Diversity In Living Organisms

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The Animal Kingdom can be further classified into ten divisions. Their key characteristics are given below:

True body cavity is present in these animals. The body is divided into segments and hence the name Annelida.

Each segment is lined one after another and contains a set of organs. Examples: Earthworm, leech, Nereis, etc.

Animals have jointed appendages which gives the name arthropoda.

The exoskeleton is present which is made of chitin. This is the largest group of animals; in terms of a number of species. The circulatory system is open, which means blood flows in the coelomic cavity. Examples: cockroach, housefly, spider, prawn, scorpion, etc.

1. The body is made up of a coelom (cavity) with a single opening.
2. The body wall is made up of two layers of cells (diploblastic).
3. Some of the species live a solitary life while others live in colonies.
4. Examples: Hydra, Jellyfish, Sea anemone, etc.

The body is covered with spines, which gives the name echinodermata.

Body is radially symmetrical. The animals have well-developed water canal system, which is used for locomotion.

Skeleton is made of calcium carbonate. Examples: Starfish, sea urchins, etc.

1. The animal has soft body; which is enclosed in a hard shell. The shell is made of calcium carbonate.
2. The circulatory system is open and kidney like the organ is present for excretion.
3. The body has well developed muscular feet for locomotion. Examples: Snail, mussels, octopus, etc.

1. The body is bilaterally symmetric and there are three layers in the body wall.
2. Animals are cylindrical in shape.
3. A pseudocoelom is present and hence organs are absent.
4. Examples: Roundworms, pinworms, filarial parasite (Wuchereria), etc.

1. The body is flattened from top to bottom and hence the name Platyhelminthes.
2. These are commonly known as flatworms.
3. The body wall is composed of three layers of cells (triploblastic). Because of three layers, it is possible to form some organs as well. But a proper ceolom is absent in Platyhelminthes and hence proper organs are absent.
4. They are free-living or parasitic animals. Examples: Planaria, liver fluke, tapeworm, etc.

1. These animals have pores all over their body.
2. The pores lead into the canal system.
3. Water flows through the canal system and facilitates entry of food and exchange of other materials.
4. The animal is not differentiated into tissues.
5. The body is covered with a hard outer skeleton.
6. These are commonly known as sponges.
7. They are marine animals. Examples: Sycon, spongilla, euplectelea, etc.

1. Animals are bilaterally symmetrical, triploblastic and ceolomate.
2. Notochord is present at least at some stages of life. Notochord is a long rod-like structure which runs along the back of the animal.
3. This provides attachment points for muscles. It also separates the nervous tissues fromt he gut.
4. Examples: Balanoglossus, herdmania, amphioxus, etc.

The notochord is replaced by a spinal column during the embryonic stage.

Following are the main characteristics of vertebrates:

1. Notochord present; which is replaced by the spinal column.
2. Dorsal nerve chord is present.
3. Animals are triploblastic and coelomate.
4. Animals have paired gill pouches.
5. Vertebrates are divided into two super classes, viz. pisces and tetrapoda.