4 copies of a DNA molecule result from two replications of a single DNA molecule
homeostasis is done throughout the whole body not particular parts or organs so when the body temperature rises the sweat glands all-over the body secretes sweat to lower down the temperature of the body
You can restore damaged ecosystems by planting trees on land where forests have been cut down. Or you can encourage people around you to live in ways that don't hurt the environment.
Human egg cell
But human egg cell is the one of the largest cells in the human body that can be seen with naked eye. i.e we are able to see it without the help of a magnification device. The size of this cell is about 0.12 mm in diameter.