Ways to gain nutrition

• Heterotrophic - Greek, heteros “different” + troph “nutrition”
  An organism that must obtain nutrition from fixed carbon (organic material) and cannot produce such materials itself.
  
• Autotrophic - Greek, auto “self” + troph “nutrition”
  Organisms that can synthesize fixed carbon from CO₂ or other non-organic sources using light or inorganic chemicals as an energy supply for synthesis (such as photosynthetic plants and algae).
  

Heterotrophic Classification Based on Type of Organism Ingested

• Herbivore-Latin, herba "a herb" + vorare "to devour"
  An animal that eats only plant material, including suspension feeding on small algal cells (microherbivory ) grazing or biting pieces of larger plants ( macroherbivory).
  
• Carnivore- Latin, caro "flesh" + vorare "to devour"
  An animal that eats only animal material. This includes predators that kill live prey and scavengers that feed on dead animal material.
  
• Omnivore- Latin, omnis "all, every" + vorare “to devour”
  An animal that eats both plant and animal material. This includes many scavengers, as well as microherbivores that do not discriminate between phytoplankton cells and animal eggs or embryos of similar size and some grazers that normally eat large algae or plants but opportunistically eat small animals that are encountered during grazing.

• Grazers slowly work over a surface (such as rock, sediment, plant, shell) and continually gather and ingest food as they go. Grazers are usually herbivores.
  
• Predators actively hunt, capture and kill their prey, and are usually carnivores.
  
  

Classification based on Environmental Source of Food

• Suspension feeding is the removal of suspended food particles from the water column using some sort of capture device. The capture device may be moved through the water to collect the food particles, or water can also be brought into the organism where the nutrients are collected by some sort of filtering apparatus and the remaining water is expelled. The particles can be algae or small animals (including eggs, embryos, and larvae).
  
• Filter feeding is a form of suspension feeding in which water is pumped through a mesh-like screen that retains particles larger than the size of the holes in the mesh. Many suspension feeders actively capture single food particles on cilia, hairs, mucus, or other structures, and few actually use a sieve (possibly because the particles are small, water is viscous, and a lot of energy is needed to pump a viscous fluid through very small holes).
  
• Deposit feeding is simply swallowing large amounts of sediment and digesting the nutritious organic matter on the sediment grains (leaving the remainder to be expelled). Selective deposit feeders use tentacles, mouthparts, or other structures from within a burrow or at the surface of the sediment to pick up algae and detritus while leaving behind the inorganic parts of the sediment (mud or sand).

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