How might natural selection on single-gene traits lead to evolution?

Natural selection on single-gene traits can lead to changes in allele frequencies and thus to changes in phenotype frequencies. How does natural selection affect polygenic traits? Affects the relative fitness of phenotypes and thereby produces one of three types of selection: directional, stabilizing, or disruptive.

Eukaryotic cells are theorized to have evolved from prokaryotes called the endosymbiotic theory. this explains that the most primitive eukaryotic cell engulfed a prokaryotic cell (by the process of phagocytosis) that is capable of cellular respiration and another prokaryotic cell that is capable of photosynthesis. these prokaryotic cells eventually became organelles and these organelles are the mitochondria and the chloroplast

If you remove all the lions from the savanna it will lead to a increase of gazelle and a increase of cheetahs becasue of no competition