Abiotic factors are physical and biotic factors are biological.
For example, parasitism and mutualism are biotic factors and soil pH is an abiotic factor.
Both biotic and abiotic factors are important in ecology which aims to understand the relationships between species and their environment. A biotic factor such as interspecific competition (between species) leads to the development of ecological niches over time, this can be an evolutionary process where organisms develop particular characteristics to be able to avoid competition.
Birds are great examples of evolution to avoid competition since they have different shaped beaks based on their diet. We explain these differences in evolutionary history using classification systems.
Learn more about ecology with the Environmental Sampling Quiz and this quiz on the levels of organisation in ecology.