VMBO Year 2 · HAVO/VWO Years 2–3 · Nutrition and digestion · Section 2.6

Feeding and digestion in mammals

Plants, animals or both

Mammals can be grouped by their usual diet: herbivores eat plant material, carnivores mainly eat other animals, and omnivores eat both. Their teeth and digestive systems show adaptations to their food.

Plant material contains cell walls made partly of cellulose, which mammals cannot digest using their own enzymes. Microorganisms help many herbivores break it down. Animal tissues lack cellulose cell walls and are generally easier to process in this respect.

Herbivores

Herbivores often have a long digestive tract relative to body length, providing time and space for microbial fermentation. A cow's tract can be described in school comparisons as roughly 25 times its body length, depending on how length is measured.

Many have ridged grinding teeth, with hard enamel ridges that help crush plant material during chewing. Their canines may be absent or reduced.

Carnivores

Carnivores generally have a shorter digestive tract because they do not rely on extensive cellulose fermentation. A dog's tract is often given as about 5.5 times its body length in school comparisons, though measurements vary.

Carnassial teeth have sharp surfaces that pass one another like scissor blades and cut meat. Large, pointed canines help grip prey, tear flesh and defend the animal.

Omnivores

Omnivores, including pigs and humans, often have a digestive tract of intermediate relative length and rounded-cusp teeth suited to crushing and grinding varied foods.

Canines vary between species: some are large and sharp, while human canines are closer in size to the incisors. Humans also use tools and cooking to cut food and make many foods easier to digest.