Animal functions
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Animal Classification
Animals are classified according to how they are related to other animals. These relationships are determined by an animal's body structure, the way the animal develops, and its DNA. DNA is a chemical in cells that controls an organism's inherited characteristics. Vertebrates are animals with a backbone. Invertebrates are animals without a backbone.
Vertebrates
There are five mayor groups of vertebrates. They are fishes, amphibians, reptiles, birds, and mammals.
Fishes
A fish is vertebrate that lives in water and uses fins to move. Most fishes are ectotherms. They have scales and obtain oxygen through gills. They make up the largest group of vertebrates.
Jawless fishes have no jaws or scales. They scrape, suck, and stab their food. Their skeletons are made of cartilage, a tissue more flexible than bone. Fish with jaws, scales, and skeletons made of cartilage are cartilaginous fishes. Bony fishes have jaws, scales and a pocket on each side of the head that holds the gills.
Reptiles
A reptile is an ectothermic vertebrate that has scaly skin and lungs and lays eggs on land. To live on land, an animal must have adaptations that keep water in its cells. The skin of reptiles is thick and helps keep water inside their bodies.
Amphibians
You may know that some amphibians such as frogs can be noisy neighbors. Frogs, toads, and salamanders are examples of amphibians. An amphibian is a vertebrate that is ectothermic and spends its early life in water and its adult life on land. In fact, the word amphibian means “double life”. Most amphibians spend their adult lives on land.
Birds
A bird is an endothermic vertebrate that lays eggs and has feathers and four-chambered heart.
Mammals
Mammals are endothermic vertebrates that have skin covered with fur or hair, and a four-chambered heart. The young are fed with milk produced by organs, called mammary glands, in the mother´s body.
Monotremes lay eggs. Marsupials are born at an early stage of development, and they usually continue to develop in a pouch on the mother´s body. A placental mammal develops inside its mother´s body until its body systems can function independently. Materials are exchanged between the mother and the embryo trough an organ called placenta.
Fishes
A fish is vertebrate that lives in water and uses fins to move. Most fishes are ectotherms. They have scales and obtain oxygen through gills. They make up the largest group of vertebrates.
Jawless fishes have no jaws or scales. They scrape, suck, and stab their food. Their skeletons are made of cartilage, a tissue more flexible than bone. Fish with jaws, scales, and skeletons made of cartilage are cartilaginous fishes. Bony fishes have jaws, scales and a pocket on each side of the head that holds the gills.
Reptiles
A reptile is an ectothermic vertebrate that has scaly skin and lungs and lays eggs on land. To live on land, an animal must have adaptations that keep water in its cells. The skin of reptiles is thick and helps keep water inside their bodies.
Amphibians
You may know that some amphibians such as frogs can be noisy neighbors. Frogs, toads, and salamanders are examples of amphibians. An amphibian is a vertebrate that is ectothermic and spends its early life in water and its adult life on land. In fact, the word amphibian means “double life”. Most amphibians spend their adult lives on land.
Birds
A bird is an endothermic vertebrate that lays eggs and has feathers and four-chambered heart.
Mammals
Mammals are endothermic vertebrates that have skin covered with fur or hair, and a four-chambered heart. The young are fed with milk produced by organs, called mammary glands, in the mother´s body.
Monotremes lay eggs. Marsupials are born at an early stage of development, and they usually continue to develop in a pouch on the mother´s body. A placental mammal develops inside its mother´s body until its body systems can function independently. Materials are exchanged between the mother and the embryo trough an organ called placenta.
Vertebrates diversity
At some point on their lives all chordates have three characteristics: a notochord, a nerve cord a nerve cord, and pouches in the throat area. Most chordates also have a backbone.
Notochord: Flexible rod that supports a chordate's back.
Nerve cord: The nerve chord connects the brain to nerves in other parts of the body.
Throat pouches: At some point on their lives have a pouches in their throat area. In most vertebrates, the pouches disappear before birth.
In addition to the notochord the nerve chord and the throat pouches, most chordates have a backbone. The backbone or spine, runs down the center of the back and replaces the notochord. The backbone is made of many small bones called vertebra. The backbone protects the spinal chord. The skull and ribs are other key parts of an endoskeleton.
Notochord: Flexible rod that supports a chordate's back.
Nerve cord: The nerve chord connects the brain to nerves in other parts of the body.
Throat pouches: At some point on their lives have a pouches in their throat area. In most vertebrates, the pouches disappear before birth.
In addition to the notochord the nerve chord and the throat pouches, most chordates have a backbone. The backbone or spine, runs down the center of the back and replaces the notochord. The backbone is made of many small bones called vertebra. The backbone protects the spinal chord. The skull and ribs are other key parts of an endoskeleton.