∞ generated and posted on 2024.10.29 ∞
For example, the progression of an organism from its first point of existence to the formation of the next generation's first point of existence.
| A life cycle can start at any specific point in an organism's existence and then end at any specific but nevertheless consistent point in the existence of that organism's offspring. In considering life cycles, however, focus is typically on a combination of what it takes for an organism to reach reproductive maturity and then how reproduction takes place. This will be the case regardless of whether an organism's reproduction is sexual or instead asexual. With sexual organisms, however, an important part of the life cycle will be finding a mate. Here we focus especially on the life cycles of plants, but start with consideration of life cycles of fungi. An important thing to be conscious of are both the similarities and differences between the life cycles of the bryophytes (e.g., mosses), pterophytes (e.g., ferns), and conifers (e.g., pines) as well as the angiosperms (flowering plants). |
The above video discusses the very basics of what the spores of plants and fungi consist of, particularly from a genetics perspective.
The above video is a nice introduction to fungi and mushrooms, with nice images, but isn't very detailed about fungal life cycles.
The above video is another nice introduction to fungi and mushrooms, with more detail, but doesn't focus sufficiently on fungal life cycles for our needs.
I usually try to avoid posting straight lectures (other than of myself!), but this one on the Basidiomycota life cycle was the best on this subject that I was able to find on YouTube. Note that in the photos in the video, with mycelia overlying a mushroom, e.g., starting around 2:50, the mycelia are shown much (much) larger than they actually exist as in reality. Also, around 4:37 the narrator mentions "two rounds of meiosis", but really he ought to have just said that meiosis had occurred since meiosis involves two rounds of cell division and that is what he is talking about there. Alas, and around 4:40 the narrator describes spores germinating ("it's going to germinate four sexual spores"), and that's just poor usage as spores germinate after they have dispersed, just as is also the case for seeds, and this is rather than while still within the fruiting body (i.e., within the mushroom). Oh man, and fragmented hyphae are not asexual spores. Still, the above video was the best that I at least so far have been able to find… For more on just what fungi are all about, see the above-posted videos as well.
The above video is an abstract representation of just what gametophytes represent. Remember, they are haploid plants that mitotically produce gametes!
The above video is an abstract representation of just what sporophytes represent. Remember, they are diploid plants that meiotically produce spores!
The above video walks through the life cycle of a moss, which is a kind of bryophyte. Pay attention the various details associated with the alternation of generations as you will see many of those details again when looking at the life cycles of more complex plants.
The above video shows fern sporophytes emerging from soil.
The above video walks through the life cycle of a fern, which is a kind of pterophyte. Pay attention the various details associated with the alternation of generations as you will see many of those details again when looking at the life cycles of more as well as less complex plants.
The above video walks through the life cycle of a pine, which is a kind of conifer/gymnosperm. Pay attention the various details associated with the alternation of generations as you will see many of those details when looking at the life cycles of less complex plants (bryophytes and pterophytes) as well as in the life cycle of flowering plants (angiosperms).
The above video walks through the life cycle of a flowering plant, also known as an angiosperm. Note that a monocot is a plant that starts with a single embryonic leaf (cotyledon) rather than the two embryonic leaves of a dicot.
If you still are struggling with diploid versus haploid and sporophyte versus gametophyte, etc., i.e., in plant alternation of generations, watch this video. It's pretty awesome! (Remember, "n" is short for haploid while "2n" is short for diploid.)
Just because carnivorous plants are pretty cool, there is the above video. OK, more paleontology than life cycles, but still pretty cool.
These are the fungi that we had on display. Note that a morchella is a 'true morel'.
Focusing in on Aspergillus conidiophores.
Our moss life cycle poster.
Exercise 3.2: Focusing in on a young moss gametophyte. Mature moss gametophytes are the majority of what you see when you look at a moss plant.
Exercise 3.3: Focusing in on a moss archegonial head slide. This is part of the gametophyte generation and it is within here that the egg will form and eventually will be fertilized. This item is basically identical to 3.5.
Exercise 3.6: Moss mature capsule, part of the moss sporophyte (the very top of it).
Exercise 3.6: Focusing in on a moss mature capsule with spores inside. The capsule is part of the sporophyte generation while the spores are the first cells of the gametophyte generation.
Our fern life cycle poster. Note the fern sori, which are not seen otherwise in this lab.
Exercise 4.1: Focusing in on fern spores within a fern sporangium. Sporangia are part of the sporophyte generation and the spores are the first cells of the gametophyte generation.
Exercise 4.2: Focusing in on a fern prothallium with embryo. This is the gametophyte and it is within here that the sporophyte generation is forming (the embryo).
Exercise 4.3: Focusing in on a fern archegonium. This is part of the gametophyte generation and it is within here that the egg will form and eventually will be fertilized. This item is basically identical to 4.5.
Exercise 4.6a: Focusing in on a fern prothallium with young sporophyte. Note that you goal is not only to view the young sporophyte as shown here but a mature sporophyte as well (which is not shown here).
Exercise 4.6b: Fern prothallium with young sporophyte. And then we move on to a much bigger and older fern sporophyte.
Exercise 5.2: A pine female gametophyte, surrounded by parental sporophyte tissue.
Exercise 5.3: Focusing in on a mature pine pollen.
Exercise 5.4a: Pine female cone.
Exercise 5.4a: Focusing in on a pine female cone.
Exercise 5.4b: A pine male cone.
Exercise 5.4b: Focusing in on a pine male cone.
Exercise 5.5: Focusing in on a mature pine embryo.
Exercise 5.6: Pine sporophytes, and lots of other sporophytes as well.