Invertebrates made Simple !!

1) Poriferans (Sponges)

1.  They are found in sea / fresh water.
2. They are pore bearing animals having large number of pores in their bodies.
3. They obtain food and oxygen from water currents which enter the body through pores.
4. Waste is removed from the large opening present at the top.
5. They remain fixed to the sea floor.
6.They have radially symmetrical or asymmetrical body.

Examples are Sycon and Spongilla.

2) Coelenterata ( Cnidarians )

1.  They are found in marine environment.
2. They have radially symmetrical body.
3. The body is hollow, tube like.
4. Only one opening "mouth" is present.
5. The mouth is surrounded by tentacles.
6. Tentacles have stinging cells called cnidoblasts.
7. They either stick to some rock or float in water.
Examples are Hydra & Jellyfish.



3) Platyhelminthes (Flat worms)

1.  They are found in water or moist land.
2. They are simplest worms without legs.
3. Their body is flattened ribbon like.
4. They have bilaterally symmetrical body.
5. The body has one opening only.
6. Some flatworms are parasitic in nature and found in body of vertebrates.
7. Body cavity is absent. Examples are Tapeworm and Planaria


4) Nemathelminthes (Round worms)

1.  They are found in fresh/marine water or moist land.
2. Their body is bilaterally symmetrical.
3. The body has two openings, mouth and anus.
4. They have cylindrical unsegmented body.
5. Mostly, they are parasitic in nature.
6. They reproduce by laying eggs.

Examples are Pinworm and Ascaris

5) Annelids (Segmented worms)

1.  They are found in moist soil and pond water.
2. They have soft, cylindrical, segmented body.
3. Their body is bilaterally symmetrical.
4. Some are parasites in nature (leech).
5. They have special organs of excretion called nephridia.
6. They have a body cavity.

Examples are Earthworm and Leech


6) Arhtropoda ( Animals with jointed legs)

1.  They are found in air, on land and in water.
2. They have segmented body.
3. Their body is bilaterally symmetrical.
4. Thin body is divided into three regions - Head, Thorax and Abdomen.
5. They have jointed legs.
6. They have tough outer covering called exoskeleton.

Arthopods are furthter divided into four subgroups

A) Arachnida

1. Thorax and head region is fused.
2. Four pair of legs present.
3. Wings and antennae are not present
4. Hard exoskeleton is present.
Examples are Scorpions and Spiders

B) Crustacea

1. Thorax and head region is fused.
2. Appendages are present on all segments.
3. Variable number of legs present.
4. Two pair of antennae present.


Examples are Lobster and Shrimp

C)Myriapoda

1. Their body is divided into many segments.
2. Some have 02 pair of legs per segment. Example is millipede.
3. Some have 01 pair of legs per segment. Example is centipede.
4. Exoskeleton present.

Examples are Millipede and Centipede

D)Insects

1. The body is divided into three regions - Head, Thorax and Abdomen.
2. 03 ( Three ) pair of legs are present.
3.Two/One pair of wings may be present. Some insects are wingless too.
4. Mostly they have a pair of antennae.


Examples are Ants and Butterfly



7) Mollusca (Soft Bodies Shelled Animals)

1.  The body is soft unsegmented.
2. Often external hard shell is present.
3. Shell may be single, coiled or two shells are attached on one side.
4. Some have shell inside their body.

Examples are Octopus and Cuttlefish

 

8) Echinodermata (Spiny-skinnedAnimals)

1.  They are found in Marine habitat.
2. Their body is having radial symmetry.
3. Body is covered with sharp spines.
4.The body has two openings - mouth and anus.
5. Large number of tiny tube like feet are present which ends in suckers

Examples are Starfish and Urchin

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