Ch_21 - Chapter 21 Nutrition & Digestion Overview:...

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Unformatted text preview: Chapter 21 Nutrition & Digestion Overview: Obtaining and processing food Human Digestive System Diets Nutrition • Animals obtain and process nutrients in a variety of ways • Humpback whales eat small fishes and crustaceans called krill – This painting shows how the whales corral their food using “bubble nets” Getting Their Fill of Krill • Humpback whales strain their food from seawater using large, brushlike plates called baleen – When they feed, they take in large amounts of seawater in which the fish and krill live – They must filter out the water in order to get a meal • In a typical day, a humpback whale’s digestive system will process as much as 2 tons of fish and krill – They store the excess energy they harvest in the form of blubber – In about 4 months, a humpback whale eats, digests, and stores as fat enough food for an entire year • Animal diets are highly varied – Herbivores are plant-eaters – Carnivores are meat-eaters – Omnivores eat both plants and other animals Animals ingest their food in a variety of ways OBTAINING AND PROCESSING FOOD • Omnivores – Ingest both plants and animals – Some animals are suspension feeders, consuming particles from water • Herbivores – Feed mainly on plants • Carnivores – Mainly eat animals that eat plants – Some are fluid feeders, sucking liquids • Ingestion The Four Stages of Food Processing – Is another word for eating • Digestion – Is the breakdown of food to small molecules • Absorption – Is the uptake of the small nutrient molecules by the body’s cells • Elimination – Is the disposal of undigested materials from the food we eat • Mechanical digestion Digestion: A Closer Look – Begins the process – Involves physical processes like chewing • Chemical digestion – Is the breakdown of food by digestive enzymes • Chemical digestion – Proceeds through hydrolysis reactions • Hydrolases – Are enzymes that catalyze digestive hydrolysis reactions • In animals, chemical digestion is contained safely within some kind of compartment Digestive Compartments • Food is digested in compartments housing hydrolytic enzymes • Most animals have a specialized digestive tract • Relatively simple animals have a sac with a single opening – This is called a gastrovascular cavity – Example: hydra •...
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This note was uploaded on 02/03/2011 for the course BIOL 140 taught by Professor Lewis during the Spring '11 term at DeVry Alpharetta.

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Ch_21 - Chapter 21 Nutrition & Digestion Overview:...

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