What is holozoic nutrition holo means-whole zoikos means-of animals
• is a method of nutrition.• involves the ingestion of liquid or solid organic material.• digestion, absorption and assimilation of it.• to utilize it.
• This method suggests phagocytosis where the cell membrane completely surrounds a food particle.• This type of nutrition occurs mainly in single celled organisms such as Amoeba.
5 steps of holozoic nutrition.• 1. (ingestion):Here, the food is first taken into the body through an opening called a mouth (ingestion).• 2. (digestion): then it is converted into a simple and soluble form by various enzymes (digestion);• 3. (absorption )simplified products thus formed are then absorbed (absorption);• 4. Assimilation); the conversion of nutrient into the fluid or solid substance of the body (Assimilation);• 5. (egestion): and finally the undigested part of food is removed from the body (egestion).
Amoeba proteus• It has intracellular mode of digestion.• Intra means inside the cell.• It feeds on many tiny (small) organisms .• These organisms live in fresh water and shallow lakes.• It also feeds on particulate organic matter.
Ingestion• Food may be ingested at any point on its surface.• When it comes in contact with food it puts out pseudopodia ( podia means feet) around it.
• These pseudopodia fuse together around food particle forming a food vacuole
food vacuole• This food vacuole undergoes many changes as digestion proceeds.• First it grows smaller• The larger• Again smaller.
Role of Lysosomes• Lysosomes contain hydrolytic enzymes ,fuse with food vacuole and enzymes are secreted in food vacuole.
First phase of digestion• It includes killing and softening of food in acidic medium(pH 5.6).• Later it becomes alkaline pH 7.3 during which digestion is completed.
Absorption through fine canals• When digestion is complete in food vacuole ,membrane makes numerous small canals.
• The products of digestion are passed into the canals and into surrounding cytoplasm.• Later it is used by amoeba for various metabolic reactions.
Egestion• Un digested material leaves amoeba through a process called egestion in to water around amoeba.• It takes place at any point on its surface.