SPM Biology 2014

Question

7 . Diagram 7.1 shows the development of follicles in ovarian cycle.

Rajah 7.1 menunjukkan perkembangan folikel dalam kitar ovari.

(a) Explain what happens during stages I and II in the ovarian cycle.

Terangkan apa yang berlaku semasa peringkat I dan peringkat II dalam kitar ovari.

 

(b)(i) A woman takes contraceptive pills to prevent pregnancy. The content of the pills inhibits the secretion of follicle stimulating hormone (FSH) by the pituitary gland. Explain the effect of taking contraceptive pills on stage I in the ovarian cycle.

Seorang wanita mengambil pil perancang untuk mencegah kehamilan. Kandungan pil itu merencat perembesan hormon perangsang folikel (FSH) oleeh kelenjar pituitary. Terangkan kesan pengamvilan pil penrancang terhadap peringkat I dalam kitar ovari.

(ii) Explain what are the causes for stage III to occur and its effect.

Terangkan apa yang menyebabkan peringkat III berlaku dan kesannya.

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(c) Diagram 7.2 shows the cross section of stems, X and Y of two dicotyledonous plants.

Rajah 7.2 menunjukkan keratan rentas batang X dan batang Y daripada dua tumbuhan dikotiledon.

(i) Stem X is from the plant that undergoes a primary growth. Stem Y is from the plant that undergoes a secondary growth. Explain the differences in structure between stems X and Y.

Batang X ialah daripada tumbuhan yang mengalami pertumbuhan primer. Batang Y ialah daripada tumbuhan yang mengalami pertumbuhan sekunder. Terangkan perbezaan dalam struktur antara batang X dengan batang Y.

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(ii) Diagram 7.3 shows the growth curve of a perennial plant. Explain the growth patter of the plant.

Rajah 7.3 menunjukkan lengkuk pertumbuhan bagi tumbuhan saka (bermusim). Terangkan corak pertumbuhan bagi tumbuhan itu.

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Answer ( 1 )

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    2021-03-01T14:44:20+08:00

    7.a) Stage I

    -The mature Graafian follicle ruptures, the secondary oocyte is released via ovulation into the Fallopian tube.

    Stage II

    -The follicle tissue which remains develops into the corpus luteum.

    -Small amounts of oestrogen and large amounts of progesterone is secreted by the corpus luteum.

    -Oestrogen and progesterone causes a negative feedback which inhibits the production of follicle stimulating hormone (FSH) and lutenizing hormone (LH).

    -With this the development of follicles is halted and ovulation is prevented.

     

    b)i)By taking contraceptive pills, the secretion of FSH is inhibited thus follicle development is halted.

    -There is also low production of LH, thus ovulation does not occur and Stage I is prevented.

     

    ii)-Stage III occurs when there is no fertilization (ovum doesn’t fuse with sperm).

    -The corpus luteum will disintegrate.

    -Without it, there will be low levels of oestrogen and progesterone.

    -The endometrium lining starts to breakdown as well and be discharged as  menstruation.

     

    c)i)

    Primary growth  Secondary growth
    Primary growth is important for cell elongation and cell division. Thus during this time, the stems have a smaller diameter as there is vertical growth instead.  Secondary growth is where plants grow laterally to increase girth size thus the stem has a larger diameter.
    Outer layer of the stem is non-woody as plants do not require as much support.  Plants at this stage require more support thus the outer cork layer forms a woody bark. 

    The bark also helps to minimise the loss of water. 

    Only has primary xylem and phloem. Has secondary xylem and phloem. This is to transport more water, minerals and nutrients to the plant. 

    ii) -Perennial plants have unlimited and continuous growth.

    -Thus as seen in the graph, the height of the plant keeps increasing.

    -Its annual growth shows a sigmoid curve. So as it continuously grows, the graph shows a series of sigmoid curves.

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