Retention of the female gametophyte with developing young embryo on the parent sporophyte for some time, is first observed in Pteridophytes.

Pteridophytes are a group of vascular plants that include ferns, horsetails, and club mosses. They are unique in their reproductive process, specifically in the retention of the female gametophyte with the developing young embryo on the parent sporophyte for some time.

Explanation:

Evolutionary Significance:
The retention of the female gametophyte with the developing young embryo on the parent sporophyte is an important evolutionary adaptation. It provides several benefits for the survival and development of the embryo.

Protection and Nutritional Support:
By retaining the female gametophyte with the developing embryo, the sporophyte provides protection and nutritional support to the developing embryo. The female gametophyte, also known as the prothallus, contains nutrients and provides a suitable environment for the embryo to grow. This increases the chances of successful embryonic development and survival.

Enhanced Dispersal:
The retention of the female gametophyte with the embryo also enhances the dispersal of the species. As the embryo develops, it produces spores that are dispersed to new locations, increasing the geographic range of the species. By being attached to the parent sporophyte, the embryo can disperse more effectively and increase the chances of successful colonization in new habitats.

Increased Survival:
The retention of the female gametophyte with the developing embryo increases the chances of survival for the embryo. The parent sporophyte provides a stable and protected environment for the embryo, shielding it from unfavorable external conditions such as desiccation, predation, and competition. This increases the chances of successful germination and establishment of the young sporophyte.

Conclusion:
In conclusion, the retention of the female gametophyte with developing young embryo on the parent sporophyte for some time is first observed in Pteridophytes. This adaptation provides several advantages, including protection, nutritional support, enhanced dispersal, and increased survival for the developing embryo.