50.1
What Do Animals Require from Food?
1069
Energy can be measured in calories
1069
Energy budgets reveal how animals
use their resources 1070
Sources of energy can be stored in
the body 1071
Food provides carbon skeletons for
biosynthesis 1072
Animals need mineral elements for
a variety of functions 1073
Animals must obtain vitamins from
food 1073
Nutrient deficiencies result in diseases
1074
50.2
How Do Animals Ingest and Digest Food?
1075
The food of herbivores is often low
in energy and hard to digest 1075
Carnivores must detect, capture, and
kill prey 1075
Vertebrate species have distinctive
teeth 1076
Animals digest their food extracellularly
1076
Tubular guts have an opening at each
end 1077
Digestive enzymes break down complex
food molecules 1077
50.3
How Does the Vertebrate Gastrointestinal
System Function? 1078
The vertebrate gut consists of concentric
tissue layers 1078
Mechanical activity moves food through
the gut and aids digestion 1079
Chemical digestion begins in the mouth
and the stomach 1080
What causes stomach ulcers? 1081
The stomach gradually releases its
contents to the small intestine 1082
Most chemical digestion occurs in
the small intestine 1082
Nutrients are absorbed in the small
intestine 1083
Absorbed nutrients go to the liver
1084
Water and ions are absorbed in the
large intestine 1084
The problem with cellulose 1084
50.4 How Is the Flow of Nutrients
Controlled and Regulated? 1085
Hormones control many digestive functions
1086
The liver directs the traffic of the
molecules that fuel metabolism 1086
Regulating food intake is important
1087
50.5
How Do Animals Deal with Ingested
Toxins? 1089
The body cannot metabolize many synthetic
toxins 1089
Some toxins are retained and concentrated
1089
