1. Lecture 4. Digestion and Nutrition
Major Nutritional Modes
Mode of Nutrition Energy Carbon Source Examples
Source
Autotrophs
Photoautotrophs Light CO2 Photosynthetic prokaryotes,
including cyanobacteria; plants;
certain protists
Chemoautotrophs Inorganic CO2 Certain prokaryotes (i.e.
chemicals Sulfolobus)
Heterotrophs
Photoheterotroph Light Organic Certain prokaryotes
compounds
Chemoheterotrophs Organic Organic Many prokaryotes and protists;
compounds compounds fungi; animals; parasitic plants

2. Dietary categories
1. Herbivores

3. Dietary categories
2. Carnivores

4. Dietary categories
3. Omnivores

5. Dietary categories
4. Saprophagous
deer fly (Chrysops callidus)
Woodlice (Trachelipus ratzeburgii)
hermit beetle (Osmoderma eremita) red ant (Formica pallidefulva )

6. Feeding Adaptations
Suspension feeder – sifts through food particles in the water
Baleen whale
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7. •
bivalve molluscs use
their gills as feeding
devices

8. •
herring and other suspension-feeding fishes use gill rakers
to strain plankton

9. krill
•
whalebone whales filter out plankton, mainly large
crustaceans called krill, with whalebone or baleen

10. Feeding Adaptations
Deposit feeder – eats its way through dirt or sediments
and extract partially decayed organic material (detritus)
consumed along with the soil or sediments
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11. Feeding Adaptations
Substrate feeder – lives in or on its food source,
eating its way through the food
Leaf miners
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12. Feeding Adaptations
Fluid feeder – sucks nutrient-rich fluids from a living
host and is considered a parasite
Mosquito
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13. Feeding Adaptations
Bulk feeder – eats relatively large pieces of food
Python
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14. Cephalopod
molluscs have
beak-like jaws
which serve as
tearing devices

15. •
chewing mouthparts
adapted for seizing
and crushing food
•
mandibles are strong,
toothed plates whose
edges can bite or tear
•
maxillae hold the
food and pass it
toward the mouth

16. •
birds lack teeth
•
bills are often
provided with
serrated edges
•
In some, the upper
bill is hooked for
seizing and tearing
prey

17. Four types of teeth found in mammals:
•
incisors, for biting, cutting, and stripping
•
canines, for seizing, piercing, and tearing
•
premolars, for grinding and crushing
•
molars, for grinding and crushing

18. •
an elephant’s tusk is a
modified upper incisor
•
used for defense,
attack, and rooting
•
a male wild boar has
modified canines that
are used as weapons

20. Types of Digestive System
•
Incomplete – there is only one opening; no anus
Paramecium Hydra

21. Types of Digestive System
•
Complete – there is a mouth opening and an anus

22. Four Main Stages of Food Processing
•
Ingestion – the act of eating
•
Digestion – breaking food down into molecules
small enough for the body to absorb
•
Absorption – small molecules are taken in
by the animal’s cells
•
Elimination – undigested material passes out of
the digestive compartment

23. •
digestion is entirely intracellular in
protozoa and sponges

24. •
radiates, turbellarian flatworms,
and ribbon worms (nemerteans)
practice both intracellular and
extracellular digestion
•
in extracellular digestion, certain
cells lining the lumen of alimentary
canals form digestive secretions;
other cells function in absorption
•
for arthropods and vertebrates
digestion is almost entirely
extracellular

25. Gut movement
•
alternate constriction of
rings of smooth muscle of
the intestine
•
constantly divide and
squeeze contents back
and forth
•
for mixing of food
•
waves of contraction of
circular muscle behind
the gut and relaxation in
front of bolus
•
sweeps food down the
gut

27. Human Digestive
System Salivary glands

28. Human Esophagus
Food is called bolus if it passes
•
through the esophagus

29. Human Stomach

30. Food is called
•
chyme after it
passes through the
stomach

31. •
trypsin, chymotrypsin, and carboxypeptidase
are secreted in inactive form by the pancreas
–
the intestinal enzyme,
enteropeptidase, converts
inactive trypsinogen into
active trypsin
–
active trypsin then
activates the other two

32. Human Small Intestine
•
Made up of three regions:
1. duodenum
- Nearest to the stomach; 26 cm in length
- With Bruner’s glands
-
produce mucus-rich alkaline secretion with
bicarbonates to
-
protect the duodenum from the acidic content
of chyme;
-
provide alkaline condition for the intestinal
enzymes to be active; and
-
lubricate the intestinal walls

33. Human Small Intestine
•
Made up of three regions:
2. jejunum
- Next to duodenum; 2.5 m in length
3. ileum
- Last segment of the small intestine; 3.5 m in length
- Contains Peyer’s patches
-
Organized lymphoid tissues
-
Protects the intestinal lumen from pathogenic
bacteria

35. •
Food is called chyle once it is in the small intestine

36. Human Large Intestine
•
the colon recovers water that has entered the alimentary canal
as the solvent to various digestive juices
•
the large intestine harbors a rich flora of mostly harmless
bacteria
•
the terminal portion of the colon is called the rectum, where
feces are stored until they can be eliminated

40. Regulation of Digestion
CCK - cholecystokinin

41. •
the length of the vertebrate digestive system is
also correlated with diet

42. •
ruminants (deer, cattle, and sheep) have the
most elaborate adaptations for a herbivorous
diet

43. Nutritional Requirements
•
A nutritionally adequate diet satisfies three
needs:
–
fuel (chemical energy) for all the cellular work of the
body
–
organic raw materials animals use in biosynthesis
(carbon skeletons to make many of their own
molecules)
–
essential nutrients

44. –
If the diet of a person or other animal is chronically
deficient in calories, undernourishment results
–
an animal whose diet is missing one or more
essential nutrients is said to be malnourished
–
marasmus, general undernourishment from a diet
low in both calories and protein
–
kwashiorkor, protein malnourishment from a diet
adequate in calories but deficient in protein
–
overnourishment or obesity results from excessive
food intake

45. •
in mammals, a hormone called leptin,
produced by adipose cells, is a key player in a
complex feedback mechanism regulating fat
storage and use

46. Appetite-regulating hormones
•
ghrelin (stomach wall)
–
triggers feelings of hunger as mealtimes approach
•
leptin (adipose tissue)
–
suppresses appetite
•
PYY or peptide-tyrosine-tyrosine (small intestine)
–
after meals
–
appetite suppressant; counters ghrelin
•
insulin (pancreas)
–
a rise in blood sugar level after a meal

47. •
animals require 20 amino acids to make proteins
•
essential amino acids must be obtained from
food in prefabricated form
–
eight amino acids are essential in the adult human
(phenylalanine, lysine, isoleucine, leucine, valine,
methionine, tryptophan, and threonine) with
histidine and arginine essential for normal growth of
children

48. •
protein deficiency from a vegetarian diet can
be avoided by eating a combination of plant
foods that complement each other to supply all
essential amino acids

49. •
vitamins are organic molecules required in the
diet in small quantities
•
13 vitamins essential to humans have been
identified
•
water-soluble vitamins generally function as
co-enzymes

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51. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

52. •
Minerals are simple inorganic nutrients, usually
required in small amounts
–
humans and other vertebrates require large
quantities of calcium and phosphorus for the
construction and maintenance of bone
–
iron is a component of the cytochromes and of
hemoglobin
–
while sodium, potassium, and chloride have a
major influence on the osmotic balance between
cells and the interstitial fluids, excess consumption
of salt (sodium chloride) is harmful