The same family, different fates! These two sea elves not only look weird, but also look alike!

For the survival and continuation of the species, animals will try every possible means, and having babies is also an important strategy. Many animals that are smaller in size and at the bottom of the food chain often adopt the strategy of having many children, gaining the probability of survival by quantity, such as the joking saying we often hear, "high productivity is like that." However, those animals that are larger in size and have a more stable living environment often adopt the strategy of having a small number of elite children, giving birth to only a few at a time, and focusing on eugenics.

The ammonites and nautilus in the Mesozoic oceans that I want to talk to you about today are examples of these two strategies leading to different fates. Ammonites and nautilus are from the same school, both belong to the cephalopod class, and have similar appearances, which often make it difficult to distinguish them. In the Mesozoic Era, ammonites were once prosperous, with a wide distribution, rapid evolution, and a wide variety of species. In contrast, after experiencing the glory of the first half of the Paleozoic Era, the nautilus gradually declined, and the nautilus was more primitive. Looking at these points alone, it seems that ammonites have a greater chance of winning, but 65 million years ago, they became extinct with the dinosaurs, while the nautilus has "survived" to this day and is still known as a "living fossil." The two results of this life and death have a lot to do with their strategies for having children.

Let’s first look at ammonites. They choose shallow sea areas rich in plankton and produce a large number of small eggs with a diameter of about 0.5 mm. The ammonite babies after hatching are naturally very small. Those smaller plankton are the food of the ammonite babies. In such an environment, ammonites live a very comfortable life.

Let's look at the nautilus. They choose to lay eggs in deeper waters, and only lay a few to dozens of eggs each time. However, each egg is very large, about 4 cm in size. The hatched nautilus babies are smaller than the adult ones, but their appearance is the same, and they are already able to prey on fish independently.

If this environment could be maintained, the ammonite family would probably be able to continue to thrive. However, at the end of the Cretaceous period, the Earth's climate gradually cooled and the sea level dropped. As a result, the shallow seas rich in plankton gradually disappeared. The ammonite babies that feed on plankton found it difficult to survive and eventually withdrew from the Earth's stage. Although the Nautilus was not an outsider to climate change, it was lucky enough to survive because the deep sea was less affected.

Nautilus fossil

Jade ammonite fossil

In fact, no matter which strategy is adopted, it is a trade-off and choice made in the process of species evolution. There is no difference between the two strategies, and both can effectively continue the race. The two completely different fates of ammonites and nautiluses certainly have an element of luck, but for us humans, they are of certain reference significance.

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