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Protostome Animals

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Title: Protostome Animals


1
Protostome Animals
  • Chapter 32

2
Protostome Animals
  • Protostomes are bilaterally symmetric, coelomate
    animals
  • Undergo early development differently than
    deuterostomes
  • Contains the most successful phylum, Arthropoda
    and some very obscure phyla, Echiura ( about 135
    species)
  • Phyla have distinct body plans, feeding
    apparatuses, and locomotions

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4
Why Do Biologists Study Protostomes?
5
Arthropods
  • Most diverse and numerous phylum of animals
  • 925,000 known and identified
  • Live in almost every know habitat
  • Cause important diseases

6
Crustaceans and Mollusks
  • Crustaceans and mollusks are consumers,
    predators, and scavengers in many marine food
    chains
  • They are among the most expensive and
    sought-after seafood

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8
Insects, Spiders, and Mites
  • Insects eat about a third of the crops planted by
    farmers
  • They are the most economically important group of
    protostomes
  • Dominant consumers, predators, and scavengers in
    all terrestrial ecosystems
  • Most flowering plants are pollinated by insects

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10
How Do BiologistsStudy Protostomes?
11
How Do Biologists Study Protostomes?
  • Based on data obtained from
  • morphology studies
  • the fossil record
  • molecular phylogenies

12
Protostome Early Development
  • Researchers have drawn some general conclusions
    about protostomes
  • Protostomes undergo spiral cleavage after
    fertilization.
  • During gastrulation, the initial invagination
    that forms in the embryo becomes the mouth.
  • A body cavity, or coelom, may form within blocks
    of mesodermal tissue.

13
Protostome Symmetry
  • Protostomes are bilaterally symmetric
  • Have a distinctive head and posterior region.
  • All protostomes have three embryonic tissues.

14
Protostome Segmentation
  • Some protostomes may exhibit segmentation
  • Their bodies have a series of compartments with
    repeated structures.

15
Prehistoric Protostomes
  1. Most protostome phyla first appear in the Burgess
    Shale faunas, dated at about 525515 million
    years ago

16
Protostomes are Monophyletic
  • Molecular phylogenies support the hypothesis that
    protostomes are a monophyletic group
  • A branching event occurred within the lineage,
    producing two groups
  • the Lophotrochozoa and the Ecdysozoa.

17
Analyzing Morphological Traits
18
Coelom Development
  • Radical changes occurred in coelom formation as
    protostomes diversified
  • Acoelomate species arose again
  • Pseudocoelom, arose independently in certain
    protostome groups.
  • Most protostomes have bodies with a basic
    tube-within-a-tube design
  • arthropods and mollusks have specialized body
    plans where the coelom is drastically reduced

19
Tube- Within-A-Tube
20
  • Arthropods and mulluscs have a hemocoel
    (blood-hollow) that provides space for internal
    organs and fluid circulation

21
Evaluatin Protostome History
  • Two major events occurred in the fossil record of
    protostomes
  • Extinction of the trilobites, a marine arthropod,
    about 250 million years ago,
  • The appearance of insects about 400 million
    years ago

22
Evaluating Molecular Phylogenies
  • Molecular phylogenies support the hypothesis
    that protostomes are a monophyletic group that
    diverged into two major subgoups.

23
What Themes Occur in the Diversification of
Protostomes?
24
Protostome Diversification
  • Phylogenetic analyses suggests that repeated
    water-to-land transitions occurred as protostomes
    diversified
  • Two of the most important problems that animals
    had to solve were
  • exchanging gases
  • drying out

25
Protostome Diversification
  • Protostomes solved these problem in different
    ways
  • The evolution of specialized body plans provided
    a foundation for diversification in the most
    species-rich lineages
  • The arthropods and mollusks

26
Feeding
  • A wide diversity of feeding strategies is
    reflected in the diversity of mouthparts found in
    protostome animals

27
Movement
  • Variation in movement depends on
  • The presence or absence of limbs and
  • the type of skeleton that is present
  • Several evolutionary innovations allowed
    protostomes to move in unique ways

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29
Jointed Limbs
  1. Jointed limbs allow for precise swimming and
    running movements

30
Wings
  1. Insects were the first organisms that had wings
    and could fly

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32
Muscular Foot
  1. The muscular foot allowed mollusks to glide along
    surfaces

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34
Water Propulsion
  1. The muscle-lined mantle allowed the squid to use
    jet propulsion to propel itself backward

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36
Reproduction and Life Cycles
  • Can reproduce asexually via parthenogenesis
  • Unfertilized eggs that develop into offspring
  • Commonly reproduce via sexual reproduction
  • Two innovations occurred during protostome
    diversification (1) evolution of metamorphosis
    and (2) an egg that would not dry out on land.

37
Key Lineages of Protostomes
38
Lophotrochozoans
  • Named for two distinctive morphological traits
    (1) a feeding structure called a lophophore and
    (2) a type of larvae called a trochophore

39
Rotifera (Rotifers)
  • Rotifers have a corona of cilia at their
    anterior that is used for suspension feeding

40
Platyhelminthes (Flatworms)
  • This group includes (1) the free-living
    flatworms, (2) the endoparasitic tapeworms, and
    (3) the endo- or ectoparasitic flukes

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42
Annelida (Segmented Worms)
  • Annelids have a segmented body plan and a coelom
    that functions as a hydrostatic skeleton

43
Mollusca (Mollusks)
  • Most species-rich and morphologically diverse
    group in the Lophotrochozoa.
  • Specialized body plan based on a muscular foot, a
    visceral mass, and a mantle that secretes a
    calcium carbonate shell
  • Bivalves are suspension feeders
  • The other three groups of mollusks are herbivores
    or predators

44
MolluscaBivalvia (Clams, Mussels, Scallops,
Oysters)
  • The bivalves have two separate shells, made of
    calcium carbonate, that are hinged

45
MolluscaGastropoda (Snails, Slugs, Nudibranchs)
  • Have a large muscular foot on their ventral side
    and many lack shells

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47
MolluscaPolyplacophora (Chitons)
  • The Greek word roots that inspired the name
    Polyplacophora mean many-plate-bearing
  • Have eight calcium carbonate plates along their
    dorsal side

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49
MolluscaCephalopoda(Squid, Nautilus, Octopuses)
  • Have a well-developed head and a foot that is
    modified to form long, muscular tentacles
  • They also have large brains and eyes with
    sophisticated lenses.

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51
Ecdysozoans
  • All members of this lineage grow by
    moltingshedding of the exoskeleton or external
    covering (cuticle)

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53
Nematoda (Roundworms)
  • Unsegmented worms with a pseudocoelom
  • Tube-within-a-tube body plan
  • No appendages
  • Common parasites of humans and plants

54
Arthropoda (Arthropods)
  • Most successful lineage of eukaryotes
  • Distinguished by segmented bodies and
    sophisticated exoskeletons
  • The body is organized into distinct head and
    trunk regions
  • Most species have compound eyes
  • Long tentacle-like appendages called antennae

55
ArthropodaMyriapods (Millipedes, Centipedes)
  • Relatively simple bodies with a series of short
    segments, each with one or two pairs of legs

56
ArthropodaChelicerata (Spiders, Ticks, Mites,
Horseshoe Crabs, Daddy Longlegs, Scorpions)
57
Chelicerates
  • Most are terrestrial
  • Includes the arachnids
  • Bodies consist of anterior and posterior regions
  • Named for appendages called chelicerae found near
    the mouth

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59
ArthropodaInsecta (Insects)
  • Distinguished by having three body regions
    head, thorax, and abdomen
  • Three pairs of walking legs on the ventral side
    of the thorax
  • In most species, two pairs of wings are mounted
    on the dorsal side of the thorax

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61
ArthropodaCrustaceans (Shrimp, Lobster, Crabs,
Barnacles, Isopods, Copepods)
62
Crustaceans
  • Segmented body divided into the cephalothorax and
    the abdomen.
  • Many crustaceans have a carapacea platelike
    section of their exoskeleton that covers and
    protects the cephalothorax
  • Mouthparts called mandibles that bite or chew.

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