4 (a) Plants use nitrate ions to make proteins and chlorophyll - Edexcel - GCSE Biology - Question 4 - 2018 - Paper 1

Bacteria are the primary organisms that convert nitrogen to nitrate ions during the nitrogen cycle. They perform this process through nitrogen fixation and nitrification, which make nitrogen available for plant uptake.

To calculate the surface area to volume ratio, we use the formula:

$\text{Surface Area to Volume Ratio} = \frac{\text{Surface Area}}{\text{Volume}}$

For the root hair cell:

• Surface Area = 36,000 µm²
• Volume = 288,000 µm³

Thus,

$\text{Surface Area to Volume Ratio} = \frac{36,000}{288,000} = \frac{1}{8}$

So the surface area to volume ratio is 1:8.

Root hair cells increase the surface area of the plant's roots, allowing for more effective absorption of water and minerals from the soil. This adaptation enhances the plant's ability to uptake essential nutrients, thereby supporting overall growth and health.

From February to June, the number of algae in the lake shows an increasing trend. This increase can be attributed to several factors:

1. Warmer temperatures during spring promote the growth of algae as they thrive in warmer conditions.
2. Longer daylight hours in spring enhance photosynthesis, leading to increased algal reproduction. Therefore, the increase in temperature and light availability contributes significantly to algal growth during this period.