Invertebrates (overview)
No backbone · most animals on Earth
Invertebrates are animals without a backbone. Insects, spiders, worms, mollusks, and jellyfish are all invertebrates. Over 95% of animal species are invertebrates!
What makes them this type?
- No vertebral column (backbone)
- Huge variety of body plans
- Many have exoskeletons or shells instead
- Live in every habitat
- Include insects, arachnids, mollusks, worms, and more
Examples
Earthworm Soil recycler
Butterfly Insect invertebrate
Octopus Mollusk invertebrate
Starfish Echinoderm — tube feet
Crab Crustacean with a shell
Centipede Many legs, fast hunter
Motion Notes (for Animation & Drawing)
- Worms: peristalsis (squeeze waves)
- Crabs: sideways scuttle
- Starfish: slow tube-foot ripples
Learn More
“Invertebrate” is a big umbrella word — not one type, but many types that lack a spine.
Vertebrates (fish, amphibians, reptiles, birds, mammals) are the minority of species, even though they feel familiar.
Use this page as a map: then dive into insects, arachnids, mollusks, and jellies for details.
Fun Facts
- If you weighed all animals, insects alone would outweigh humans many times over.
- Some invertebrates (like octopuses) are incredibly intelligent.
- Fossils of invertebrates appear hundreds of millions of years ago.