Lauren BoylesBiol 112 502Assignment #3

Vascular Seed Plants

The characters on the cladogram include Green algae, mosses, ferns, conifers, and

angiosperms. Each of these organisms, in their own, contributed to the evolution and creation of

life. Billions of years ago, the earth was barren; there was no vitality, no color. It was a gaseous

wasteland, covered with volcanoes burping hot ash into the atmosphere. As time progressed,

thankfully, so did life.

The progression of growth of algae (and cyanobacteria) led to an eventual oxygenation of

the atmosphere. As the amount of oxygen increased, the temperature began to fall. The

atmosphere gradually stabled, all due to a tiny plant. The first land plants were non vascular

plants; these included bryophytes (mosses), hepatophytes (liverworts), and anthoceraphytes

(hornworts). Mosses need to live in moist areas so that the water can carry their reproductive

cells to each other, and the plants may continue to reproduce. These plants are what made it

possible for other organisms to colonize on land. As plants evolved, they gained height and

vascular tissue.

Pterophyta, Ferns, are one of those plants. Ferns have gametophytes and sporophytes

separate from one another, however, male and female features are both present on the

gametophyte. Ferns have sporangia in clusters (called a sorus) under the leaves of the fern, and

the spores that emerge from them are carried away. The height of plants only rose higher and

higher; the following character on the cladogram are gymnosperms.

Gymnosperms include cycads, ginkgophyta, and confierophyta. These grow as trees;

each of these have even more advanced ways of spreading their reproductive cells. In confiers,

male and female cones are both present in the tree, same as the gametophytes of ferns. In the

ovuliferous scales of the female cone, the megasporangium is held; in the male cone with

microsporophylls, microsporangium reside in the microsporohylls. Gymnosperms have, what are

called, “naked” seeds, meaning the seeds are not enclosed by ‘fruit’ or ovaries. This means, they

do not bear fruit, however, gymnosperms provide shelter for many organisms, as well as

providing lumber for construction and sale, resin, and turpentine.

Lauren BoylesBiol 112 502Assignment #3

Fruit would be the final adaptation in land plants on the cladogram; it provides a wider

seed dispersal, and protection for the seed. Fruits are eaten, their seeds digested by animals and

then deposited in another places through fecal matter. Others are transported by the weather,

wind or water. Not only are fruits unique to angiosperms, but flowers are as well. The flower is a

“specialized shoot” that helps attract carriers to carry on pollination, which leads to double

fertilization (another unique trait to angiosperms). Once fertilization has occurred, a polyploid

endosperm develops. This is the fruit. The fruits, of course, provide food and nourishment to

animals and humans. They’re a huge part of the economy as well, fruits are a big part of the

production business; both as the base for many independent farms and as a small section of a larg

grocery chain.