Four chambered heart keeps oxygenated and deoxygenated blood separate and has double circulation while three chambered heart has a single circulation. Two chambered heart only has single atrium and single ventricle
4 billion years ago the temperature was much higher due to repeated volcanoes and hot gases present in the atmosphere. There weren't any live forms on earth. ... The atmosphere had a different concentration of gases on the earth. There were no life sustaining gases.
Answer:
The correct answer is A. Since the Earth has a tilted angle of 23.5 degrees as it moves around the sun, the amount of sunlight that is received by the hemispheres vary from time to time. This is mainly responsible for the changes in the temperature and daylight hours, which are the indicators of the changes in seasons.
In this case, when one hemisphere of the Earth is tilted toward the sun, it receives more sunlight than the other end. Therefore, this region experiences summer, wherein the daylight is longer and the temperature is warmer
