Plant Diversity II: The Evolution of Seed PlantsChapter 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 land30.1

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

Reducedgametophytes

Heterospory

Ovules

Pollen

Seeds

Microscopic male andfemale gametophytes(n) are nourished andprotected by thesporophyte (2n)

Microspore (gives rise toa male gametophyte)

Megaspore (gives rise toa female gametophyte)

Ovule(gymnosperm)

Integument (2n)

Megaspore (n)

Megasporangium(2n)

Pollen grains make waterunnecessary for fertilization

Seeds: survivebetter thanunprotectedspores, can betransportedlong distances

Seed coat

Food supply

Embryo

Femalegametophyte

Malegametophyte

Gymnosperms bear “naked” seeds, typically on cones30.2

GymnospermsEx: Cycads, Ginkos, Gnetos,

ConifersSEED!

Inside a seed is the female gametophyte

Pollen is male gametophyte If sperm reaches ova, zygote

formsSeeds help plants survive

harsh conditionsGymnosperms have a

naked seed (cones)

The reproductive adaptations of angiosperms include flowers and fruit29.3

Angiosperms Ex: Very diverse plants (monocots,

dicots) Flower – helps plants reproduce Fruit – helps seed dispersal

Human welfare depends greatly on seed plants30.4

Plant Uses and Benefits

Plant Uses and Benefits