Fitness is the survival or reproductive rate in which a genotype or phenotype have the ability to reproduce more successfully or leave offsprings relative to other genotypes or phenotypes. It is the quantitative representation of natural or sexual selection. It is represented by w.
Cells from the cheek are a type of epithelial cell, similar to skin. ... They can be seen faintly even at 40x (scanning power), but the most dramatic images are at 400x where the nucleus is clearly visible as a dark spot in the center of the cell.