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Invertebrates

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Title: Invertebrates


1
Chapter 33
  • Invertebrates

2
Lets meet the Invertebrates
3
Life Without a Backbone
  • Invertebrates
  • Are animals that lack a backbone
  • Account for 95 of known animal species

Xmas Tree Worm
4
A review of animal phylogeny
5
Invertebrate diversity
6
Invertebrate Diversity
7
Invertebrate Diversity
8
Sponges (Phylum Porifera)
  • Sponge characteristics
  • Sessile
  • Porous body
  • Choanocytes flagellated collar cells generate a
    water current through the sponge and ingest
    suspended food by phagocytosis
  • Live in both fresh and marine waters
  • Lack true tissues (groups of similar cells that
    form a functional unit). All animals except
    sponges belong to the clade Eumetazoa, the
    animals with true tissues
  • Most sponges are hermaphrodites (each individual
    functions as both male and female)

9
Sponges
  • Sponges are suspension feeders
  • Capturing food particles suspended in the water
    that passes through their body

10
Cnidarians (Phylum Cnidaria)
  • A diverse range of both sessile and floating
    organisms including hydras, jellies, sea
    anemones, and corals
  • Cnidarian characteristics
  • radial symmetry
  • gastrovascular cavity (digestive compartment)
  • Cnidocytes

movie
11
Cnidarian Body Plan
  • Relatively simple diploblastic (two germ layers),
    radial body plan
  • Basic body plan of a cnidarian is a sac with a
    central digestive compartment, the gastrovascular
    cavity
  • A single opening functions as both mouth and anus
  • There are two variations on this body plan
  • The sessile polyp and the floating medusa

12
Cnidarian Feeding
  • Cnidarians are carnivores
  • That use tentacles to capture prey
  • The tentacles are armed with cnidocytes
  • Unique cells that function in defense and the
    capture of prey

Threads can inject poison into the prey, or stick
to or entangle the target
13
Classes of Phylum Cnidaria
14
Hydrozoan Life Cycle
The zygote develops into a solid ciliated
larva called a planula.
The planula eventually settles and develops
into a new polyp.
5
6
15
Classes Hydrozoa, Scyphozoa, Cubozoa, and
Anthozoa
16
Cnidarian Classes
  • In the class Hydrozoa
  • Most hydrozoans alternate between polyp and
    medusa forms. Freshwater Hydras exist only in the
    polyp form.
  • In the class Scyphozoa
  • Jellies (medusae) are the prevalent form of the
    life cycle
  • In the class Cubozoa, which includes box jellies
    and sea wasps
  • The medusa is box-shaped and has complex eyes
  • Class Anthozoa includes the corals and sea
    anemones
  • Which occur only as polyps

Hydra
Purple coral
17
Hydra movie 1
18
Hydra movie 2
19
Coral reproduction
20
Jellyfish movie
21
Bilateria
  • Most animals have bilateral symmetry
  • The vast majority of animal species belong to the
    clade Bilateria
  • Which consists of animals with bilateral symmetry
    and triploblastic development

22
Flatworms
  • Members of phylum Platyhelminthes
  • Live in marine, freshwater, and damp terrestrial
    habitats. Some are parasitic.
  • Are flattened dorsoventrally and have bilateral
    symmetry
  • Undergo triploblastic development
  • Are acoelomates (lack a coelom) with
    gastrovascular cavities.
  • Lack a digestive system entirely and absorb
    nutrients across their body surface.

23
Flatworm Classes
24
Turbellarians
  • Are nearly all free-living and mostly marine

25
Turbellarians
  • Planarians are common examples of turbellarians
  • They have light-sensitive eyespots and
    centralized nerve nets

26
Monogeneans and Trematodes
  • Live as parasites in or on other animals They
    parasitize a wide range of hosts
  • Most monogeneans are parasites of fish
  • Trematodes (Flukes) that parasitize humans spend
    part of their lives in snail hosts

27
Tapeworms (Class Cestoda)
  • Are also parasitic and lack a digestive system

28
Rotifers (Phylum Rotifera)
  • Are tiny animals that inhabit fresh water, the
    ocean, and damp soil
  • Rotifers are smaller than many protists
  • But are truly multicellular and have specialized
    organ systems
  • Rotifers have an alimentary canal
  • A digestive tube with a separate mouth and anus
    that lies within a fluid-filled pseudocoelom
  • Some species of rotifers reproduce by
    parthenogenesis
  • In which females produce more females from
    unfertilized eggs

29
Rotifers (Phylum Rotifera)
30
Rotifer movie 2
31
Three Phyla of Lophophorates Ectoprocts,
Phoronids, and Brachiopods
  • Lophophorates have a lophophore
  • A horseshoe-shaped, suspension-feeding organ
    bearing ciliated tentacles that trap suspended
    food particles

32
Ectoprocts
  • Are colonial animals that superficially resemble
    plants

33
Phoronids
  • Are tube-dwelling marine worms ranging from 1 mm
    to 50 cm in length

34
Brachipods
  • Superficially resemble clams and other
    hinge-shelled molluscs
  • But the two halves of the shell are dorsal and
    ventral rather than lateral, as in clams

35
Nemerteans (Phylum Nemertea)
  • Commonly called proboscis worms or ribbon worms
  • The nemerteans unique proboscis
  • Is used for defense and prey capture
  • Is extended by a fluid-filled sac
  • Nemerteans also have a closed circulatory system
  • In which the blood is contained in vessels
    distinct from fluid in the body cavity

36
Molluscs (Phylum Mollusca)
  • Phylum Mollusca Includes snails and slugs,
    oysters and clams, and octopuses and squids
  • Mollusc characteristics
  • Body plan muscular foot, visceral mass, and a
    mantle
  • Mantle is a fold of tissue that drapes over the
    visceral mass and secretes the shell.
  • Most molluscs are marine, though some inhabit
    fresh water and some are terrestrial
  • Molluscs are soft-bodied animals, but most are
    protected by a hard shell
  • Most molluscs have separate sexes with gonads
    located in the visceral mass
  • The life cycle of many molluscs includes a
    ciliated larval stage called a trochophore

37
Mollusc anatomy
38
Classes of molluscs
39
Chitons
  • Class Polyplacophora is composed of the chitons
    (Oval-shaped marine animals encased in an armor
    of eight dorsal plates)

40
Gastropods
  • About three-quarters of all living species of
    molluscs belong to class Gastropoda

41
Gastropods
  • Gastropod characteristics
  • Most are marine, but there are also many
    freshwater and terrestrial species
  • Possess a single, spiraled shell
  • Slugs lack a shell or have a reduced shell
  • The most distinctive characteristic of this class
    is a developmental process known as torsion,
    which causes the animals anus and mantle to end
    up above its head

42
Bivalves (Molluscs of class Bivalvia)
  • Include many species of clams, oysters, mussels,
    and scallops
  • Have a shell divided into two halves

43
Bivalves
  • The mantle cavity of a bivalve contains gills
    that are used for feeding as well as gas exchange

44
Clam locomotion
45
Cephalopods
  • Class Cephalopoda includes squids and octopuses
  • Carnivores with beak-like jaws surrounded by
    tentacles of their modified foot

46
Octopus
  • Most octopuses creep along the sea floor in
    search of prey

47
Squid
  • Squids use their siphon to fire a jet of water,
    which allows them to swim very quickly

48
  • One small group of shelled cephalopods
  • The nautiluses, survives today

49
Annelids
  • Annelids
  • Segmented worms
  • Have bodies composed of a series of fused rings
  • 3 Classes Oligochaeta, Polychaeta, Hirudinea

50
Classes of Annelida
51
Oligochaetes
  • Oligochaetes (class Oligochaeta)
  • Are named for their relatively sparse chaetae
    (bristles made of chitin)
  • Include the earthworms and a variety of aquatic
    species
  • Earthworms eat their way through the soil,
    extracting nutrients as the soil moves through
    the alimentary canal
  • Which helps till the earth, making earthworms
    valuable to farmers

52
Earthworm anatomy
53
Polychaetes
  • Members of class Polychaeta possess paddlelike
    parapodia that function as gills and aid in
    locomotion

54
Leeches
  • Members of class Hirudinea are blood-sucking
    parasites, such as leeches

55
Nematodes (roundworms)
  • Nematodes are nonsegmented pseudocoelomates
    covered by a tough cuticle
  • Among the most widespread of all animals,
    nematodes, or roundworms
  • Are found in most aquatic habitats, in the soil,
    in moist tissues of plants, and in the body
    fluids and tissues of animals

56
Nematode movie
57
Nematodes
  • The cylindrical bodies of nematodes are covered
    by a tough coat called a cuticle

58
Nematodes
  • Some species of nematodes are important parasites
    of plants and animals

Trichinella spiralis encysted in human muscle
tissue
59
Arthropods
  • Arthropods are segmented coelomates that have an
    exoskeleton and jointed appendages
  • Two out of every three known species of animals
    are arthropods
  • Members of the phylum Arthropoda
  • Are found in nearly all habitats of the biosphere

60
Arthropod Characteristics
  • The diversity and success of arthropods
  • Are largely related to their segmentation, hard
    exoskeleton, and jointed appendages
  • Arthropods have an open circulatory system
  • In which fluid called hemolymph is circulated
    into the spaces surrounding the tissues and
    organs
  • A variety of organs specialized for gas exchange
    have evolved in arthropods
  • The body of an arthropod is completely covered by
    the cuticle, an exoskeleton made of chitin
  • When an arthropod grows it molts its exoskeleton
    in a process called ecdysis

61
Segmentation
  • Early arthropods, such as trilobites showed
    little variation from segment to segment
  • As arthropods evolved the segments fused, and the
    appendages became more specialized
  • The appendages of some living arthropods are
    modified for many different functions

62
Subphyla of Arthropoda
63
Cheliceriforms
  • Named for clawlike feeding appendages called
    chelicerae
  • Includes spiders, ticks, mites, scorpions, and
    horseshoe crabs
  • Most of the marine cheliceriforms are extinct
  • But some species survive today, including the
    horseshoe crabs

64
Cheliceriforms
  • Most modern cheliceriforms are arachnids
  • A group that includes spiders, scorpions, ticks,
    and mites

65
Arachnids
  • Arachnids have an abdomen and a cephalothorax
  • Which has six pairs of appendages, the most
    anterior of which are the chelicerae. (4 pairs of
    walking legs)

66
Myriapods
  • Subphylum Myriapoda
  • Includes millipedes and centipedes
  • Millipedes, class Diplopoda
  • Have a large number of legs
  • Each trunk segment has two pairs of legs
  • Centipedes, class Chilopoda
  • Are carnivores with jaw-like mandibles
  • Have one pair of legs per trunk segment

67
Insects
  • Subphylum Hexapoda, insects and their relatives
  • Are more species-rich than all other forms of
    life combined
  • Live in almost every terrestrial habitat and in
    fresh water
  • The internal anatomy of an insect includes
    several complex organ systems

68
Insect anatomy
69
Insects
  • Flight is one key to the great success of insects
  • An animal that can fly can escape predators, find
    food, and disperse to new habitats much faster
    than organisms that can only crawl

70
Metamorphosis
  • Many insects undergo metamorphosis during their
    development
  • In incomplete metamorphosis, the young, called
    nymphs
  • Resemble adults but are smaller and go through a
    series of molts until they reach full
    size (example grasshoppers)
  • Insects with complete metamorphosis have larval
    stages specialized for eating and growing that
    are known by such names as maggot, grub, or
    caterpillar
  • The larval stage looks entirely different from
    the adult stage
  • Metamorphosis from the larval stage to the adult
    stage occurs during a pupal stage

71
Metamorphosis
movie
72
26 Orders of Insects
73
26 Orders of Insects
74
Crustaceans
  • While arachnids and insects thrive on land
  • Crustaceans, for the most part, have remained in
    marine and freshwater environments
  • Crustaceans, subphylum Crustacea
  • Typically have biramous (branched) appendages
    that are extensively specialized for feeding and
    locomotion

75
Decapods
  • Decapods are all relatively large crustaceans
  • And include lobsters, crabs, crayfish, and shrimp

76
Decapod movie
77
Planktonic crustaceans
  • Planktonic crustaceans include many species of
    copepods
  • Which are among the most numerous of all animals

78
Barnacles
  • Barnacles are a group of mostly sessile
    crustaceans whose cuticle is hardened into a shell

79
Deuterostomes
  • Echinoderms and chordates are deuterostomes
  • Chordates and echinoderms share the
    characteristics of deuterostomes
  • Radial cleavage
  • Formation of the mouth at the end of the embryo
    opposite the blastopore

80
Echinoderms
  • Echinoderm characteristics
  • Sea stars and most other echinoderms are
    slow-moving or sessile marine animals
  • A thin, bumpy or spiny skin covers an
    endoskeleton of hard calcareous plates
  • Unique to echinoderms is a water vascular system
  • network of hydraulic canals branching into tube
    feet that function in locomotion, feeding, and
    gas exchange

81
Echinoderm movie
82
Echinoderm anatomy
83
Echinoderm classes
84
Sea Stars
  • Sea stars, class Asteroidea
  • Have multiple arms radiating from a central disk
  • The undersurfaces of the arms bear tube feet,
    each of which can act like a suction disk

85
Brittle Stars
  • Brittle stars have a distinct central disk and
    long, flexible arms

86
Sea Urchins and Sand Dollars
  • Sea urchins and sand dollars have no arms, but
    they do have five rows of tube feet that function
    in movement

Sand Dollar
87
Sea Lilies and Feather Stars
  • Sea lilies live attached to the substrate by a
    stalk
  • Feather stars
  • Crawl about using their long, flexible arms

88
Sea Cucumbers
  • Sea cucumbers do not look much like other
    echinoderms
  • They lack spines, and their endoskeleton is much
    reduced

89
Sea Daisies
  • Sea daisies were discovered in 1986
  • And only two species are known

90
Chordates (Phylum Chordata)
  • Chordates
  • Two subphyla of invertebrates as well as the
    hagfishes and the vertebrates
  • Share many features of embryonic development with
    echinoderms

91
Review of Animal Phyla
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