How do meiosis and fertilization give rise to genetic variation within sexually reproducing populations? How does asexual reproduction differ from sexual reproduction? How does a greater variety of descendants benefit a population? Explain the relationship between genetic variability and natural selection.
While asexual reproduction does not give rise to genetic variations as all daughter cells are produced by mitosis, sexual reproduction does give rise to genetic variation via the different combinations of genetic materials that result during meiosis and fertilization. Without sexual reproduction, offspring are genetically identical to the parents and to each other: Such a group of individuals is called a clone. Sexual reproduction augments variation in a population by recombining chromosomes and the genes they bear. Humans with twenty-three types of chromosomes can produce 223 different chromosomal combinations (even without cross-over occurring) through meiosis and can produce chromosomal combinations through fertilization. Sexual reproduction makes possible this genetic re assortment and thus increases variations among individuals. The greater variety of descendants, the greater the chance that some will be well-adapted to changing environment conditions and survive to further propagate the species. Thus, genetic variability is the raw material on which natural selection acts, promoting the survival of well-adapted individuals and
