Wednesday, July 29, 2020

Animal Kingdom - Notes | Class 11 | Part 3: Platyhelminthes and Aschelminthes

4. ANIMAL KINGDOM

PHYLUM PLATYHELMINTHES (FLATWORMS): GENERAL CHARACTERS

  1. Grades of organization:
    • Organ & Organ system.
  2. Symmetry:
    • Bilateral symmetry.
  3. Germ layers:
    • Triploblastic.
  4. Coelom:
    • Acoelomate
  5. Habit and habitat:       
    • Mainly aquatic. Endoparasites.
    • Some are free-living.
  6. Digestive system:          
    • Incomplete.
  7. Respiratory system:
    • Absent
  8. Circulatory system:
    • Absent
  9. Reproduction:
    • Asexual (fragmentation) and Sexual.
    • Hermaphrodite.
    • Internal Fertilization.
    • Development is indirect.
    • Many larval stages.
  10. Unique features:
    • Unsegmented, dorso-ventrally flattened body (except tape worms).
    • Excretion and osmo-regulation by Flame cells (protonephridia).
    • Parasites have Hooks & suckers.
    • Some absorb nutrients from the host through their body surface.
  11. Examples:
    • Taenia solium (Tape worm), Fasciola (Liver fluke), Planaria (shows high regeneration capacity).

PHYLUM ASCHELMINTHES (ROUNDWORMS): GENERAL CHARACTERS

  1. Grades of organization:
    • Organ system.
  2. Symmetry:
    • Bilateral symmetry.
  3. Germ layers:
    • Triploblastic.
  4. Coelom:
    • Pseudocoelomate.
  5. Habit and habitat:       
    • Aquatic and terrestrial. Free living or parasitic in plants & animals.
  6. Digestive system:          
    • Complete. Tubular alimentary canal with well-developed muscular pharynx.
  7. Respiratory system:
    • Absent
  8. Circulatory system:
    • Absent
  9. Reproduction:
    • Dioecious (Sexes are separate).
    • Sexual reproduction.
    • Internal fertilization.
    • Development is direct or indirect.
  10. Unique features:
    • Body is circular in cross section.
    • Syncytial epidermis.
    • Thick cuticle.
    • An excretory tube to remove body waste through excretory pore.
    • Sexual dimorphism (Morphological differences between male and female. E.g. females are longer than males).
  11. Examples:
    • Ascaris (Roundworm), Ancylostoma (Hookworm), Wuchereria (Filarial worm).
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