Final answer:
Producers, such as plants and phytoplankton, are always the first in the food chain after the sun, because they use photosynthesis to create their own food and are the energy source for other organisms.
Step-by-step explanation:
The organism that always comes first in food chains, after the sun, is c. Producers.
In food chains, producers refer to photosynthetic organisms like plants or phytoplankton, which harness the sun's energy through photosynthesis. These producers are at the bottom of the food chain and create their own food, which in turn serves as an energy source for herbivores, the primary consumers. Herbivores, such as rabbits and deer, eat the producers and are followed by carnivores (secondary consumers), which eat herbivores, and then tertiary consumers that eat other carnivores. Decomposers are not the first in the food chain but play a crucial role in recycling nutrients by breaking down dead plant and animal matter, ultimately returning those nutrients to the ecosystem for use by producers once again.
After the sun, the organism that always comes first in food chains is producers. Producers are photosynthetic organisms (plants or phytoplankton) that convert light energy into food through photosynthesis. They are at the base of the food chain and provide energy for other organisms in the ecosystem.
For example, in an ocean ecosystem, a possible food chain is: phytoplankton - krill - fish - shark. Phytoplankton, as producers, create their own food through photosynthesis and provide energy for the krill, which are herbivores. The fish, as carnivores, eat the krill, and the shark, also a carnivore, eats the fish.