Blog 2 Semester Two Double Fertilization

BIO AP BOW
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Describe double fertilization.

Fertilization takes place between sperm cells and two cells within an ovule.  The ovule contains the reproductive cell, megaspore. The megaspore undergoes meiosis to produce 4 haploid megaspores.  In most species, three degenerate leaving one megaspore.  The remaining megaspore undergoes mitosis to produce 8 haploid nuclei who share the same cytoplasm.   These 8 haploid nucleic structure is called the embryo sac.  Cell walls form between most of the embryo sac.  Three cells form near the micropyle, two are called the synergids and one of the cells is the egg.  The remaining two nuclei stay together in one large main cell.  The egg cell and the single cell will soon take part in double fertilization.  But before this event can happen, the sperm has to enter the female reproductive organs.  To reach the embryo sac, a pollen grain begins to germinate, sending a long pollen tube the the style and the ovary of the female flower.  The generative cell(one of the haploid cells) goes down the pollen tube. The generative cells undergoes mitosis to make 2 haploid sperm cells.  Once the pollen tube reaches the micropyle of the ovule, it digests its way into the synergids, releasing the sperm cells.  The synergid degenerates, and one sperm cell fertilizes the egg cell, producing a diploid zygote.  The remaining sperm cell, fuses with the polar nuclei and makes  triploid(3) cells.  When the zygote turns into an embryo, the triploid cells develops into the endosperm( food for embryo).



http://bcs.whfreeman.com/thelifewire/content/chp39/3902001.html

Semester Two Extra Credit Blog

In your blog please give me some feedback on last semester

What topics really confused you?
At first, the first month i was really confused about everything.  Until we started to have lectures and then I started to understand the topics a little bit more.  The topics that confused me first semester were the cells. Especially Cell division.  I did not feel that we spend enough time going over this topic.  I am also confused about RNA structure and function.

What topics do you feel very clear on?
I feel clear about the Kingdoms of fungi, prokaryotes, eukaryotes and viruses.  I also really have a lot of knowledge on the unit on behavioral ecology and ethology.  I feel like this units are the ones that I understood the most.

What lab/ activity was your favorite? Why?
My favorite lab for fist semester was the transpiration one because my group had to present it to the whole class. I learned how the different environments affect the growth rate of plants.  How photosynthesis is greatly affected by heat and how transpiration speeds up in windy conditions.  I also learned transpiration occurs very slow in the night in most plants.  Guard cells, xylem and phloem are important factors in the process of transpiration.  I really enjoyed doing this lab because we got the chance to control 5 factors that affect the rate of transpiration in plants and i believe i got a better understanding on the process osmosis and diffusion.

What lab/activity was your least favorite? Why?
The lab that I did not enjoy doing was the plant chromatography.  My group was really confused on the procedures probably because i do not recall having a group presentation before starting the lab.  We finally got how to do the lab correctly the last 20 minutes of class.  The other thing that made our data get results that were way off was that the other groups that we had to collaborate with, were confused as well.  I think we should have a group presentation for each lab we do for clarity.

If you could change something about the class to make it better, for instance the type of homework (not the amount) what would it be and why?
I DO NOT like the simulations we do.  To be honest, i really do not learn new things from them.  I rather do labs in class with hands on experience that online.  I think the lab simulations are only taking up time for other things we can do such as taking notes or other review material on the unit we are covering.  The Blogs i do enjoy doing because they help me refresh my memory on the topics we are learning in class.  I also DO LIKE having daily quizzes because it will help me know what i need to work on and study for the A.P test.