As the climate warms, animals will also change their shapes. Which animals are the most special?

Scientists found that with the warming of the climate, many animals became smaller. For example, scientists have found that sheep on an island in Scotland have shrunk by an average of 5% in the past 24 years; For example, scientists compared the skulls of nearly 300 polar bears and found that in the past 20 1 1 year, today's polar bears have shrunk by 2% to 9%. But scientists have also found that warming will also make some reptiles bigger. Why is this?

Archaeological evidence: climate warming makes mammals smaller.

At the 73rd annual meeting of the North American Vertebrate Society held in June, 2018+0/2000, Philip Gingrich, a paleontologist at the University of Michigan, published his own discovery: 53 million years ago, there was an unusually high temperature period on the earth, during which mammals showed a trend of "dwarfing". A study shows that there was another "Paleocene-Eocene extreme heat event" 2 million years before the unusually high temperature that Gingrich paid attention to: 55 million years ago, the average temperature of the earth reached its peak, when the size of mammals had shrunk.

Evolutionary history of horse body shape

Researchers at the University of Florida and the University of Nebraska discovered the evolution of horses that occurred 56 million years ago. Professor Jonathan Bloch, curator of the Florida Museum of Natural History, said that the size of a horse is directly related to the temperature of the earth. The warmer the climate, the smaller the horse, and vice versa.

In Bigfoot Basin, Wyoming, fossil researchers studied the evolution of Archaeopteryx. In 654.38+0.3 million years, Archaeopteryx shrank from 65.438+0.2 pounds to 8.5 pounds, which is very close to the size of domestic cats, and then increased to 65.438+0.5 pounds in the next 45,000 years.

At first, these horses were similar in size to Schnauzer, and then they became very small, once as big as domestic cats, and then they increased significantly. This change trend is completely consistent with the global temperature change trend, that is to say, at the beginning of global warming, the horse's body size becomes very small, and then the global temperature drops, and the horse's body size increases obviously.

Why does the climate have an impact on animal body shape?

There are many reasons why animals shrink in size. There is a certain relationship between the size of animals and the temperature change itself. According to Bergman's law, in the geographical variation of warm-blooded animals, the number of animals of the same species living in colder climate is greater than that living in warmer climate.

The physiological mechanism of individual size response to temperature change is also related to metabolic level, growth rate and sexual maturity age. Body shape change is a thermal protection mechanism for animals. The smaller the body size, the larger the relative volume of the surface skin heat dissipation area, which is beneficial to heat dissipation. Scholars have put forward some theories about the phenomenon of mammal's shrinking body size, including: when the temperature rises to about 35℃ and lasts for a long time, it is difficult for mammals to adjust their body temperature, and the nutrients obtained from edible plants begin to decrease. In this case, a smaller size is a wise choice.

bergmann's rule

If we compare the animals in the Arctic with those in other regions, we will find an interesting phenomenon. Animals in the Arctic seem to be larger than similar animals in other regions. This is because the cold climate will not only slow down the growth rate of thermophilic bacteria, but also make them mature later. So its growth cycle is longer, so it can grow bigger. This is the famous Bergman's law. After a lot of field observation and research, Bergman believes that for the same warm-blooded animal, the colder the place, the bigger the individual. As an interesting inference, scientists point out that the colder the place, the shorter the appendages and appendages, because it helps to conserve heat.

Will climate warming make reptiles bigger?

But a new study shows that high temperature is a disaster for humans and most animals, but it is a good thing for reptiles. A warm climate will produce smaller mammals, but reptiles will become bigger. When the temperature peaked 55 million years ago, horses were only the size of today's domestic cats, and snakes were once as big as horses.

Scientists have discovered fossils of sea turtles 60 million years ago, which are as big as breakfast tables, and a giant snake called Titan Python, which is almost as long as a bus. Snakes, turtles and many other reptiles rely on the environment to regulate their body temperature. These animals are called "cold-blooded animals".

Almost all reptiles are cold-blooded, which means that their body temperature is not fixed, but changes with the change of external temperature. When the temperature is low, they can't get the physical strength needed for normal physiological activities, but high temperature weather can help them get their body temperature like mammals, thus enhancing their physical activity ability.

More than 200 million years ago, most parts of the earth were very hot and humid. From the South Pole to the North Pole, it is a tropical climate. Except for some deserts, most areas are covered by tropical rain forests. In this case, reptiles multiplied and became bigger, and dinosaurs began to rule the earth.

Humans will become smaller in the future.

According to the changes in the size of some animals in history, scientists predict that the size of human beings will become smaller in the future. If climate warming continues on the current scale, the size of human beings and many large mammals may be halved in tens of thousands of years. By then, the human height will reach about 1 meter, and the "dwarf world" described in science fiction may become a reality.

It is easier for animals to get smaller than to get bigger.

Scientists who study the evolution of mammals show that it takes about 24 million years to evolve from mice to elephants. On the contrary, getting smaller is much faster than getting bigger. It took only 654.38 million years for the elephant to become a dwarf elephant, which is one tenth of the speed at which the dwarf elephant grew into an elephant. Researchers have counted the sizes of 28 mammals (including elephants, primates and whales) from different continents and ocean basins for 70 million years, and concluded that it is much faster to get smaller than to get bigger.