You all know that the animals are divided into two big groups, the vertebrates that have an internal skeleton formed by bones and the invertebrates that have no bones. All the invertebrates are oviparous, and we classify them into 6 big groups:
The sponges are aquatic animals, that are sac-shaped and their body is full of pores. It is very easy to remember this group because many times we use them in the shower for our personal hygiene. Yes, many of the sponges we use in the shower are invertebrate animals.
The jellyfish are invertebrate animals that live in the ocean. Their bodies are gelatinous and have tentacles. The truth is that when they appear in the beach it is very annoying because their tentacles have small venomous stingers that produce very unpleasant bites.
Worms are soft and long invertebrate animals that move by dragging their body on the ground because they have no feet. They can be aquatic or terrestrial. There are some worms that can be harmful and that is why we must be careful with them.
The echinoderms are exclusively aquatic animals. Their bodies have calcareous plates that form a shell. Some echinoderms are balloon shaped and are covered in spikes that they use to defend themselves, like sea urchins. Others are star-shaped and are of course called starfish.
The arthropods are the most abundant animals on the earth. Of every 100 animals, that exist, 80 are arthropods. These invertebrate animals have their body covered by an external skeleton called a cuticle. The most common way to classify the arthropods is the number of legs they have. This way we can classify them into four big groups.
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