7.4.1: Trophic levels
Not started yet — this one needs some love.
Trophic levels are numbered feeding levels in an ecosystem.
Trophic level 1 starts with plants and algae.
Further trophic levels are numbered according to how far the organism is along the food chain.
Level 1: plants and algae make their own food and are called producers.
Level 2: herbivores eat plants or algae and are called primary consumers.
Level 3: carnivores that eat herbivores are called secondary consumers.
Level 4: carnivores that eat other carnivores are called tertiary consumers.
Apex predators are carnivores with no predators.
Decomposers break down dead plant and animal matter by secreting enzymes into the environment.
Small soluble food molecules then diffuse into the microorganism.
Common exam mistakes
Do not put decomposers into one numbered trophic level; they break down material from different levels.
Do not confuse decomposer digestion with animals eating food; decomposers secrete enzymes outside themselves.
Diffusion is how the small soluble food molecules enter the microorganism; do not swap this for active transport unless the question states it.
Apex predator means no predators in that ecosystem, not that it eats every organism in the food chain.