Ecology

Carbon dioxide is the primary greenhouse gas because its molecular structure allows it to absorb and emit infrared radiation, trapping heat in the atmosphere. In contrast, nitrogen and oxygen make up the majority of the atmosphere but do not absorb infrared radiation, meaning they do not contribute to the greenhouse effect.

In a forest ecosystem, a single large producer, like a tree, can support numerous herbivorous insects, resulting in an inverted pyramid of numbers. In contrast, grassland ecosystems feature an upright pyramid because thousands of individual grass plants are needed to support a smaller number of herbivores.

Tropical rainforests exhibit the highest primary productivity because abundant sunlight, warm temperatures, and consistent rainfall year-round optimize photosynthetic activity. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

• !In contrast, nitrogen and oxygen make up the majority of the atmosphere but do not absorb infrared radiation, meaning they do not contribute to the greenhouse effect.

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