Chapter 41Animal Nutrition

Types of Feeders• Suspension feeders sift through water to obtain

small food particles• Fluid feeders suck nutrients from a host• Substrate feeders live on their food sources• Bulk feeders eat large pieces of food

Nutritional Needs

To function properly an animal needs to consume…

• Fuel.• Organic raw materials for biosynthesis.• Essential nutrients which can’t be synthesized

through biosynthesis.

Fuel• Animals synthesize ATP from other fuel sources

and use ATP to power many bodily functions.• Animals oxidize carbohydrates, fats, and proteins in

that order as fuel for ATP synthesis.• Severe situations regarding fuel consumption are…

– Undernourishment, a prolonged caloric deficit.– Overnourishment (obesity), a prolongued surplus of fat in

a diet

Raw Organic Materials• An Animal needs to synthesize complex chemicals

needed to function. This is called biosynthesis.• Carbon skeletons and sources of organic nitrogen

are necessary to synthesize these molecules• These are readily available in the environment

Essential Nutrients• Essential Nutrients are important to bodily function

but cannot be synthesized by the animal. An animal’s diet must provide these.– Essential amino acids: 8 different monomers necessary for

protein synthesis– Essential fatty acids: Certain unsaturated fatty acids. – Vitamins: 13 different organic molecules which have a

wide array of bodily uses. They can be either water soluble or fat soluble.

– Minerals: Inorganic compounds

• Malnutrition arises when an animal lacks essential nutrients.

Regulation• Glucose Regulation is controlled by the antagonistic

hormones insulin and glucagon. – Insulin: Stimulates blood glucose levels to drop– Glucagon: Stimulates blood glucose levels to rise

• Hunger Regulation is controlled by four hormones– Leptin, Insulin, and PYY suppress appetite– Ghrelin increases appetite

Food Processing

Food Processing• Step 1: Ingestion of nutrients• Step 2: Digestion of macromolecules• Step 3: Absorption of monomers• Step 4: Elimination of undigested waste

Types of Digestion• Intracellular digestion occurs when food is digested

in the vacuoles of cells • Extracellular digestion occurs when some food is

digested in designated cavities outside of cells. • There are two types of digestive cavities

– The gastrovascular cavity is a sac with a single opening – The complete digestive tract (alimentary canal) has two

openings. Food only moves in one direction. This cavity contains more specialized compartments for digestion.

• Hydrolytic Enzymes break down polymers and are used in all types of digestion

The Mammalian Digestive Tract

The Oral Cavity, Pharynx, and Esophagus

• During chewing in the oral cavity, salivary amylase helps break down carbohydrates

• After chewing the tongue shapes the food into a bolus

• The food is swallowed into the Pharynx (throat) next– The Pharynx opens to the

trachea and esophagus

• The epiglottis covers the trachea when swallowing

• Peristalsis (rhythmic smooth muscle contraction) moves the food down the esophagus

The Stomach• A sphincter called the

cardiac orifice regulates entrance to the stomach.

• The stomach secretes gastric juice.– This mixes with the food

to form acid chyme.

• The acidity of the gastric juice activates the hydrolytic enzyme pepsin

• The pyloric sphincter regulates flow of acid chyme into the small intestine

The Small Intestine• The first 25 cm of this is the duodenum. In

the duodenum… – Juices from the Pancreas buffer the acid chyme.– The liver secretes bile salts to help digest fats– The epithelium contains and secretes hydrolytic

enzymes

• Structures in the epithelium called villi and their appendages called microvilli help absorb nutrients– In the villi are capillary beds and lacteals from the

circulatory and lymphatic systems respectively– The lacteals drain into larger lymphatic vessels– The capillary beds drain into the hepatic portal

vein of the liver

The Large Intestine (Colon)• A sphincter in a T-shaped junction controls the

entrance into the Large Intestine• The colon reabsorbs most of the water which the

small intestine left in the mixture• Undigested material moves through the colon by

way of peristalsis into the rectum– The undigested material is now known as feces and is

soon discarded

Evolutionary Adaptations to the Digestive System• Carnivores have developed sharper teeth while

herbivores have developed broader and more rigid teeth

• Herbivores have developed longer digestive tracts• Herbivores have developed symbiotic relationships

with bacteria that digest cellulose