Final answer:
Historical ecology integrates past cultural and environmental processes to understand human-nature interactions over time, while an ecosystem approach focuses on present interactions among organisms and their environment. A keystone species has a far-reaching impact on ecosystem balance and its removal can significantly change ecosystem structure. Ecologists study ecosystems through observation, experimentation, and modeling, including understanding food chains and webs.
Step-by-step explanation:
Historical ecology is an interdisciplinary field of research that combines the study of ecosystems with the investigation of cultural, environmental, and historical processes that have shaped human interactions with the environment over time. It often involves looking at changes in landscape patterns, species distribution, and ecological processes from a historical perspective. In contrast, the ecosystem approach focuses more narrowly on the interactions between living organisms, including humans, and their physical environment. It examines how these interactions affect the flow of energy, the cycle of nutrients, and the dynamics of ecosystems without necessarily emphasizing historical perspectives.
A keystone species is a species that has a disproportionately large impact on its natural environment relative to its abundance. These species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in the ecosystem and helping to determine the types and numbers of various other species in the community. When a keystone species is removed, it can lead to significant changes in the ecosystem, sometimes causing a cascading effect that alters the entire ecosystem's structure and function. Examples of keystone species include the sea otter, which is essential for maintaining kelp forest ecosystems by controlling sea urchin populations.
Ecologists study ecosystem structure and dynamics using various methods, including observational studies, experiments, and ecosystem modeling. Ecosystem models help in understanding complex interactions and predicting future changes. The foundational understanding of ecosystems includes knowledge about food chains and food webs which are vital for comprehending the energy flow and interactions among different species.