The size of the gastrointestinal tract may vary under different circumstances. F

Question

The size of the gastrointestinal tract may vary under different circumstances. For instance, small birds and mammals lengthen their intestinal tract during winter seasons and shorten them during summer. Similarly, pythons increase the GI tract after a meal and between meals the gut atrophies. Similarly, children with protein deficiency have small guts than those eating normally. In each of these cases explain why the gut size varies. What are the benefits and consequences of these changes? Why might natural selection favor plastic rather than static gastrointestinal morphology? What digestive specializations would you anticipate given the strictly vegetarian diet.

Explanation / Answer

Plants are a primary pure and good source of nutrients, however they aren't digested very easily and therefore herbivores have to eat large quantities of food to obtain all they require. Herbivores like cows, horses and rabbits typically spend much of their day feeding. To give the micro-organisms access to the cellulose molecules, the plant cell walls need to be broken down. This is why herbivores have teeth that are adapted to crush and grind. Their guts also tend to be lengthy and the food takes a long time to pass through it.

The guts of carnivores are usually shorter and less complex than those of herbivores because meat is easier to digest than plant material. Carnivores usually have teeth that are specialised for dealing with flesh, gristle and bone. They have sleek bodies, strong, sharp claws and keen senses of smell, hearing and sight. They are also often cunning, alert and have an aggressive nature.

Similarly small birds and mammals lengthen their GI tract during winter as winter offers much food to the animals in comparison to the summer.Also pythons have flexible GI tracts as they can accomodate preys which are sometimes more than its own size.Hence these increase their GI tracts in order to accomodate larger preys and decrase their GI tracts when there is no prey available.

The extreme lack of protein causes an osmotic imbalance in the gastro-intestinal system causing swelling of the gut diagnosed as an edema or retention of water.

Strictly vegetarian diet ensures the GI tract to be long and complicated as cellulos digestion needs longer time when compared to non veg diets.

Natural selection favours plastic rather than static gastrointestinal morphologyas there are diffrent animals and they have diffrent niches depending upon different resources.Thus digestion also varies from one animal to the other and accordingly the whole of gut has evolved into different features in diffrent animals to accomodate all the changes in their eating habits.If this was static then the survival of all those different animals would have been very difficult.

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