A cross section of a leaf shows that it is a complex organ built of several different kinds of specialized tissues. The tissues, in turn, are built of specialized cells, and the cells, of organelles. Epidermis covers the upper and lower surfaces of the leaf.
<span>By producing melanin (pigment), the skin protects the underlying structures from ultraviolet light's harmful rays while producing vitamin D, which works with calcium for multiple body processes.
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Vitamin D is produced by the skin when it is exposed to the sunlight. Ultraviolet B (UVB) is the part of the sun's rays that affects the skin to produce such vitamin.
<span>The primordial germ cell in the embryo undergoes mitosis to produce a spermatogonial stem cell.
The spermatogonial stem cell undergoes mitosis. The new cells could either be stem cells or spermatogonium cells.
The spermatogonium undergoes mitosis to generate a primary spermatocyte.
*** Up until this point, all cells are diploid ****
The primary spermatocyte (diploid) undergoes MEIOSIS I to generate TWO haploid secondary spermatocytes.
Each secondary spermatocyte undergoes MEIOSIS II to generate a total of FOUR early spermatid.
The spermatid mature in the seminiferous tubule, and once they are completely mature they are released into the lumen.
Now called sperm cells, they pass into the epididymis, where they are stored until time to be released during ejaculation
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The highest between 25 and 50;the lowest between 55 and 74
Hi lovely,
The answer you're looking for would be the activation or inactivation of genes.
