so, i have the option to take anatomy and physiology (not an AP, a dual credit class) next year. however, i don’t really have any interest in the field of science and don’t plan to pursue it in the future. should i still take the class for rigor or is it okay if i TA for a US History class with a teacher that i like? what do you guys recommend i do? i am a rising senior btw.
I don’t think you will get much benefit from the anatomy and physiology class given you don’t plan to pursue science in college. On the other hand, serving as a TA for a US history class with a teacher you like sounds like a great opportunity. Having that on your resume shows that your teacher had confidence in both your mastery of the material and your ability to do the job, and you might get a good recommendation letter out of it as well.
Go with what you like 
It would help others help you if you:
A. Describe the alternative courses you could take instead.
B. Describe the rest of your past and proposed schedule.
C. Indicate whether you have all of biology, chemistry, and physics in your past and proposed schedule.
Just for reference, I have taken all three years of required science at my school (physics, chemistry, biology). This time slot basically comes down to anatomy, being a TA, or taking a study hall.
Done!