Explanation:

Animals are divided into two main categories - vertebrates and invertebrates. Vertebrates have a backbone, while invertebrates do not. Invertebrates are the most diverse group of animals and make up over 90% of the animal kingdom. Here are some reasons why invertebrates are so numerous:

Adaptability:

Invertebrates are highly adaptable and can live in almost any habitat on Earth, from the deep ocean to the driest deserts. They have evolved a wide range of survival strategies, such as camouflage, mimicry, and defensive mechanisms like stingers or toxins.

Reproductive potential:

Invertebrates are generally small and reproduce quickly, which allows them to rapidly colonize new environments. Many invertebrates also have complex life cycles with multiple stages, which can increase their reproductive potential even further.

Diversity:

Invertebrates come in many different shapes and sizes, from microscopic protozoa to giant squid. They also have a wide variety of body plans and structures, such as exoskeletons, tentacles, and jointed legs.

Examples of invertebrates:

Some examples of invertebrates include insects, spiders, crustaceans, mollusks, and worms. These animals play important roles in ecosystems, as they are often preyed upon by larger animals and help to decompose organic matter. Invertebrates also benefit humans in many ways, such as by pollinating crops, producing silk, and serving as a source of food and medicine.

Therefore, it can be concluded that invertebrates make up the largest group of animals in the world, accounting for more than 90% of all animal species.