Final answer:
Ecology focusing on changes in one species is population ecology, which studies the number and fluctuations of individuals in a species over time.
Step-by-step explanation:
Ecology that focuses on dynamic changes occurring in one species is population ecology. Population ecology examines the number of individuals of one species in an area and how and why that number changes over time.
For example, it could involve studying the fluctuating numbers in an antelope population or tracking how a species responds to various biotic and abiotic factors. Characteristics of a population such as distribution, abundance, density, and life strategies are quantified by ecologists to analyze and understand the shifts within that population.