The group with the most species is that of the arthropods - insects, arachnids and crustaceans. But molluscs and the three groups of worms also make up a good part. Vertebrates is just another group like the arthropods for example - "invertebrates" is incredibly general. There are way more invertebrates than vertebrates.
If you mean by main group, vertebrates, because they are invertebrates. But if by main, you mean greatest by number then whether you count them as one celled animals or invertebrates they are much more numerous. They are certainly important to us. Scientists are saying that more than half of the cells in our body are bacteria. If this is so then my little one celled guys are very important to me. What do you mean by main group??
Worms make up the largest group of complex invertebrates.
invertebrates
invertebrates
Invertebrates do not have backbones.Examples of invertebrates are earthworms,insects,squids etc... Invertebrates are paraphyletic group.
The smallest group of invertebrates are sponges. They live in the ocean, fresh water ,lakes. and streams. Some things attach themselves to other things so they can get food.
Octopods.
Crustacean
mollusks :)
Walruses mostly eat invertebrates. Invertebrates are animals that do not have backbones
insects
Beetles are invertebrates