Excretion
Excretion
Excretion cleans up after respiration.
Respiration is a chemical reaction that takes glucose (sugar) and oxygen to produce energy. But it also produces water and carbon dioxide as bi-products.
Excretion gets rid of carbon dioxide, water, and other, possibly harmful, substances from your body.
Your lungs excrete carbon dioxide as you breathe out, your kidneys filter out nasties to produce urine, removing nitrogen waste from your body, and your skin sheds excess salt through sweat.
The lungs excrete carbon dioxide
The kidneys filter out waste and toxic substances
The skin excretes salt through sweating
All vertebrate animals produce nitrogen waste in one form or another. The type of waste that is produced depends on where and how the animal lives.
Waste water
Kidneys filter waste and unwanted chemicals out of your blood to clean and purify it. Jerboas (pictured right) are desert animals that do not want to waste water by producing too much urine, so their kidneys have adapted to reabsorb a lot of water, giving them very concentrated urine.
Fact File
Name: Comb-toed jerboa
Group: Mammals
Country of origin: Kazakhstan
Excretes: Very concentrated urine - it lives in a dry environment so it is important for it not to lose water.
Diet: Seeds, plants and insects - they get all of their water from their food
Need to know: Jerboas have long back legs and can jump up to 3 metres in a single bound!
Birds do not want to carry around lots of water to make urine - it would make them too heavy to fly!
Instead, they make a dry paste called uric acid - you would know if you saw it. Uric acid is the white stuff you see in their droppings!
Remember, there is one type of waste product that is not excreted from the body: the poo!
That's right, although it is a part of the body's waste, it is not a bi-product of your metabolism like urine is - it is expelled from the body, not excreted!
