This is the first week of presentations. Fun Fun Fun. Actually, this is probably the easiest presentation to make just because seed plants are everywhere. This lab is pretty harmless. Not much of what you'll see here will be on tests. It will however be on quizzes and the lab practical. If you sense me stressing the lab practical, you've been paying attention. Its a big deal. Don't count on doing well for this thing. It is not something you can cram for. You can't beat the practical, you can only hope to survive it.
Seed plants are thought to have sprung from the seed ferns (Pteridospermophyta) ~286 MYA during Permian times. They are significant in that they display HETEROSPORY - they all produce two kinds of spores - large spores (Megaspore or ovule - the "female" spore) and a small spore (microspore or pollen grain - the "male" spore). They also produce SEEDS (pretty obvious, eh?) which is composed of three parts:
The nice thing about seeds is that they are protected by their integument. They're relatively cheap in that they're not huge structures and dont require a long time to produce. Heterospory is great for seed plants because pollen doesn't need water. It can be carried by air or animals straight to the female structures of the plant. It is because of this that seed plants dominate land. They're much better adapted to dry land than are ferns or mosses which need water because their sperms swim. Note that in moist areas, ferns and mosses are still around in abundance.
Ok, just like in the lab book, I will arrange the various taxonomic levels AND include a reason why they go there.
Seed plants are all vascularized. This means they have xylem and phloem which are the equivalent of arteries and veins. Xylem take water from the roots and distribute it to the rest of the plant. Phloem bring nutrients back down from the leaves, the primary site of photosynthesis.
I am not going to go terribly in depth for this lab. Know your life cycles, know your life cycles, know your life cycles. Know that heterospory and seeds/cones allowed for the takeover of dry land. Vascularization played a supporting role in the takeover of land because it allowed plants to get larger, since they could move water from the ground to higher points in the plant.
"Gymnos" means "naked" in Greek. A gymnasium is a place for sport because the Greeks sported in the nude. Gymnosperm = "naked sperm" or "naked seed". These types of plants produce seeds with no covering. Conifers are considered to be gymnosperms even though they have a cone (male cone = staminate cone/female cone = ovulate cone) because they dont protect the seed itself with a parent tissue. Cycads are large palm tree lookalikes with a large cone in the center.
Angiosperms are flowering plants. Angiosperms break into two groups: monocots and dicots. Its usually fairly easy to visually identify which is which:
Another thing you should know is the structure of the flower itself. Know the sepal from the stamen from the pistil.