Why is crossing over of the chromosomes during meiosis important?

In the respiration-photosynthesis cycle shown above, what are the products of cellular respiration that belong in box 2?

Which member of the following food chain will be least affected by ddt, a pesticide water pollutant, if bio-magnification is occurring? algae> zooplankton> crayfish> leopard frog> large mouth bass

If a force of 40 newtons moves a cart a distance of 9 meters, the work done is nm. if the same force moves the same cart three times that distance, the work done is nm.