Slide 1
The non-flowering seed plants are those plants that produce seeds but do not produce flowers or fruits.
Slide 2
The gymnosperms arose about 300 million years ago when conditions on earth were drier than they had been.
At this time, all of the earth's land masses were connected in one super continent called Pangaea. This super continent helped to create drier conditions and this created a new habitat for plants to move into.
The gymnosperms have adaptations that make them better able to tolerate dry conditions than either the nonvascular or the vascular seedless plants.
Slide 3
The gymnosperms are our first example of a seed plant. In the seed plants we see a further development in the trend toward a reduced gametophyte.
In the seed plants, the gametophyte is fully reduced and dependent upon the sporophyte for nutrition.
The female gametophyte stays completely within the sporophyte tissue. The male gametophyte is the pollen grain - it briefly leaves the sporophyte tissue when it travels to the female gametophyte prior to fertilization.
Slide 4
Seeds are multicellular resistant structures that houses the embryonic sporophyte and provides a food supply for the developing embryo.
Seeds are used to disperse embryos into the environment away from the parent plant.
Gymnosperm seeds are "naked" - they are not surrounded by fruit the way the seeds ofthe angiosperms are.
Slide 5
The seed plants produce pollen. Pollen is not found in the nonvascular or the vascular seedless plants.
Pollen is the male gametophyte that houses the sperm.
Pollen grains have a hard coat that protects the sperm cells during the process of their movement to the female gametophyte (cones in gymnosperm and flowers in the angiosperms)
Gymnosperms do not usually use animals to spread their pollen - they tend to use the wind. So the pollen of most gymnosperms has wing-like structures that allow them to fly better.
Angiosperms tend to use animals as pollinators so their polen tends to have rigid projections that better enable to grains to attach to the surface of an animal.
Slide 6
The gymnosperms used to be the most abundant plant group on earth but today there are fewer than 750 species.
There are four phyla of gymnosperms but none of these groups is thought to be monophyletic.
Slide 7
The first two groups of gymnosperms are the cycads and ginkgos. Both of these groups retain the primitive characterstic of flagellated sperm even though they do not require water for reproduction. The sperm actually swim through a tube that grows from the pollen grain into the female cone.
Both the
cycads and ginkgos are dioecious - this means that there are separate sexes -
one plant is male and the other is female.
The cycads are a tropical
and subtropical groups of plants.
The ginkgos are considered to be a living fossil - there is only a single species in the whole group - the plant Ginkgo biloba. This is the tree that is the source of the dietary suplement Ginkgo biloba.
Slide 8
The gnetophytes are the next group of gymnosperms. They have many charactersistics that make them unique but we are going to focus on the fact that this is the first group of plants we are looking at that has the advanced characterstic of non-motile sperm.
The gnetophytes include some strange plants like Welwitschia and ephedra.
Slide 9
Ephedra is also known as Ma huang or Chinese ephedra. It is the source of the dietary supplement known as ephedra.
Ephedra is a stimulant that decreases apetite - unfortunately it can also cause heart attacks or strokes and has been linked to a number of deaths - including the deaths of young, healthy athletes. In 2004 the Food and Drug Administration banned the use of ephedra in supplements in the US.
Slide
10
The last group of gymnosperms is the conifers. This group also has non-motile sperm is recognized as being plants that have cones and evergreen leaves.
Most of the conifers are monoecious - both sexes are found on one tree.
The conifers are noteable for having the largest
known tree - the General Sherman tree that lives in Sequoia National Park -
and the oldest known tree - the Methuselah tree in the White mountains of
California is just shy of 5000 years old!