Mahinoor B.

a) 24

• A pollen mother cell (PMC) is a diploid cell (2n), so it contains the full set of chromosomes (2n = 24).

b) 12

• Microspores are produced via meiosis, which halves the chromosome number (n = 12).

c) 25

• Step 1: Each meiotic division of a single PMC produces 4 microspores (pollen grains).

• Step 2: To calculate the divisions needed: frac{100 \text{ pollen grains}}{4 \text{ microspores per division}} = 25 meiotic divisions.

d) 200

• Step 1: 1st Mitosis: Each of the 100 microspores undergoes 1 mitotic division to form a vegetative cell and a generative cell.

  \text{Divisions} = 100 \times 1 = 100

• Step 2: 2nd Mitosis: Each of the 100 generative cells undergoes 1 mitotic division to form two male gametes.

  \text{Divisions} = 100 \times 1 = 100

  Step 3: Total Mitotic Divisions:

  text{Total} = 100 + 100 = 200

• Center: $(0, 0)$

• Orientation: Horizontal major axis (along the x-axis, as $16 > 9$)

• Semi-Major Axis ($a$): $4$ (since $a^2 = 16$)

• Semi-Minor Axis ($b$): $3$ (since $b^2 = 9$)

• Focal Distance ($c$): $\sqrt{a^2 - b^2} = \sqrt{16 - 9} = \sqrt{7} \approx 2.65$

• Major Axis Vertices: $(\pm 4, 0)$

• Minor Axis Vertices (Co-vertices): $(0, \pm 3)$

• Foci: $(\pm\sqrt{7}, 0)$

• Length of Major Axis: $2a = 8$

• Length of Minor Axis: $2b = 6$

• Eccentricity ($e$): $\frac{c}{a} = \frac{\sqrt{7}}{4} \approx 0.661$

• Directrices: $x = \pm\frac{a^2}{c} = \pm\frac{16}{\sqrt{7}}$

• Length of Latus Rectum: $\frac{2b^2}{a} = \frac{2(9)}{4} = \frac{9}{2} = 4.5$