I'm planning to do a Bio IA.
If possible it needs to be something related to yeast.
No measuring respiration or fermentation. Already Done.
Make sure that it is appropriate for a Senior IA.

No elementary cool magic trick experiments.
If you don't know what an IA is don't answer. (IB Students)

Explanation:

Look into Antimicrobial Peptides and the usage of yeasts to fight the bacterial resistance to antibiotics. Due to the rising bacterial resistance, scientists are using Antimicrobial Peptides (AMPs) as an alternate way to fight this crisis.

Where does yeast come into play?  Yeasts are becoming a go-to organism for genetic engineering and recombinant protein production and a source to idenitfy how these AMPs work so that we could possibly target those pathways.

Read the "Antimicrobial Peptides: Recent Insights on Biotechnological Interventions and Future Perspectives" journal article to see if this is something you would like

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.

the correct answer to this question is #5