Excretion

Excretion
Definition
The removal of harmful substance produce in the metabolic process from the body is called Excretion.
Excretion in Plant
In plant rate of catabolic process is very slow and waste product are produce in less amount. They are used again in their anabolic process.
Waste Substance of Plant
The substance which are produce in excess amount are

• Water
• CO2 and O2
• Ions

Removal of Water
Extra water is removed from the body of plant by two methods.
Transpiration
The extra amount of water removed in the form of vapor through stomata is called transpiration.
Guttation
When water is removed from plant in the form of drop this process is called Guttation. Guttation occur special opening called hydathods. Guttation take place in those plant which grow in tropical rain forest.
Release of Oxygen and Carbondioxide

• In day time plant used CO2 for photosynthesis process and released O2.
• In night time plant released CO2 and inhale O2 gas.

Ions
Excess amount of ion are deposit into dead cell of plant body such as bark.
Thermoregulation
The maintained the temperature of the body with in a range is called thermoregulation.
Thermoregulation in Plant
The normal range of temperature in plant is 10oC to 35oC. The adaption of plant to low and high temperature are as follows.
Low Temperature

• At low temperature the nature of plasma membrane is changed and produce crystalline structure due to which transport of solute is slow.
• To control this condition plant cell produce unsaturated.
• At freezing point ice crystal are formed in the cell. But the plant of cold region change the composition of solute of cell so ice crystal are not formed in cytoplasm they form in cell wall. This condition is known as freezing tolerance.

High Temperature

• High temperature has more harmful than low temperature for plant.
• Due to high temperature all enzyme are denature and metabolic process stop. So plant increase rate of transpiration and cool the body.
• At above 40oC plant produce heat shock protein. They protect the enzyme from destroying.
• In some plant shiny cuticle is present which protest them from high temperature.
• In some plant leaves are reduce in size.

Osmoregulation In Animal
Osmoregulation in Terrestial Animal
In land animals excretion of water take place through body surface so they have develop number of strategies to maintain Osmoregulation.
Water Proof External Covering Epidemics present in reptile, mammal cuticle present in insect which prevent the water loss from their body.
Storage and Excretion of Solid Wastes
In birds, reptile and insect store nitrogenous waste uric acid. Uric acid insoluble in water and help to reabsorption of water in cloeca. Uric acid excreted the body in the form of paste and crystal.
Use of Metabolic Water
Some mammal fat is converted into simple compound and during this process water is produce which is reused in the body. Camel, Kangroo used metabolic water.
Storage of Harmful Waste
In mammal urea in kidney which is helps in reabsorption of water.
Osmoregulation in Aquatic Animal
Osmoregulation in fresh water animal is maintained by two methods.
1. By Contractile Vacuole
2. By producing dilute urine
1. By Contractile Vacuole
Fresh water unicellular organism have contractile vacuoles. Water with dissolved CO2 and uric acid is collected from the endoplasm into the contractile vacuole, which increase in size up to a maximum and burst released the extra substance in environment. In Amoeba and Paramicium the amount of water and other substance remain in balanced by contractile vacuole.
2. By Producing Dilute Urine
Fresh water fishes have hypertonic body fluid as compare to surrounding water. Fisher released extra amount of water in the form of dilute urine and absorb some essential ion from outside to maintain the salt and water content in the body.
Osmoregulation in Marine Animal
Marine water fishes have hypotonic body fluid than surrounding because sea water have high concentration of salt so these fishes drink water continuously and the salt excreted out along with concentrated urine. They also excrete salt through gills.
Excretion in Animal
In animal removal of nitrogenous waste from the body is very essential. Animal have particular organ to excrete out nitrogenous waste.
Waste Substance of Animal
Animal produce different type of waste substance such as
1. Ammonia
2. Urea
3. Uric Acid
4. Creatinine
5. Hypozenthine
1. Ammonia

• It is a small molecule of gas. Its formula is NH3.
• It is highly soluble in water.
• It is very toxic compound
• It is dissolved in water and removes by simple diffusion method through skin or by urine.
• It is excretory substance of aquatic animal e.g. fishes.

2. Urea

• Urea is less soluble in water.
• Its formula is CO(NH2).
• Urea is very less toxic substance because its 1,00,000 time less toxic then NH3.
• Urea is produce as a result of metabolism in the liver from ammonia.

NH3 + CO2 ——> Citruline ——> Aginine ——> Urea

• This process required energy.
• Urea is the excretory product of mostly land animal like mammals.

3. Uric Acid

• Its formula is C5O3N4H4.
• It is not soluble in water.
• Uric Acid is less toxic than urea.
• Uric Acid released from the body in paste like substance or urete crystal.
• Urid Acid is the excretory product of insect, birds and reptile.

Excretion in Hydra
(Exetory Substance (NH3))
Hydra is a water living animal. In this body the excretory products are produced in the form of NH3. It is excreted out the gastrovascular cavity and then removed from the body along with water.
Excretion in Planaria
(Exetory Organs)
In planaria nitrogenous waste excrete out through skin and special excretory organ called flame call or protonephridia.
Structure of Excretory System and Functions
In the body of planaria there is a system of branch tube like bodies. There are two longitudinal excretory trunks one on either side of the body.
Nephredipores
They open to the out side by small pore called nephredipores.
Flame Cell
Internally these excretory trunk divide and redivide into number of small branches at the end of the branch special cell are present are called flame cell. The flame cells are club-shaped hollow cells. In their internal cavity many cilia are attached which perform movement just like flame of candle.
Functions
All the waste product of main branches absorb by flame cell because the movement of cilia of flame cell. When the excretory product come into the longitudinal excretory system they are removed out of the body through the nephrediopore.
Excretory Organs
The excretory system of earthworm consist of small, coiled tubes called Metanephredia. It is present in each segment.
Structure of Nephredium
Each Nephredium consist of three part.
1. Nephrostome
It is a rounded, ciliated funnel with the opening.
2. Bladder
Main body of nephridum consist of coiled tubular part and wide part called bladder.
3. Nephridiopore
The bladder opens outside by a small pore on the skin are called nephridiopore.
Excretion
As fluid moves along the tubule, epithelium reabsorbs the salt from lumen and send to blood vessels surrounding the nephridium. The left over appears as urine containing nitrogenous waste.
Excretion in Cockroach
Excretory Organs
Cockroach have special tube like excretory structure are called “Malphighian Tubules”. It is present between the mid gut and hind gut. It is embedded in the blood.
Excretion
Malphighian tubules absorb all nitrogenous waste from blood and pour them into illium. The latter part of tubules reabsorbs important substance. The uric acid when come into rectum, it also reabsorbs water and salt, so uric became almost dry then it is excreted out of the body.