I believe the answer is different versions of a gene :)
Answer:
Until recent history,extinctions have always happened gradually and on a small scale.
Explanation:
Extinction occur when environmental factors like natural disaster,habitat fragmentation,over exploitation,global change don't favor the survival of species thus gradually leads to extinction of species.
Some times human activity becomes the major problem for extinction.More over,poor reproduction,decline in population number and genetic inbreeding also leads to extinction.
99% of all species that exist on earth become disappeared.
Evolution leas to speciation which leas to formation of new species but species become extinct when they are unable to survive against competition.
In summer, the temperature of Vermont is lower than that in Florida. And the temperature is an important factor influences the gas dissolving ability. When temperature increases, the ability will decrease. So there is more dissolved oxygen in Vermont's lake.