Plant Diversity II: The Evolution of Seed Plants Chapter 30

Learning Targets

Review  Multicellular green algae (Chara) gave rise to first land plants 475 mya  Bryophytes (mosses) – lack vascular tissues and roots, no seeds, gametophyte dominant  Pterophytes (ferns) – have vascular tissues and roots, no seeds, sporophyte dominant, swimming sperm

Seeds and pollen grains are key adaptations for life on land 30.1

Seeds vs. Spores Spores  No protection or support for embryo  Rely on environmental conditions for dispersal  Short lifetime (no dormancy) Seeds  Provide protection and support for embryo  Dispersal via various means (fruits  animals)  Dormancy allows a waiting period for ideal conditions

Five Derived Traits of Seed Plants Reduced gametophytes Heterospory Ovules Pollen Seeds Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovule (gymnosperm) Integument (2n) Megaspore (n) Megasporangium (2n) Pollen grains make water unnecessary for fertilization Seeds: survive better than unprotected spores, can be transported long distances Seed coat Food supply Embryo Female gametophyte Male gametophyte

Gymnosperms bear “naked” seeds, typically on cones 30.2

Gymnosperms  Ex: Cycads, Ginkos, Gnetos, Conifers  SEED!  Inside a seed is the female gametophyte  Pollen is male gametophyte  If sperm reaches ova, zygote forms  Seeds help plants survive harsh conditions  Gymnosperms have a naked seed (cones)

The reproductive adaptations of angiosperms include flowers and fruit 29.3

Angiosperms  Ex: Very diverse plants (monocots, dicots)  Flower – helps plants reproduce  Fruit – helps seed dispersal

Human welfare depends greatly on seed plants 30.4

Plant Uses and Benefits