siemenkasveissa

Siemenkasvit, also known as Spermatophytes, represent a major division of the plant kingdom characterized by the production of seeds. This is their defining feature, distinguishing them from seedless vascular plants like ferns and mosses. Seeds are crucial for reproduction, as they contain an embryo, a stored food supply, and a protective outer coat. This structure allows for dispersal and survival in various environmental conditions.

The life cycle of seed plants involves alternation of generations, with a dominant sporophyte stage. Within the sporophyte, specialized structures called sporangia produce spores. In seed plants, megaspores develop into ovules, which contain the female gametophyte, and microspores develop into pollen grains, which contain the male gametophyte. Fertilization occurs when a pollen grain reaches an ovule, leading to the formation of a zygote that develops into an embryo within the seed.

Siemenkasvit are further divided into two major groups: gymnosperms and angiosperms. Gymnosperms, meaning "naked seeds," produce seeds that are not enclosed within a fruit, such as conifers and cycads. Angiosperms, or flowering plants, have seeds enclosed within a fruit, which develops from the ovary of a flower. This group is the most diverse and widespread of all plant divisions, playing a vital role in ecosystems and human life.