Vertebrates and invertebrates biology lesson for kids: 1st, 2nd, 3rd, 4th, 5th, 6th and 7th grades biology lesson.
There are two main groups of animals: vertebrates and invertebrates. The main difference between these two is that vertebrates have backbones, and invertebrates don’t. Each of these two groups has subgroups that all have their own adaptations to survive in their environments.
Vertebrates have well developed internal skeletons, and can get very big. The biggest animals that have ever lived, blue whales, are vertebrates. Even though they are usually big, they make up only about 2% of all the animal species in the world! Along with their skeletons, vertebrates also have very well developed nervous systems, each with a brain that controls it.
Vertebrates are divided into fish, amphibians, birds, reptiles, and mammals. They all share a basic body plan: a head that has a brain, a digestive system with a mouth and a separate anus, and they usually have limbs. These limbs are sometimes specialised in unique ways. The forelimbs of birds, for example, are modified into wings, allowing them to fly through the air.
Invertebrates don’t have internal skeletons. Some of them have no skeleton at all, like worms. Other invertebrates do have skeletons, but they are external. These animals are called arthropods, and include insects, arachnids (spiders, scorpions, etc.), and crustaceans (crabs, lobsters, shrimp, etc.). Their external skeleton (called an exoskeleton) are hard, and provide them with protection, even from drying out.
Some invertebrates are very simple, having a sack-like digestive system with only one opening for the mouth and the anus. Flatworms and cnidarians (which includes jellyfish) are examples of these kinds of animals.
Because invertebrates don’t have internal skeletons to support their bodies, they usually don’t get very big. Some of them are very small and move very slowly, especially the ones that have no skeletons at all. Soft-bodied invertebrates may not have skeletons, but many of them have shells for protection. Snails and oysters, for example, have hard shells that they can either close or curl up inside; that makes it harder for predators to eat them.
As different as vertebrates and invertebrates are, they all have, at one point of their life cycle, a flexible rod that runs the length of their bodies. For vertebrates, this is replaced by the spinal cord and backbones early in their lives. Invertebrates, on the other hand, only keep the notochord during the embryo and larval stages.
As you can see, vertebrates and invertebrates are very different from each other, and each group is very diverse in itself!