Jussi Lehtonen, Geoff A. Males and females are a fundamental aspect of human reproduction, yet procreation is perfectly possible without this division into two sexes. Biologically, males are defined as the sex that produces the smaller gametes e.
The external structures of the male reproductive system are the penis, the scrotum and the testicles. Penis — The penis is the male organ for sexual intercourse. It has three parts: the root, which attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the cone-shaped end of the penis.
Gametes are an organism's reproductive cells. They are also referred to as sex cells. Female gametes are called ova or egg cells, and male gametes are called sperm.
A Newcastle University study involving thousands of families is helping prospective parents work out whether they are likely to have sons or daughters. The work by Corry Gellatly, a research scientist at the university, has shown that men inherit a tendency to have more sons or more daughters from their parents. This means that a man with many brothers is more likely to have sons, while a man with many sisters is more likely to have daughters. The research involved a study of family trees containing information onpeople from North America and Europe going back to
We have already seen that, even in humans, there is more to this substance than meets the eye. It contains proteins that, when mixed together, can forge a mating plug. But this list of ingredients is just the tip of the iceberg.
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More about how the environment can affect sex ratios of children. The chances for a boy or a girl are a lot like the chances of getting heads. A female bluestreak cleaner wrasse can turn into a male when necessary.
People have sex for pleasure, reproduction, or both. Pregnancy happens when an egg and sperm successfully meet through intercourse or in vitro fertilization. What do they look like, and how many do we all have?
Cell Reproduction and Conception. Most human cells are frequently reproduced and replaced during the life of an individual. However, the process varies with the kind of cell.
Since the late s, scientists have explored how to produce sperm where all of the chromosomes come from a female donor. Creating female sperm was first raised as a possibility in a patent filed in  by injecting a woman's cells into a man's testicles, though the patent focused mostly on injecting altered male cells into a man's testes to correct genetic diseases. InJapanese scientists partially confirmed such techniques by creating chicken female sperm in a similar manner. It is therefore concluded that most of the W-bearing PGC could not differentiate into spermatozoa because of restricted spermatogenesis.