A biological cycle, or rhythm, that is approximately 24 hours long is called a circadian cycle
Bio accumulation of DDT lead to bird eggs with weak shells and non viable offspring. The lethal effects of DDT on birds was first noted in 1950; scientists discovered that earthworm was accumulating the DDT pesticide and that the robins that were preying on the earthworms were been poisoned. Further research revealed that the chemical cause thinning of the egg shell and production of non viable offspring. The chemical has since been banned in USA.
