Haiku 1 and 2 feel like a matched pair to me. Not only do they both involve images of sunlight and blackness and water, but they both invoke a sense of loss.
Haiku 1 is expertly executed in the classic haiku style; concrete natural images evoking a mood, followed by a twist in the last line that changes the mood, while carrying on the natural motif. I wanted to say "the water motif", but as I look back at the poem, I realize that water is never explicitly mentioned in the first two lines. It's just implied by the "glittering" of the light and how "polished" the rock is, to such a degree that my mind filled it in. I really love how you implied water in the first two lines without using any water words.
Haiku 2 is a little more experimental, in that the mood of loss slowly builds from line to line, rather than coming in as the twist at the end. I'm not quite sure how to interpret the "black" in the last line, though. Are you talking about a beach with black sand, or is it the darkness of night? (If the latter, it's an abrupt transition that skips over the gloaming.)
Can I just say that I love Tanka 1? You're not afraid to grapple with the big questions, and they don't come much bigger than the relationship between nature and artifice. And the parallels in the first two lines are amazing! You draw out the similarities with the reuse of "hum" in the first line and then use parallel structure and internal rhyme all packed into the second line. Have you considered abandoning the tanka form for this one? I realize that you have to do tanka for this homework assignment, but I think this could be professionally publishable afterwards if you had the freedom to make the structure of the conclusion resonate with its content the same way that you did in the first two lines. You're already tweaking the line length in the first two lines (which is not a bad thing) and using non-tanka techniques like internal rhyme.
Tanka 2 is also approaching big themes, in this case the accumulation of small changes that together make a big impact. But the last line throws me; origami is the art of paper folding, not paper cutting. Have you thought about using "jianzhi" (the Chinese art of paper cutting) or "mon kiri" (Japanese paper cutting) instead of "origami"?