1)overview of Non-Chordates and Chordates:
1. Non-Chordates (Invertebrates)
● Definition: Animals without a notochord, no backbone, and usually simpler body
organization.
● Symmetry: Can be radial (like jellyfish) or bilateral (like worms).
● Body Cavity: Can be acoelomate, pseudocoelomate, or coelomate.
● Examples: Sponges, Coelenterates, Flatworms, Roundworms, Annelids, Arthropods,
Molluscs, Echinoderms.
● Key Features:
○ No vertebral column
○ Mostly soft-bodied (except arthropods with exoskeleton)
○ Reproduction can be sexual or asexual
○ Respiration through skin, gills, or tracheae
2. Chordates (Vertebrates & Some Invertebrates)
● Definition: Animals with a notochord at some stage of development; most have a
backbone.
● Key Features:
○ Notochord – flexible rod along the body
○ Dorsal hollow nerve cord
○ Pharyngeal gill slits – at least during embryonic stage
○ Post-anal tail – at least during embryonic stage
○ Endoskeleton (in vertebrates)
● Examples:
○ Invertebrate Chordates: Tunicates (Sea squirts), Lancelets
○ Vertebrate Chordates: Fish, Amphibians, Reptiles, Birds, Mammals
● Other Characteristics:
○ Advanced organ systems
Bilateral symmetry
○ Closed circulatory system (in vertebrates)
Simple distinction:
Feature Non-Chordates Chordates
Notochord Absent Present (at least embryonic)
Backbone Absent Present (mostly vertebrates)
Body Cavity Acoelomate/Pseudocoelomate/Coelom Coelomate
ate
,Nervous Simple or ladder-like Dorsal, hollow,
System well-developed
Examples Sponges, Arthropods Fish, Birds, Mammals
2) differences between Non-Chordates and Chordates
Feature Non-Chordates Chordates (Vertebrates &
(Invertebrates) some Invertebrates)
Notochord Absent Present at least during
embryonic stage
Backbone/Vertebral Absent Present in vertebrates
Column
Body Symmetry Radial or bilateral Bilateral
Body Cavity Acoelomate, Pseudocoelomate, Coelomate
or Coelomate
Segmentation Usually absent or less Well-developed (vertebrae,
prominent (except some) muscles)
Nervous System Simple, nerve net or ladder-like Dorsal hollow nerve cord,
highly developed
Skeleton Exoskeleton (in some), mostly Endoskeleton (internal
soft-bodied bones/cartilage)
Circulatory System Open or closed (simple) Closed, well-developed
Circulatory Pigments Simple or absent (haemocoel) Hemoglobin in blood
Respiration Skin, gills, tracheae Gills (fish) or lungs (terrestrial)
Excretory System Simple, diffusion, flame cells, Kidneys, complex excretory
nephridia system
Digestive System Incomplete or simple tubular gut Complete, specialized
digestive system
Locomotion Cilia, muscles, or hydrostatic Well-developed muscles with
skeleton skeleton support
Sense Organs Simple (ocelli, statocysts) Well-developed (eyes, ears,
nose, etc.)
Reproduction Sexual or asexual Mostly sexual, specialized
organs
, Development Direct or simple indirect Often indirect (larval stages)
or complex embryology
Size & Complexity Mostly small and simple Generally larger and complex
Examples Sponges, Coelenterates, Tunicates, Lancelets, Fish,
Worms, Arthropods, Molluscs, Amphibians, Reptiles, Birds,
Echinoderms Mammals
3) Types of Non-Chordates
1. Phylum Porifera (Sponges)
○ Symmetry: Asymmetrical
○ Body: Pores and canals, no true tissues
○ Example: Sycon, Spongilla
2. Phylum Coelenterata / Cnidaria
○ Symmetry: Radial
○ Body: Diploblastic, body wall with epidermis & gastrodermis
Special feature: Stinging cells (cnidocytes)
○ Example: Hydra, Jellyfish
3. Phylum Platyhelminthes (Flatworms)
○ Symmetry: Bilateral
○ Body: Triploblastic, acoelomate
○ Example: Planaria, Taenia (tapeworm)
4. Phylum Nematoda (Roundworms)
○ Body: Pseudocoelomate, unsegmented, tubular gut
○ Example: Ascaris, Ancylostoma
○ Symmetry: Bilateral
5. Phylum Annelida (Segmented Worms)
○ Symmetry: Bilateral
○ Body: Coelomate, segmented body (metamerism)
○ Example: Earthworm, Leech
6. Phylum Arthropoda (Jointed-legged Animals)
○ Symmetry: Bilateral
○ Body: Segmented, exoskeleton of chitin, jointed appendages
○ Example: Cockroach, Crab, Butterfly
7. Phylum Mollusca (Soft-bodied Animals)
○ Symmetry: Bilateral
○ Body: Coelomate, soft body, often with shell
○ Example: Snail, Octopus, Clam
8. Phylum Echinodermata (Spiny-skinned Animals)
○ Symmetry: Radial (adult), bilateral (larva)
○ Body: Coelomate, spiny skin, water vascular system
○ Example: Starfish, Sea urchin
1. Non-Chordates (Invertebrates)
● Definition: Animals without a notochord, no backbone, and usually simpler body
organization.
● Symmetry: Can be radial (like jellyfish) or bilateral (like worms).
● Body Cavity: Can be acoelomate, pseudocoelomate, or coelomate.
● Examples: Sponges, Coelenterates, Flatworms, Roundworms, Annelids, Arthropods,
Molluscs, Echinoderms.
● Key Features:
○ No vertebral column
○ Mostly soft-bodied (except arthropods with exoskeleton)
○ Reproduction can be sexual or asexual
○ Respiration through skin, gills, or tracheae
2. Chordates (Vertebrates & Some Invertebrates)
● Definition: Animals with a notochord at some stage of development; most have a
backbone.
● Key Features:
○ Notochord – flexible rod along the body
○ Dorsal hollow nerve cord
○ Pharyngeal gill slits – at least during embryonic stage
○ Post-anal tail – at least during embryonic stage
○ Endoskeleton (in vertebrates)
● Examples:
○ Invertebrate Chordates: Tunicates (Sea squirts), Lancelets
○ Vertebrate Chordates: Fish, Amphibians, Reptiles, Birds, Mammals
● Other Characteristics:
○ Advanced organ systems
Bilateral symmetry
○ Closed circulatory system (in vertebrates)
Simple distinction:
Feature Non-Chordates Chordates
Notochord Absent Present (at least embryonic)
Backbone Absent Present (mostly vertebrates)
Body Cavity Acoelomate/Pseudocoelomate/Coelom Coelomate
ate
,Nervous Simple or ladder-like Dorsal, hollow,
System well-developed
Examples Sponges, Arthropods Fish, Birds, Mammals
2) differences between Non-Chordates and Chordates
Feature Non-Chordates Chordates (Vertebrates &
(Invertebrates) some Invertebrates)
Notochord Absent Present at least during
embryonic stage
Backbone/Vertebral Absent Present in vertebrates
Column
Body Symmetry Radial or bilateral Bilateral
Body Cavity Acoelomate, Pseudocoelomate, Coelomate
or Coelomate
Segmentation Usually absent or less Well-developed (vertebrae,
prominent (except some) muscles)
Nervous System Simple, nerve net or ladder-like Dorsal hollow nerve cord,
highly developed
Skeleton Exoskeleton (in some), mostly Endoskeleton (internal
soft-bodied bones/cartilage)
Circulatory System Open or closed (simple) Closed, well-developed
Circulatory Pigments Simple or absent (haemocoel) Hemoglobin in blood
Respiration Skin, gills, tracheae Gills (fish) or lungs (terrestrial)
Excretory System Simple, diffusion, flame cells, Kidneys, complex excretory
nephridia system
Digestive System Incomplete or simple tubular gut Complete, specialized
digestive system
Locomotion Cilia, muscles, or hydrostatic Well-developed muscles with
skeleton skeleton support
Sense Organs Simple (ocelli, statocysts) Well-developed (eyes, ears,
nose, etc.)
Reproduction Sexual or asexual Mostly sexual, specialized
organs
, Development Direct or simple indirect Often indirect (larval stages)
or complex embryology
Size & Complexity Mostly small and simple Generally larger and complex
Examples Sponges, Coelenterates, Tunicates, Lancelets, Fish,
Worms, Arthropods, Molluscs, Amphibians, Reptiles, Birds,
Echinoderms Mammals
3) Types of Non-Chordates
1. Phylum Porifera (Sponges)
○ Symmetry: Asymmetrical
○ Body: Pores and canals, no true tissues
○ Example: Sycon, Spongilla
2. Phylum Coelenterata / Cnidaria
○ Symmetry: Radial
○ Body: Diploblastic, body wall with epidermis & gastrodermis
Special feature: Stinging cells (cnidocytes)
○ Example: Hydra, Jellyfish
3. Phylum Platyhelminthes (Flatworms)
○ Symmetry: Bilateral
○ Body: Triploblastic, acoelomate
○ Example: Planaria, Taenia (tapeworm)
4. Phylum Nematoda (Roundworms)
○ Body: Pseudocoelomate, unsegmented, tubular gut
○ Example: Ascaris, Ancylostoma
○ Symmetry: Bilateral
5. Phylum Annelida (Segmented Worms)
○ Symmetry: Bilateral
○ Body: Coelomate, segmented body (metamerism)
○ Example: Earthworm, Leech
6. Phylum Arthropoda (Jointed-legged Animals)
○ Symmetry: Bilateral
○ Body: Segmented, exoskeleton of chitin, jointed appendages
○ Example: Cockroach, Crab, Butterfly
7. Phylum Mollusca (Soft-bodied Animals)
○ Symmetry: Bilateral
○ Body: Coelomate, soft body, often with shell
○ Example: Snail, Octopus, Clam
8. Phylum Echinodermata (Spiny-skinned Animals)
○ Symmetry: Radial (adult), bilateral (larva)
○ Body: Coelomate, spiny skin, water vascular system
○ Example: Starfish, Sea urchin
