By Teacher Imy Cajigas Science class How are animals classified?

Animals are classified based on their similarities and differences… Scientists divided the animal kingdom into two main groups, vertebrates and invertebrates. Vertebrates are divided into five classes: 1. Fish 2. Amphibians 3. Reptiles 4. Birds 5. Mammals

Fish Are usually cover with scales. They live only in water and breathe through gills. Fish are cold- blooded and most lay eggs.

Amphibians Are covered with a smooth skin. They can live both on land and in water. They breathe with lungs or gills or both. They are cold- blooded, and hatch from eggs.

Amphibians The Chinese giant salamander can grow up to 1.8m in length and evolved independently from all other amphibians over one hundred million years before Tyrannosaurus rex.

Reptiles Reptiles are covered with scales. Most reptiles lives on land, but some can live in water. They use lungs to breathe. Reptiles are cold- blooded. Reptiles usually lay eggs instead of having live births.

More about reptiles This group of vertebrates includes alligators, crocodiles, lizards, snakes, turtles, tortoises, and tuataras.

Alligator vs. Crocodile The eyes of an alligator glow red when a light is shined on them. Alligators tend to have wide, U-shaped, rounded snouts, while crocodiles tend to have longer, more pointed, V-shaped snouts. The fourth tooth on the lower jaw sticks up over the upper lip on crocodiles, so you can see it when their mouths are closed. In alligators, this fourth tooth is covered up. Alligators live in fresh water, while crocodiles live in salt water environments.

Birds Birds are covered with feathers. They usually live on land. Birds use lungs to breathe. They are warm- blooded. All birds lay eggs.

Mammals All mammals have hair or fur. Most live on land but a few live in water. They use lungs to breathe. Mammals are warm- blooded, they control their body temperature. Most mammals have live births.

Facts about mammals A killer whale has no fur. But it does have thick skin. This skin is lined with blubber. Blubber is a layer of fatty tissue just beneath a marine mammal’s skin

Invertebrates Animals that do not have backbones are invertebrates. Most of the animals in the world are invertebrates. Some of these are jellyfish, worms, insects, spiders, and lobsters.

Arthropods Arthropods are animals with jointed legs. They are the largest group of invertebrates. Insects, spiders, crabs, and shrimps are all arthropods. Their legs and bodies are divided into sections. Arthropods are covered by a hard, lightweight outer skin, or exoskeleton.

Other groups of invertebrates Some other groups include sponges, sea stars, worms and mollusks.

Mollusks A snail is one type of mollusk, they move by using a muscular structure called a foot. Some snails live on water environments while others live on land. Most mollusks are a few centimeters long but some can get very large like the giant squid. Some mollusks like oysters don’t move very far. Others, such as octopuses, are fast swimmers.

Mollusks

Comprehension questions What are the five divisions of vertebrates? What do all vertebrates have in common? What are some major groups of invertebrates? You discover an animal with a hard outer skin and jointed legs. What is it? Name some animals that are classified as arthropods.