Rough-skinned newts and common garter snakes are in an "evolutionary arms race." In this phenomenon, two species continually evolve adaptations against one another to increase their own chance of survival. Rough-skinned newts produce tetrodotoxin, a type of poison, as a defense mechanism. Most common garter snakes have some resistance to the toxin. In areas where common garter snakes and rough-skinned newts coexist, rough-skinned newts express very high levels of tetrodotoxin, and common garter snakes have evolved a very high degree of resistance to tetrodotoxin.

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they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.

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water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. weathering is the breaking down or dissolving of rocks and minerals on earths surface. once a rock has been broken down, a process called erosion transports the bits of rock and minerals away.