Describe how adaptations result in fitness? Why do individuals with low
levels of fitness die?

adaptations are changes in genetic material which develop new strong characteristics and increase fitness of an individual. any change in genetic material leads to development of a new phenotypic character. for example immunity of an organism modified and better respond to any disease as compared to an individual with this unadapted charachter (immunity). according to Darwin's concept of survival of the fittest only those organisms which have modified/adapted characteristics survive fit while the others with low fitness will lost.

Explanation:

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;

not: both offer magnification to the atomic level.