Introduction to Invertebrates Chapter 29 Mader: Biology 8th Ed. Outline • • • • Evolution of Animals Sponges Cnidarians and Comb Jellies – Hydra – Obelia Bilateral Symmetry – Flatworms – Roundworms Mader: Biology 8th.
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Transcript Introduction to Invertebrates Chapter 29 Mader: Biology 8th Ed. Outline • • • • Evolution of Animals Sponges Cnidarians and Comb Jellies – Hydra – Obelia Bilateral Symmetry – Flatworms – Roundworms Mader: Biology 8th.
Introduction to Invertebrates
Chapter 29
Mader: Biology 8th Ed.
Outline
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•
•
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Evolution of Animals
Sponges
Cnidarians and Comb Jellies
– Hydra
– Obelia
Bilateral Symmetry
– Flatworms
– Roundworms
Mader: Biology 8th Ed.
Evolution of Animals
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•
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.
Mader: Biology 8th Ed.
Evolution of Animals
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–
Symmetry
Radial - Two identical halves.
Bilateral - Definite right and left halves.
Type of Coelom
Pseudocoelom
Coelom
Protostome - First embryonic opening
becomes the mouth.
Dueterostome - Second embryonic
opening becomes the mouth.
Mader: Biology 8th Ed.
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.
Mader: Biology 8th Ed.
Simple Sponge Anatomy
Mader: Biology 8th Ed.
True Tissue Layers
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Total of three possible germ layers.
– Ectoderm, endoderm, and mesoderm
Animals in phlyum Ctenophora (comb
jellies) and in phylum Cnidaria (cnidarians)
develop only ectoderm and endoderm.
– Diploblasts
Radially symmetrical
Mader: Biology 8th Ed.
Cnidarian and Comb Jelly
Mader: Biology 8th Ed.
Comb Jellies
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Small, transparent, and often luminescent.
Most of body composed of mesoglea.
Largest animals propelled by beating of cilia.
Capture prey with tentacles.
Mader: Biology 8th Ed.
Cnidarians
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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.
Mader: Biology 8th Ed.
Cnidarian Diversity
Mader: Biology 8th Ed.
Hydra
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Freshwater cnidarians.
– 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.
Mader: Biology 8th Ed.
Hydra
Mader: Biology 8th Ed.
Obelia
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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.
Mader: Biology 8th Ed.
Obelia
Mader: Biology 8th Ed.
Bilateral Symmetry
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•
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
Mader: Biology 8th Ed.
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
Mader: Biology 8th Ed.
Planarians
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–
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Excretory organ functions in osmotic
regulation and water excretion.
Can reproduce asexually
Hermaphroditic
Practice cross-fertilization
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Parasitic Flatworms
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Parasitic flatworms are flukes (trematodes)
and tapeworms (cestodes).
– Well-developed nerves and
gastrovascular cavity are unnecessary.
Flukes
– Usually named for type of vertebrate
organ they inhabit.
Reproductive system well developed.
Usually hermaphroditic.
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Transmission of Schistosomiasis
Mader: Biology 8th Ed.
Parasitic Flatworms
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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.
Mader: Biology 8th Ed.
Life Cycle of Taenia
Mader: Biology 8th Ed.
Pseudocoelom
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Pseudocoelom is 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)
– Nonsegmented, generally colorless
worms.
– Several parasitic roundworms infect
humans.
Mader: Biology 8th Ed.
Roundworm Anatomy
Mader: Biology 8th Ed.
Parasitic Roundworms
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Ascaris
Trachinella - Trichinosis
Dirofilaria - Heartworms
Wuchereria - Elephantiasis
Mader: Biology 8th Ed.
Rotifers
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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.
Mader: Biology 8th Ed.
Rotifer
Mader: Biology 8th Ed.
Review
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•
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Evolution of Animals
Sponges
Cnidarians and Comb Jellies
– Hydra
– Obelia
Bilateral Symmetry
– Flatworms
– Roundworms
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.