Digestive system
There may be incomplete or complete digestive system.
1. Incomplete digestion
· The digestion in which only one opening is present which act as mouth as well as anus.
· Digestive track is absent or not much well developed.
Example Hydra
2. Complete digestion
· The digestion in which two openings are present.
· One act as mouth and other act as anus.
· Well-developed digestive track is present.
Example higher invertebrates
Snail
Ø If the digestion is within the cell it is called intracellular digestion (amoeba, paramecium).
Ø If the digestion is outside the cell, then it is called extracellular digestion (higher animal).
Circulatory system
In invertebrates haemolymph is present which act as blood.
1. Open circulatory system
· Haemolymph directly bath the tissues without moving into vessels.
Example Snail, insects
2. Closed circulatory system
· Haemolymph moves in closed vessels and bathes the tissues.
Example Octopus
Excretory system
1. Body surface
· The membrane is present which act as semi permeable and waste materials are illuminated through this membrane.
Example Hydra
2. Flame cells
· Flame like cells are present which have cilia and these cells also called solenocytes.
Example Planaria
3. Rennet system
· This system is for the excretion of round worms.
· This system is also called H-system.
Example Ascaris
4. Nephridia
· Their function is just as kidney perform in humans for excretion of wastes products.
· These are pore like openings.
Example
5. Malphigean tubules
· Duct/tube like structures present in insects for the purpose of illumination of waste products.
Example insects especially cockroach
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