Classifying Animals

Classifying Animals What are Vertebrates? Think of your favorite animal. What animal did you think of? Chances are, you probably thought of a vertebrate. Vertebrates are animals that have a spine or backbone. Vertebrates can be classified into 5 main groups. Mammals make up the first group. Mammals are vertebrates that are warmblooded, have hair, and give birth to live young. Some examples of mammals are humans, whales, monkeys, and pigs. Can you think of any more mammals? Reptiles make up the next group. Reptiles are cold-blooded, have scales, and lay eggs to reproduce. Some examples include snakes, lizards, and turtles. Can you think of any more reptiles? Amphibians are the next group. Amphibians and reptiles sometimes get confused, but they have some differences. Like reptiles, amphibians are cold-blooded and lay eggs. However, unlike reptiles, they have moist skin that is smoother and can live on both land and in water. They also have webbed feet. Some examples are frogs and salamanders. Can you think of more amphibians? Birds make up the fourth group. Birds are warm-blooded, have feathers and wings, and lay eggs to reproduce. Some examples include owls, eagles, and penguins. Can you think of any more birds? The last group is fish. Fish are coldblooded, have scales and fins, and lay eggs to reproduce. They also breathe underwater using gills. Some examples include trout, goldfish, and salmon. Can you think of any more fish? After reading about all the different groups of vertebrates, you might think that they make up most of the living creatures on Earth. This is not true! Vertebrates only make up about 4% of living things. The other 96% are made up of invertebrates. Crazy! What are Invertebrates? Invertebrates are all animals that do not have a backbone. They are the opposite of vertebrates. While you might have trouble thinking of animals that would be an invertebrate, they make up 96% of all animals on Earth! Let’s look at some groups of invertebrates more closely. One group of invertebrates are insects. There are over 1 million species of insects. Most insects have six jointed legs and a symmetrical body. They can crawl or fly. Some examples include bees, grasshoppers, and ants. Another group are mollusks. Mollusks have a soft body and often times have no legs. Some mollusks have an outside shell that they use for protection. Some examples are snails, oysters, and octopuses. Another group are crustaceans. Crustaceans have jointed legs and a skeleton on the outside of their body, called an exoskeleton. Some examples are crabs, lobsters, and shrimp. Worms are another group. Worms don’t have legs and often times live in soil, water, or even inside other animals! Some examples are tapeworms, leeches, and earthworms. Spiders, centipedes, and scorpions make up another group. Many people think these would be part of the insect group, but technically they are not. Most insects have 6 legs whereas this group has 8 legs or more! Some examples include tarantulas and millipedes. Finally, there are a variety of marine animals that don’t fit into one of the other groups that are invertebrates. Sponges, coral, jellyfish, and sea anemones are a few examples. Invertebrates are all around us, but most of the time we don’t even notice. So the next time you are out and see an insect or a worm, stop and say hi to your friendly, neighborhood invertebrates! Option Amphibians Imagine being able to live both in water and on land. Humans can't do it, but amphibians can! Amphibians are animals that live both in water and on land. The word amphibian comes from a Greek word that means “to live a double life.” To understand the life cycle of an amphibian, let’s take a closer look at an American toad. Like all amphibians, toads are coldblooded. An amphibian’s body temperature changes as the outdoor temperature changes. Some amphibians hibernate during the winter. Some toads dig deep underground. Other amphibians like frogs bury themselves in mud at the bottom of a pond. Hibernating amphibians can survive for months. They do not eat or Amphibians can live both in water and on land. move, using only the fat stored in their body to stay alive. Frogs and toads—and all amphibians—are also vertebrates which means they have backbones. Amphibians are a very interesting animal group. Amphibians are the only type of animal that have both gills and lungs. As adults, they live on land but lay eggs in the water. The Greek meaning of the word amphibian makes perfect sense! Option Fish Scientists study the characteristics of animals. They do this to divide the animal kingdom into different groups, such as mammals and reptiles. One group of animals within the animal kingdom is fish. Fish are aquatic animals, meaning that they spend their lives underwater. Most fish are coldblooded. Their body temperature changes with the temperature of the water. Fish are also vertebrates, meaning they have backbones. In fact, they are the largest group of animals on Earth that are vertebrates. Earth is covered mostly by water, so it makes sense that fish are the most common vertebrates. There are many different types and sizes of fish. Fish come in many sizes and colors. Fish lay eggs underwater. They also eat and sleep under water. Fish do not sleep in the same way mammals sleep. Fish can’t close their eyes because they don’t have eyelids. When they sleep, they float around or find a place to hide while they rest. Like other animals, fish need to breathe oxygen. But fish do not have lungs like people and they do not breathe oxygen from the air. Instead, they have gills just behind their heads. Fish gills take oxygen out of the water, so that fish can breathe. But gills do not work well outside water. They cannot take oxygen out of the air. Fish have scales that cover their skin. The scales protect the skin and help fish move easily through the water. Fish also use the different fins on their body and their tails to swim. They are able to glide through the water, rapidly changing direction by using their fins and tail. Option Reptiles Reptiles are cold-blooded animals that have backbones. They live both on land and in water like amphibians. Reptiles have lungs from the time they are born, not gills, like amphibians. Reptiles also lay eggs. Some reptile eggs have soft shells and some have hard shells. They lay their eggs on land. A few snakes hold the eggs inside their bodies until they hatch. Very few rare reptiles do give birth to live young, never making real eggs. Many different groups of animals are classified as reptiles. These include animals such as crocodiles, alligators, turtles, tortoises, snakes, and lizards. Crocodiles, turtles, snakes, and lizards are all reptiles.