NUTRITION- types of nutrition

Nutrition:
The process by which organisms obtain energy to maintain life functions and matter to create and maintain their structure.


Autotrophic nutrition:
Organisms synthesise their own complex organic molecules from simpler molecules using light or chemical energy.

-Phototrophic organisms obtain energy from sunlight to carry out photosynthesis.

-Chemoautotrophic organisms use energy from chemical reactions to synthesise organic molecules.


Heterotrophic nutrition:
Organisms cannot produce their own organic molecules so they consume other organisms which do.

1. Holozoic- Organisms with specialised digestive systems.
           >Carnivores eat other animals
           >Herbivores eat plant material only
           >Omnivores eat both plant and animal material
           >Detrivores feed on dead matter

Process:
Ingestion --> Digestion --> Absorbtion --> Assimilation --> Egestion

2.Saprotrophic- Feed on dead/decaying matter and do not have a specialised digestive system.

Process:
-Enzymes are secreted from the tips of the fungal hyphae to digest dead organic matter.
-Enzymes perform extracellular digestion.
-Products of digestion are absorbed and transported through the fungal mycelium.

3. Parasitic- Parasites are organisms that live on (ectoparasite) or in (endoparasite) a host. They obtain nutrients from the host and always cause harm and sometimes even death.


Unicellular organisms-
Animal-like Protoctista, like the Amoeba, use holozoic nutrition.
Oxygen and glucose are transported through the membrane by diffusion, facilitated diffusion, or active transport.

Large molecules are taken in via endocytosis and a vacuole forms around the food. Lysosomal enzymes fuse with the food vacuoles and products are absorbed into the cell cytoplasm. Indigestible remains are egested by exocytosis.
           
Multicellular organisms- 
Hydra have a cylindrical shape and tentacles at the top of their body which have stinging cells.
The tentacles paralyse the prey and take them through the mouth into the sac-like hollow body cavity, called the Gastrovascular cavity, where digestion begins.

The products of digestion are absorbed and indigestible remains are egested through the mouth as they only have a single opening in their digestive system.



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