Why do animals adapt
Live primal animals
What are living primal animals?
The exact life span of a species cannot be determined in advance. Too many factors play a role in survival: for example the food supply, climate changes, global catastrophes and of course humans. On average, however, a species lives about ten million years before becoming extinct one way or another. But not all animals that are affected by extreme influences die out immediately.
On the contrary: they adapt. In evolutionary theory, it is assumed that animals that have an advantage over their conspecifics due to a certain mutation (i.e. genetic change) are more likely to survive and thus pass on their genetic material. The mutation prevails over several generations and the species adapts to the environment. Through this mechanism, living beings are subject to a constant process of development.
However, Charles Darwin, who put forward this theory, himself recognized that there are animals that seem to evade this principle. He himself called them "living fossils". This term is a contradiction in terms, because fossils are the fossilized remains of primeval organisms that are anything but living.
The reason for this formulation is clear, however: some animals were long thought to be extinct. The only evidence of their existence in the past was fossils. It was all the more surprising that naturalists suddenly rediscovered some of these animals - and they were alive and well. This new discovery is also called the Lazarus effect.
Far more astonishing than their mere existence was and is the fact that these species apparently had hardly changed for several million years. This applies at least to the appearance of the animals (phenotype). It is true that today the genetic structures (genotype) of living animals can be examined, but only a stone imprint of their ancestors is available. A blood test is therefore excluded.
Nevertheless - with many fossils the anatomy of the animals can be recognized and analyzed in great detail. In comparison to their living relatives, there are hardly any differences.
Reasons for undisturbed survival
But how could these animals survive for millions of years without adapting significantly? Scientists have been dealing with this question for a long time - because there is no uniform explanation here either. Usually three different factors are cited that explain such a "non-development":
The first reason often cited is a relatively secluded habitat. Here the situation between the species has "leveled off" and there is simply no need to develop further in order to survive.
A second explanation is that the species live in a rather hostile environment, such as the deep sea, in which other animals cannot survive or can only survive with great difficulty. Due to their "monopoly" they remain safe and do not have to change either.
The third theory states that living prehistoric animals are often not too specialized, for example in a certain food source, and thus can better survive changes in the environment without having to make significant changes to their organism.
There is also the assumption that living prehistoric animals have special genetic features that prevent mutations from being passed on and thus rule out evolution. So far, however, this thesis has not been confirmed.
Die out? Not with us!
In the various geological ages there have been regular waves of extinction several times - for example at the end of the "Permian" around 250 million years ago. When the masses of earth collapsed to form the supercontinent Pangea, the consequences were catastrophic for many animals: seas disappeared, there were numerous volcanic eruptions and the atmosphere darkened.
This was a catastrophe, especially for aquatic life, because the upper layers of the oceans warmed up and their chemical equilibrium was out of joint. About 96 percent of the species disappeared from the oceans.
One species, however, did not seem to have any problems with the inhospitable environment: the sea urchin. He coped surprisingly well with the hostile circumstances and then experienced a true heyday.
But this species was not the only one that could easily cope with environmental changes. Long before that, in the Devonian Age (410 to 360 million years ago), many species became extinct, although not as massive as in the Permian.
A genus that fell victim to evolution back then was the tankfish that had dominated up to then. Despite their massive build and hunting skills, they could not prevail. In contrast, their contemporaries, the cartilaginous fish, still exist today - for example as sharks.
Probably the best-known example of a mass extinction occurred on the border between the Cretaceous and the Tertiary about 65 million years ago. Scientists suspect that at this time a gigantic meteorite the size of Mount Everest hit the Yucatán Peninsula (Mexico).
The devastation that followed fell victim to dinosaurs and countless other species. And yet: some survived, for example crocodiles and turtles. They do not need very specialized nutrition and if there is a lack of food they can go into a rigidity that allows them to survive.
Worse than natural disasters
Since life has existed on earth, nature has mostly determined which species make it permanently and which not. Many of the living primal animals known today did not get away unscathed either. Eight out of nine biological coelacanth families have already died out.
But never in history have even such resilient animals been threatened to the same extent as they are today. Because humans are far more dangerous than any ice age or meteorite impact. In evolution, it is perfectly normal for around two to three animal species to become extinct every year. But since humans became the dominant species on this planet, an estimated 20,000 animal species disappear forever each year.
A current example of how threatened the primordial animals are is the death of coral reefs that are millions of years old due to environmental pollution and man-made climate changes. So a question that should be asked in connection with "living fossils" is: will they survive us too?
Author: Jennifer Dacqué
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