Digestive Excretory Notes

Digestive Excretory Notes - Digestive System Digestive...

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Digestive System Digestive System Comparison Heterotrophs obtain food by eating other organisms and have adaptations that allow them to be able to get and digest food. Many protozoans (amoebas and paramecium) capture food by phagocytosis and enclose it in a food vacuole. Lysosomes secrete enzymes that are used to break down food within the cell in a process called intracellular digestion. Sponges do not have a digestive system but instead filter the water passing over them and digest the nutrients within their amoebocytes. The process of obtaining food by passing water through a part of the body that strain out food is called filter feeding . Most multicellular heterotrophs have diets that consist of food particles to large to digest within individual cells; therefore their food is digested outside of their cells in a process called extracellular digestion. Extracellular digestion can occur within a cavity or completely outside of an organism. Simple invertebrates, such as hydra and other cnidarians have incomplete digestive systems. Wastes that are digested must be expelled through the mouth. Enzymes in the gastrovascular cavity break down food consumed by the hydra. Animals with a true coelom (body cavity) have a complete digestive system and food travels in one direction from the mouth to the anus. The digestive process is divided into several stages and has regions in which food is 1) moistened , 2) stored (some animals), 3) physically broken down (chewing or grinding), 4) chemically broken down (enzymes break food particles into simple nutrient molecules), 5) nutrients absorbed and 6) digestive wastes expelled. Earthworms have several special structures involved in the digestive process. They include the esophagus, crop (storage), gizzard (grinding), intestine (absorption) and anus. Birds
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Digestive Excretory Notes - Digestive System Digestive...

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