Chapter 12 Lesson 3

Chapter 12 Lesson 3

By Georgia Fleming

Lesson 3

Digestion and Excretion

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The Importance of Digestion and Excretion

• Waste products that are not used by the body are removed by excretion.​

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The Importance of Digestion and Excretion

• Excretion is important for survival because it removes harmful substances from the body.

• Just as different animals have different structures for gas exchange, they also have different structures to obtain and process nutrients and to remove wastes.

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The Importance of Digestion and Excretion

• The type of digestive structures an animal has depends on what type of food it eats.

• Chewing food is usually the first step of digestion.

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The Importance of Digestion and Excretion

• You often can tell what type of diet an animal eats by looking at the structures that it has for feeding.

• Animals that eat only plants such as grass often have wide teeth used for chewing and sometimes a few sharp teeth that can cut through twigs.​

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The Importance of Digestion and Excretion

• Animals that eat insects use teeth with sharp points for chewing.

• Animals that eat only meat bite and hold food with teeth in the front of the mouth and cut up food with pointed teeth in the rear of the mouth.

• Animals that eat plants and meat have sharp teeth that cut up food and wide, flat teeth that grind up food.

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The Importance of Digestion and Excretion

• Filter feeding involves taking in water with food, pushing the water out through a filtering structure, and then eating the organisms that remain.

• Some whales take a mouthful of water and push it out through baleen, a material similar to the bristles of a broom.

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The Importance of Digestion and Excretion

• Some animals, particularly insects, have specialized mouthparts for eating.

• Most animals have specialized structures that are used for digestion.

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The Importance of Digestion and Excretion

• Cows and sheep have stomachs with many chambers that are used to digest food.

• A(n) crop is a specialized structure in the digestive system where ingested material is stored.

• A(n) gizzard is a muscular pouch similar to a stomach that some toothless animals use to grind hard foods.

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The Importance of Digestion and Excretion

• The process in which nutrients from digested food are taken into the body is called absorption.

• Enzymes are chemicals in digestive systems that help break food into small parts so cells can absorb the nutrients.

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The Importance of Digestion and Excretion

• In animals that have closed circulatory systems, nutrients from the intestines are absorbed by capillaries.

• In animals that have open circulatory systems, nutrients enter the blood directly after absorption.

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Excretion

• Waste materials are removed from the body during the process of excretion.

• Types of wastes animals excrete depend on the environments where they live.

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Excretion

• In organisms that do not have filtering mechanisms, waste materials are excreted as water moves in and out of the animal’s pores.

• Many aquatic animals remove liquid wastes using kidneys.

• The kidneys of fish excrete mostly water, plus other wastes such as ammonia.

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Excretion

• Terrestrial animals also have kidneys, but they excrete less water than aquatic animals excrete when they remove wastes.

• Most animals that live on land excrete urea as a waste product rather than ammonia.

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Excretion

• Birds conserve water by excreting uric acid instead of ammonia or urea.

• Solid wastes leave an animal’s body in the form of feces.

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Multiple Choice

What process moves nutrients from the digestive system to the circulatory system?

• absorption

• digestion

• excretion

• diffusion