Excretion is the removal of waste products resulting from metabolic activities, essential for all organisms, utilizing specialized organs in multicellular species. In humans, the excretory system comprises kidneys, ureters, the urinary bladder, and urethra, and processes around 190 liters of blood to produce 0.9-2 liters of urine daily through filtration and reabsorption in nephrons. Different organisms exhibit various excretion modes, such as ammonotelism, ureotelism, and uricotelism, adapting their processes based on environmental conditions.

2. What is Excretion?
Excretion is the process by which the waste products
produced during metabolic activities is removed from
the body.
● In unicellular organisms,the waste products are
removed from the cells into the surroundings by
diffusion.
● In multicellular organisms,the waste products are
removed through specialised organs.
● Excretion takes place in all organisms.

3. ● The most important waste products are CO2,
nitrogen compounds,and salts.
● CO2-: produced during cellular respiration (in
addition to water)
● Nitrogen compounds-: (ammonia,urea and uric acid)
produced by the breakdown of amino acids (protein
digestion)
● Salts-: produced by metabolism

4. Why do we need to excrete ammonia?
● All organisms produced ammonia as they metabolise
nutrients(protein digestion)
● Ammonia is a nitrogenous waste that is toxic and must be
removed the body
● How an organism removes ammonia depends upon where
they live.

5. Mode of Excretion-:
● Ammonotelism-: The process of eliminating ammonia from the body is
known as ammonotelism, and the organisms which exhibit this nature
are called ammonotelic.
● Ureotelism-: In some mammals and amphibians, urea is excreted as
the metabolic waste products. Such organisms are called ureotelic.
● Uricotelism-: Uricotelic animals remove nitrogenous wastes as uric
acid in the form of pellets or paste.
● Aminotelism-:Certain molluscs and echinoderms excrete excess amino
acids. This feature is called aminotelism.
● Guanotelism-: Spiders convert the ammonia into guanine before
excretion.

6. Excretion in Human being
Excretory system consist of Pair of
kidney,pair of ureters,urinary
bladder,urethra.The process includes-:
Kidney:2 kidneys are located in the
abdomen,one on either side of
backbone.Left kidney is larger and higher
than right kidney.
1.Urine produced in the kidney passes
through the ureters into urinary bladder
where it is stored until it is released
through urethra.

7. 2. Internally a kidney is made of numerous
microscopic units called nephrons.
The function of kidney is filtration of blood
to excrete the waste products of
metabolism.The kidney filters about 190
litres of blood to produce 0.9-2 l of urine
daily.
3.Each nephron has cup shaped upper end
called Bowman’s Capsule.It contain bundles
of blood capillaries called glomerulus.The
Bowman’s capsule and glomerulus together
form globular body called renal corpuscle.

8. 4.The blood in the capillaries of glomerulus come from aorta by renal
arteries and after passing through glomerulus it returns to the
posterior vena cava via renal vein.The blood entering into glomerulus
carries waste material which are filtered out in the Bowman’s
capsule.
5.Filteration is possible because walls of glomerular capillaries and
Bowman’s capsule are very thin and selectively permeable.
Thus membrane allow only small molecules and water in the blood to
pass through them.
6.Once the waste is filtered out,the blood free from waste goes into
renal vein from where it goes into heart through posterior vena cava.

9. 7.The fluid containing waste material is forced out of
glomerular capillaries in the Bowman’s Capsule.The
filtered out fluid is called Glomerular Filtrate.
8.Bowman’s Capsule leads to a long tubular structure
before meeting collecting duct. During the flow of
glomerular filtrate in this long tube,reabsorption of
useful material take place.

10. 9.The fluid reaching the end of collecting duct is called
urine.
10.Finally the urine moves through ureter and collects in
the urinary bladder till thrown out of body.

11. Some amazing facts
● Reptiles and birds excrete their nitrogenous wastes as
uric acid in the form of a white paste. This allows
efficient water retention and it can be stored more easily
in the egg. Both uric acid and faeces are expelled through
a common opening called the cloaca. Their waste is usually
two-coloured: part white (uric acid) and part green or
black (organic waste)
In vertebrates and organisms:

12. ● Aquatic animals usually excrete ammonia directly into the
water, as this compound is soluble and there is ample water
available for dilution. In terrestrial animals ammonia-like
compounds are converted into other nitrogenous materials as
there is less water in the environment, and ammonia itself is
toxic.
● Many bird species, especially seabirds, can also excrete salt via
specialized nasal salt glands, the saline solution leaving through
nostrils in the beak.

13. The Mystery Behind Bird Poop
● Unlike mammals,birds do not urinate.
● Their kidneys extract nitrogenous waste from the
bloodstream,and excrete in the form of uric acid.
● Uric acid has a very low solubility in water,so it emerges as a
white paste.

14. 1.The average person pees about 3000 times a year.
2. Water forms 95% of the urine.
3. The biggest vein in your body is the one that leads to kidneys.
4. The average adult bladder can hold 16-24 ounces of urine.
5. A liver would be about 3 pounds in an average human.
6. The liver is rubbery to touch.

15. 7. One kidney (approximately) measures to about 4 inches.
8. The average person's lung measures about 12 inches.
9. An average person sheds from about 30000 to 40000 skin cells
every minute.
10. Kidney stones can be the size of a golf ball.
11. Most common symptom in kidney cancer is blood in the urine.
12. In the period of 24 hours, your blood has to pass through the
kidneys as many as 300 times!

16. 13.The human bladder is as big as an average human brain.
14. Urine contains urea which can make the plants and flowers
grow healthier.
16.The human bladder can stretch to hold about 400ml of urine.
17. Urine stays in the bladder for up to 5 hours before discharge
depending on the amount of liquid consumed if the urinary system
is healthy.
18. Nerves send signals to the brain when the bladder needs to be
emptied, with this indication you will feel the urge to empty your
bladder.

17. Thank you