10 Mass Extinctions

Life is a struggle for survival. Animals live under constant stress to obtain enough food to eat by being as well adapted to their environments as they can. Animals who are poorly adapted will, in times of hardship, starve, fail to reproduce, and eventually die out completely. Throughout Earth’s history, life has constantly been taking new forms which are immediately tested for survival. When the climate or environment changes drastically, many animals who are poorly adapted for their new situation become extinct. Mass extinctions are when a substantial proportion of Earth’s life has vanished completely, leaving no further fossils or descendants. These events have been occurring since nearly the first appearance of life itself. All the animals alive today are merely the descendants of creatures who have been lucky enough to have met the adaption requirements each time their world changed. Here we look at ten of the biggest extinction events in Earth’s history.
End-Ediacaran Extinction
During the Ediacaran period, complex life had begun to take form for the first time on Earth. Tiny bacteria had evolved into the more complex and specialized Eukaryotes, some of which grouped together to increase their chances of finding food and avoiding becoming food. Most of these odd creatures did not leave a record because they had no skeletons; they were soft and tended to rot when they died rather than fossilize. Only in peculiar circumstances could fossils form, such as a creature lying on soft mud which suddenly hardened and left an imprint. These few fossils tell us of seas full of strange and alien creatures who resembled modern worms, sponges, and jellies. However, these creatures were dependent upon oxygen, as are we. The oxygen levels began to fall and world-wide extinctions occurred 542 million years ago. Over 50% of all species died. The huge numbers of dead creatures decomposed and make up some of today’s fossil fuels. The exact cause of the lowering oxygen levels is unknown, however, this mass extinction made room for the Cambrian explosion, a sudden diversifying of complex creatures beyond mere worms.


Some bees share a lot in common with people who are drawn to adventure.

  • Some honeybees are more prone to seek out novelty and adventure than others.
  • More than 1,000 genetic differences affect a bee’s likelihood of being a thrill-seeker.
  • On the molecular level, novelty-seeking bees share many similarities with thrill-seeking people.
Within their buzzing societies, some honeybees are more likely to take risks than others, and according to a new study, these novelty-seeking bees have genetic similarities with people who are drawn to adventure.
The study, which is the first to dissect the molecular basis of risk-taking behavior in bees, might eventually aid in honeybee conservation.
what we call “personality” can be traced back to deeply ancient roots, offering yet more evidence that we share far more in common with distantly related creatures than many people are comfortable accepting.
“You look at animals and they look really different and they act really different, but when you drill down deeper and look at the genomics, you find these deep commonalities,” said Gene Robinson, an entomologist, geneticist and neuroscientist at the University of Illinois at Urbana-Champaign. “When you see this kind of result, you can say that personality is not a human invention.”
Among the many fascinating features of honeybee social structure, some members of the hive act as food scouts. Contrary to how models predict animals should behave, these scouts – which make up between five and 25 percent of bees in a hive – don’t return again and again to good sources of food. Instead, they tell their friends about an excellent bunch of flowers. Then, they strike off into the great and dangerous unknown in search of new, yet still undiscovered flower patches.
To find out what drives that kind of risk-taking behavior in honeybees, Robinson and colleagues started by using an experiment to classify as scouts those bees that were driven to seek out newly introduced feeders. The majority of bees played it safe and chose to stick with the feeder they were trained on.
Next, the researchers analyzed and compared the genes of both groups of bees, which revealed more than 1,000 genetic differences between risk-taking scouts and their more conservative peers. What’s more, the team reports today in the journal Science, the genes and neurochemical pathways involved showed many parallels with the genes and pathways that are known to influence risk-taking behavior in mammals, including people.
In another line of tantalizing research, scientists have linked so-called thrill-seeking genes in people with a greater propensity for a wide range of behaviors, including alcohol and gambling addictions, promiscuity, skydiving and even an affinity for Wall Street stock trading. Among other brain chemicals, the feel-good neurotransmitter dopamine plays a role, giving novelty-prone people a rewarding feeling when they do something new. Robinson and colleagues used information about the genetics of thrill seeking in mammals and people to guide their search for genes that might affect analogous behavior in bees.
When the scientists experimentally manipulated genes implicated in risk-taking by turning their expression up or down, they were able to increase or decrease the probability that individual bees would become food scouts. That allowed the team to draw a direct link between particular genes and novelty-seeking behavior.
In order to qualify as what we think of as personality traits, certain kinds of behaviors have to apply in different contexts. The researchers were able to demonstrate this kind of consistency in honeybees by showing experimentally that food-scouting bees were more than three times as likely to also scout out new nest sites compared to less-adventurous bees.
Honeybees pollinate about a third of all of the food crops we eat, so understanding what influences bee behavior and how bees make decisions could some day become key information in efforts to protect and conserve the insects.
And while bees certainly don’t have complex and nuanced personalities like people do, the new research offers a long view of how certain behaviors may have come to be so widespread throughout the animal kingdom, said Hans Hofmann, a behavioral genomicist at the University of Texas at Austin.
“I’m not going to tell you this is going to cure disease or give us more honey -- I’m not going to rule that out, but that wouldn’t come from this as an immediate consequence,” Hofmann said, adding that the pathways that influence novelty seeking now appear to date back to at least the time when honeybees and humans shared a common ancestor.
“We like to think we’re different and better than everything else,” he added. “I think this tells us more about ourselves in terms of where we come from on a more philosophical level. This tells us more about ourselves.”


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