In exactly 15 words can you explain how the arm bends and straightens?

What causes temperature extremes in the desert

Look at the photo of the leaf. which term best describes this leaf?

Which scientific design has both practical limitations and limitations due to scale? studying the effect of bleach on the growth of mold spores exposing cultures of duckweed to different intensities of light observing the replication of dna molecules with a hand lens using colored marbles to model a cross between two colors of rabbits