12. What is industrial melanism?

it is an evolutionary mechanism by which many arthropods evolved into having darker pigmentation or melanism due to industrial pollution, soot deposits, etc

Explanation:

industrial melanism was observed in the population that lived near or around industries during the industrialization period. it helped organisms like  moths to camouflage in the environment to protect them from predators. Lichens are used as natural pollution indicators and they were not found growing around areas where industries were located, indicating high pollution levels. the industries produced a lot of harmful gases like sulphur dioxide and emitted soot deposits. due to heavy pollution in and around the area, the organisms living inside its parameter started to evolve in order to survive. before industrial revolution, there were only white moths (Biston Betularia). however, during this period it evolved into a black moth to camouflage with the darker tree barks and to save itself from its predators.

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answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: