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2. Coelenterates

2. Coelenterates. (phylum Coelenterata). The word coelenterate means “ hollow body cavity”. All coelenterates contain a central cavity with only one opening. There are two general body forms found among the coelenterates. POLYP. MEDUSA.

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2. Coelenterates

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  1. 2. Coelenterates (phylum Coelenterata)

  2. The word coelenterate means “hollow body cavity”.

  3. All coelenterates contain a central cavity with only one opening .

  4. There are two general body forms found among the coelenterates. POLYP MEDUSA

  5. The Polyp form is usually sessile and has a cylindrical body with a mouth and tentaclesat the upper free end. Corals and Hydras are examples

  6. Characteristics of coelenterates ; - The members of this group arejellyfish, sea anemones, corals and polyps .

  7. - The habitat of coelenterates is salt water but some of them live in fresh water.

  8. - They do not have a complete nervous system but they have nerve net .

  9. - Coelenterates have a sac like gut which serves as mouth and is surrounded by tentacles.

  10. - Their respirationmethod issimilar to that of sponges. They respire only by means of diffusion across the cell membrane.

  11. -Although most coelenterates reproduce sexually, some of them reproduce by budding

  12. - Coelenterates have two definite tissue layers; an ectoderm and an endoderm.

  13. The structure of a hydra is a typical example of a coelenterate. It consists of a body wall within which is the gastro vascular cavity.

  14. A group of tentacles surrounds the mouth that opens into the cavity.

  15. The body wall of coelenterates has an outer layer (ectoderm), an inner layer (endoderm) and

  16. an intermediate layer, the mesoglia. The intermediate layer contains cells and jelly like substances.

  17. The gastro vascular cavity serves both as a circulatory and digestive system.

  18. It is surrounded by an inner layer of the body that is made up of secretory cells and columnar cells.

  19. These cells have the ability to engulf food particles. They are digested and then diffuse form the body.

  20. SUMMARY Coelenterates - Coelenterates have a central body cavity with one opening.

  21. Most Coelenterates have stinging cells called nematocysts on their tentacles.

  22. Coelenterates sting and capture their prey, which they digest in the central body cavity. Waste products are released through the mouth.

  23. Coelenterates (Phylum Coelenterata) 1. Digestive cavity2. Two life stages: attached polyps and free-swimming medusa

  24. 3. Tentacles with stinging cells4. Radial symmetry5. Nerve net6. Aquatic organisms

  25. Hydra

  26. The hydra is a simple multicellular animal about 5 millimeterslong from the tip of its tentacles to its base. The body of the hydra is a hollow cylinder made up of two layers of cells.

  27. The outer layer is the ectoderm. The ectoderm is in direct contact with the aquatic environment 2. The inner layer is theendoderm.The endoderm lines the gastro vascular cavity.

  28. Hydra is in contact with water because water freely enters and leaves the gastro vascular cavity through the mouth

  29. endoderm tentacles cnidoblast ectoderm nematocytes

  30. The hydra captures its food with its tentacles. When a water flow or some other small animal comes in contact with a tentacle, the discharge their long threads. Some of the threads wind around the prey, nematocysts

  31. while others inject a poison that paralyzes the animal. By movements of the tentacles, the food is stuffed through the mouth and into the gastrovascular cavity , where digestion begins

  32. CORAL

  33. CORAL

  34. Corals Corals are small polyp that grow in colonies. Unlike hydras, they are surrounded by a hard skeleton

  35. Corals, like all coelenterates, are soft-body organisms.but corals use minerals in the water to build a hard protective covering of limestone.

  36. When the coral dies, the hard outer covering is left behind. Corals

  37. Coral • The mouth of this coral is surrounded by tentacles. • What is the function of tentacles?

  38. Algae live inside the coral`s body. The algae help make food for the coral.

  39. Since algae need sunlight to make food , corals must live in shallow water where sunlight can reach them. This relationship between a coral animal and alga plant is among the most unusual in nature

  40. Coral, like all coelenterates, are soft-bodied organisms. But coral use minerals in the water to build a hard protective covering of limestone.When the coral dies, the hard outer covering is left behind.

  41. Sea Anemones

  42. Sea anemones look like underwater flowers. However, the “petals” are really tentacles, and their brilliant coloring helps attract passing fish.

  43. When a fish passes over the anemone`s stinging cells,the cells poison the fish. The tentacles then pull the fish into the anemone`s mouth, and the stunned prey soon is digested.

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