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Cell Theory
The invention of the compound microscope in the 17th century stimulated the interest in living things not visible to the naked eyes. Thus, Robert Hooke discovered 'cells' in 1665 by examining cork slices (,under a crude microscope. He was actually describing the spaces occupied by the cells limited by the cellulose walls. Hooke and his contemporaries also described cells from other plants and animals.
Figure: A generalized plant (a) and animal (b) cell. No one cell of either plant (a) or animal (b) has all the characteristics shorn in these composite figures. Both these are
However, cell theory, one of the greatest and most basic generalizations of biology, was formulated only about 200 years later. Two German investigators, Schleiden a botanist (1838), and Schwann, a zoologist (1839) are credited with presenting independently the first concise, yet comprehensive, statements about the cell. They pointed out that, "All plants and. animals are made up of small fundamental units called cells and that some organisms are unicellular and others, multicellular." Subsequent researched to the expansion of this concept by including further information on cells. We know that cells are surrounded by cell membrane and contain cytoplasm and nucleus and, most importantly, cells divide into roughly equal daughter cells by a process called cell division. Thus it became known that new cells come into existence only by the division of previously existing cells. In other words, cells do not arise by spontaneous generation from nonliving matter. It follows that all cells living today can trace their ancestry back to those which existed in ancient times.
Gum Tragacanth Gum tragacanth, the exudation of Astragalus species, is defined as the "dried gummy exudate" obtained from Astragalus gummifer Labillardiere. Gum tragacanth is
Q. Percentage ratio of ash in honey? Standards allow ash content in honey up to 0.5 per cent, but the ash of genuine honey seldom exceeds 0.35 per cent. It is determined by cha
Xerarch - Kinds of Succession When the succession takes place in drier area, i.e., the succession progresses from xeric to mesic conditions. It is further subdivided as:
Why do plants need to exchange gases with the environment? Plants require to do gas exchange because they create aerobic cellular respiration (like animals) and they need to ge
living organisms and their excretory products
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Q. What are the major events of the second mitotic period? The second mitotic period is the metaphase. In metaphase the following events occur condensed chromosomes bind in the
Briefly explain about Pickled vegetables These are produced by spontaneous lactic acid fermentation. Fermentation improves the digestibility and wholesomeness of the product.
Segments of Environment: The environment is not a simple distribution of gases but is highly complex and structured. It comprises of four segments: Lithosphere
Define Historical example of Ecosystems Science? Mathematical and statistical tools are central to enhancing our understanding of large-scale systems and contain, for instance,
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