3.1 Nutrition

• Modes of feeding in insects
• Structure of insect mouthparts and their functions
• Types of beaks in birds and their functions
• Diversity in feeding modes
• Heterotrophic nutrition in animals
• Mammalian dentition and dental formulae
• The human digestive system
• Digestive enzymes and digestion along the gut
• Absorption, assimilation and egestion
• Ruminant and non-ruminant digestion
• Nutrition in Kenyan livestock

• relate the structure of mouthparts of insects to their functions
• illustrate mouthparts in different insects
• relate the structure of beaks of birds to their functions
• appreciate diversity in feeding modes of insects and birds
• describe modes of heterotrophic nutrition in animals
• relate the structure of mammalian teeth to diet
• work out and interpret dental formulae
• describe the regions of the human alimentary canal and their functions
• explain the action of digestive enzymes in each region of the gut
• relate villus structure to absorption
• compare ruminant and non-ruminant digestion
• apply knowledge of dentition and digestion to Kenyan livestock

“How can you tell what an animal eats by looking at its mouth?”

“Why can a cow live on grass when a human cannot?”

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1. Insect mouthparts
   40 min · 2 practice tasks · quiz
   Four ways of getting food into an insect, and why each looks as it does.
2. Beaks of birds
   40 min · 2 practice tasks · quiz
   Reading a bird's diet from the tool on the front of its head.
3. Heterotrophic nutrition in animals
   40 min · 1 practice tasks · quiz
   Animals cannot make food. They take it ready-made, and the five processes of holozoic nutrition are the same sequence from a grasshopper to a cow.
4. Structure of a mammalian tooth
   40 min · 1 practice tasks · quiz
   Birds have a beak. Mammals have teeth, and a tooth is a living organ with a hard working surface.
5. Dental formulae and diet
   40 min · 1 practice tasks · quiz
   A short code for the teeth in one half of the mouth tells you what the animal eats.
6. The human alimentary canal
   40 min · 1 practice tasks · quiz
   A nine-metre tube from mouth to anus, plus three organs that add secretions but never see the food.
7. Digestion in the mouth and stomach
   40 min · 1 practice tasks · quiz
   Starch meets amylase in the mouth. Protein meets acid and pepsin in the stomach. Each room has a pH, and the wrong pH stops the enzyme.
8. Enzymes in the gut
   40 min · 1 practice tasks · quiz
   Each digestive enzyme has one substrate, one product and one pH. Bile is not on the list.
9. The ileum and absorption
   40 min · 1 practice tasks · quiz
   Digestion is pointless unless the products can leave the tube. A villus is a surface-area machine.
10. Colon, assimilation and egestion
    40 min · 1 practice tasks · quiz
    Water is reclaimed in the colon. Cells then use what was absorbed. What was never absorbed leaves as faeces.
11. Ruminants and non-ruminants
    40 min · 1 practice tasks · quiz
    A cow lives on grass because bacteria in a four-chambered stomach digest cellulose. A pig cannot.
12. Nutrition in Kenyan livestock
    40 min · 1 practice tasks · quiz
    Dentition and gut type decide whether napier, browse, camel shrub or maize meal is a diet or a waste of money.