People generally categorize organisms into two main types: those with simple structures and those with complex structures.

Humans undoubtedly occupy the pinnacle of this pyramid because of our highly complex bodies and superior intelligence.

The primary reason behind human intelligence lies in our developed brain, which aids in risk avoidance, critical thinking, and ultimately our dominance over the planet. The brain has played a crucial role in the survival and proliferation of our species.

Did you know? In the depths of the ocean resides a creature lacking a brain and possessing a very simple body structure. At first glance, it resembles two overlapping plastic bags floating in water, seemingly harmless and devoid of any threat. Yet, it has thrived in the ocean for hundreds of millions of years and shows a tendency to further expand its dominance over the seas.

This marine creature is a jellyfish. You might be familiar with this name; biology teachers often use it as an example when discussing the origins of life. It is one of the earliest creatures to inhabit the ocean and has survived unchanged for over 600 million years. Despite its unchanged body structure over this period, its vitality and disruptive capabilities are not to be underestimated.

On the surface, jellyfish appear frail and non-threatening, lacking any predatory abilities. However, they are carnivorous, feeding on fish, small shrimp, and various plankton to sustain themselves. Most jellyfish have dozens of long, thin tentacles that they use to capture prey. These tentacles are covered with stinging cells; when a prey organism comes into contact, these cells puncture its cell walls and inject toxins.

The jellyfish then waits for its prey to die from the toxins before consuming it, employing tactics similar to other carnivorous animals.

Interestingly, many other marine organisms, such as sea anemones, corals, and hydroids, also possess stinging cells on their surfaces and are collectively referred to as cnidarians.

However, their harmful capabilities are much less potent compared to jellyfish. Jellyfish are ubiquitous in the oceans, inhabiting both deep seas and shallow shores. They not only prey on other creatures but can also accidentally harm humans. Thus, when cnidarians are mentioned, jellyfish are often the first to come to mind.

Jellyfish, like many organisms, come in various species with differences in shape and characteristics. Among them, the box jellyfish stands out as notorious. Its stinging cells contain toxins several times more potent than those of other jellyfish, making it highly lethal.

When it detects prey, the box jellyfish deploys its tentacles, triggering the discharge of its stinging cells through physical reactions. These stinging cells attach to the prey, paralyze it with further injections, and eventually lead to its death, after which the jellyfish consumes it.

Despite their prowess, humans are not the targets of jellyfish attacks. Firstly, they are no match for humans, and secondly, they cannot ingest large organisms. Therefore, theoretically, humans and jellyfish should exist on separate, parallel paths, never intersecting.

However, as mentioned earlier, jellyfish are found not only in the deep ocean but also in shallow coastal waters. Instances of humans being stung by jellyfish while playing in shallow waters are not uncommon.

Mild reactions to jellyfish stings cause a sensation akin to an electric shock, leaving toxin residues in the skin that cannot be ignored. Over time, the affected area may swell and harden, and some victims may experience headaches or nausea. In severe cases, contact with certain types of jellyfish can lead to immediate fainting or death, highlighting their formidable danger.

Some have hypothesized about the collective power of jellyfish when grouped. If a single malignant jellyfish can cause such harm, imagine the potential when they gather in large numbers. Researchers studying this phenomenon have observed that when schools of fish or shrimp pass through jellyfish aggregations, they often face annihilation in moments, leaving no trace behind.

Jellyfish are not only ruthless predators but also exhibit a territorial consciousness in their survival domain. They aggressively disrupt fishing activities by entangling nets, causing them to rupture under the strain. This poses significant economic losses for fishermen. Moreover, jellyfish can block river mouths, impeding normal water flow and exacerbating their detrimental effects on human activities.

Unfortunately, despite efforts using advanced technology to eradicate them, clearing jellyfish from rivers proves challenging. In recent years, their proliferation has worsened due to human-induced factors such as nutrient-rich pollution from wastewater, overfishing of fish stocks, and rising sea temperatures—all contributing to favorable conditions for jellyfish survival and reproduction.

Some scholars speculate that if jellyfish continue to proliferate at this rate, they may eventually dominate the oceans, displacing fish species. It's remarkable how such inconspicuous creatures in the water can unleash such powerful predatory abilities. Hence, one should not judge based on appearances, a principle that holds across the animal and plant kingdoms.