medusae) stage

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Obelia Life Cycle
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Bilateral Symmetry

• Ribbon worms (phylum Nemertea)
• Have distinctive proboscis
• Flatworms (phylum Platyhelminthes)
• Majority are parasitic
• Organ-level organization
• No specialized circulatory or respiratory
  structures
• Have undergone cephalization
• Ladder-type nervous system

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Ribbon Worm, Lineus
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Free-living Flatworms

• Planarians (genus Dugesia)
• Live in freshwater habitats
• Head is bluntly arrow shaped
• Auricles function as sense organs
• Two light-sensitive eye spots
• Three kinds of muscle layers
• Outer circular layer
• Inner longitudinal layer
• Diagonal layer

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Planarian Anatomy
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Planarians

• Planarians, cont.
• Excretory organ functions in osmotic regulation
  and water excretion
• Can reproduce asexually
• Hermaphroditic
• Practice cross-fertilization

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Parasitic Flatworms

• Parasitic flatworms are flukes (trematodes) and
  tapeworms (cestodes)
• Well-developed nerves and gastrovascular cavity
  are unnecessary
• Flukes
• Reproductive system well developed
• Usually hermaphroditic

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Life Cycle of Schistosomiasis
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Parasitic Flatworms

• Tapeworms
• Have anterior region with modifications for
  attachment to intestinal wall of host
• Behind head region, scolex, a long series of
  proglottids are found
• Segments each containing a full set of both male
  and female sex organs
• Complicated life cycles

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Life Cycle of a Tapeworm, Taenia
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Pseudocoelom

• Pseudocoelom
• A false body cavity that is incompletely lined
  by mesoderm
• Provides a space for internal organs and can
  serve as hydrostatic skeleton
• Roundworms (phylum Nematoda)
• Non-segmented, generally colorless worms
• Several parasitic roundworms infect humans

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Roundworm Anatomy
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Parasitic Roundworms

• Ascaris Intestinal roundworm
• Trachinella - Trichinosis
• Dirofilaria - Heartworms
• Wuchereria - Elephantiasis

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Filarial Worm
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Rotifers

• Rotifers (phylum Rotifera)
• Named for crown of cilia resembling a rotating
  wheel
• Serves as both as an organ of locomotion and aids
  direction of food to mouth

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Rotifer
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Review

• Evolution of Animals
• Multicellularity
• Sponges
• True Tissues
• Cnidarians and Comb Jellies
• Hydra
• Obelia
• Bilateral Symmetry
• Flatworms
• Roundworms
• Body Cavities
• Acoelomates
• Psuedocoelomates
• Eucoelomates

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