Lamprey

is a jawless vertebrate related to

lamprey

and the most primitive known vertebrate animal. They are so primitive that Julien has no ridges.

Pufferfish is

a bony fish

and shark is

cartilaginous fish

, so according to traditional biology According to the grading method, the lowest level is hagfish, followed by shark, and the highest level is pufferfish.

In fact, biology has now downplayed the classification of high and low levels. Sharks have existed for 180 million years and have always been at the top of the

food chain

. Biology But it is lower than the crucian carp. In fact, the survival of the fittest and the advanced and low levels of evolution have been slowly faded. Because organisms do not have a fixed direction of evolution. For an environment, there must be one or more structures that adapt to the environment. When the environment changes, similar structures will become cumbersome, and structures that were originally cumbersome may become cumbersome. It is a weapon of adaptation. When the environment changes back, the species that emerged later will still be a burden, and the surviving species that appeared first become the adaptation champions again. Even if no species survived in the last round, when the environment changes back, Structures with similar strategies will still reappear, allowing some species to adapt to new environments. For example, biological evolution is like a drop of ink on parchment, which spreads in all directions. The environment is like a drop of wax on parchment, which blocks the ink. Diffusion in certain directions, but if we remove the wax drop, the ink will quickly replenish from the surroundings and fill the space where the wax drop is removed. If you just look at the fixed position of the wax drop, you can judge the distance from the center of the ink drop. Nearby areas are spread first, and the direction of diffusion is from the center outward. But when you observe the changes after removing the wax droplets, you will see that the ink spreads from all sides

around

< p> The center of the wax droplet spreads. The direction of diffusion here is completely different from the original one, but it is realized under the same principle. This means that the positions on the parchment (analogous species) are not divided into high and low levels. , what determines the order in which they appear (analogous to diffusion) is whether their adjacent positions have been diffused (analogous to parchment soaked in ink) and whether they themselves have been dripped with wax (analogous to the adaptability of species to the environment). As long as both conditions are met, the species will definitely appear, regardless of whether there are already other species that are "higher" or "lower" than it.