Gymnosperms

Cycads: We have a LOT of stuff for cycads. The huge orange cone-like structure is the MICROstrobilus of a cycad. Students usually get a kick out of that. I pass it around--there are a few microsporophylls loose and floating around as well--and let the students see the cup-shaped hollows where the pollen grains were stored. There is a deceased Cycad with two fronds, one of which has most of the leaflets peeled off it to show the rachis. The trunk is very short and fat; notice how the base of the leaf remains attached to provide a bark-like protection to the plant. In a jar are some megasporophylls, complete with a few 'berry-like' ovules. A student also donated a live cycad, hopefully it's still alive, in a pot. In addition, there's a collection of cycad leaves. I offer bonus points to students who can locate a cycad and eithe bring me a frond (make sure it's not a fern frond) or tell me precisely where the ones on campus are. There are cycads between the Koldus Garage and the Corps dorms...that limits the search area nicely. There is also at least one cycad near the McDonalds near Northgate. If students can go out, look, and identify it as a cycad, I give them a point...but they need to know the location precisely. I go over the cycad life-cycle in depth; most of the other gymnosperm lifecycles are just repeats of the same thing.

Ginko: There IS a ginko on campus! It's decades old, and looks like a sapling. I do NOT allow students to pick leaves off it!!!! It needs all the help it can get. I usually offer bonus points to the students who locate it: it is somewhere between Butler and the area around the Student Computing Center, with Lubbock bordering one side and the library bordering the other. It isn't reproductive, but has some great "short shoots" to show the students. Lots of stuff in the Atlas about Ginkoes, too. There are some preserved female berries, but do NOT open the jar!!!! A female ginko tree produces berry-like structures with a scent amazingly similar to dog poop..... If someone has a female ginko in a four-block radius, you can tell because people keep stopping to check the bottom of their shoes..... The male Ginko produces catkins. There is a preserved sheet of Ginko bilboa with catkins on it AND the y-shaped female structure that grows into the large ovule. Point out to the students that their is an entire division dedicated to ONE species...pretty neat.

For the Gnetophytes, we have live samples. To the best of my knowledge, the whisk-broom looking thing is an Ephedra, aka a Mormon Tea plant. Decongestants like sudafed have Pseudoephedrine in them.....guess where we got the medicine from? There is a nice, jointed, woody stem of Gnetum in the lab as well as an herbarium sheet of it. Welwitschia I just show as a link on the computer and in the extra lab books. An important feature of the Gnetophytes is the prescence of VESSEL ELEMENTS; these are ONLY found in the Gnetophytes and the angiosperms...which tells a bit about evolution right there!

Confers have both a life cycle in the lab book AND a rolled-up poster. Go over the life cycle thoroughly. Explain how the megasporangia are located on a megasporophyll, just like in the fern allies. However, the megasporophyll is very tough and woody (the blades on a pine cone!). The sporangia (two per megasporophyll) are enclosed by a layer called an integument. In the sporangium, a SINGLE megaspore mother cell grows, rather than thousands. As always, that sporophyte cell undergoes meiosis, producing four haploid spores. Three of them die, and the fourth one grows into the gametophyte like all other spores do.....but it's still inside the sporangium, which is still inside the integument, which is still on the megasporophyll and still on the cone! I liken it to the Russian dolls where you can open the top, and there's a doll inside a doll inside a doll inside a doll....and finally, a little baby doll in the very inside.

That spore grows into a very small female gametophyte. It's getting all it's nutrients from the sporophyte, so it doesn't need a stem, leaves, roots, and all that other stuff. All it has to do is make an egg....and it makes TWO. Two archegonia are produced, each with an egg. When the pollen grain lands, only ONE of those archegonia (just like in mosses!) gets to be the lucky winner, and the egg in it becomes a zygote, then a small embryonic sporophyte. So, just like the old lady that swallowed a fly, you have an embryonic sporophyte inside the remains of the archegonia inside the remains of the female gametophyte inside the remains of the megasporangia inside the integument on the pine cone megasporophyll!!! And each megasporophyll has TWO ovules, so produces TWO seeds. I like to try and find pine cones that are mostly opened but haven't released all their seeds yet. On the ones in class, you can see the two indentations where the two seeds rested. If you get one with some seeds still in it, you can give the students forceps and have them pull the seeds out of the cone...which is a great way to drive home the lesson. I also have a ziploc bag with the male strobili (called catkins) and a LOT of yellow powder, which is the pollen. You can put some of that in a drop of water and make your own pollen slide if you'd like, or use the prepared slides. Notice how MUCH pollen is produced....Gymnosperms aren't evolved enough (at least the conifers) to use insects for pollination. They rely on wind pollination, so they have to make a LOT of pollen.

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