MODE OF NUTRITION
- 1. Autotrophic Nutrition is the type of nutrition in which the organisms are able to manufacture their own food. Organisms which can manufacture or synthesize their own food are called autotrophs. Autotrophic nutrition is carried out by all green plants through the process of photosynthesis and by some certain bacteria through the process of chemosynthesis
2.Heterotrophic Nutrition is the type of nutrition in which organisms cannot manufacture their own food but depends directly on plants for their own food such organisms are called heterotrophs, most heterotrophs are fungi, protozoa and some bacteria
There are various types of heterotrophic nutrition as follows
- Holozoic Nutrition: This is the type of nutrition in which solid complex food substances are ingested and changed them into simple, soluble form during digestion. The processes involved holozoic nutrition includes ingestion digestion, absorption, assimilation and egestion. These processes are applicable to simple animals from protozoans such as Amoeba and Paramecium to complex organisms including man.
- Parasitic Nutrition or Parasitism: This is an association between the organisms of different species in which the smaller organisms called parasite depend on the larger partner called host for food and nutrients at the expense of the host i.e. causing harm and diseases to the host. For example association between round worm and man. Parasitic nutrition is also seen in plant where the plant parasite develops haustoriun with which it absorbs nutrient from the host cassytha and cuscuta (dodder plant). Other are phytophtora black pod parasite of cocoa.
- Symbiotic Nutrition or Mutualistic Nutrition: This is a type of nutrition in which two organisms of different species live together to derive mutual benefit from their association. The partners may be a plant to plant, animal to animal e.t.c. examples of organism that engage in symbiosis are lichens (an association of algae and fungus partnership). The green alga manufactures food for both organisms while the fungus protects the alga and absorbs water from the atmosphere for the use of alga. Another example is hermit crab inhabiting on molluscian shells carry other organisms on the skills. The organism may be a group of sea anemones which afford concealment protection for the crab and themselves obtain transport, better oxygenation and possible particles floating up while the crab is feeding.
- Saprophytic Nutrition: This is a form of feeding in which the organism derives its food from the remain of dead and decaying organic matter such as plant and animal. The organism is called saprophyte while the process is called saprophytism. This mode of nutrition is exhibited by some bacteria, fungi and some animals. Saprophytes secrete digestive enzyme onto the substrate (the organic matter) on which they feed digestion take place outside the organism. This type of digestion is called extra cellular digestion and it is the process that causes the decay. The extracellular enzymes the organism released to the food surface act only in the presence of moisture and the chemical reactions are usually being speeded up by a rise in the temperature.
Is an association between the organisms of different species in which only one partner benefit from the relationship while the other neither gains nor suffer any harm. For example, the association between shark and remora fish.
These are plants which apart from being autotrophic and photosynthetic feed on insect or small animal to supplement their protein needs. These insectivorous plants are found in nitrogen poor habitats, and they do trap insects as source of nitrogen. The insects are attracted by their colour, scent or sweet secretion (nectar) of the plants. They also have enzymes with which they digest the insects before being absorbed into their body. These plants include Venus fly trap (Dioaea), sundew plant(Drosera), the pitcher plant(Nepenthes) and bladderwort (urtricularia).
Filter feeding is feeding mechanism being used by some aquatic animals to feed on tiny microorganisms in the water called phytoplankton (plant) and zooplankton (tiny animal).These aquatic animals have to wallow in water through sieve-like structure on their body in order to collect large quantity in the water current. Examples of filter feeders are mosquito larva, mussels, duck, prawn, lobster etc.
Fluid feeding is a method of feeding adopted by some animals which involve feeding on fluid material from plant (nectar) or blood of animals or man. They have special mouth parts for piercing the skin of their prey e.g. mosquito. Other insects such as aphids feed on the sap of plant whose mouth part is for piercing and sucking. Some larger animals such as bees, butterfly and humming birds suck the nectar of flowers.