Animals: The Invertebrates

1
Animals The Invertebrates

• Chapter 23

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Key Concepts

• All animals are multicelled, aerobic
  heterotrophs
• Animals originated about 900 million years ago
• Comparisons of body plans of existing animals
  with fossil records reveal that there were
  several trends in the evolutions of certain
  lineages

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Key Concepts

• Divergences gave rise to two major lineages
  those of the mollusks, annelids, and arthropods
  and the other one to the echinoderms and
  chordates
• The arthropods, especially the insects, have been
  the most successful animal groups

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Evolutionary Tree Diagram
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Overview of the Animal Kingdom

• Animals
• Multicellular
• Heterotrophs
• Oxygen is required
• Sexual reproduction (some asexual)
• Motile - in part of life cycle
• Embryonic development
• Mitotic cell divisions in embryo
• Tissue layers
• Ectoderm, Endoderm, Mesoderm

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Diversity in Body Plans

• Vertebrates
• Mammals birds, reptiles, amphibians,
  fishes
• Invertebrates
• No backbones

• Body symmetry Cephalization ( sense in the
  head)
• Gut
• Body cavity
• Segmentation

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Examples of Body Symmetry

• Radial
• Live in water
• Bilateral
• Mirror image

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Type of Body Cavity in Animals

• Gut, body cavities, segmentation

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Type of Body Cavity in Animals

• Lined body cavity

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SpongesSuccess in Simplicity

• No symmetry, tissues, or organs

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SpongesSuccess in Simplicity
A basket sponge releasing a cloud of sperm
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Tissues in a Jellyfish
The sea nettle, a jellyfish (Chrysaora)
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Stages in Cnidarian Life Cycles

• Both polyp and medussa body forms

Physalia Portuguese Man-of-War
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FlatwormsTurbellarians, Flukes Tapeworms
Nervous system in a Planarian
Reproductive system in a Planarian
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Tapeworms

• Parasitic
• Scolex
• Proglottids
• Hermaphroditic

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Roundworms

• Most abundant multicelled animal
• Bilateral symmetry
• Cylindrical body
• Cuticle
• Complete digestive system
• Male and female

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Flukes

• Parasitic
• Sexual or asexual phases
• Two hosts
• Snail
• Human

Life Cycle of Schistosoma japonicum
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A Sampling of Mollusks

• Mollusk
• Soft body
• Shell
• Mantle
• Fleshy foot

• Gastropods-snails
• Chitons
• Bivalves-clams
• Cephalopods-squid

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Evolutionary Experiments with Body Plans
Radula is used to scrape food into the mouth
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Evolutionary Experiments with Body Plans
Body Plan of a clam
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Evolutionary Experiments with Body Plans
Body Plan of a cuttlefish, a cephalopod
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Annelids Segments Galore

• Bilateral
• Segmented
• Earthworms
• Leeches
• Polychaetes

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Earthworm Body Plan
Coelomic chambers
A nephridium
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Earthworm Body Plan
Portion of the closed circulatory system
Part of the digestive system
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Earthworm Body Plan
Part of the nervous system
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Arthropods The Most Successful Organisms on
Earth-Arthropods

• Over one million species
• Trilobites (extinct)
• Chelicerates
• Spiders
• Crustaceans
• Barnacles and crabs
• Uniramians
• Centipedes, millipedes, insects

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Adaptations of Insects and Other Arthropods

• Hardened exoskeleton
• Jointed appendages
• Fused and modified segments
• Respiratory structures
• Specialized Sensory Structures
• Division of labor

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A Look at Spiders
Organization of a Spider Body
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A Look at Crustaceans

• Shrimps, lobsters, crabs, barnacles

A Copepod
A Lobster
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Life Cycle of a Crab
Continuous molting
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A Look at Insect Diversity

• Head, thorax, abdomen
• Sensory antennae
• Mouthparts
• 3 pairs of legs
• 2 pairs of wings
• Malphigian tubules
• Waste disposal
• Life cycles

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A Look at Insect Diversity Examples of Appendages
Grasshopper
Butterfly
Mosquito
Fly
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Examples of Post-Embryonic Development
Silverfish
True bugs
Fruit flies
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The Puzzling Echinoderms

• Echinoderms
• Sea star
• Sea urchin
• Sea cucumber
• Brittle stars

• Body walls
• Spines, spicules
• Radial symmetry
• Decentralized nervous system
• Water-vascular system

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The Puzzling Echinoderms
Sea urchin
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Key Aspects of the Radial Body Plan of a Sea Star
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In Conclusion

• Animals are multicellular, aerobic heterotrophs
  that ingest or parasitize other organisms
• Animals range from structurally simple placozoans
  and sponges to vertebrates

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In Conclusion

• Almost all animals more complex than cnidarians
  show bilateral symmetry, form tissues, organs,
  and organ systems
• All mollusks have a fleshy soft body, and a mantle

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In Conclusion

• The annelids, have a segmented body, complex
  organs, and coelomic chambers
• Arthropods are the most successful of all groups
  in terms of diversity, numbers, distribution,
  defenses, and capacity to exploit food resources
• Echinoderms have spines, spicules, or plates in
  their body wall
• developed by M. Roig