HL 1 Biology

11.4b Oogenesis

• AA-CC: 277-9; DBQ: 278

<<Oogenesis>>

  • the production of egg cells in the ovaries
  • 2 main types of ovary tissue: medulla + cortex
  • Process
    • starts in ovaries of female fetus
    • germ cells in fetal ovary divide by mitosis, cells formed move to cortex
    • when fetus’s 4-5 months old = the cells grow + start to divide by meiosis
    • 7th month = still in first division of meiosis + single layer of cells (follicle cells) formed around them
    • primary follicle: cell that started to divide by meiosis, together with surrounding follicle cells
    • mature follicle: contains secondary oocyte

<<Male and Female Gametes>>

  • similarities: contain haploid nucleus + both have microtubule organizing centrioles
  • differences:  sperms are long, have a flagella tail ; ovary has many components including the cytoplasm, layer of gel composed of glycoproteins.

<<Comparing Spermatogenesis and Oogenesis>>

  • testes continue to produce sperm from puberty onward
  • sperms pass out of testis through epididymis (narrow tubes)
  • millions sperms moved when male ejaculates
  • semen made with various components: seminal vesicle and prostate gland
  • seminal vesicle; alkali help sperm from the vagina’s acidity
  • FEMALES: first division of meiosis produces one large cell + one small cell
  • small cell = first polar body and degenerates/dies
  • large cell goes to second division of meiosis; completing it after fertilization
  • only large cell (the female gamete) survives
  • process occurs during menstrual cycle once and usually only egg cell is produce

===================DBQ========================

Sizes Of Sperm (p.278)

1) The graph of tail length and cross-sectional area of protein fibres in the eight species of animal.

2) Looking at the graph above, we can see the relationship between the tail length and cross-secional area of protein fibers to be proportional. As the length of the sperm is larger, the cross-sectional area of fibrous sheaths is larger as well. Although with the limited amount of data, there is not an exact conclusion to different situations.

3) Reasons for the relationship include the stress felt shearing stress in longer sperm; needs thick cross-sectional area in order to support. Looking at the graph we can see that the dimensions of all the data is related to the overall size of the sperms.

4) There is not necessarily a relationship between the size of an animal and the size of tis sperm. Thus we know that the size of the sperm does not necessarily follow the size or height of the animal/human.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s