Variability is the raw material for natural selection. Specialized features of organisms which allow them to perform useful functions are called adaptations . Similar body plans suggest common origins. Analogy - body parts with similar function , without regard to origin. Similar functions but different structures suggest different origins.
Organic evolution refers to changes in populations.
It is influenced by both genetics and environment. All organisms go through changes in appearance during their lifespan. This is called ontogeny . In each of these examples, no genetic change is involved. The genotype remains the same, but the phenotype varies dramatically .