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BIOLOGY FORM 4. INVERTEBRATES ARTHROPODS. ARTHROPODS. Phylum TARDIGRADA Phylum PENTASTOMA Phylum ONYCHOPORA. What is Arthropods. Protostome Very diverse BUT share TWO characteristics anatomical features:

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biology form 4

BIOLOGYFORM 4

INVERTEBRATES

ARTHROPODS

arthropods
ARTHROPODS
  • Phylum TARDIGRADA
  • Phylum PENTASTOMA
  • Phylum ONYCHOPORA
what is arthropods
What is Arthropods
  • Protostome
  • Very diverse BUT share TWO characteristics anatomical features:
  • Pair of legs along all OR part of the body (served by ganglionic swellings on the latitudinal nerve cords
  • Pseudocoelomic body cavities (filled with blood – haemocoels)
slide4
Cont.
  • Arthropod body plan:
    • Small anterior region (acron)
    • Equivalent posterior portion (telson) without legs
    • Number of intervening section (segments) with a pair of legs each
  • BUT non-leg-associated (respiratory, excretory) organs are not serially repeated
what is phylum tardigrada
What is Phylum TARDIGRADA?

400 living species in 1 class

  • Characteristics[size: 0.05 – 1.2 mm]
  • Bilaterally symmetrical, minute, squat
  • Body more than 2 cell layer thick
  • Straight gut
  • Body monomeric –
    • four pair of short unjointed claw-bearing legs
    • Crawl by extrinsic muscle
    • Legs served by nerve ganglia
  • Well develop pseudocoelomic cavity => hydrostatic skeleton
  • Body wall with cuticle-covered epidermis without muscle
    • Non-chitinous cutilce moulted, bear spines or thickened into plates
    • Network of smooth muscle criss-cross the body
slide10
Cont.

100 species placed in 1 class

  • Characteristics[size: 2 – 16 cm long]
  • Bilaterally symmetrical, flattened, vermiform
  • Body more than 2 cell layer thick
  • Straight gut
  • Body monomeric –
    • annular
    • 2 pair claw-bearing legs at anterior
    • OR two pair of claw
  • Pseudocoelomic hydrostatic skeleton
  • Body wall with cuticle-covered epidermis
    • Layer of striated circular and longitudinal muscle
    • Cuticle chitinous, porous and moulted
phylum onychopora1
Phylum ONYCHOPORA

70 species placed in 1 Class, 1 Order

  • Characteristics[size: up to 15 cm long]
  • Bilaterally symmetrical, elongately and cylindrically vermiform
  • Body more than 2 cell layer thick
  • Straight gut bearing pair of mouthpart with 2 claw-like mandible
    • Fore- and hind-guts line with cuticle without digestive diverticula
  • Body 14-43 pairs of short unjointed fleshy legs along
    • Each leg: hollow evagination of body, padded terminally, with pairing claws and intrinsic muscle
    • Legs associated with a pair of heart ostia and excretory organ
  • Well developed haemocoelomic body hydrostatic skeleton with tubular heart but no other blood vessel
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