Since the time Earth developed the quality of sustaining life, life has always gone under the process of evolution. Life started from single celled organisms and developed stage by stage. One organism extinct to develop into its better developed species or even at times it happens that some animals get erased from the surface of the earth due to extreme environmental condition.

EXTINCT ANIMALS: Species of animals which existed in the surface of the earth once upon a time but has no current existence, this may have been a result of extreme environmental condition or some other condition for existence. For example, we have dinosaurs, Dodo.

ENDANGERED ANIMALS: The species of animals which have only a few animals left on the surface of the earth and are in the mouth of being extinct are known as endangered, currently this is a result of poaching i.e., unethical killing of wild animals with purpose or change in the climate due to pollution and other factors. For example, we have the Royal Bengal Tiger.

We cannot do anything for the species which are extinct but we can definitely take steps and save our endangered species. Poaching laws should be made stricter and it should be taken care that people follow them.

Different types of animals :

Scientists sort the different types of animals in the world into categories based on certain characteristics. Animals are generally grouped into six types of aninals. The system for animal classifications is called taxonomy.

The Animal Kingdom :

All animals belong to a biological kingdom called kingdom Animalia. This kingdom is then broken down into over 30 groups. About 75% of all species on earth are aninals. Animals are then broken down into two types : vertebrates and invertebrates.

* Animals with a backbone are vertebrates.

* vertebrates belong to the phylum called phylum chordata.

* vertebrates are classified into five classes. They are amphibians, birds, fish,mammals, and reptiles.

* Animals without a backbone are invertebrates.

* Most invertebrates are in the phylum Arthropoda.

1. Amphibians :

All amphibians are vertebrates, and they need moist environment or water to survive.

* They are cold- blooded.

* They absorb water and breathe through their thin skin

* They have at least one special king gland used for defense.

* Most follow the life cycle of egg-larva- adult.

* examples : frog , newts, salamanders, toads.

2. Birds

Birds are a type of warm- blooded vertebrate that are adapted to fly.

* Not all birds can fly, but they do all have wings.

* Birds have beaks that help them catch and swallow food.

* The digestive system of a bird allows it to eat whenever it can and digest that food later.

* Birds lay egg to reproduce.

* They are endothermic, mening they maintain their own constant body temperature.

* They are bipedal, which means they have two legs.

* They have hollow bones and their bodies are covered in feathers.

* Birds belong to the class called Aves.

* Examples : albatrosses, chickens, hummin birds, falcons, falmingoes, ostriches, owls, parrot, penguins, pigeons.

3. Fish :

Fish are also vertebrates, and they are considered the oldest-known vertebrates.

* They are ectothermic, or cold- blooded, which means they rely on their surroundings to regulate their body temperature.

* Fish have funs.

* Most, but not all, fish have bodies covered in scales and breathe through gills.

* Fish live under water.

* Examples : eels, hangfish, lampreys, minnows, rays, salmon, seahorses, sharks.

4. Mammals :

Mammals are another type of vertebrate that belongs to the class Mammalia.

* young mammals get nourishment from milk produced by their mothers.

* Most mammals have hair.

* Their jaw is hinged directly to their skull unlike all other vertebrates.

* Almost aĺl mammals give birth to live bsbies.

* They are endothermic, or warm- blooded.

* Examples : there are over 5500 living species of mammals all over the world. Aardvarks, bats, elephants, hamsters, human, rabbits, rhinoceroses, whales.

5. Reptiles :

Reptiles are thought to be the first vertebrates to live completely on land. But, not all reptiles live only on land today.

* They are cold- blodded, or ectothermic

* They lay eggs to reproduce.

* They have four legs or descended from animals with four legs.

* They breathe through lungs

* Their bodies are covered in scales or scutes.

* Examples : crocodiles, geckos, lizards, sea turtles, snakes, tortoises.

Invertebrates :

Approximately 95% of all animals are invertebrates. Invertebrates do not have a backbone. There are different types of invertebrates, but they all share a few characteristics.

• They are made up of many cells that work together, or multicellular.

• Most, but not all have tissues, cells that work together in a more complex way.

• Most, but not all, can move.

• There are over 35 phyla of invertebrates.

• They generally have soft babies.

Types of Invertebrates :

There are eight phyla of invertebrayes that are alive today.

* Annelida – have a segmented body and primitive brain

* Arthropoda – have jointed appendages and an exoskeleton.

* Cnidaria – have tissues and an incomplete digestive system

* echinodermata – have some type of spiny structure on their bodies

* Mollusca – generally have sofy bodies and a hard exoskeleton.

* Nematoda – unsegmented with worm- shaped bodies

* platyhelminthes – have soft, ribbon- like worms with no respiratory system.

* porifera – multicellular organisms living in water with no organs or tissues.

Examples : anemone( cnidaria) , clams ( mollusca), coral,