Summary of Feeding Strategies and Classification
Animals have evolved multiple mechanisms to exploit different types of food
in the ocean. These feeding strategies can be classified according to the
type of food ingested and the environmental source of the food.
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).
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 (
- 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.
Heterotrophic Classification Based on
- 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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