My course load is 18 units first term and 12 units second term. These are the courses I have:

FIRST TERM

BIOLOGY 2D03
BIOLOGY 2F03
ENVIR SC 2C03
HISTORY 2T03
LIFE SCI 2D03
RELIG ST 2G03

SECOND TERM

BIOLOGY 2B03
ENVIR SC 1A03
LIFE SCI 2A03
ORIGINS 2LU3

Based on this, is it ok if my course load is uneven or should I do some modifications to my schedule. But most of the courses are only available during one term so I have no choice but to take the course then.

That really depends on you. Can you handle 6 courses in one semester? How badly do you want to take each of those courses in first semester? I have done six a semester before and found it beyond stressful, and my grades suffered, but lots of people handle six courses a semester very well. If you are the type of person who is good at time management and is willing to dedicate the time to do six courses, more power to you. Lots of people do it every year and do just fine, but you may want to look at how much you really want each of those courses.

Another thing to consider if you don't timetable shuffle is picking up an extra course second semester, one from next year, so you can carry 5 courses. It would help you get ahead, and 4 is pretty light.

Good luck!

I STRONGLY STRONGLY STRONGLY advise you NOT to have an unbalanced courseload.
Do whatever you can to try to make it even. You really dont want to be handling 6 courses in one semester

I've done 6 and 5 in 2nd year and that semester with 6 courses was hell on earth. Really wouldn't recommend it unless you have at least 2-3 bird courses in there.

I agree, I also did 6 courses a term during my third year, though my grades did not suffer and It was possible to balance it out. It was hard and during my final exam schedule, I had four finals back to back. I would also not advise it.

I've had 6 courses in one term and 4 courses the other term for 3 years in a row. As long as you work hard and don't slack off too much, you should be fine
The only tricky part was exams.

I agree with Kathy2, it's exams that are tricky. I had 6 courses in a semester last year and was otherwise fine. It does just planning.

6 courses ain't bad. Man up.