Active transport.
Passive transport, being its opposite, requires no energy at all. Therefore, active transport would require energy or ATP in order to move across.
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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:
We have heard about Respiration. In human beings, respiration is a cellular activity which takes place in the presence of oxygen and in result produces carbon dioxide. Jamal model is a clear manifestation of that process. Medulla is the region of a brain that controls the respiration activity. When we breathe we take in oxygen and the excess amount of carbon dioxide is removed from out body.
Brains cells have capability to detect the carbon concentration in blood and add excess amount of carbon from body to the air.
