Seed plants. Phylum Coniferophyta the conifers. Phylum Cycadophyta the cycads.
Lab 9 - Gymnosperms and Angiosperms. When mosses and liverworts first evolved, they dominated the terrestrial environment. But they were soon challenged by the more advanced tracheophytes.
The kingdom plantae or plant kingdom comprises hundreds of thousands of different species. They live in every type of habitat, from frozen Arctic tundra to tropical rain forests and deserts. These range in size from minute, almost microscopic duckweeds, to massive giant sequolas, some of them are the largest organisms that has ever lived.
A homosporous life history occurs in nearly all bryophytes and in most pteridophytes lower vascular plants. It is characterized by morphologically identical spores that germinate to produce bisexual both male and female gametophytes in pteridophytes but either bisexual or, more usually, unisexual either male or female gametophytes in bryophytes. Each mature gametophyte bears gametangia sex organs that produce gametes. Each antheridium male gametangium forms many motile flagellate spermand each archegonium female gametangium forms one nonmotile egg.
Sperm is the male reproductive cell. In the types of sexual reproduction known as anisogamy and its subtype oogamythere is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell. A uniflagellar sperm cell that is motile is referred to as a spermatozoonwhereas a non-motile sperm cell is referred to as a spermatium.
Cycads, like all seed-producing plants, have a dominant diploid sporophyte phase in their life cycle—this is the large, familiar, green plant seen in nature. Cycads and other gymnosperms do not have true flowers and their seeds are borne naked. In the more evolutionarily recent angiosperms flowering plantsthe seed is enveloped by a coat or fruit which originates from the ovary.
The first plants to colonize land were most likely related to the ancestors of modern day mosses bryophyteswhich are thought to have appeared about million years ago. They were followed by liverworts also bryophytes and primitive vascular plants—the pterophytes—from which modern ferns are descended. The life cycle of bryophytes and pterophytes is characterized by the alternation of generationswhich is also exhibited in the gymnosperms and angiosperms.
Chapter Key Features of Vascular Plants previously discussed in lecture:. Both homosporous and homosporous plants have free-living gametophyte. All require water for fertilization - flagellated sperm.
The first plants to colonize land were most likely closely related to modern-day mosses bryophytes and are thought to have appeared about million years ago. They were followed by liverworts also bryophytes and primitive vascular plants, the pterophytes, from which modern ferns are derived. The life cycle of bryophytes and pterophytes is characterized by the alternation of generations. The completion of the life cycle requires water, as the male gametes must swim to the female gametes.