The randomness in the alignment of recombined chromosomes at the metaphase plate, coupled with the crossing over events between nonsister chromatids, are responsible for much of the genetic variation in the offspring. To clarify this further, remember that the homologous chromosomes of a sexually reproducing organism are originally inherited as two separate sets, one from each parent. Using humans as an example, one set of 23 chromosomes is present in the egg donated by the mother. The father provides the other set of 23 chromosomes in the sperm that fertilizes the egg. Every cell of the multicellular offspring has copies of the original two sets of homologous chromosomes. In prophase I of meiosis, the homologous chromosomes form the tetrads. In metaphase I, these pairs line up at the midway point between the two poles of the cell to form the metaphase plate. Because there is an equal chance that a microtubule fiber will encounter a maternally or paternally inherited chromosome, the arrangement of the tetrads at the metaphase plate is random. Thus, any maternally inherited chromosome may face either pole. Likewise, any paternally inherited chromosome may also face either pole. The orientation of each tetrad is independent of the orientation of the other 22 tetrads.
Explanation:
Compound microscope
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Further explanation</h3>
In 1665, Robert Hooke used a compound microscope to observe cells. Hooke observes the cell walls of dead plants (in the form of cork) when they appear under a microscope. He named it the cell because it looked similar to a cellula or small room inhabited by monks.
Development of microscopy:
- 1590: Hans and Zacharias Janssen, as Dutch lens grinders, mounted two lenses in a tube to produce the first compound microscope.
- 1660: Robert Hooke published <em>Micrographia</em>, containing detailed observations of biological materials made with the best compound microscope.
- 1676: Anton van Leeuwenhoek was the first person to observe a live cell under a microscope, i.e., the algae Spirogyra.
- 1931: Ernst Ruska constructed the first electron microscope. With the invention of the electron microscope, many infectious agents smaller than bacteria could be seen.
Until now, we can see how important the use of microscopes, especially in microbiology, that is the study of microorganisms.
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Keywords: compound microscope, Robert Hooke, cells first observed, cork, dead plant, walls, Anton van Leeuwenhoek
As the human population increases, stressors are being placed on the environment. <u>Decreases in availability of </u><u>natural resources</u> is one consequence of this growth.
Population- A population is the total number all organisms belonging to the identical species that really are present in a given location at the same time and have the potential to interbreed. Individuals need to be able which can mate with other members of a population and give birth to viable children for interbreeding to take place.
Natural Resources- Without human assistance, natural resources are present on planet. We can get water, wood, food, and energy from natural resources. Without natural resources, life is not conceivable. Oil, coal, natural gas, metals, stone, and sand are examples of natural resources.
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Maxine miles runs a marathon in 2 hours and 40 minutes. Most of the ATP for this activity is supplied by AEROBIC glucose breakdown. ATP is the energy coin of the cell.
Cellular respiration refers to the metabolic processes by which aerobic cells produce ATP by using the energy stored in the chemical bonds of foods (e.g., glucose) and oxygen.
Muscle cells can produce ATP by both cellular respiration (aerobic conditions) and acid lactic fermentation (anaerobic conditions).
Acid lactic fermentation is a less efficient pathway than cellular respiration, but cellular respiration is slower than fermentation, thereby muscle cells use this pathway (acid lactic fermentation) when there is not enough oxygen in the body.
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