The physical area in which an organism lives . One pound is approximately equal to half a kilogram. All living things are made of cells. Ribosomes are the respiration centers of a cell. Most human cells have 23 chromosomes.
Haploid cells have twice the normal number of chromosomes.
Gregor Mendel first proposed the chromosome theory. Sex-linked traits have genes located only on the X chromosome. Any change in the DNA of an organism is known as a mutation. The tendency to develop cancer is thought to be hereditary. Anything that damages cells will cause cancer.