This idea was used by George Cuvier to explain the extinction of species. Catastrophism was opposed by uniformitarianism during the late 18th and 19th centuries. Creationism the belief that all species were created as they are today and that they have not undergone any evolution since then. This view is usually based primarily on the Book of Genesis in the Judeo-Christian Bible. Chromosomes are composed primarily of DNA and protein.
Chromosomes are visible only under magnification during certain stages of cell division.
Descent with modification is another way of describing evolution . They are usually seen in terms of being food getting opportunities in the environment. The term is also frequently used to refer to the appearance of a new species. Examples of fossils are mineralized bones and plant parts as well as casts and imprints. In the Linnaean classification system, genus is the category immediately above species .