Life cycle of gymnosperms is diplontic, which means the dominant phase of the life cycle is the diploid stage. In the gymnosperm life cycle, the sporophyte generation is dominant and the gametophyte generation is reduced and dependent on the sporophyte.

The life cycle of gymnosperms can be divided into several stages:

1. Sporophyte Generation:
- The life cycle begins with the sporophyte, which is the diploid phase of the plant. The sporophyte is the mature and visible form of the gymnosperm, such as a pine tree.
- The sporophyte produces reproductive structures called cones. There are two types of cones: male cones (microsporangiate cones) and female cones (megasporangiate cones).

2. Male Gametophyte Formation:
- The male cones produce microspores through meiosis. Each microspore undergoes mitosis to form a multicellular male gametophyte called pollen grain.
- The male gametophyte consists of a tube cell and generative cell. The tube cell helps in the growth of the pollen tube, while the generative cell divides to form two sperm cells.

3. Female Gametophyte Formation:
- The female cones produce megaspores through meiosis. Only one megaspore survives and undergoes mitosis to form a multicellular female gametophyte called the embryo sac.
- The embryo sac consists of several cells, including an egg cell, two synergids, three antipodal cells, and a central cell with two polar nuclei.

4. Pollination:
- Pollination is the transfer of pollen grains from the male cones to the female cones. It can occur through wind or with the help of insects and animals.
- When a pollen grain reaches the female cone, it germinates and forms a pollen tube that grows towards the embryo sac.

5. Fertilization:
- The pollen tube enters the embryo sac, and one sperm cell fuses with the egg cell, resulting in the formation of a zygote (2n).
- The other sperm cell fuses with the two polar nuclei, leading to the formation of a triploid endosperm (3n), which serves as a nutrient source for the developing embryo.

6. Embryo Development:
- The zygote develops into an embryo within the embryo sac. The embryo consists of an embryonic axis and one or two cotyledons.
- The embryo is protected by the female cone, which eventually develops into a seed.

7. Seed Dispersal:
- The mature seed is released from the female cone and dispersed by wind, water, or animals.
- The seed can remain dormant until it finds a suitable environment for germination.

In summary, the life cycle of gymnosperms is diplontic, with the sporophyte generation being dominant. The male and female gametophytes develop within the cones, and fertilization leads to the formation of seeds, which are dispersed for further growth and reproduction.