Vertebrate Animals: Exploring the Five Main Groups
Vertebrate Animals
Vertebrate animals have bones, as well as skin, muscles, sense organs, and a brain. The five main vertebrate groups are:
- Fish
- Amphibians
- Reptiles
- Birds
- Mammals
Some vertebrates are cold-blooded, like fish, amphibians, and reptiles. Others are warm-blooded, like birds and mammals.
The body temperature of cold-blooded animals depends on the environment and changes if the surrounding area is cold or hot. When a cold-blooded animal is cold, it moves slowly and seeks a warmer area.
In contrast, warm-blooded animals maintain a constant temperature, regardless of the weather.
Fish
Fish live in water, including fresh, brackish, and saltwater environments. They have a simple skeleton made of hard bones, except for sharks and stingrays, whose bones are cartilaginous.
Fish bodies are covered with scales, and they have fins to move through the water. Like all animals, fish need to breathe to get oxygen. Land animals get oxygen from the air, while fish extract oxygen from the water through their gills.
The breathing process in fish is as follows:
- Water enters through the mouth.
- Water passes over the gills.
- Oxygen in the water is absorbed by the gills, while carbon dioxide is released into the water.
- Water exits the fish’s body.
Young fish typically hatch from eggs. A female fish can lay thousands of eggs, some of which die and serve as food for other animals.
Fish are economically important because many species are consumed by humans.
Amphibians
The name “amphibian” means “two lives” because part of their life cycle takes place in water and part on land. Amphibians do not have scales; their skin is soft, moist, and sticky. Most amphibians lay eggs in water, and their offspring, called tadpoles, develop there.
Tadpoles breathe through gills and have tails. As they grow, they develop into their adult form and begin breathing through lungs.
Almost all amphibians feed on insects. Frogs and toads belong to this group.
Reptiles
Reptiles have dry, scaly skin and breathe with lungs. They hatch from eggs laid on land. The eggs have a protective covering to prevent them from drying out.
Reptiles look like their parents from birth, unlike amphibians, which undergo metamorphosis.
Reptiles include crocodiles, turtles, lizards, and snakes, which are the largest and most diverse group.
Birds
Birds are the only animals with feathers. They have wings for flying and two legs for walking. They have lungs and a highly developed sense of sight, but a poor sense of smell. Most birds build nests where females lay eggs and chicks hatch. Some birds are carnivorous, some are herbivorous, and others are omnivorous.
There are over 9,000 species of birds, ranging from tiny hummingbirds to large eagles.
Mammals
If an animal has hair, feeds on breast milk at birth, and breathes through lungs, it is a mammal.
There are terrestrial and aquatic mammals, such as whales and dolphins. Some mammals can fly, like bats. Mammals range in size from tiny mice to enormous elephants and blue whales.
There are three groups of mammals: those that lay eggs (like the platypus, the only mammal with this characteristic); marsupials, whose embryonic development finishes in a pouch outside the mother’s body (like kangaroos); and placental mammals, which develop inside the mother’s body and are the most abundant and common, ranging from mice and rabbits to cows and humans.
Distinguishing Similar Animals
Although some animals look very similar, there are always distinguishing features:
- Crocodiles vs. Alligators: Crocodiles have long, pointed heads; alligators have shorter, rounded heads and upturned noses. Mexico has both crocodiles and alligators.
- Rabbits vs. Hares: Rabbits have plump bodies, small, pointed ears, and short legs. Hares have slender bodies, large ears, and long, thin legs.
- Tortoises vs. Turtles: Tortoises have legs with claws, while turtles have flippers.
- Frogs vs. Toads: Frogs have smooth skin, while toads have rough, bumpy skin.
- African vs. Asian Elephants: African elephants are larger than Asian elephants. African elephants have large ears, three toes on their hind legs, and a trunk that ends in two points. Asian elephants have smaller ears, four toes on their hind legs, and a trunk that ends in a single tip.
- Leopards vs. Jaguars: Leopards have black, circular rosettes on a yellow background. Jaguars have larger rosettes with a spot inside each one. Black panthers are not entirely black; in the light, their skin shows rosettes similar to a leopard’s.