Adaptations to different diets

Adaptations to different diets

When reptiles and amphibians ingest their food they swallow it whole. Mammals retain their food in the mouth whilst they cut and chew it. They're the only vertebrates to have a palate separating their nasal and mouth cavities, so they can hold food in the mouth and chew whilst breathing.

• A carnivore eats only animals, its diet is mostly protein so its small intestine is short in relation to its body length, reflecting the ease with which protein is digested.
• A herbivore eats only plant material, its small intestine is long in relation to its bod length as plant material isn't readily digested and a long gut allows enough time for digestion and absorption of nutrients.
• The gut of an omnivore, such as a human, is intermediate in length.

The carnivore's large intestine is straight with a smooth lining. That of a herbivore or omnivore is pouched. It can stretch to accommodate the larger volume of faeces produced in digesting plants, much of which is cellulose. The large intestine is also long, with villi, where water is absorbed.

Dentition

As food must be cut, crushed, ground or sheared, according to diet mammals have evolved different types of teeth, specialised for different functions to suit the diet. Humans have four types of teeth, incisors, canines, premolars and molars. The teeth are less specialised than those of herbivores and carnivores because humans are omnivores.

Dentition of herbivores

Plant cell walls are tough to eat due to cellulose and lignin, and, in some plants, silica. The teeth of herbivores are modified so that the cells are thoroughly ground up before entering the stomach.

A grazing herbivore such as a cow or sheep, has incisors on the lower jaw only, and the canine teeth are indistinguishable from them in shape and size. The animal wraps its tongue around the grass and pulls it tight across the leathery 'dental pad' on its upper jaw then the lower incisors and canines slice through it.

• A gap called the diastema separates the front teeth from the side teeth, or premolars. The tongue and cheeks operate in this gap, moving the freshly cut grass to the large grinding surfaces of the cheek teeth, or molars.
• The molars interlock. The lower jaw moves from side to side and produces a circular grinding action in a horizontal plane. With time the grinding surfaces on the teeth become worn, exposing sharp-edged enamel ridges, which further increase the efficiency of grinding. The teeth have open, unrestricted roots so they continue to grow throughout the animals life, replacing material worn down by chewing.

A herbivore doesn't need strong muscles attached to its jaws as food isn't likely to escape. Its skull is relatively smooth, reflecting the absence of sites for strong muscles to attach.

Denition of carnivores

Carnivorous mammals such as dog, have teeth adapted for catching and killing prey, cutting or crushing bones and tearing meat:

• The sharp incisors grip and tear muscles from bone.
• The canine…