stated clearly presents
What caused life's Major evolutionary transitions?
When looking at the fossil record and trying to list the most significant events in our evolutionary history
You might want to list the earliest known fish species able to survive at least temporarily on Dry land
You might also want to list the first known ape fossils which just like us appear to have walked on two legs
While these fossils do represent fascinating transitions into new lifestyles
They don't represent large jumps in complexity the differences between two-legged and four-legged
creatures Mainly come down to slight adjustments and how joints fit together [to]
[see] a truly large evolutionary jump what researchers call a major evolutionary transition
We have to travel back much further in the fossil record in
the late 1830s
anatomist Theodor Schwann
Formalized the idea that the human body instead of being a single living thing is actually a collection of individual living cells
Today we tend to shrug this off as common knowledge, but think how amazing this is
you are a
Colony the earliest multi-celled animals found so far in the fossil record [were] primitive [sponge-like] creatures living in the sea
Before them all living things. We know of were single-celled and came in three different types
Bacteria and Archaea which both tend to be extremely [small] and then we have eukaryotes most of which are still microscopic
But far larger and much more complex than the others
the cells that made up the first sea sponges and the cells that make up [your] body today are strikingly similar to single-celled eukaryotes [the]
[main] difference is that your cells can no longer survive on their own?
Instead trillions of them that's trillion with a t are all working together in near perfect harmony to make you
you
the move from single-celled creatures to multi-celled animals was a major evolutionary transition as a
Result your [body] now represents two distinct layers of life you as a whole and you as a colony
bizarre as this fact is
Are stranger things?
inside the cells of all eukaryotes
Single-celled and multi-celled there are tiny structures called mitochondria
Scientists used to think these structures were simply body parts of the larger cell in
the late 1960s However Lynn Margulis piecing together the discoveries of many others demonstrated
Beyond reasonable doubt that
Mitochondria were once free-living Bacteria
Mitochondria have their own genes they live reproduce and even die on their own inside their larger hosts
Mitochondria feed on the nutrients our cells produce, but they are not parasites in
Return for the food they consume they build and secrete special molecules called atp
Molecules that our cells [use] as a source of energy kill the mitochondria and the larger cell will also die
This discovery means that you are not just two layers of life
but three you as a whole you as a colony of cooperating cells and each of your cells as an
interdependent community of Its own
Profound as that is there's more inside
Each of your cells in each of your mitochondria there is a genome a large collection of genes that together
allow yourselves to grow
function and Reproduce in
the early 1970s
[Theodore] [döner] was investigating the cause of an illness in potato plants the culprits he discovered were the smallest
simplest reproducing structures ever to be described
He called them viroids. They are not cells. They are not even viruses instead. They are single free living genes
Moving from plant to plant by hitching a ride on insects farming equipment or even a wind
Viroids use the chemistry and nutrients inside plant cells to [reproduce]
the existence of free living genes strongly suggests that the genome of the first cells on Earth and
By relation the genome in your cells today can actually be thought [of] as a collection of individual genes
Working together in Cooperation in other words your body represents four layers of life
you your colony of cells the many communities making up each one of your cells and
collection of genes that make up every cell's genome
Each new layer of Life is the result of what scientists call a major evolutionary transition?
What was the cause of these transitions the answer is?
Cooperation a
Major Transition starts when free living creatures team up to form a cooperative group in the early stages of cooperation
Participants are free to come and go as they [please] [if] a group sticks together long enough however
Division of labor will often evolve different participants begin specializing in different tasks as time goes on
Individuals may become so specialized that they can no longer survive on their own [if] the entire group becomes locked into cooperation
Depending fully on one another to survive and reproduce a new super organism has been forged and they made your evolutionary transition is
complete
From this point on the entire group will evolve together as one
Models describing natural situations that might promote the evolution of major transitions have been put forth by scientists such as John Maynard Smith
[fior] Sonck Mary stuart West and w d hamilton using these models
Researchers have been able to Mimic natural scenarios in the lab
Allowing us to directly witness the beginnings of major transitions [evolved] in
1998
researchers set up a mini Ecosystem with small mouths protists and
single-celled algae the protists could easily swallow individual algal cells
But had trouble eating cells that happen to stick together after reproducing in
less than just 20 generations
the algae evolved
multicellular cooperation they form groups of eight tightly connected cells that could not [be] eaten by the protists [a]
similar experiment on single-celled yeast in 2011
Showed that [just] 32 days after multi-celled colonies evolved clear division of labor also evolved giving rise to unique cell types
specializing in different tasks
these two experiments show us how multi-celled organisms may have first evolved, but what about
mitochondria and their permanent merger with eukaryotes
In a long-term study ending in 2008 a protist that normally eats Bacteria was seen swallowing a species of algae
Apparently on accident that it was not able to digest
Inside the protists the algae was able to grow and reproduce
when the protists reproduced as well
both daughter cells contained algae
after several years and many many generations
researchers found that when Bacteria was scarce
Protists containing algae were much more likely to survive than those without
They avoided starvation by feeding off the waste products the algae produced
This was the start of a [Brand-new] relationship
Strikingly similar to what we find between [our] [cells] and the mitochondria [that] live inside
So to sum things up what caused life's major evolutionary transitions
the answer is
cooperation
major transitions begin when a group of organisms join forces to better survive and reproduce if
cooperation continues long enough a new super organism may Emerge one that can then go [on] to reproduce and evolve as a whole and
The pathway that led [to] animals along with humankind [at] least three major transitions have been identified
resulting in four layers of Life within your own body
Experiments in the laboratory have allowed us [to] directly witness the beginnings of major new Transitions evolve. I'm
John Perry and that's Major evolutionary transitions
stated clearly
This animation was based on a paper by stuart west and his colleagues called Major evolutionary transitions and individuality
In it stuart goes over the three transitions. I showed in this animation plus several others
Certain insects like bees and ants have gone through an extra evolutionary transition. That humans never went through
When you look at a colony of bees
You're actually looking at a [superorganism] the entire hive reproduces and evolves as if it were a single living thing
For more on that evolutionary transition check out the video produced by Oxford's brilliant and lovely anis [Dosan] hey
I'm an ace and my Youtube channel is draw curiosity
So long for now
stay curious
you