Final answer:
Sexual reproduction requires two key conditions: fertilization, which involves the union of two haploid gametes, and meiosis, which reduces chromosome number to maintain ploidy level across generations.
Step-by-step explanation:
In the field of population genetics, sexual reproduction functionally involves two necessary conditions: fertilization and meiosis. Fertilization is the union of two haploid gametes from two different individuals to form a diploid zygote. Meiosis is the nuclear division process that reduces the chromosome number by half to produce haploid gametes, ensuring that the chromosome number remains constant across generations. These processes contribute to the genetic diversity of organisms, which is essential for adaptation and survival in changing environments.
Fertilization involves the combination of genetic material from two parents, leading to genetically unique offspring. This process promotes variation within a species. On the other hand, meiosis ensures that sexually reproducing organisms can continue to reproduce over time without doubling the number of chromosomes in each generation. By reducing the chromosome number in gametes, meiosis maintains the species' ploidy level.