Vertebrates vs Invertebrates
One of the BIGGEST divisions in the animal kingdom: VERTEBRATES (animals WITH a backbone) vs INVERTEBRATES (animals WITHOUT a backbone). You can feel your own backbone — it's the row of bones (vertebrae) running down your back. All mammals, birds, reptiles, amphibians, and fish are vertebrates. But these are only about 3% of all animal species!
INVERTEBRATES are the OTHER 97% of all animal species. They include: INSECTS (most numerous animals on Earth — bees, ants, beetles, butterflies). ARACHNIDS (spiders, scorpions). CRUSTACEANS (crabs, lobsters, shrimp). MOLLUSKS (snails, clams, octopuses, squid). ECHINODERMS (starfish, sea urchins). WORMS, JELLYFISH, SPONGES, and many more. They live everywhere — water, soil, air, even on other animals.
True or false: there are MORE species of insects alone than ALL vertebrate species combined.
Why so many invertebrates. (1) Many are SMALL — they fit into tiny niches. (2) Many reproduce FAST — quicker evolution. (3) They have EXOSKELETONS or no skeletons — fewer constraints on body form. (4) They were HERE FIRST — invertebrates have been around for over 500 million years (vertebrates are younger). Despite being smaller, they outnumber and outweigh us many times over.
Backyard Survey
Spend 10 minutes outside. Count: how many vertebrates do you see (birds, squirrels, dogs)? How many invertebrates (insects, spiders, worms)? Most yards have 10-100x more invertebrates than vertebrates.
Vertebrates often get the spotlight, but invertebrates do most of life's heavy lifting. They pollinate plants, decompose waste, build coral reefs, and feed nearly everything. They're Earth's essential workers.
Want to keep learning?
Sign up for free to access the full curriculum — all subjects, all ages.
Start Learning Free