Answer:
Air pressure is the weight of air molecules.
Explanation:
Air pressure can be described as the force generated by the weight of air on the surface of the Earth. The size and number of the air molecules determine the air pressure.
When the number of molecules in the air increases, it generates more force on the Earth's surface and we say that it is regarded as a rise in the atmospheric pressure. A mercury barometer is a device which is used to measure the air pressure.
Answer:
d.The wing-assisted incline running theory postulates that wings were initially used to maintain balance while climbing up slopes.
Explanation:
Two theories were given to explain the origin of avian flight. The top-down theory suggested that the birds' ancestors were tree dwelling species. They took help of wings to glide from tree to tree in order to avoid predator or catch prey. The bottom up theory suggested that the birds' ancestors were ground dwelling species. They took help of wings to maintain a balance and provide a lift for efficient running.
Wing-assisted incline running was a mixture of both the above theories and gave a balanced view point. According to it, birds' ancestors used wings to maintain a balance while running up inclined slopes. The wings helped them to save energy while scaling slopes and eventually a flight mechanism was also developed.
The answer is 3
Explanation:
