I would guess that the answer would be :'<span>These organisms dig more shallow burrows than they used to.</span>' If the crabs actively dig burrows, as many crab species do, and a layer of oil has persisted in the lower soil strata, it makes sense that the crabs would be reducing the depths of their burrows to avoid contact with the oil. The other possibility is that the crabs might might migrate to deeper waters, but this is less likely because the crabs would be evolved to utilise the intertidal zone.
Carbon dioxide is a byproduct of respiration while oxygen is a byproduct of photosynthesis.
Remember that a byproduct is a secondary product that is made in the synthesis of another. It is unintended and excreted.
Answer - B
Fish and reptiles both are ectothermic but fish have gills and reptiles have lungs. Ectothermic organisms do not have an internal mechanism of regulating their body temperature and are dependent on their atmosphere for temperature regulation. Fish, reptiles and invertebrates are examples of ectothermic organisms.
One is that it allows for variation which allows better chance of survival and evolution.
