Animals
Animals are multicellular eukaryotes that need to hunt for food to survive rather than get its energy from the sun (as plants do). From the Great Barrier Reef, to the great white shark, to you reading this, those are all, in some sort in animal. There are nearly 1 ½ million known species of animals, and this is a very small percentage of all the animals on earth that have not been named. This is far too many to just make a list of, so scientists divide this number into smaller groups, called phyla. Species are grouped into phyla based on their body features, inside characteristics, behavior, adaptations, and the way they obtain food.
Most animals are invertebrates. In fact, 95% of all animal species on earth are invertebrates. Invertebrate means that they have no backbone. The other 5% have a backbone, including humans, and they are called vertebrates. Vertebrates make up part of 1 phyla, while invertebrates make up tens of other phyla. Phyla are classified into bigger groups. First, the animal kingdom is divided into two groups: Parazoa and Eumetazoa. Parazoans are simple animals, which stay in one place most of their life. They do not have any tissues, which means they don’t have organs. Instead, they have specialized ways to survive. Eumetazoans, on the other hand, are more complicated and many move around for their whole life. Also, they have tissues, which means it’s possible for them to have organs.
Further classification is still being discussed, but many scientists believe that Eumetazoa is divided into 2 smaller groups, which are Radiata and Bilateria. These are classified with their symmetry. Bilaterians have bilateral symmetry and animals in Radiata have radial symmetry. Further divisions after this do not exactly agree with each other. Some scientists believe that Bilateria is divided into Deuterostomia and Protostomia. However, some phyla show characteristics that are a mix of both. Also, Protostomia is so big that some scientists divide it into further classification.
Phyla, however, is not quite the smallest group, because 1 1/2 million species just grouped into a few phyla is going to still be many species per phyla. Instead, scientists animals into smaller groups called classes. However, even inside classes, scientists group animals into 3 even smaller groups. From the very bottom at each individual species, species are grouped into genera (singular: genus), genera are grouped into families, families are grouped into orders, orders are grouped into classes, classes are grouped into phyla, and phyla are grouped into kingdoms. There are a few different kingdoms. The main 6 are Archaebacteria (bacteria-like creatures that dwell in harsh environments), Eubacteria (true bacteria), Protista (protists, which are now separated into many different kingdoms), Fungi (mushrooms, yeast, mold, and more), Plantae (plants), and Animalia or Metazoa (animals).
Most animals are invertebrates. In fact, 95% of all animal species on earth are invertebrates. Invertebrate means that they have no backbone. The other 5% have a backbone, including humans, and they are called vertebrates. Vertebrates make up part of 1 phyla, while invertebrates make up tens of other phyla. Phyla are classified into bigger groups. First, the animal kingdom is divided into two groups: Parazoa and Eumetazoa. Parazoans are simple animals, which stay in one place most of their life. They do not have any tissues, which means they don’t have organs. Instead, they have specialized ways to survive. Eumetazoans, on the other hand, are more complicated and many move around for their whole life. Also, they have tissues, which means it’s possible for them to have organs.
Further classification is still being discussed, but many scientists believe that Eumetazoa is divided into 2 smaller groups, which are Radiata and Bilateria. These are classified with their symmetry. Bilaterians have bilateral symmetry and animals in Radiata have radial symmetry. Further divisions after this do not exactly agree with each other. Some scientists believe that Bilateria is divided into Deuterostomia and Protostomia. However, some phyla show characteristics that are a mix of both. Also, Protostomia is so big that some scientists divide it into further classification.
Phyla, however, is not quite the smallest group, because 1 1/2 million species just grouped into a few phyla is going to still be many species per phyla. Instead, scientists animals into smaller groups called classes. However, even inside classes, scientists group animals into 3 even smaller groups. From the very bottom at each individual species, species are grouped into genera (singular: genus), genera are grouped into families, families are grouped into orders, orders are grouped into classes, classes are grouped into phyla, and phyla are grouped into kingdoms. There are a few different kingdoms. The main 6 are Archaebacteria (bacteria-like creatures that dwell in harsh environments), Eubacteria (true bacteria), Protista (protists, which are now separated into many different kingdoms), Fungi (mushrooms, yeast, mold, and more), Plantae (plants), and Animalia or Metazoa (animals).