Revision: Diversity in the Living World >> Animal Kingdom Biology Science (English Medium) Class 11 CBSE

Hermaphrodites are those organisms in which the sexes are not separate i.e. both male and female reproductive organs occur in the same individual.

• Meaning - Heterotrophic, multicellular eukaryotes; cells lack a cell wall; cannot produce their own food.
• Nutrition - Mode of nutrition is holozoic (food obtained by ingestion); food is digested in an internal cavity; food is stored as glycogen or fat.
• Reproduction - By sexual reproduction - copulation of male and female followed by embryological development.
• Other features - Follow a definite growth pattern; higher forms have elaborate sensory and neuromotor mechanisms (nervous system and sensory organs); most are capable of locomotion.
• Cell structure - Has a nucleus and membrane-bound organelles; no chloroplasts (hence cannot photosynthesise); no cell wall (unlike plants and fungi).

• The animal kingdom is classified based on level of organisation, symmetry, and body cavity.
• Cellular-level organisms are asymmetrical and belong to Porifera.
• Tissue-level organisms show radial symmetry and include Cnidaria and Ctenophora.
• Organ/organ system level organisms show bilateral symmetry and are further classified based on the body cavity.
• Based on body cavity:
  Acoelomates → Platyhelminthes,
  Pseudocoelomates → Aschelminthes,
  Coelomates → Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata, Chordata.

• Chondrichthyes are marine fishes with a cartilaginous skeleton and streamlined bodies.
• They have a ventral mouth, separate gill slits, and no operculum.
• Skin has placoid scales, modified as teeth; no air bladder is present.
• They are cold-blooded with a two-chambered heart; some have electric organs or poison stings.
• Sexes are separate, fertilisation is internal, and many are viviparous.
• Examples: Scoliodon, Pristis, Carcharodon, Trygon.

• Osteichthyes are bony fishes found in both marine and freshwater habitats.
• They have a bony endoskeleton, a terminal mouth, and gills covered by an operculum.
• Skin has cycloid or ctenoid scales and an air bladder for buoyancy.
• They are cold-blooded with a two-chambered heart and separate sexes.
• Fertilisation is mostly external and they are oviparous.
• Examples: Labeo, Catla, Exocoetus, Hippocampus.