Gymnosperms: The Naked Seed Plants

What does the term “gymnosperm” mean?

“Naked seed,” referring to seeds that are not enclosed in fruits.

Where are gymnosperm seeds typically found?

On cones rather than inside fruits.

What are the four major phyla of gymnosperms?

1️⃣ Cycadophyta (cycads)
2️⃣ Ginkgophyta (ginkgo)
3️⃣ Gnetophyta (gnetophytes)
4️⃣ Coniferophyta (conifers)

When did gymnosperms first appear?

Around 305 million years ago.

During which era did gymnosperms dominate Earth’s flora?

The Mesozoic Era (the “Age of Cycads”).

What environmental change favored gymnosperms over ferns?

A drier climate, which gymnosperms tolerated better due to pollen and seeds.

What is the dominant generation in gymnosperms?

The sporophyte (diploid) generation.

Where do gametophytes develop in gymnosperms?

Within cones (pollen cones and ovulate cones).

What are pollen cones?

Male cones that produce microspores, which develop into pollen grains.

What are ovulate cones?

Female cones that produce megaspores, which develop into female gametophytes.

How is fertilization achieved in gymnosperms?

By wind-dispersed pollen, not by water.

How long does fertilization take after pollination in most conifers?

About one year.

What structure does the gymnosperm seed develop from?

The fertilized ovule.

What do gymnosperm seeds contain?

An embryo, food supply, and protective seed coat.

Cycadophyta (cycads)

Palm-like plants with large cones; flagellated sperm; many are endangered.

Ginkgophyta (ginkgo)

A single living species (Ginkgo biloba); fan-shaped leaves; tolerant of pollution; flagellated sperm.

Gnetophyta (gnetophytes)

Includes Ephedra and Welwitschia; varied habitats; some traits similar to angiosperms.

Coniferophyta (conifers)

Largest gymnosperm group; mostly evergreen trees such as pines, firs, and redwoods.

What does a mature pine tree represent?

The sporophyte generation.

What do microsporangia in pollen cones produce?

Microspores, which develop into pollen grains (male gametophytes).

What do ovulate cones contain?

Ovules, each with a megasporangium where a female gametophyte develops.

How is fertilization achieved in conifers?

The pollen tube delivers sperm directly to the egg.

After fertilization, what happens to the ovule?

It becomes a seed, containing the embryo and stored food.

How are conifer seeds dispersed?

By wind or sometimes animals.

What are the reproductive advantages of seeds in conifers?

Protection, dormancy, and nutrient supply for the embryo.