herbivores, carnivores and omnivores

similarities between physical and chemical digestion

- both are two forms of digestion that occur in mammals
- both break down large pieces of food into smaller pieces that can be absorbed across the small intestine into the blood
- both occur in the mouth, stomach and the small intestine
- both are needed for effective digestion = together allow mammals to absorb the nutrients needed for key life processes

differences between physical and chemical digestion

both forms of digestion work differently:
- physical breakdown: mechanical breakdown
- chemical breakdown: digestive enzymes

different purposes:
- physical: increase surface area available for digestive enzymes
- chemical: break bonds holding the food molecules together so that they are small enough to be absorbed through the gut into the blood

amount of each digestion in a location:
- physical: majority occurs in the mouth
- chemical: majority occurs in the small intestine

process involved:
- physical: several patterns of mechanical breakdown eg. chewing, churning and peristalsis
- chemical: involves a series of chemical reactions using digestive enzymes

why do mammals need both physical and chemical digestion

- physical digestion breaks up large pieces of food which increases the surface area available for the digestive enzymes in chemical digestion
- this increases the efficiency of chemical digestion as it breaks this food down for absorption

overall:
- both physical and chemical digestion is needed for maximum nutrients to be obtained from the food that mammals eat

herbivore digestion

- tough plant material means that chewing is important so they have amylase enzymes in the mouth to start digesting starch
- have enzymes in the stomach, rumen or caecum to digest the cellulose that makes up the majority of their diet (cellulose-digesting enzymes)

carnivore digestion

- mainly meat-based diet = protein digestion is important
- chewing is less important so they don't have amylase in the mouth
- have strong acid in their stomachs so that pepsin work to digest the protein