What are the four division of animals?

There isn't a universally accepted system of dividing animals into exactly four distinct groups. However, a common and widely used approach is to classify animals based on their body structure and evolutionary relationships, which leads to the following major categories:

1. Vertebrates: These are animals with a backbone, also known as a spinal column. This group includes mammals, birds, reptiles, amphibians, and fish.

2. Invertebrates: These are animals without a backbone. This is the largest and most diverse group of animals, encompassing everything from insects and worms to jellyfish and snails.

3. Protostomes: This category includes animals with a protostome developmental pattern, where the first opening in the embryo becomes the mouth. This group includes many invertebrates, such as mollusks, annelids, arthropods, and flatworms.

4. Deuterostomes: This category includes animals with a deuterostome developmental pattern, where the first opening in the embryo becomes the anus. This group includes echinoderms (starfish, sea urchins, etc.) and chordates, which include vertebrates.

It's important to note that:

* This classification is based on evolutionary history and shared characteristics.

* The divisions are not always clear-cut, and there are exceptions to the rules.

* There are other ways to classify animals, such as by their habitat, diet, or mode of reproduction.

Ultimately, there's no single "right" way to divide animals into four groups, but this classification provides a useful framework for understanding animal diversity.