Why do some plants lose their leaves in autumn?

To survive in the cold during winters, the deciduous trees shed their leaves. They live leafless for many months, thereby conserving water and avoiding frost damage. As the temperature begins to fall at the onset of autumn, the soil gets too cold for most broad based leaves to take up enough water. To avoid further loss of water by transpiration, the trees begin to shed their leaves. The trees begin to withdraw the chlorophyll before the leaves is shed, imparting various brilliant color to them depending upon the pigment left behind. Some evergreen trees like pine never lose their leaves even though they inhabit colder regions. They have thin, needle like leaves that have loss transpiration rate and, hence very low water loss.

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How Many Type of Keys on a Keyboard?

Friends you know a keyboard is the most important part of a computer. It consists of different sets of keys that help us to enter information into the computer. Today we will discuss about keyboard and its keys types and use. A standard keyboard has 104 keys. Types of Keys in a Keyboard: Alphabet Keys Number Keys Special Keys Function Keys Navigation Keys 1. Alphabet Keys: 26 alphabet keys are present on a keyboard from A to Z. these keys are not present in the alphabetical order. These keys are used to type words, sentences or paragraphs. 2. Number Keys: These keys are used for typing numbers. These keys are present above the top row of the alphabet keys and also present on the right side of the keyboard. 3. Special Keys: Keyboard has more special keys such as Space bar Key, caps lock key, backspace key, shift key, enter key, symbol keys and tab key etc. 4. Function Keys: 12 function keys are present on a keyb...

Advantage and Disadvantage of Computer Generations

All computer generations have some advantage and disadvantage today we explain some computer generation advantages and disadvantages. First Generation Computers (1946-1959) The computers produced during the period 1946-1959 with the them technology are regarded as the first generation computer. These computers were manufactured with the vacuum tubes. These tubes were used in the arithmetic and logical operations. Advantages: They were capable of making arithmetic and logical operations. They used the electronic values in place of the key punch machines or the unit record machines. Disadvantages: They were too big in size, very slow, low level of accuracy and reliability. They consumed lot of electricity, generated a lot of heat and break down frequently. Second Generation Computers (1959-1965) The computer produced during the period 1959-65 with technology is known as second generation computers. These comp...

What is Vacuum Tube

A vacuum tube is, reasonable enough, a sealed glass tube containing a vacuum in which are present several electronic elements: the cathode, anode, grid, and filament. When the cathode and anode are heated by the filament, and a voltage is applied across them, current flows between the cathode and anode. If a grid is inserted between them, the flow can be controlled by changing the grid between a positive and negative voltage. The grid voltage can be quite small, and the plate voltages can be quite high, thus providing an amplifying capability. More importantly for computers, switching the grid voltage causes the tube to act as a switch with respect to the plates. Thus, we have an electronically controlled switch that is much faster than a relay. A type of vacuum tube also served as a popular storage mechanism, the Cathode Ray Tube (CRT). Other memory devices used during the period include mercury or glass delay lines, and magnetic core memory. Vacuum tubes, however, are la...

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