Within an ecosystem, which group of organisms is responsible for performing photosynthesis and making food?

Introduction / Context:
Ecosystems contain producers, consumers and decomposers. Producers carry out photosynthesis and form the base of the food chain. Understanding the term autotroph is fundamental in ecology and biology, because it labels these self feeding organisms that convert light energy into chemical energy.

Given Data / Assumptions:

• Photosynthesis is the process by which certain organisms produce food using light, carbon dioxide and water.
• Producers are usually plants, algae and some bacteria.
• The term autotroph refers to organisms that make their own food.

Concept / Approach:
Autotrophs are organisms that can synthesise their own organic food from inorganic raw materials. Photoautotrophs use light energy in photosynthesis, while chemoautotrophs use chemical energy. In most school level ecology questions, autotrophs refer to green plants and algae that carry out photosynthesis. Heterotrophs, in contrast, cannot produce their own food and must consume other organisms. The made up terms xylotrophs and monotrophs are distractors here.

Step-by-Step Solution:
Step 1: Recall that producers in a food chain are organisms that perform photosynthesis. Step 2: Connect producers with the term autotrophs, meaning self feeders. Step 3: Note that heterotrophs include herbivores, carnivores and omnivores that depend on producers and other consumers for food. Step 4: Recognise that xylotrophs and monotrophs are not standard ecological categories used for producers. Step 5: Select autotrophs that make food using light energy as the correct group responsible for photosynthesis.

Verification / Alternative check:
Textbooks describe terrestrial ecosystems with green plants at the base and aquatic ecosystems with phytoplankton as primary producers. These organisms contain chlorophyll and use sunlight to convert carbon dioxide and water into glucose and oxygen. They are called autotrophs because they produce their own food. Consumers like animals and many microbes, which form higher levels of the food chain, are heterotrophs and cannot photosynthesise.

Why Other Options Are Wrong:
Option a refers to xylotrophs feeding on wood and dead trees, which would be decomposers or specialised heterotrophs rather than primary producers.

Option c mentions monotrophs that eat only one type of food, which again describes a specialised consumer, not a producer.

Option d explicitly identifies heterotrophs that depend on other organisms for food, which is the opposite of autotrophs that make their own food.

Common Pitfalls:
Students sometimes confuse autotrophs with herbivores because both are related to plants. Herbivores eat plants, but they do not make their own food. Another pitfall is not recognising invented distractor terms such as xylotroph and monotroph. Focusing on the key root auto for self and troph for feeding helps remember that autotrophs are self feeders.

Final Answer:
The group that performs photosynthesis in an ecosystem is autotrophs that make food using light energy.