How Do Humans Reproduce?
The reproduction in human beings differs from other living things because we are complex organisms. Unlike bacteria, the simplest living things, our reproduction involves a male and female to mate. For bacteria, normally it is asexual, meaning there is no need for a male and female partner to mate. A single bacterium, which is single one celled organism, can divide into two new one celled organism. This process of cell division is called mitosis for most one celled organism or binary fission for prokaryotic cells.
As female and male human being mate, the egg of a female becomes fertilized by the sperm of the male. Although arthropods like grasshoppers also mate, the egg of a grasshopper contains a little yolk to support the egg cell when it develops after fertilization.
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Since the yolk is small, several germ cells contained in a single egg support the primary germ cell providing nourishment after fertilization. Human eggs do not have yolk, after fertilization the developing baby is nourish by the mother through the umbilical cord.
Another group of animals living in the water also differ from human egg. Unlike land dwelling animals, aquatic animals like fish have their eggs in water were the exchange of nutrients and waste is easy to achieve. Therefore some fish eggs do not have much yolk to support the embryo during development. Although unlike human egg, they normally have gelatinous materials that cover the egg and provide additional nourishment. To humans this is the reason why we have amniotic fluids to allow nutrients to enter our body and waste to come out.
Even our closest relatives, the bear which is a mammal, still differ from our reproduction. In female human beings, normally only one egg can be fertilized at one time. This is because only one egg is released by the ovary during the ovulation period. For bear one or more eggs can be fertilized at a time producing typically 4 to 5 cubs. When the human egg is fertilized it forms a zygote that undergoes a 9 month gestation period before coming out as a young baby. References Materials provided by student.