5. Eumetazoa (i.e. everything except Parazoa)
• Animals with true tissues that form after
gastrulation
• Embryos have distinct layers
– Inner endoderm forms the “gastrodermis”
– Outer ectoderm forms the “epidermis” and “nervous
system”
– Middle mesoderm (only in bilateral animals) forms the
muscles
• True body symmetry
– Radial symmetry
– Bilateral symmetry 5
6. Phylum Cnidaria
• Most marine, few fresh water species
• Diploblastic
• Bodies have distinct tissues but no organs
– No reproductive, circulatory, or excretory systems
• No concentrated nervous system
– “Latticework” or “net” of nerve cells
– Respond to touch, gravity, light
6
9. • Body plan has single opening (mouth) leading to
gastrovascular cavity lined by gastrodermis
– GVC is the site of extracellular digestion (key
innovation), which is followed by phagocytosis
– Most gas exchange occurs here
– Waste discharge
– Formation of gametes in many
• 2 layers to body
1.Epidermis
2.Gastrodermis
– Mesoglea between layers
9
10. • Gastrovascular space also serves as
hydrostatic skeleton
– Provides a rigid structure against which
muscles can operate
– Gives the animal shape
• Many polyp species build an exoskeleton
of chitin or calcium carbonate around
themselves
– Some build an internal skeleton
10
14. • Only one opening to digestive cavity
– Muscular contractions in the pharynx allows
food to be ingested and torn into small bits
• Lack circulatory system
– Diffusion for gas transport
– Gut functions in digestion and food
distribution
– Some particles digested extracellularly
– Cells engulf particles by phagocytosis
– Tapeworms (parasitic flatworms) lack
digestive systems – absorb food directly
through body walls 14
17. • Have an excretory and osmoregulatory system
– Network of fine tubules runs through body
– Metabolic wastes are excreted into the gut and
eliminated through the mouth
• Simple nervous system
– Anterior cerebral ganglion and ventral nerve cords
– Eyespot can distinguish light from dark
• Reproduction
– Most are hermaphroditic
– Undergo sexual reproduction
– Also have capacity for asexual regeneration
17
21. Phylum Mollusca
21
• Second in
diversity only
to arthropods
• Include snails,
slugs, clams,
octopuses and
others
• Some have a
shell, some do
not
22. Mollusk Body Plan
• Mantle
– Epidermal sheet
– Secretes the shell (if there is one)
• Foot
– Primary means of locomotion for many
– Divided into arms or tentacles in cephalopods
• Internal organs
– Coelom is highly reduced
– Digestive, excretory, and reproductive organs
are concentrated in a visceral mass
22
25. • Shell
– Protects against predators and adverse
environments
– Secreted by outer surface of mantle
– Clearly not essential (some mollusks have a
small or absent)
– Typical shell has 2 layers of calcium
carbonate
• Internal layer may be mother-of-pearl or “nacre”
• Pearls are formed by coating foreign object with
nacre to reduce irritation
25
26. • Radula
– Characteristic of most mollusks
– Rasping, tonguelike structure used in feeding
– Used to scrape up algae
– In predatory gastropods, modified to drill
through clam shells
– In Conus snails, modifies into harpoon with
venom gland
– Bivalves do not have a radula
• Gills used in filter feeding
26
29. 29
Class Polyplacophora (Chitons)
• Marine mollusks that have oval bodies
• 8 overlapping dorsal calcareous plates
• Body is not segmented under the plates
• Most chitons are grazing herbivores
30. Class Gastropoda
• Limpets, snails, slugs
• Marine, freshwater, and terrestrial animals
• Most have a single shell – some lost it
• Heads typically have pairs of tentacles
with eyes
• Exhibit “torsion”
– Mantle cavity and anus are moved from the
posterior to the front
30
31. • Torsion should not be confused with coiling
• Coiling – spiral winding of the shell
31
32. • Nudibranchs are active predators
– Exposed gills
– Many secrete distasteful chemicals
– Some extract nematocysts from cnidarian
prey and transfer them to their body surface
32
33. 33
Class Bivalvia (Bivalves)
• Includes clams, scallops, mussels, oysters,
and others
• Most marine, some freshwater
• No radula or distinct head
• Have 2 shells (valves) hinged together
– Adductor muscles counter hinge ligament
• Water enters through inhalant siphon and
exits through exhalant siphon
35. Class Cephalopoda
• More than 600 strictly marine species
• Active marine predators
• The only mollusks with closed circulatory system
• Foot has evolved into a series of arms equipped
with suction cups
• Largest relative brain sizes among invertebrates
• Highly developed nervous system
35
37. • Living cephalopods lack external shell
– Except chambered nautilus
– Squid and cuttlefish have internal shells
• Jet propulsion using siphon
• Ink can be ejected from siphon
• Chromatophores allow for changing skin color
for camouflage or communication
37
38. 38
Phylum Annelida –
segmented worms
• Body plan
– Head has well-developed cerebral ganglion
– Segments divided internally by septa
– Closed circulatory system
– Ventral nerve cord
– Complete digestive tract
44. • By far the most successful animals
– Well over 1,000,000 species (2/3 of all named
species)
• Arthropods affect all aspects of human life
• Divided into four extant classes
• Chelicerata
• Crustacea
• Hexapoda
• Myriapoda
44
47. Arthropod Morphology
Part of arthropod success explained by:
•Segmentation
– Head, thorax, abdomen
•Exoskeleton
– Made of chitin and protein
– Protects against water loss
– Must undergo “ecdysis” – molting
•Jointed appendages
– Evolution has modified some into antennae,
mouthparts, or wings
– Can be extended and retracted 47
48. • Open circulatory
system
• Nervous system
– Double chain of
segmented ganglia
– Ventral ganglia control
most activities
• Can eat, move, or
copulate with brain
removed
48
Head Thorax Abdomen
Spiracles
Tympanum
Compound
eye
Ocellus
Antennae
Brain
Aorta Stomach Ovary
Heart Rectum
Mouth
Crop Gastric
ceca
Malpighian
tubules
Nerve
ganglia
a.
b.
49. • Compound eyes are found in many
arthropods
– Composed of independent visual units called
ommatidia
• Other arthropods have simple eyes, or
ocelli
– May be in addition to compound eyes
– Have single lenses
– Distinguish light from darkness
49
51. • Respiratory system
– Many marine arthropods have gills
– Some tiny arthropods have no structure for
gas exchange
– Terrestrial arthropods use tracheae
– Many spiders use book lungs
51
52. Class Chelicerata
• Spiders, ticks, mites, scorpions, daddy
long-legs, horseshoe crabs, sea spiders
• Most anterior appendages called
chelicerae
52
53. Class
Crustacea
• Largely marine, some freshwater
• Crabs, shrimps, lobsters, barnacles, crayfish, copepods,
pill bugs, sand fleas
• Gas exchange through gills or across cuticle
53
54. • Decapod crustaceans
– Shrimps, lobsters, crabs, and crayfish
– Have 10 feet (5 pairs of thoracic appendages)
– Exoskeleton usually reinforced with CaCO3
– Cephalothorax covered by carapace
54
56. Class Hexapoda
• Insects are by far the largest group of
animals
– Number of species and number of individuals
• More than half of all named animal
species
• Approximately one billion billions (1018
)
insects are alive at any one time
56
60. External features
•Three body regions
1. Head
2. Thorax has three segments, each with a pair
of legs (=6 legs)
3. Abdomen
•Most insects have compound eyes
60
61. 61
The aquatic larvae of
mosquitoes are quite active.
They breathe through tubes
at the surface of the water,
as shown here. Covering the
water with a thin film of oil
suffocates them.
62. • Insect life histories
– Many insects undergo metamorphosis
– Simple metamorphosis (grasshoppers)
• Immature stages similar to adults
– Complete metamorphosis (butterflies)
• Immature larva are wormlike
• A resting stage, pupa or chrysalis, precedes the
final molt into adult form
62
63. Class Myriapoda
• Centipedes
– One pair of appendages per segment
– Carnivorous – poison fangs
• Millipedes
– Two pairs of appendages per segment
• Each segment is a tagma of 2 segments
– Herbivores
63
64. Phylum Echinodermata
• Exclusively marine
• Deuterostomes
with an
endoskeleton
• Pentaradial
symmetry, but
bilateral as larvae
• Sea stars, brittle
stars, sea urchins,
sand dollars, sea
cucumbers
64
65. • Water-vascular system
– Radially organized
– Radial canal extends from ring canal into
each body branch
– Water enters through madreporite
– Flows through stone canal to ring canal
– Tube feet – may or may not have suckers
• Ampulla – muscular sac at base
• Used in movement, feeding, gas exchange
65
