Plants and animals in the wild change over time due to tiny mutations. Different organisms with different mutations creates diversity in a population. When a mutation is helpful to an organism, it is known as an adaptation. Over time, organisms with helpful mutations outcompete other organisms in a process called natural selection. Speciation takes place when a population of organisms can't reproduce with the population it came from.
Birds with different types of beak mutations are better suited to eat different types of foods.