Kingdom Animalia – The Animal World
Kingdom Animalia includes all multicellular, eukaryotic, heterotrophic organisms that lack cell walls and show locomotion in at least one stage of life.
- Multicellularity
- Heterotrophic
- Flexible body
- Motility
Basis of Animal Classification
Main criteria used to classify animals:
- Presence of notochord
- Symmetry
- Coelom
- Organization level
- Segmentation
3. Non-chordates (Invertebrates)
Animals without notochord – constitute ~95% of all animal species
- Porifera
- Cnidaria
- Platyhelminthes
- Nematoda
- Annelida
- Arthropoda
- Mollusca
- Echinodermata
4. Chordates
Animals with notochord (at least during some stage of life)
- Chordate features
- Urochordata
- Cephalochordata
- Vertebrata
- Vertebrate classes
Non-chordates vs Chordates – Quick Comparison
| Feature | Non-chordates (Invertebrates) | Chordates |
|---|---|---|
| Notochord | Absent | Present (at least in embryo) |
| Dorsal nerve cord | Absent or ventral | Present (hollow) |
| Pharyngeal gill slits | Absent | Present (at some stage) |
| Post-anal tail | Absent | Present (at some stage) |
| Skeletal system | Mostly exoskeleton or hydrostatic | Mostly endoskeleton |
| Examples | Sponge, Jellyfish, Earthworm, Insect, Starfish | Fish, Frog, Snake, Bird, Human |