Bioenergetics

and Digestion

Core Concepts • Nutritional requirements

– Animals are heterotrophs that require food for fuel, carbon skeletons, and essential nutrients.

– Metabolic rate provides clues to an animal’s bioenergetic strategy.

• Evolutionary adaptations of feeding mechanisms and digestive systems

– Diverse feeding adaptations have evolved among animals.

– Structural adaptations of digestive systems are often associated with diet.

– Symbiotic microorganisms help nourish many vertebrates.

• Overview of food processing

– The four main stages of food processing are ingestion, digestion, absorption, and elimination.

– Digestion occurs in specialized compartments.

– The oral cavity, pharynx, and esophagus initiate food processing.

– The stomach stores food and performs preliminary digestion.

– The small intestine is the major organ of digestion and absorption.

– Reclaiming water is a major function of the large intestine.

– Hormones regulate digestion.

– Reclaiming water is a major function of the large intestine.

• Nutrition and disorders of the human digestive system

– A healthful diet provides both fuel and building materials.

– Nutritional disorders damage health.

Keywords absorption

alimentary canal

amebocytes

anorexia

bile

bolus

brush border

bulimia

cecum

chyme

complete digestive tract

crop

digestion

duodenum

elimination

endocytosis

enzyme

esophagus

essential nutrient

extracellular digestion

filter feeders

gallbladder

gastrovascular cavity

gizzard

heterotroph

ileum

incomplete digestive tract

ingestion

intracellular digestion

jejunum

large intestine

liver

malnutrition

microvilli

minerals nutrition obesity pancreas peptic ulcers peristalsis phagocytosis pharynx salivary glands small intestine sphincters stomach undernutrition vesicles villus vitamins

Bioenergetics

of an animal 1. Food

• Fuel • C-skeletons • essential

nutrients 2. ATP

• resting metabolism • activity • temperature

regulation

3. Excess for biosynthesis

4. 85-90% of energy from food is lost as heat

Do plants have

digestive systems?

Carnivorous plants with primitive digestive systems

Habitats with N-poor soils

Adaptation: occasionally feed on animals

Pitcher plant – Heliamphora nutans

Flypaper trap – Pinguicula gigantea

Sundew– Drosera capensis

Venus fly trap– Dionaea muscipula

Insect traps

Glands in trap secrete digestive

enzymes

Nutrients absorbed by

leaves

Evolution of digestion

Different types depending on diet and lifestyle

All must accomplish 1. Ingestion 2. Digestion

Mechanical breakdown Chemical breakdown

3. Absorption 4. Elimination

Digestion occurs in specialized compartments

Intracellular

digestion (evolved in single-celled protists, retained in simplest animals)

PROTISTS Paramecium

Intracellular digestion (Protists, Porifera)

SPONGES

Extracellular

digestion

FUNGI

• Sedentary heterotrophs living in or on food supply

• Saprotroph/parasites

• No internal cavity release digestive enzymes

Image from http://www.aber.ac.uk/fungi/graffeg/decomp/digestion-by-hypha.jpg

Image from http://www.anselm.edu/homepage/jpitocch/genbio/digesthydra.jpg

Extracellular and intracellular digestion Incomplete digestive system

CNIDARIANS Hydra

Extracellular and intracellular digestion Incomplete digestive system

PLATYHELMINTHES Planaria

Extracellular digestion Animals with complete digestive systems

NEMATODA to VERTEBRATES Earthworms

• 20 cm long with ~ 100 segments

– 1st – mouth

– Last – anus

• Eats its way through soil

Feeding adaptations for ingestion

Suspension-feeders

Deposit-feeders Substrate feeders

Fluid feeders Bulk feeders

Vertebrate dentition

Comparison of vertebrate digestive systems

Mammalian digestion General plan

ACCESSORY DIGESTIVE ORGANS

Organs of the GI tract

Comparison of mammalian digestive systems (Diet plays an important role in the length and structure)