Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

Which statement best describes a primary consumer?

1. A carnivore that eats secondary consumers

2. An organism that breaks down dead material

3. A herbivore that consumes producers

4. A plant that undergoes photosynthesis

The correct answer is: A herbivore that consumes producers

A primary consumer is best described as a herbivore that consumes producers. Primary consumers play a crucial role in an ecosystem by feeding directly on plants, also known as producers. These organisms rely on the energy captured by plants through photosynthesis to fuel their growth and reproduction. In this way, primary consumers serve as a bridge between the producers and higher trophic levels, such as secondary consumers (carnivores that eat primary consumers) and tertiary consumers. Herbivores, which include various species such as rabbits, deer, and many insects, form the foundation of the food web as they convert the energy stored in plant biomass into forms that can be utilized by predators. This relationship underscores the critical function that primary consumers hold in ecosystem dynamics, energy transfer, and maintaining balance within food chains. The other options do not accurately define primary consumers. Carnivores that eat secondary consumers describe a tertiary consumer. Organisms that break down dead material are decomposers, and a plant undergoing photosynthesis refers to primary producers themselves.