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.
Prokaryotic cells lack a defined nucleus, but have a region in the cell, termed the nucleoid, in which a single chromosomal, circular, double-stranded DNA molecule is located.
C. light-years is the best to describe the distance
Answer:
In thermodynamics, a closed system can be described as a system which can exchange energy from outside but matter cannot be transferred from such a system. This means that the resources present on the Earth cannot be transferred or replaced and the waste can also not be removed. By understanding the concept of the closed system, humans should recognize the fact that many resources such as minerals present on the Earth cannot be replaced and hence, resources should be utilized effectively in a conserved manner. Also, as waste cannot be removed hence humans should stop forming such waste products which cannot be removed or recycled.
Answer:
a gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide, chlorofluorocarbons, and other pollutants.
