Compare and contrast the events and results of oogenesis and spermatogenesis. What will be an ideal response?
ANSWER: In males, the production of sperm, known as spermatogenesis, occurs in the testes. Cells
called spermatogonia line the tubules of the testes and divide by mitosis from puberty until
death, producing daughter cells called spermatocytes. Spermatocytes undergo meiosis, and
the four haploid cells that result are called spermatids. Each spermatid develops into a mature
sperm. The tubules within the testes contain many spermatocytes, and large numbers of
sperm are always in production.
In females, the production of gametes is called oogenesis and takes place in the ovaries.
Cells in the ovary known as oogonia begin mitosis early in embryonic development and
finish a few weeks later. During meiosis I, one cell, destined to become the female gamete,
receives about 95% of the cytoplasm and is called a secondary oocyte. The larger cell
becomes the functional gamete (the ovum) and the nonfunctional, smaller cells are known as
a polar bodies. If the secondary oocyte is fertilized, meiosis II is completed quickly and the
haploid nuclei of the ovum and sperm fuse to produce a diploid zygote.
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The loss of O2 in the atmosphere 600-800 million years ago was likely due to the "fossilization" of organic matter
trapped in Earth's crust.
a. True b. False
What leaves the nucleus after transcription is complete?
Nitrogen fixation is an energy-yielding process.
Answer the following statement true (T) or false (F)
Why are lichens generally absent in cities?
A. They are sensitive to pollution. B. They need more light. C. They are sensitive to the high noise levels. D. They are aquatic organisms. E. They need other plants around them.