Final answer:
Mutations in germ-line cells lead to evolutionary changes because they form progeny, enabling the mutation to be passed on to offspring. Somatic cell mutations, although they can lead to cancer, do not contribute to evolution as they are not inherited.
Step-by-step explanation:
Mutations that occur in germ-line cells are the only ones that lead to evolutionary change because B. germ cells form progeny. This means that when a mutation occurs in germ cells, which are the cells that develop into sperm or ova, this mutation can be passed on to the offspring and every cell in the offspring will carry the mutation. This includes hereditary diseases such as Tay-Sachs disease, cystic fibrosis, hemophilia, and sickle-cell anemia, among others.
On the contrary, mutations in somatic cells (the cells that are not involved in reproduction) are not passed on to offspring. These mutations can lead to cancer if cell division becomes uncontrolled, forming benign or malignant tumors. However, such somatic mutations do not contribute to evolutionary change because they are not heritable.