How Do Organisms Reproduce-Sexual Reporoduction Flashcards
Why is it best that there are more variations?
The creation of two new cells from one involves copying of the DNA as well as of the cellular apparatus. The DNA copying mechanism, as we have noted, cannot be absolutely accurate, and the resultant errors are a source of variations in populations of organisms. Every individual organism cannot be protected by variations, but in a population, variations are useful for ensuring the survival of the species. It would therefore make sense if organisms came up with reproductive modes that allowed more and more variation to be generated.
Is the normal dna copying enough variation for a species
While DNA-copying mechanisms are not absolutely accurate, they are precise enough to make the generation of variation a fairly slow process. If the DNA copying mechanisms were to be less accurate, many of the resultant DNA copies would not be able to work with the cellular apparatus, and would die.
How can the process of making variants be speeded up
Each new variation is made in a DNA copy that already has variations accumulated from previous generations. Thus, two different individuals in a population would have quite different patterns of accumulated variations. Since all of these variations are in living individuals, it is assured that they do not have any really bad effects. Combining variations from two or more individuals would thus create new combinations of variants. Each combination would be novel, since it would involve two different individuals. The sexual mode of reproduction incorporates such a process of combining DNA from two different individuals during reproduction.
how do complex organisms reproduce
many multi-cellular
organisms have found for the problem mentioned above is to have special
lineages of cells in specialised organs in which only half the number of
chromosomes and half the amount of DNA as compared to the nonreproductive body cells. This is achieved by a process of cell division
called meiosis. Thus, when these germ-cells from two individuals combine
during sexual reproduction to form a new individual, it results in reestablishment of the number of chromosomes and the DNA content in
the new generation.
describe the male gamete
The germ cell which is smaller and motile is called the sperm. It is made in the testes. It is called the sperm.
describe the female gamete
the germ cell which is bigger, non-motile and contains the energy source for the zygote to grow is called the female gamete. It is made on the ovaries. it is called the ovum
