Lab Test 2: Alternation of Generations

Compare and contrast the reproductive structures and stages between mosses and ferns.

Both ferns and mosses don't have seeds. They both use an alternation of generation type of reproductive cycle. But mosses are nonvascular plant, meaning they don't have vascular tissue (xylem and phloem), instead have simpler tissue. Ferns are vascular and their dominant generation is the sporophyte. Also the male and female gametophyte parts are on the same plant. On mosses, the gametophyte is the dominant generation and the male and female gametophyte parts are seperate.

Summarize the overall life cycle of mosses.

First, spores are released from a capsule, this opens a small, lidlike structure, operculum, that degenerates. One spore germinates and forms a branched, filamentous protonema from which a leafy gametophyte develops. The gametophyte has organs that allows for sexual reproduction. Sperm is released by the antheridium, attracted into a neck of an archegonium, and the sperm and egg form a zygote. The zygote becomes sporophyte after cell division. At the same time, archegonium divides to form the protective calyptra. The sporophyte usually consists of a capsule and a seta. Asexual reproduction occurs within the capsule and process occurs again.

Compare and contrast the life cycle of mosses (seedless vascular plants) with both gymnosperms (conifers) and angiosperms (flowers)

Mosses are gametophyte dominant. In mosses, fertilization forms a zygote which grows into a sporophyte. The sporophyte releases a new gametophyte. Gymnosperms, such as pine, grow higher up on a tree. The woody scale has 2 ovules, in each ovule is a megaspore that develops into a female gametophyte, which form seeds. Microspores form pollen (male gametophyte), the pollen are released and contain eggs in their ovules. In angiosperms, pollen develops in anther of stamen. Ovules contain embryo sac (female gametophyte) which are in ovaries of flowers. The pollen transfers through animal or wind. The egg and sperm form a zygote inside the ovule which produces a seed, this grows into a sporophyte later.

What is the significance of seedless vascular plants such as mosses from an evolutionary standpoint?

Seedless vascular systems also helped develop other vascular systems, roots and leaves. Plants were also able to grow taller because of vascular systems. If plants didn't have vascular systems, then they would be mosses. If humans didn't have vascular systems, we'd be a big blob of cells. Seedless vascular plants made a major breakthrough in plant evolution because they developed a way to transport materials around the plant body.

Compare and Contrast between vascular and nonvascular mosses.

Vascular plants such as the dusty rock moss contain vascular tissue made up of xylem and phloem. These plants have better nutrient transport systems and can therefore survive more easily on land than nonvascular plants. Vascular plants are also taller than non-vascular such as pyxie moss are limited in their ability to perform gas exchange and nutrients transfer due to a lack of vascular tissue.