activity 2 - amphioxus

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activity 2 - amphioxus

  1. 1. amphioxus
  2. 2. introductionOrganisms under Subphylum Cephalochordata:• Has no distinct head• But has a notochord that extends to the head part of the body.
  3. 3. introduction:Amphioxus: - means “sharp at both ends” - a living amphioxus is semitransparent but becomes opaque when immersed in preserving fluids.
  4. 4. Amphioxus and the Vertebrates
  5. 5.  No cephalization No paired sense organs
  6. 6. Has notochord that remains throughout lifeHas no vertebral column Notochord
  7. 7. Has pharyngeal slits but in large numbers
  8. 8. Dorsal, hollow nervous system No brain or cranium
  9. 9. Metameric muscles (myomeres) but extendes to theanterior tip of the head
  10. 10. Two-layered skin – epidermis and dermis But outer layer is one-cell thick
  11. 11. Well-developed circulatory system Lack blood cells, muscular heart Pulsating blood vessels
  12. 12. Is coelomateBut gretly restricted
  13. 13. External morphology of amphioxus
  14. 14. MYOMERE S •Lie immediately under the thin skin throughout the entire length of the body •Provide locomotionMYOSEPTA a connective• tissuepartition to whichlongitudinal muscle bundlesattach•It separates the myomeres
  15. 15. GONADS•Visible through the bodywall and bulge into the water-filled atrium, into whichsperm or eggs are shed ATRIOPORE •It is where the excess water , gametes and metabolic wastes exits
  16. 16. BUCCALCIRRI •Partially strain the water as it enters the vestibule and monitor it chemically
  17. 17. Dorsal and ventral fin rays: maintains balance during locomotion
  18. 18. GILL SLITSEYESPOT OCELLI GILL BARS WHEEL ORGAN
  19. 19. GILL SLITS : where water goes through; where strings of mucus travelling across them trap tiny food particlesGILL BARS : supports between gill slitsOCELLI : light-sensitive organ; it assist in orienting the animal as it burrows in the sand
  20. 20. WHEEL ORGAN : retrievessome of the heavier food particlethat miss the mouth, and itdirects these through the mouthand into the pharynx along withthe water stream
  21. 21. Internal Structure of Amphioxus
  22. 22. Parts and FunctionNotochord: protects and support the dorsal nerve cord; serves as the major skeletal support throughout lifeNerve cord: serves as central nervous system.Pharynx: passage way for water, food and air.Atrium: serves as a collecting chamber for respiratory water that has passed over the gills.
  23. 23. Intestine: major site for digestion of food.Anus: excretion of waste
  24. 24. Anterior end
  25. 25. Vestibule: collecting chamber for sea waterOral hood: serves as entrance and storageVelum: works as valve and filter; surrounds the mouthVelar tentacles: prevent undesirable objects from entering the digestive cavity
  26. 26. Amphioxus spend much of their time buried in gravel or mud on the ocean bottom
  27. 27. When feeding, they let the anterior part of the body project from the surface of the gravel so that they can filter food particles from water passing through their gill slits.
  28. 28. FEEDING:
  29. 29. Feeding:Once the food is in the pharynx it is processed as follows. Epibranchial groove Hypobranchial groove or endostyle
  30. 30. They burrow into sand using rapid movements of the bodyThe continuity of the notochord to the very tip of the rostrum may be an adaptation for burrowing in sand.
  31. 31. The animals swim by contracting the muscle blocks, or myomeres, that run from end to end on each side of the body.
  32. 32. The blocks on each side are staggered, producing a side-to-side movement of the body when swimming.

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