100
Cells may be prokaryotic or eukaryotic cells. Eukaryotic cells have a nucleus that
contains deoxyribonucleic acid (DNA) whereas in prokaryotic cells, the DNA is not
encapsulated in a nucleus.
DNA is the cell’s genetic material that contains many genes. Genes are the basic
physical as well as functional units of heredity.
Subatomic particle
Atom
Molecule
Macromolecule
Organelle
Cell
Tissue
Organ
Organ System
Complex Multicellular
Organism
Fig. 3.6 Illustration
showing complex
arrangement of chemicals
that makes an organism
3 Fundamentals of Biology for Environmental and Medical Professionals