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G.R. Although insectivorous plants carry out photosynthesis like other plants, yet they feed on insects?
Insects are the plant source of organic nitrogen while normal green plants obtain inorganic form of nitrogen from the soil . Nitrogen is needed for building plant proteins.
2. Commensalism:is a relation between different partners where one benefits while the other neither benefits nor gets harmed.
| 1st partner | Benefits | Other partner (neither benefits nor harmed) | |
| 1.Remora | Uses the shark as transport , protection and feeds on materials dropped by it. | Shark | 
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| 2.Zak Zak bird | Feeds on remains of food from crocodile teeth. | Crocodile | 
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| 3. Sea anemone | Helps in transportation and feeds on the remains of food from the crab. | Hermit crab |  
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| 4.Bird on elephant back | Feed on insects in between the skin folds. | Elephant or rhinoceros | 
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| 5. Flat Worms | Feeds on the food remains of the crab. | Crab (gills) | |
| 6.Bacteria | Get food from the animal digestive system without harming it. | Animal (digestive system) | |
| 7.Minute marine organisms | Obtain shelter and food. | Sponge |
3- Mutualism:is a relationship between 2 organism living together &exchanging benefits .
1st Partner
 Benefits
| Other partner Benefits |
 1. Nodular bacteria
(gets carbohydrates from the plant in order to release energy needed for nitrogen fixation)
| Leguminous plants (gets nitrogenous compounds to build their proteins) |
 2. Hydra
(gets food and shelter from algae)
| Green algae (gets nitrogenous compounds to build their proteins) |
  3. Termites (white ants)
(gets food)
| Protozoa Flagellate (live in termite’s intestine & digest the cellulose of plant fibers and wood vessels changing it into simple sugar to feed from it) |
Crop rotation system: Farmers cultivate legumes before cotton and other crops that consume the soil salts, leguminous plants are harvested leaving their roots and bacteria under the soil where they decay releasing their nitrogenous compounds in the soil which increases its fertility.
4- Parasitism:is a relationship between 2 individuals where one (parasite benefits) by obtaining its food either partially or totally digested from its (host)which gets harmed.
Parasites are classified in two ways :