In the biosphere, living organisms are interrelated and interdependent on one another and on their physical environment for survival. This life supporting system of interacting organisms and environment is known as what?

Introduction / Context:
Ecology deals with the relationships between living organisms and their environment. In the biosphere, no living organism exists in complete isolation. Each species interacts with other species and with non living factors such as air, water, and soil. The combined system of living and non living components that function together in a balanced way is described by a specific term. This question asks you to identify that term from common options used in environmental science.

Given Data / Assumptions:

• The description mentions living beings that are interrelated and interdependent.
• It also refers to a life supporting system, implying inclusion of non living environmental components.
• The options are ecosystem, mountain range, forest, and atmosphere.
• We assume standard ecological definitions.

Concept / Approach:
An ecosystem is defined as a functional unit consisting of living organisms (the biotic community) interacting with each other and with the non living environment (abiotic factors) such as climate, soil, water, and nutrients. A forest is a particular type of ecosystem with dominant trees, a mountain range is a landform, and the atmosphere is the layer of gases surrounding the Earth. The correct term must capture both living and non living components interacting together as a system.

Step-by-Step Solution:
Step 1: Identify key phrases in the question such as "living beings are inter-related and interdependent" and "life supporting system". Step 2: Recall that an ecosystem includes producers, consumers, decomposers, and the physical environment, all interacting through flows of energy and cycles of nutrients. Step 3: A mountain range is primarily a physical feature and does not by itself guarantee a description of all interactions between organisms and environment. Step 4: A forest is a type of ecosystem dominated by trees and other vegetation, but the term forest does not generalise to all life supporting systems in the biosphere. Step 5: The atmosphere is a component of the environment, mainly the gaseous layer, but does not include the full set of living and non living interactions by itself. Step 6: Therefore, the most appropriate term for the described life supporting system is ecosystem.

Verification / Alternative check:
Ecology texts define an ecosystem as a structural and functional unit of the biosphere, in which biotic and abiotic components are linked by nutrient cycles and energy flows. Examples include lakes, forests, grasslands, and agroecosystems. Each of these can be described as a life supporting system where organisms depend on each other and on non living resources. This matches the wording in the question and supports ecosystem as the correct term.

Why Other Options Are Wrong:

• Mountain range: A geological feature that may host ecosystems but is not itself defined mainly by biological interactions.
• Forest: A specific type of ecosystem; the question is about the general concept, not just forested areas.
• Atmosphere: The gaseous envelope around Earth, which is an important abiotic component but does not alone describe the total life supporting system.

Common Pitfalls:
Some learners may choose forest because they associate it strongly with biodiversity and wildlife. Others may think of atmosphere because life needs air to survive. However, the question emphasises interdependence among organisms and their environment, which directly points to the more general concept of an ecosystem. To avoid confusion, remember that an ecosystem includes all living components plus physical factors, not just one type of habitat or one environmental layer.

Final Answer:
This interrelated and interdependent life supporting system is called an ecosystem.