How would the body be affected if red blood cells had low levels of hemoglobin?

The body would not receive enough oxygen. Hemoglobin binds O2 and transports it throughout the body. At first, the body tissues would be hypoxic.

Don't know how much detail you need, but later, hormones would increase breathing rate and blood pressure to bring in more oxygen and pump blood harder. Also, different hormones would stimulate blood cell production.

the missing space is phylum

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.