In this video, we're looking at trophic levels, where you're basically just the different levels within a food chain. So in this one here, the grass would be trophic level 1, the rabbit would be trophic level 2, the snake is trophic level 3, and the hawk is trophic level 4. The first trophic level is always a producer, like a plant or an algae. and we call them producers because they're able to use photosynthesis to produce their own food, using energy from sunlight. And this is where all the energy in the entire food chain comes from. The second trophic level is made up of primary consumers, which basically means first consumers, because these are the first organisms in the food chain that consume other organisms.
and they can also be called herbivores, because they only eat plants and algae. The organisms in the third trophic level are known as secondary consumers, because they're the second level of consumers in the chain, and they're also known as carnivores, because they eat other animals. From this point onwards, the pattern just keeps repeating, with organisms of the fourth trophic level, known as tertiary consumers, because tertiary means third.
And again, they'll also be known as carnivores. Now, different food chains in different ecosystems will have different numbers of trophic levels, but you usually won't get any more than four or five. This is because every time you go up a trophic level, some of the energy gets lost, and so there's not enough energy to sustain organisms in much higher trophic levels. The general rule is that only about 10% of the energy that's in each trophic level actually gets passed on to the organisms in the next level. So if we started with 1,000 joules worth of energy in trophic level 1, that would be reduced to 100 joules in trophic level 2, then 10 joules in trophic level 3, and only a single joule by trophic level 4. Regardless of how many levels there are though, the carnivores at the very top of the chain, who don't have any predators, are known as apex predators.
One group of organisms that don't fit neatly into this pattern are omnivores, like bears, because they eat both producers and other animals. In general, we place omnivores in trophic level 3. because they eat primary consumers. However, because they also eat producers, it's not really a perfect fit. The other groups we need to mention are decomposers and detritivores. These are organisms like bacteria, fungi, and some small animals like worms.
What they all have in common is that they help to decompose the plant and animal matter in the environment. This allows them to recycle nutrients from animals and plants back into the ground, which can then be used again by producers. Anyways, that's everything for this video, so if you found it useful then please do give us a like and subscribe, and cheers for watching!