So, this my second to last blog! I SEE THE LIGHT! Anyway, this is about embryonic development and also the cycle for plant reproduction in specific plants. It jumps around a little bit, but that is because these notes are straight from the discussion we had. So, bear with me.
So, we started our discussion with Mr. Ludwig by talking about Apoptosis. This is programmed cell death in your body; basically telling your cells to die. Why is this necessary? Well, for example, when you are an embryo, your hands are all webbed together. If your body didn’t do apoptosis than we would still have webbed fingers. Your body tells those cells to die so there isn’t a web.
Then we learned about the different stages of a developing embryo. One of the stages we went over is when it is a Blastula. This when the embryo is just a ball of cells. Then you have gastrulation which is when your ball of cells starts to cave inwards to create multiple layers and one small opening. This small opening is called the blastopore (which is important so remember it for later). This is actually what will end up creating a lot of your guts and stuff. More advanced embryos will have 3 layers. The outer most is the Ectoderm which will end up creating the nervous and integumentary systems. The middle layer is the Mesoderm, which brings forth muscles and bones. And last is the Endoderm with your guts and schtuff.
Most experiments done on embryos involve removing or implanting in the embryo to see what happens. The other ways people study embryos is by marking a part of it and watching it as the embryo develops, using fluorescent dye and using genetic markers from a similar yet different species.
There are also cells in embryos call neural crest cells. There are a dorsal root ganglions on either side of the spinal cord in the developing fetus. They are a set of nerve cells and are mainly sensory nerves. In order to be on your sides, where they are supposed to be, they have to migrate there.
So, remember how I talked earlier about the blastopore of an embryo. Well this is important when you start talking about more advanced animals compared to less advanced animals. The most advanced set of animals are called Deuterostomes. In these animals the blastopore turns into the anus and the mouth is created in another area.
The next animals are Protostomes. In these animals, the mouth comes from the blastopore and there is only one opening. One example of this is a jellyfish. And the last animals are Diploblastic. These animals only have 2 germ layers and have radial symmetry.
The next subject we brought up is the difference between Analogous and Homologous. Analogous means that similar characteristics didn’t come from the same ancestor, but they have a similar function. For example, bird wings and insect wings both have a similar function but are obviously not from the same ancestor. Homologous are characteristics that have a similar function and arise from a common ancestor.
SO, now we get to talk about plants. I think most of our AP class agrees that plants are a pain the butt. But here we go.
Today we are talking about Sporophytes and Gametophytes. The first plants we talk about are Ferns. Here is a little picture to help you out.
With these plants you have a diploid and a haploid generation. Sporophyte is the diploid generation and in ferns, this is the generation you are used to seeing. The Sporophyte creates the spores through meiosis. They go to the Gametophyte and then, through mitosis you get female and male gametes. These then get fertilized and and turn into a Sporophyte again. Below is the picture for the moss.
Now we get to learn about moss. The moss that you see around is the gametophyte, which is the haploid. The sporophyte in moss is a stalk that grows out of the top of the gametophyte.
In seeding plants the gametophyte is buried inside the sees. It is more buried inside the plant but it is still there. Almost all seeds have dual fertilization. One part gets fertilized and becomes food for germinating seed and the other part becomes the embryo.
Well, that was fun! I hope I didn’t confuse you too much.