51.2 How Do Animals Ingest and Digest Food?

1
51.2 How Do Animals Ingest and Digest Food?

• Heterotrophs acquire nutrition in different ways
• Saprobes absorb nutrients from dead organic
  matter (e.g., protists and fungi).
• Detritivores or decomposers actively feed on dead
  organic matter.
• Predators feed on living organisms.

2
51.2 How Do Animals Ingest and Digest Food?

• Herbivores prey on plants.
• Carnivores prey on animals.
• Omnivores prey on plants and animals.
• Filter feeders filter small organisms from an
  aquatic environment.
• Fluid feeders include mosquitoes, leeches,
  aphids, hummingbirds.

3
51.2 How Do Animals Ingest and Digest Food?

• The food of herbivores is low in energy and hard
  to digest.
• So they must spend a lot of time feeding and
  processing their food.
• Many have specialized adaptations such as the
  elephants trunk, a long neck, teeth for
  grinding, and specialized digestive enzymes and
  processes.

4
51.2 How Do Animals Ingest and Digest Food?

• Carnivores have specialized adaptations for
  detecting, killing, and ingesting prey
• Bats use echolocation to locate prey pit vipers
  use infrared radiation.
• Prey capturespider webs, snake venom, etc.

5
51.2 How Do Animals Ingest and Digest Food?

• Digestion begins with the teeth.
• Mammalian teeth
• Enamel, composed of calcium phosphate covers the
  crown
• Dentine, (bony material) in the crown and root
• Pulp cavity, contains blood vessels, nerves, and
  dentine-producing cells

6
Figure 51.6 Mammalian Teeth (Part 1)
7
51.2 How Do Animals Ingest and Digest Food?

• Shapes and organization of teeth are adaptations
  to different diets
• Incisorsused for cutting, chopping, or gnawing
• Caninesfor stabbing, gripping, or ripping
• Molars and premolarsshearing, crushing, or
  grinding

8
Figure 51.6 Mammalian Teeth (Part 2)
9
51.2 How Do Animals Ingest and Digest Food?

• Digestion usually begins in a body cavity.
• Gastrovascular cavities connect to the outside
  through a single openingjellyfish and other
  cnidarians.
• Tubular guts have an opening at each end. A mouth
  takes in food, and wastes are eliminated through
  the anus.

10
Figure 51.7 Compartments for Digestion and
Absorption (Part 1)
11
51.2 How Do Animals Ingest and Digest Food?

• Food is broken up in the mouth cavity by teeth,
  radula (snails), or mandibles (arthropods).
• Most birds have gizzards with small stones for
  grinding food.
• Stomachs and crops are storage chambers that
  allow for gradual digestion.

12
Figure 51.7 Compartments for Digestion and
Absorption (Part 2)
13
Figure 51.7 Compartments for Digestion and
Absorption (Part 3)
14
51.2 How Do Animals Ingest and Digest Food?

• Food particles move from the stomach into the
  intestines.
• Most digestion occurs in the intestine
  nutrients, water, and ions are absorbed across
  its walls.
• The last segment recovers ions and water and
  stores undigested waste as feces.
• A muscular rectum expels feces.

15
51.2 How Do Animals Ingest and Digest Food?

• Endosymbiotic bacteria colonize the intestines.
  They obtain nutrition from the food passing
  through and contribute to the hosts digestion.
• Microorganisms in the human gut are the
  forgotten organ. They aid digestion, prevent
  harmful microbes from establishing, and produce
  vitamins K and biotin.

16
51.2 How Do Animals Ingest and Digest Food?

• Surface area is increased in the parts of the gut
  that absorb nutrients.
• The earthworm gut has an infolding of the gut
  wall, or typhlosole.
• Sharks have a spiral valvewalls of the spiral
  have a large surface area.

17
Figure 51.8 Intestinal Surface Area and Nutrient
Absorption
18
51.2 How Do Animals Ingest and Digest Food?

• In humans, the gut wall has folds with
  finger-like projections called villi.
• Surface cells of villi have smaller projections
  called microvilli.
• The microvilli give the intestine an enormous
  surface area for absorbing nutrients.

19
Figure 51.8 Intestinal Surface Area and Nutrient
Absorption
20
51.2 How Do Animals Ingest and Digest Food?

• Macromolecules are broken down by hydrolytic
  enzymes they cleave bonds by hydrolysis.
• They are classified according to the substance
  they hydrolyze proteases, carbohydrases,
  peptidases, lipases, nucleases.

21
51.2 How Do Animals Ingest and Digest Food?

• Digestive enzymes are produced in an inactive
  forma zymogen.
• A zymogen cannot act on the cells that produce
  it.
• In the gut, a zymogen is activated by another
  enzyme.
• Cells lining the gut are protected from enzymes
  by mucus.

22
Figure 51.9 The Human Digestive System