Common Carp

The Common carp (Cyprinus carpio) is a widespread freshwater fish. Common carps are native to Asia and Eastern Europe. It was introduced to Sri Lanka in 1957.

It has been introduced into environments worldwide, and is often considered an invasive species. Common carp has dorsal and pelvic fins. Only one dorsal fin. Spines absent on fins. Barbels present attached to upper jaw. Single lateral line.

Common carp can grow to a maximum length of 75cm, a maximum weight of 6 kg. Although they are very tolerant of most conditions, common carp prefer large bodies of slow or standing water. A schooling fish, they prefer to be in groups of 5 or more. They natively live in a temperate climate in fresh or brackish water with a 7.0 - 7.5 pH. Ideal temperature range of 3 - 24 °C.

The common carps are omnivorous. The common carp is happy to eat a vegetarian diet of water plants, but will also consume insects, crustaceans, zooplanktons, and even dead fish if the opportunity arises. 
A typical adult fish can lay 300,000 eggs at a time.

2012-05-28 20:16:15

What is Water potential ?????

Water Potential
Movement of water from one location to another is due to water potential (ψw). The movement of water is driven by solute concentration and pressure gradient.

Water potential is expressed in pressure units, such as “Pascal” (Pa) or “Newton per m2” (Nm-2). Pure water has the highest water potential and by convention this is set to zero. Water always moves from region of higher ψw to one lower ψw. Two major factors affect the water potential of plants cells, osmotic potential (solute potential) ψs and pressure potential ψp

Osmotic / Solute Potential ψs
Solute potential is defined as the measure of the change in water potential of a system due to the presence of solute molecules. Plant cells have large central vacuoles with lot of dissolved materials. These dissolved materials contribute to the solute potential of the cell. When the dissolved content increase solute potential of the cell sap decreases (decreases of water potential), water tend to enter in to cells. Solute potential is always a negative value.

Pressure Potential ψp
When pressure is increased, it forces water to move from high pressure region to low pressure region. When water enters living cells by osmosis it make cells turgid and build up a pressure potential. This pressure potential will remove water from cells and prevent further entry of water. Therefore, increase of ψp increase the loss of water.

Water potential of a cell ψw
Water potential of a cell can present by following equation. ψw = ψs + ψp Students should note that the components of water potential defined in the text are sometimes given different names and symbols. In particular, the equation ψw = ψs+ ψp is often replaced by the following equivalent equation:

ψw = - π + P
In this alternative equation, P

 is the same as ψp. The symbol π

 is called “osmotic pressure” and is the negative of osmotic potential ψs. π has positive values, and ψs has negative values.

Most handbooks of physics and chemistry use the term "osmotic pressure" and the symbol π . The negative sign in front of π in the equation above accounts for the reduction in water potential (ψw) by dissolved solutes. Thus ψs = – π .

Unfortunately, some authors have mixed the conventions for ψs and π, leading to unnecessary confusion about what is meant by the symbol ψs . This confusion can be seen in some of the G.C.E. A/L marking schemes too.

Thus, ψs is sometimes incorrectly called osmotic pressure instead of osmotic potential, and it may be used as a positive quantity.

2012-05-28 20:15:46


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