Question

Hey, can someone explain moss/fern/gymnosperm and angiosperm life cycles to me? There is so many terms (and they sound so similar) that I keep getting confused. Thanks!!!!

Answer 1

It's Alt. of generations to be exact

Answer 2

What terms are confusing you?

Answer 3

Gametophyte (I felt like I understood this, but then got confused again), Gametophore, megasporocoytes, microsporocytes, microsporophylls, megasporophylls, megaspores, microspores, megasporangium

There is more but I feel like if i got these, I can udnerstand the rest

Answer 4

Ok... one really important thing to keep in mind is the reduction of the gametophyte. This is an evolutionary trend in land plants.

In mosses, the gametophyte generation dominates: the sporophyte (the seta and capsule) is relatively small and is dependent on the gametophyte (the leafy plant).

In ferns, the gametophyte has been greatly reduced but still exists as a small, weird-looking thing (vaguely hart-shaped, I think) that lives independently but is both smaller and simpler than the sporophyte. The sporophyte (that's the dominant phase in ferns) is the big leafy fern plant that you're used to seeing.

In gymnosperms and angiosperms, the gametophyte has been even FURTHER reduced and is, in some cases, only a few cells. The angiosperm male gametophyte is only 2 cells hidden away in a pollen grain.

Another trend that you should be aware of is the tendency to go from isospores to mega/microspores.

"Iso" just means "same", so isospores are going to look the same. That means a plant (e.g. a fern) will produce a whole bunch of spores that all look the same, and those spores will germinate into gametophytes, which will produce male and female gametes.

Megaspores, on the other hand, are different from microspores. The most obvious difference is that they're bigger, but they are also the spores that grow into female gametophytes. Microspores germinate into male gametophytes. When you have mega- and micro-spores, you also need different structures to produce them: a megasporangium and a microsporangium respectively. If it's on/part of a leaf, that whole thing will be called a mega/microsporophyll ("phyll" means leaf).

Answer 5

Oh, wow... thanks! I am going to go apply these to my life cycle diagram and see if it makes more sense!

Answer 6

Are you a biologist or something that you know so much?

Answer 7

Biology student. I had an exam a couple of weeks ago that covered some of this stuff, so I still have a lot of it in my brain. No guarantee that everything I wrote there is correct, but hopefully some of it will be :P

Answer 8

oh, cool! i am majoring in bio (my test is on monday!)

Answer 9

And can you explain "the reduction of the gametophytes"? Are you talking about meiosis?

Answer 10

No, I'm talking about physical reduction in size/function/etc. of the gametophyte stage of the lifecycle.

As I said above, the gametophyte stage in mosses (that's the haploid stage that produces gametes) is the green, leafy part that you think of as the moss plant. The moss sporophyte (the diploid stage that produces spores) is smaller and gets most of its food from the gametophyte.

In angiosperms, the sporophyte (diploid, spore producing) stage is the plant that you see. You don't see the gametophyte at all because it has been reduced so much and is now just a few cells that don't photosynthesise or do anything that isn't related to reproduction.

Answer 11

Oh, ok

Answer 12

This might help: http://www.mansfield.ohio-state.edu/~sabedon/campbl30_files/image027.jpg

The picture of the moss plant makes the sporophyte look more prominent than it is... sure, it sticks out like that, but the dominant generation is really the leafy gametophyte.

Answer 13

Alright, thank you. And is gametangia and gametophore the same thing? Like the gametophore grows up to be the gametangia (antheridium, archegoium)?

Answer 14

And the protonema gives rise to the gametophores... right?

Answer 15

Hm... "phore" means carrier, so I guess it must be the structure that carries the gametangia.

The protonema develops into the leafy bit of the gametophyte, the actual moss plants.