The Evolution of Seed Plants

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Gymnosperms were better suited than nonvascular plants to drier conditions.

Today, cone-bearing gymnosperms called conifers dominate in the northern latitudes.

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Phylum Ginkgophyta

This phylum consists of a single living species, Ginkgo biloba.

It has a high tolerance to air pollution and is a popular ornamental tree.

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Gymnosperm

Ginkgo biloba Pollen-producing tree with fleshy seeds

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Gymnosperm

Welwitschia

Ovulate cones

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Phylum Coniferophyta

This phylum is by far the largest of the gymnosperm phyla.

Most conifers are evergreens and can carry out photosynthesis year round.

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Gymnosperms: Conifers perform year round photosynthesis

Douglas fir

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Gymnosperms: Conifers Sequoia - One of the Largest and Oldest Living Organisms

Giant Sequoia: 2,500 tons / 1,800 - 2,700 years old

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The Life Cycle of a Pine: A Closer Look

Three key features of the gymnosperm life cycle are:

Dominance of the sporophyte generation.

The transfer of sperm to ovules by pollen.

Development of seeds from fertilized ovules.

The life cycle of a pine provides an example.

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Life Cycle of a Pine

Microsporangium (2n)

Microsporocytes (2n)

Pollen grains (n)

Pollen cone

Microsporangia

MEIOSIS

Mature sporophyte (2n)

Haploid (n)

Diploid (2n)

Key

MEIOSIS

Surviving megaspore (n)

Pollen grain

Megasporocyte (2n)

Ovule

Integument

Ovulate cone

FERTILIZATION

Pollen tube

Female gametophyte

Sperm nucleus (n)

Egg nucleus (n)

Archegonium

Seedling

Seeds

Seed coat (2n)

Food reserves (n)

Embryo (2n)

Megasporangium (2n)

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The reproductive adaptations of angiosperms include flowers and fruits

Angiosperms are seed plants with reproductive structures called flowers and fruits.

They are the most widespread and diverse of all plants.

All angiosperms are classified in a single phylum: Anthophyta.

The name comes from the Greek anthos, flower.

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