Wednesday,

Apuntes

Wednesday, February 18, 2026 1 Chapter 28: The Evolution of Seed Plants Pablo E. Gutiérrez-Fonseca, PhD University of Puerto Rico, Mayagüez Spring 2026 Wednesday, February 18, 2026 8:34 AM Overview • Evolution of seed Plants • Gymnosperms • Angiosperms • Flowers • Pollination • Double fertilization • Seed • Fruits • Angiosperm Diversity Wednesday, February 18, 2026 2 Devonian Innovations • In the Devonian (mya ~419–359), the progymnosperms, seedless vascular plants now extinct, developed thickened woody stems. • Two other innovations were pollen and seeds, which allowed plants to colonize drier habitats and spread over the terrestrial environment. • Pollen walls contain sporopollenin, an extremely resistant material. Protects from drying and chemical damage. • Seeds transformed plant evolution, allowing seed plants to dominate most terrestrial ecosystems. A seed contains an embryo, stored nutrients, and a protective coat. In seed plants, haploid gametophytes develop within spores retained inside the tissues of the diploid parent sporophyte. Devonian Innovations • In the Devonian (mya ~419–359), the progymnosperms, seedless vascular plants now extinct, developed thickened woo...