The short answer: the egg. And it is not even close. Eggs are far older than chickens Animals were laying eggs long before any bird existed. Fish and amphibians lay eggs, and the hard-shelled amniotic egg, which let animals reproduce away from water, appeared more than 300 million years ago. Dinosaurs laid eggs. Chickens arrived … Read more
Both rocks are made of large fragments, called clasts, more than 2 millimeters across (gravel size and larger), cemented together in a finer matrix. The main difference is the shape of the clasts: Why shape matters Rock fragments get rounded as they are transported. Tumbled by water along a river or by waves on a … Read more
The end result of meiosis is four haploid cells, each genetically different from the parent cell and from each other. In humans, one cell with 46 chromosomes (23 pairs) produces cells with 23 single chromosomes. These become sperm or egg cells, so that fertilization restores the full set of 46. Why halve the chromosomes? If … Read more
Dreaming about someone usually means that person, or what they represent, is on your mind, even if you are not aware of it. It does not mean they are dreaming about you, thinking of you, or sending you a message. Dream research does not support psychic or mystical interpretations, although many cultures have rich dream … Read more
