The idea of natural selection was thought of by Charles Darwin
Natural selection is the process that organisms better adapted to their environment tend to survive and produce more offspring. The 4 stages of natural selection are Reproduction, heredity, variation in Characteristics and variation in fitness.
Penguins are an example of Natural Selection because the penguins who are fast swimmers have a higher chance of survival.
The faster penguins could hunt and get around easily without being disturbed by predators.
The slower penguins however have a harder time keeping away from predators and hunting without being disturbed.
Over time the penguins began to develop slimmer flippers allowing them to hunt and escape from predators faster.
In the end the population of Penguins developed slimmer flippers and were able to thrive while hunting and swimming.