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Origin of Seed Plants

•  Review Seedless Vascular Plants •  Seed Plants

–  Life cycle –  Surviving lineages

•  Cycads •  Ginkgo, etc •  Conifers •  Angiosperms

•  Flowers and Fruits

April 3, 2019

Early vascular plant forest, carboniferous period (300 million years ago)

Permian

Jurassic Key Haploid (n) Diploid (2n)

MEIOSIS Spore dispersal

Sporangium

Sporangium Mature sporophyte (2n)

Sorus

Spore (n)

Mature gametophyte (n) Archegonium

Egg

Antheridium

Sperm

FERTILIZATION New sporophyte

Gametophyte

Zygote (2n)

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Vascular Plants

Clubmosses and friends

Ferns and Friends

Seed Plants

megaphylls

seeds

Bryophyte Pteridophytes Gymnosperm Angiosperm

All land plants alternate generations, although extensively modified

Advantages of seeds:

•  Protection

•  Dormancy

•  Dispersal

•  Carry food supply that can aid establishment of sporophyte

Figure 30.UN05 Five Derived Traits of Seed Plants

Reduced gametophytes

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)

Male gametophyte

Female gametophyte

Heterospory

Ovules

Ovule (gymnosperm)

Integument (2n)

Megaspore (n)

Megasporangium (2n)

Pollen Pollen grains make water unnecessary for fertilization

Seeds: survive better than unprotected spores, can be transported long distances

Seed coat

Food supply

Embryo

Seeds

Seed Structure

Embryo (2n sporophyte)

Gametophyte endosperm (1n)

Integument (Mom– 2n)

Gymnosperm seed contains three generations

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Generative nucleus

Pollen Coat

The pollen grain (microgametophyte)

Tube nucleus

The mature microgametophyte

Incredible diversity of pollen grain structure

Gymnosperms – unprotected seeds

Cycads Ginkgo (1 sp)

Gnetophytes Conifers

Dominant in mesozoic. <1000 living spp

(but still abundant)

Ovule

Mature sporophyte (2n) MEIOSIS

Female gametophyte

Seeds

Sperm (n) Pollen tube

Egg (n) Haploid (n) Diploid (2n)

Embryo (new sporophyte) (2n)

Pollen (n)

MEIOSIS

FERTILIZATION

The Life Cycle of a Pine Tree

To start, notice the similarities with that of ferns and mosses.

Ovule

Mature sporophyte (2n) MEIOSIS

Female gametophyte

Seeds

Sperm (n) Pollen tube

Egg (n) Haploid (n) Diploid (2n)

Embryo (new sporophyte) (2n)

Pollen (n)

MEIOSIS

FERTILIZATION

The Life Cycle of a Pine Tree

To start, notice the similarities with that of ferns and mosses. What are some differences?

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POLLEN AND SEED CONES OF A PINE

Seed cones

pollen cones Fossil cones from the Jurassic

Yew “berry”

Ginkgo “fruit”

These are Gymnosperms, so not really fruits

Not all Gymosperms have cones