When did the earliest animals on Earth appear?
Fossil record places the earliest animals on Earth (metazoa, the general term for all multicellular animal phyla except protozoa phyla) between 572 and 602 million years ago, but molecular clock studies show that their origins are much earlier, dating back about 850 million years ago.
Some scientists believe that the time difference of these hundreds of millions of years is likely to be interrupted and suppressed by the reproduction of life by many huge global glacier events.
Although like everything in the scientific community, there has been constant debate about this (the inherent incompleteness of fossil records, coupled with uncertainty in molecular clock estimates), animal life does appear before or during these global ice ages, and how did they survive?
Snowball, Mudball
According to a new study published in the journal Global Change Biology on October 12, 2022, the amazing survival strategies of polar marine life may help explain how the first animals on Earth evolved earlier than the oldest fossils suggest.
The first batch of animals on our earth must have experienced the most extreme and coldest period in the world.
The earliest fossil calculations were that animals appeared 600 million years ago, while molecular clocks were estimated to be 850 million years ago - this means that animals must have survived several global ice age influences.
At that time, the world was surrounded by ice and could not be regarded as a "ground" ball - many researchers tend to call it "snow" ball or "mud" ball.
If animal life does appear before or during these extreme glacial periods, which they face, conditions similar to modern marine habitats in Antarctica and the Arctic today, then, similar survival strategies are likely to be required.
Given that 90% of the world's ice is in Antarctica, an example of Antarctic habitat survival strategies is more representative of the conditions of the Earth or the Snowball or Mudball period than the current Arctic.
In winter, ice floes cover more than 19 million square kilometers of seas around Antarctica, and during the time when the Earth was still a “snow” ball—720 to 635 million years ago, it is believed that the entire world (510 million square kilometers) was buried in about a kilometer of ice thick and lasted between 50 and 60 million years. (There is some evidence that the ice layer at the equator is thin enough to allow seaweed to survive)
Reference survival strategies for polar marine life
From today onwards, the ice sheet has advanced and retreated for millions of years – expansion and contraction in the cold and warm times have driven the evolution of thousands of unique flora and fauna species in Antarctica.
The same is true for the evolution of animal life on Earth.
Although polar regions seems to be the most unfavorable environment for life for humans, ice sheets, floating ice shelves, icebergs and flowing seasonal sea ice all provide a glimpse of the habitat of life during the snowball and mud ball Neoproterozoic glacier events.
How do some animals in the polar regions adapt to life in and around the ice?
As an example: the bottom of sea ice can also be considered an upside-down shallow bend, with normal plankton species such as Antarctic krill (Euphausia superba) and crystal krill (Euphausia crystallophila) that feed on bacteria, diatom , debris and other microorganisms, including algae formed at the bottom of sea ice, and even sea anemones hanging upside down at the bottom of ice (Edwardsiella andrillae).
In essence, these species live by algae nurtured through the faint sunlight. But when the ice layer exceeds 20 meters, photosynthesis no longer exists. What to do with life?
"Milk yourself and then milk others" - most studies show that there are some or purely chemical synthesis of autotrophic microorganisms - able to survive with ammonium, nitrite , sulfur compounds - and then there will be animals that live by eating them.
In short, many animal life has evolved into incredible skills - whether it is animals that are inverted under the ice rather than under the sea; sponge that lives hundreds of kilometers under thick ice shelves; creatures that live freely in sea water below -2°C; life that always lives in darkness without sunlight, etc.
The lives of the Antarctic and Arctic thrived in conditions that would kill humans and most other animals – they can teach us a lot about evolution.
Go further, the two poles are also an ideal place to study the potential of life in the universe outside our planet. For example, cold satellite such as Europa (Europa), Enceladus is likely also a "snowball" - there is potential liquid water under the ice layer, which has the attractive hint of potential life.
is written at the end
By looking back at the past, you can see what the future looks like. The cat felt that no matter whether the earth turned into a world of ice or a flame, life would struggle tenaciously until the last moment.
Author thanks for your attention (- _-)
