Why do Caltech undergraduate students take classes with graduate students? Is that normal for other universities? It seems to put an unfair advantage on the graduate students.

It is true that most, if not all, Caltech undergrads take some classes that are a mix of undergrads and PhD students.  The reason for this is because we don't have enough undergraduates to justify undergrad-only courses at the advanced level -- we have about 950 undergrads across the entire Institute.  It is also the case that we expect our undergrads to be able to handle graduate-level material.

As for whether this puts an unfair advantage to graduate students... if anything it's the other way around!  PhD students by and large DO NOT CARE about grades.  If the class is graded on a curve, that means the grading will favor the undergrads.  If the class is an advanced topics paper-reading class designed to introduce PhD students to cutting edge research areas, then basically everyone gets an A/A- in the class anyways (because the grade is totally irrelevant for the purposes of the class).
What do nonvenomous snakes and venomous snakes look like? Can you post a pic showing the differences?

What country are you in?If God made snakes, he didn,t plan on specifics for us to be able to tell just from sight alone which are which.In North America... we got it the easiest of all countries that have snakes...(European snakes i do not know

I want to go to the gym, but I'm eating less. Will eating less affect my body if I workout daily?

First of all ‘eating less' is a very vague statement. You need to know at least roughly, how much is your total calorie intake and what are the amounts of protein, carbohydrates, fats & fibres contributing to this sum. Now,

How to lose 10 pounds in a week

You can't lose that much fat in one week. You might be able to do so if you are extremely overweight or if you lose a lot of water as well but if you are anywhere near a normal weight it is impossible to lose that much weight