Sexual reproduction is able to generate genetic variation in offspring by 1-independent assortment and 2-recombination during meiosis, and 3-random fertilization.
Explanation:
Sexual reproduction is a type of reproduction that increases the amount of genetic variation in offspring by three main mechanisms: independent assortment of homologous chromosome pairs and recombination during meiosis, and random union of gametes during fertilization. First, sexual reproduction is associated with the independent assortment of chromosomes during meiosis, i.e., the orientation of homologous chromosome pairs is a random process that is different for every cell that undergoes meiosis. In consequence, chromosomes assort randomly into gametes, thereby the segregation of alleles of a gene pair is independent of the segregation of another set of alleles of a different gene (as stated in the law of independent assortment). Second, sexual reproduction generates genetic variation by recombination, which is the exchange of genetic material between non-sister chromatids during meiosis I (prophase I). This genetic process (recombination) is able to generate new alleles in offspring. Third, sexual reproduction also involves the random union of two haploids (n) gametes during fertilization, which results in the formation of a diploid (2n) zygote that develops into a new individual. In humans, the sperm cell has 8 million possible (2²³) chromosome combinations, which fertilizes an ovum cell that also has approximately 8 million chromosome combinations, thereby producing a tremendous genetic variation in offspring (around 64 trillion possible zygote combinations).
The common cuckoo does not make a nest of its own, and they do not bring up their own young. Instead, the female lays her eggs in the nests of other birds. Each female cuckoo specialises in just one host species, and lays camouflaged eggs in that bird's nest.
