Feeding is the process by which organisms, typically , obtain food. Terminology often uses either the -vore, -vory, or -vorous from Latin vorare, meaning "to devour", or -phage, -phagy, or -phagous from Greek φαγεῖν (phagein), meaning "to eat".
Evolutionary history
The evolution of feeding is varied with some feeding strategies evolving several times in independent lineages. In terrestrial vertebrates, the earliest forms were large amphibious
400 million years ago. While amphibians continued to feed on fish and later insects, reptiles began exploring two new food types, other tetrapods (carnivory), and later, plants (herbivory). Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation (in contrast, a complex set of adaptations was necessary for feeding on highly fibrous plant materials).
Evolutionary adaptations
The specialization of organisms towards specific food sources is one of the major causes of
evolution of form and function, such as:
-
Mouth parts and tooth, such as in , , , , predatory animals such as Felidae and , etc.
-
Distinct forms of in birds, such as in , , , , , , etc.
-
Specialized and other appendages, for apprehending or killing (including fingers in )
-
Changes in body colour for facilitating camouflage, disguise, setting up traps for preys, etc.
-
Changes in the digestion system, such as the system of of herbivores, commensalism and symbiosis
Classification
By mode of ingestion
There are many modes of feeding that animals exhibit, including:
-
filter feeder: A form of food procurement in which food particles or small organisms are randomly strained from water.
-
Fluid feeding: obtaining nutrients by consuming other organisms' fluids
-
Bulk feeding: obtaining nutrients by eating all of an organism.
By mode of digestion
-
Extra-cellular digestion: excreting digesting enzymes and then reabsorbing the products
-
Myzocytosis: one cell pierces another using a feeding tube, and sucks out cytoplasm
-
Phagocytosis: engulfing food matter into living cells, where it is digested
By food type
is the habit in an animal species, of eating and tolerating a relatively wide variety of foods, whereas
monophagy is the intolerance of every food except for one specific type (see generalist and specialist species). is a term for intermediate degrees of selectivity, referring to animals that eat a relatively small range of foods, either because of preference or necessity.
[Johns, Timothy: The Origins of Human Diet and Medicine -- CHEMICAL ECOLOGY. ISBN 0-8165-1023-7, p. 5]
Another classification refers to the specific food animals specialize in eating, such as:
The eating of non-living or decaying matter:
There are also several unusual feeding behaviours, either normal, opportunism, or pathological, such as:
-
Cannibalism: feeding on members of the same species
-
Anthropophagy: the practice of eating human flesh
-
Autocannibalism: feeding on parts of one's own body (see also autophagy)
-
Filial cannibalism
-
Intrauterine cannibalism
-
Oophagy or ovophagy: the embryo/foetus eats sibling eggs
-
Embryophagy: the foetus eats sibling embryos
-
Sexual cannibalism: cannibalism after mating
-
Kleptoparasitism: stealing food from another animal
-
Kleptopharmacophagy: act of stealing chemical compounds for consumption
-
Lignophagia: eating wood, typically a pathological condition in some domestic animals
-
Paedophagy: eating young animals
-
Pica: appetite for largely non-nutritive substances, e.g. clay or hair, sometimes in pregnancy or in pathological states, typically a medical or veterinary concern.
-
Placentophagy: eating placenta
-
Trophallaxis: eating food regurgitated by another animal
-
Zoopharmacognosy: self-medication by eating , , and to treat and prevent disease.
An opportunistic feeder sustains itself from a number of different food sources, because the species is behaviourally sufficiently flexible.
Storage behaviours
Some animals exhibit hoarding and caching behaviours in which they store or hide food for later use.
See also
-
Consumer-resource systems
-
Dinosaur diet and feeding
-
List of abnormal behaviours in animals
-
Ingestive behaviors, the physiological behaviors of feeding
Notes
