Replication is the process by which a living organism creates a copy of itself. This can be done either through asexual reproduction, in which an organism produces offspring that are genetically identical to itself, or through sexual reproduction, in which an organism produces offspring that are a mix of its own genes and those of another organism.
In order for replication to occur, the cells of an organism must first divide. This can happen either by mitosis, in which one cell splits into two genetically identical cells, or by meiosis, in which one cell splits into four genetically diverse cells. Once the cells have divided, they must then come together and fuse their DNA in order to create a new individual.
Asexual reproduction is the most common form of replication among single-celled organisms such as bacteria and protists. Many plants and fungi also reproduce asexually. Asexual reproduction has several advantages over sexual reproduction. For one, it is much faster; an organism can produce many more offspring through asexual reproduction than it could through sexual reproduction. Additionally, since there is no need for another organism to be involved in the process, asexual reproduction does not require as much energy as sexual reproduction does. Finally, since all of the offspring are genetically identical to the parent, they are more likely to survive and thrive in similar environments.
Sexual reproduction is more common among multicellular organisms such as animals and plants. Sexual reproduction has several advantages over asexual reproduction. For one, it allows for greater genetic diversity among the population; this diversity makes it more likely that at least some individuals will be able to adapt and survive if the environment changes dramatically. Additionally, sexual selection often leads to stronger and healthier individuals being produced; this is because individuals with traits that make them better at finding mates or surviving predators are more likely to pass on their genes than those without these traits. Finally, sex chromosomes often carry deleterious alleles (variants) that can be purged from the population through meiotic drive (a process by which certain alleles become preferentially represented in gametes).