Why do living things produce waste?

Answer 1

Not everything in food can be used or digested by an animal in the time it remains in the digestive tract, and often a food might contain more nutrients than an animal's body can absorb and store during the time it is in the digestive track. The body also excretes waste to flush out toxins and by-products that the body produces during the digestion process.

Urine contains excess salt, excess sugar, dead blood cells, DNA, waste compounds produced by cellular metabolism, excess vitamins and minerals, excess water, and excess hormones.

Feces contains undigested solids and fats, DNA, bacteria, pathogens, and the remains of the digested food that the stomach and intestines have drained all the nutrients from.

Here are a few few examples of ways animals get the most out of their food and get rid of the rest:

- Owls will actually cough-up a pellet that looks like a small butterfly cocoon, when pulled apart it can be found to contain small bones, fur, and teeth that were difficult for the owl's stomach to breakdown and digest. Household cats also cough up fur balls, the result of hair they ingest during tongue bathing that simply can not be digested.

- Vitamins often contain more of minerals and vitamins than an animal or human needs or can use, excess is filtered out by the kidneys and excreted in the urine. There are exceptions however to the bodies ability to filter substance quickly, to much Vitamin A can turn a person's skin a slight orange hue, and children have become poisoned by highly toxic levels of iron after consuming large amounts (ie. full bottles) of flavored, chewable children's vitamins all at once.

- Large herbivores, such as cattle, camels, and llamas, actually give their food a little extra help after eating it. They will regurgetate already eaten food in the stomach, a substance called cud, and rechew and swallow it numerous times to give their body a better chance of digesting and absorbing everything in the low nutritional value grass or grain.

- Snakes have a very llllooonnnnggg and slow digestive track, this allows them to absorb more from their food and goes week, months, and in the case of some giant snakes, like the Anaconda, as long as a year between meals.