¶ … evolution of eukaryotic cells linked to the increase of atmospheric oxygen concentration during the Precambrian? Increase of atmospheric oxygen during the Precambrian period led to creatures which were more dependent on oxygen in the atmosphere. Oxygen levels in the atmosphere increased from 1% to 15% of the modern level of oxygen. The increase in oxygen in the air led to the evolution of more expansive lungs which were capable of taking in more air and converting it into energy. As eukaryotic cells evolved, they became more capable of respiration which added to the complexity of the evolutions of creatures.

Scientists believe that if there are no controls on the emission of CO2 from burning fossil fuels, the concentration of this gas could double by the end of the current century, leading to a significant rise in the average temperature of the Earth. What would be some of the likely evolutionary effects of this climatic change?

Scientists believe...

Since average temperatures will increase, animals would have to evolve skin which was less warm such as the eradication of fur. Certain animals, such as lizards and reptiles who already live in high temperature areas would appear in other areas. Also, the creatures would have to adapt to breathe in carbon dioxide in greater amounts which would be difficult.
3. If we were concurrently living during one of the cooler periods in the Earth's history, why should we still be concerned about human activities that are thought to contribute to global warming?

The reasons that people should be concerned about global warming and their contributions to it is that even though we…