Invertebrates are very common in nature; in fact, I'm very sure you have seen so many of them today. Generally, the Animal Kingdom is divided into two; the vertebrates and invertebrates. Out of the two, the invertebrates constitute about 95 percent of the total animal species. As of today, over two million species of invertebrates have been identified, while a lot of them are yet to be identified. This is way beyond what we have for vertebrates because the total number of vertebrates species that have been identified is just 58,000.
Invertebrates are enjoying this kind of population because they can reproduce very easily and faster, and a lot of them can adapt to severe conditions. For instance, insects like butterflies, mosquitoes have wings; as a result, they can easily escape the moment they sense any hostile environment. Another reason is that they are heterotrophic; they can feed on plants and animals.