The sled with a rough metal bottom would take more force to move over ice, because the rough surface would increase friction and the force needed.
This answer to this question is Paramecia, cilia
Chickens have 78 chromosomes.
There was no life on Earth for the first billion years because the atmosphere was not suitable for life. Earth's first atmosphere had lots of water vapor but had almost no oxygen. Later, frequent volcanic eruptions put several different gases into the air.