Arthropoda Arthropods

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Arthropoda - Arthropods

• Evolved from Annelida
• Segmented bodies with jointed exoskeletons
• More species than any other phylum tremendously
  successful body plan!
• Major divisions within this phylum include
  Insecta, Crustacea, Chelicerata or Arachnida,
  Millipedes and Centipedes

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Insects

• Three body sections head, thorax and abdomen
• Legs and wings attached to thorax
• 6 legs, and 1 pair of antennae
• Many undergo metamorphosis, from larva
  (caterpillar) to pupa to adult

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Figure 25.34Page 437
Insects
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Corn rootworm (Diabrotica virgifera)
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Centipedes

• Highly motile predators.
• 1 pair of legs per segment
• Some are poisonous

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molting centipede
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Millipedes

• More slow moving and less aggressive than
  Centipedes
• Have 4 legs (2 pairs) per body segment
• Most are small, but a few are quite large.

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Figure 25.31Page 435
Millipede
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Arachnids or Chelicerates

• Includes horseshoe crabs, spiders, ticks, mites,
  scorpions
• Two body sections, head and thorax are joined
• 4 pairs of legs come off of this cephalothorax
• Ticks and mites can carry disease
• Many spiders have painful or poisonous bites
• Scorpions can inject venom through their tail
  stinger
• Horseshoe crabs are living fossils, they have not
  changed in over 300 million years!

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Body Plan of a Spider
eye
Malpighian tubule
digestive gland
heart
brain
poison gland
book lung
ovary
silk gland
anus
mouth
sperm receptacle
spinners
pedipalp
chelicera
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Centruroides sculpturatus, a dangerous scorpion
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Crustacea

• Mostly aquatic
• Includes lobsters, crabs, shrimp, barnacles, and
  pill bugs (!)
• All breathe through gills
• All have 2 pair of antennae
• Two body sections (first two are fused, as in
  Chelicerates)
• 5 pairs of legs
• Some Crustacea, like Daphnia and Cyclops are
  microscopic or nearly so

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Body Plan of a Lobster
one of two eyes
fused segments of cephalothorax
segments of abdomen
antennae (two pairs)
food-handling appendages (three pairs)
tail fin
swimmerets
first leg
five walking legs (five pairs total)
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Body Plan of a Copepod
eye
antennae
ovary
muscle
gut
egg mass
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Echinodermata - Echinoderms

• Name means spiny skins. This phylum is most
  closely related to our own! Look them up in your
  books appendix as they are not in Chapter 14.
• Includes sea stars, sea cucumbers, sea urchins
  and crinoids
• All are marine
• All are bilaterally symmetrical as larvae, but
  have pentamerous (5-fold) radial symmetry as
  adults.
• Since adults are radial, they have no brains.
• All have a unique method of locomotion, tube
  feet and a water vascular system.

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Sea urchins
Sea cucumber
Brittle star
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upper stomach
ossicle
gonad
spine
anus
lower stomach
coelom
digestive gland
eyespot
spine
ossicle
Body plan of a sea star
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sieve plate
ring canal
ampulla
Water vascular system
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Chordata - Chordates

• This is our phylum
• All chordates have at some stage gill slits, a
  hollow dorsal nerve cord, a notochord, and a tail
  that extends past the anus.
• All of the chordates you would be familiar with
  belong to the subphylum Vertebrata. Vertebrates
  have an internal skeleton of bone or cartilage.
• The main classes of Vertebrates are sharks, bony
  fish, amphibians, reptiles, birds, and mammals.

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Galápagos shark
Manta ray
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Australian lungfish
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Ichthyostega
Acanthostega
Devonian tetrapods Primitive amphibians
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vertebral column
Turtles are reptiles
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Figure 26.15cPage 457
Basilisk lizard
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venom gland
hollow fang
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yolk sac
embryo
amnion
allantois
chorion
albumin (white of the egg)
hardened shell
This amniote egg enabled reptiles to reproduce on
land.
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Placental mammals
Flying squirrel
Harp seal
Camel
Bat
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Stepped Art
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Marsupials
Tasmanian devil
Koala