Final answer:
Gymnosperms like pines have diploid cones where male and female gametes are produced. Male cones generate pollen grains that carry sperm, while female cones contain ovules that produce eggs.
Step-by-step explanation:
The question pertains to how gymnosperms, such as pines, which are monoecious plants, can produce male and female gametes despite having diploid cones. Each cone either produces male or female gametes depending on the type of sporophylls they carry. In male cones, microsporocytes undergo meiosis to produce haploid microspores, which develop into male gametophytes or pollen grains.
Conversely, female cones contain ovules where megasporocytes undergo meiosis to produce one viable megaspore that develops into the female gametophyte. Eventually, fertilization occurs when a pollen grain's sperm nucleus unites with an egg's nucleus, forming a diploid zygote that gives rise to the embryo within a seed. This life cycle demonstrates the alternation of generations, with a dominant diploid sporophyte and distinct haploid gametophyte stages.
Sexual reproduction in gymnosperms involves the production of different types of spores within cones, which then develop into male or female gametophytes, necessary for pollination and fertilization. Fertilization results in a diploid zygote, which grows into the embryo and then into the mature sporophyte, completing the cycle.