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Kritika Trehan 8 years, 1 month ago
An erect image, in optics, is one that appears right-side up. An erect image is formed by the actual intersection of rays. It is an image in which directions are the same as those in the object, in contrast to an inverted image.
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Kritika Trehan 8 years, 1 month ago
A cell is a single electrolyte and anode/cathode chemical reaction cell. It has a characteristic voltage which is set by the chemistry.
A battery is generally a stack of series-connected cells, although typically a single celled battery is also called a battery. The voltage of a battery is the number of cells times the characteristic cell voltage.
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Kritika Trehan 8 years, 1 month ago
Breathing is brought about by inhalation and exhalation.
Mechanism of breathing in humans:
Air passes through the tiny hair in the nasal cavity. It enters pharynx and passes through larynx and windpipe before reaching the lungs. Lungs are situated inside the chest cavity and they rest on a large muscular sheet called the diaphragm. Diaphragm forms the floor of the chest cavity. The diaphragm plays an important role in inhalation and exhalation. Movement of diaphragm is brought about by special musculature.
*During inhalation, the rib cage moves outwards and the diaphragm contracts to move downwards. As the rib cage expands, the space in the chest cavity increases allowing air rich in oxygen enter the lungs.
*During exhalation, the ribs move inwards and the diaphragm relaxes to return to its normal position. The contraction of rib cage reduces the size of the chest cavity. Now air rich in carbon dioxide is driven out of the lungs.
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Kritika Trehan 8 years, 1 month ago
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Difference Between Cross Pollination and Self Pollination |
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|
Cross Pollination |
Self Pollination |
| Transfer pollen grains from a flower to stigma of another flower of different or same species | Transfer pollen grains from another to the stigma of same flower |
| The process take place in several plants like tulips, grapes, plums, apples, pears, strawberries, daffodils, raspberries and others. While, by wind for different grasses, maples trees, dandelions, catkins, and others. | The self pollination can be seen in legumes like sunflowers, orchids, peanuts, oats, peas, potatoes, wheat, peaches, and more. |
| Transferred through insects, wind, water, animals, etc. | Transfer directly onto stigma. |
| Transfers large number of pollen grains. | Transfers small number of pollen grains. |
| Allogamy is a type of reproduction. | Autogamy and Geitonogamy are types of reproduction. |
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| Self-Pollination | Cross-Pollination |
| Transfer pollen grains from the anther to the stigma of the same flower. | Transfer pollen grains from the anther to the stigma of a different flower. |
| This process can take place in the same flower or a different flower of the same plant. | This process can take place between two flowers present on different plants. |
| It occurs in the flowers which are genetically identical. | It occurs between flowers which are genetically different. |
| Few species that exhibit self-pollination – Paphiopedilum parishii, Arabidopsis thaliana | Few species that exhibit cross-pollination – apples, daffodils, pumpkins and grasses |
| Causes homogenous conditions in progenies. | Causes heterozygous condition in progenies. |
| Self-pollination increases genetic uniformity and decreases genetic variation. | Cross-pollination decreases genetic uniformity and increases genetic variation. |
| Causes inbreeding. | Causes outbreeding. |
| Reduces the gene pool. | Maintains the gene pool. |
| Produces limited amounts of pollen grains. | Produces large amounts of pollen grains. |
| In self-pollination, both the stigma and anther simultaneously mature | In cross-pollination, both the stigma and anther mature at different times. |
| Transfers a limited number of pollens. | Transfers large numbers of pollen. |
| This process is carried out even when the flowers are closed. | For cross-pollination to happen, the flower should be open. |
| No need for pollinators to transfer pollen grains. | Require pollinators to transfer pollen grains. |
| Pollen grains are transferred directly to a flower’s stigma. | Pollen grains are carried via wind, insects, animals, water, etc. |
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Krishna Pali 8 years, 1 month ago
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Galvanization (or galvanizing as it is most commonly called in that industry) is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dipgalvanizing, in which parts are submerged in a bath of molten zinc.
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Kritika Trehan 8 years, 1 month ago
Pistil, the female reproductive part of a flower. The pistil, centrally located, typically consists of a swollen base, the ovary, which contains the potential seeds, or ovules; a stalk, or style, arising from the ovary; and a pollen-receptive tip, the stigma, variously shaped and often sticky.
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Jaideep Karwasra 8 years, 1 month ago
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