How could tree rings from bristlecone pines support the theory that some areas have had periods of drought and flooding for hundreds of years

They can't

Explanation:

Why? *heh* I though you'd never ask. As they grow from season to season, coral reefs in the oceans and trees on the land both hold small different aspects in the climate. These recorded details can tell scientists about growing conditions in the oceans or on the land, but the record only grows across the collective lifetimes of the organisms that have been protected through the years. Thus, even though their records are more detailed, reefs and trees cannot provide records that are as long or ever-so-lasting as ice or sediment core records.

the genotypes would be 50% bb and 50% bb

the phenotypes would be 50% brown and 50% white. hope this : )

vote read

explanation:

plate tectonics and volcanic euptions

over time, plate tectonic processes cause continents to move to different positions on the globe.

for example, britain was near to the equator 300 million years ago, and therefore was hotter than it is today. for further details look at our climate through time poster or online map.

the movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate.

mountain ranges formed by plate tectonics. large mountain chains can influence the circulation of air around the globe, and consequently influence the climate.   warm air might be deflected somewhere cooler by the mountains.