The sexual reproduction is a source of genetic variations
The sexual reproduction
The sexual reproduction is a process by which the living organism produces the individuals with the traits differ from the parents , It occurs through two parental individuals , One is the male and the other is a female , It occurs in most higher living organisms of the plants and the animals .
The gametes formation , The gametes of male and female are formed in the reproductive cells by the meiotic division , And they contain half the chromosomes number ( N ) of the organism’s reproductive cells ( 2 N ) .
The zygote contains the genetic material from both the parents , and when it grows , it gives a new offspring with the traits of its parents , The zygote is a cell produced due to the fertilization and it contains the complete number of chromosomes of the living organisms .
The resulted offspring has new genetic traits that combine the parents’ traits , So , the sexual reproduction is a source of genetic variation from the parents to the children .
The chromosomes number of gametes is just ( N ) because the gametes are produced from the meiotic division , after the fertilization, the zygote of ( 2 N ) is produced which grows performing the organism .
The offspring’s DNA is different , It is prepared for any changes , Any diseases that affects some of the offspring will not affect all of them , The DNA variation causes the evolution , while the sexual reproduction takes time and energy to find the mate .
The sexual reproduction is the combination of ( the haploid , or a single set of unpaired chromosomes ) reproductive cells from two individuals to form a third ( diploid , or a pair of each type of chromosome ) unique offspring .
The sexual reproduction produces the offspring with the novel combinations of genes , It can be an adaptive advantage in the unstable or the unpredictable environments , As the humans , We are used to thinking of the animals as they have two separate sexes , the male and the female , in the animal kingdom , there are many variations on them .
Hermaphroditism occurs in the animals where one individual has both male and female reproductive parts , The invertebrates , such as the earthworms , the slugs , the tapeworms and the snails are often hermaphroditic .
Hermaphrodites may self-fertilize or may mate with another of their species , fertilizing each other and both produce the offspring , The self fertilization is common in the animals that have limited mobility or are not motile such as the barnacles and the clams .