Transcript Chapter 29 PowerPoint

Chapter 29
Introduction to
Invertebrates
Outline
Evolution of Animals
Multicellularity
Sponges
True Tissues
Cnidarians and Comb Jellies
- Hydra
- Obelia
Bilateral Symmetry
Flatworms
Roundworms
Body Cavities
Acoelomates
Psuedocoelomates
Eucoelomates
Introduction to
Invertebrates
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Evolution of Animals
Introduction to
Invertebrates
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
Introduction to
Invertebrates
4
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
Animals:
Multicellular, Heterotrophic Eukaryotes
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Traditional Phylogenetic Tree of Animals
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Multicellularity
Sponges
Introduction to
Invertebrates
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
Introduction to
Invertebrates
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
Introduction to
Invertebrates
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
Introduction to
Invertebrates
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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
Cnidarian Diversity
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Hydra
Introduction to
Invertebrates
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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
Anatomy of Hydra
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Obelia
Introduction to
Invertebrates
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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
Obelia Life Cycle
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Bilateral Symmetry
Introduction to
Invertebrates
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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
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
Introduction to
Invertebrates
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Planarian Anatomy
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Planarians
Introduction to
Invertebrates
Planarians, cont.
Excretory organ functions in osmotic regulation
and water excretion
Can reproduce asexually
Hermaphroditic
- Practice cross-fertilization
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Parasitic Flatworms
Introduction to
Invertebrates
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Parasitic flatworms are flukes (trematodes) and
tapeworms (cestodes)
Well-developed nerves and gastrovascular cavity
are unnecessary
Flukes
Reproductive system well developed
Usually hermaphroditic
Life Cycle of Schistosomiasis
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Parasitic Flatworms
Introduction to
Invertebrates
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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
Life Cycle of a Tapeworm, Taenia
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Pseudocoelom
Introduction to
Invertebrates
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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
Roundworm Anatomy
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Parasitic Roundworms
Ascaris – Intestinal roundworm
Trachinella - Trichinosis
Dirofilaria - Heartworms
Wuchereria - Elephantiasis
Introduction to
Invertebrates
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Filarial Worm
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Rotifers
Introduction to
Invertebrates
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
Introduction to
Invertebrates
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Ending Slide Chapter 29
Introduction to
Invertebrates