Thanks to CuriosityStream for supporting this episode!
Go to CuriosityStream.com/microcosmos to start streaming
thousands of documentaries and nonfiction TV shows.
If you know about the species Lacrymaria olor,
then you know what you're getting when you see it under a microscope.
There's the oval body, the long neck,
the grasping and reaching out for food.
It has a distinct shape, a distinct way of life.
The combination of its own genetics and its surrounding environment.
It's also distinct that even
when you look at different Lacrymaria olor and see that, sure,
these individuals don't necessarily look exactly alike, you can still spot
the underlying framework of the species that makes them resemble each other.
You see the morphology and the behavior all united under the name Lacrymaria olor.
It's like looking at a house cat.
You know they have their own colors and patterns and preferences,
but at the same time, it makes sense
why we might consider them all to be the same species.
Felis catus.
Then you look at the species Felix manul,
better known as Pallas's cat,
and the idea that these two are relatives of each other also feels right.
There is a sense of same but different.
And that can make the idea of a species seem simple enough.
There are things that are like each other, and there are things
that are less like each other.
So the idea of a species is to define individuals
so that we can define groups so that we can define relationships.
Except it is never so simple
when it comes to trying to categorize life.
Because at the end of the day,
species are only a little bit about the organisms we're looking at.
They're really more about us and how we see the world.
Life is complicated and evolving,
which means it will always be pushing against the bounds of our categorization.
But that doesn't mean we can't try.
The human attempt to define a species is an exercise in futility
that is nonetheless vital to our understanding of biology.
It provides us with the language to describe the world around us
so that we can make comparisons and find patterns.
So what even is a species?
Well, it depends on who you ask.
There have been several species concepts over the past few centuries.
One of the definitions you may be familiar with is attributed to the zoologist
Ernst Mayr who in 1942 defines species as:
“groups of actually or potentially interbreeding natural populations
which are reproductively isolated from other such groups.”
This describes what is known as the Biological Species Concept.
Two species might look the same,
but if they can't reproduce together, then they're different.
One of the major challenges with this definition
is obvious from our journey through the microcosmos.
Not all organisms interbreed.
Some reproduce asexually.
So how does one draw biological borders around species
that just make copies of themselves?
There are several other species concepts out there,
and we won't be able to explore all of them in this episode.
But one of the other salient definitions that helps avoid the challenges
of the Biological Species Concept is similar to how we started this episode:
Just look at the organisms.
Look at their morphology, describe their shape
and color in organelles and whatever strange features appear
and use that to define an individual species.
It seems as simple as saying that if it's almond shaped in body
and long and neck then it's Lacrymaria olor.
Why make it any more complicated than that?
But deciding on what traits define a morphological species is so dependent on
who is observing and describing those traits.
And it creates so many more questions for how we use morphology
to describe species and their taxonomy.
What if the neck is a little shorter?
The body a little stouter?
Does that make a different species?
And just how much can we infer about the relationships
between two species based on their appearance?
If they look similar does that mean they're close relatives,
or is that some kind of phylogenetic optical illusion?
There's no single answer to any of those questions.
It all just depends on the organisms and what it is you want to understand about them.
Let's look at Lacrymaria sapropelica,
a fellow member of the Lacrymaria genus.
Its body is stout compared to the Lacrymaria olor,
like setting down a teapot next to a champagne glass.
Most importantly, its neck doesn't seem to extend much beyond its body.
Instead of the constant stretching movement of the Lacrymaria olor’s neck,
the Lacrymaria sapropelica’s neck neck is stubby and immobile.
In fact, it looks a little bit like this
other species called Phialina caudatum,
which belongs to the genus Phialina, a genus that closely resembles Lacrymaria
except for the obvious issue of the neck.
So if Lacrymaria sapropelica doesn't
have an extending neck, why is it classified as
Lacrymaria and not Phialina?
Well, mostly because no one's taken the time to officially change it.
Naming and classifying species doesn't just happen automatically.
A person has to come along and do it.
Putting in the effort to study the creatures
and write up their reasons for changing its identity.
And, you know, sometimes that person just hasn't come along.
That's the thing about people.
We've come up with these incredible systems for describing nature.
But at the end of the day, those systems are still subject to our very human whims.
And just to emphasize how messy the process
of organizing organisms is, we should add that Phialina caudatum
actually went by another name before Lacrymaria caudatum.
But unlike Lacrymaria sapropelica,
someone did come along and do the work of revising its place.
We don't know what motivated them to take on the species.
Maybe they were constantly irritated when they read the words
“Lacrymaria caudatum.”
Maybe they just happened to be studying the species already.
Or they just wanted to publish a paper
Or maybe it's a combination of all three.
Human motivations and desires are just
as difficult to categorize as microbes.
All this messiness and subjectivity seems built into morphology.
But we live in the age of genetics now where sequencing
an organism is cheap and the data objective, right?
Yes and no.
There are ways that molecular phylogeny the use and comparison
of genetic sequences to understand evolutionary relationships
has allowed us to see past the surface similarities between organisms.
Amoebas, for example, were thought to be closely
related because of their use of pseudopodia or false feet,
but their genetic underpinnings revealed that amoebas are actually
the culmination of many different species and groups and phyla.
They just happened to resemble each other in this one major way.
And those results, the specificity they've allowed us in redefining these
species, have given us new understanding
about their evolution and behaviors.
But data, as concrete and undeniable as it
feels, is still in the eye of the beholder.
Like, let's say we found a new species with a short,
not extending neck and say we decided to name it.
Lacrymaria microcosmosii.
we're excited to find it, and we're even more excited to study
it and report all the genetic information we can find
describing the organism in terms of its genetic code
that we registered to a depository for other scientists to look at.
But then let's say that shortly after our discovery
other masters of microscopes turn up their own
Lacrymaria microcosmosii discoveries.
The morphologies match what we've described.
But when we compare our genetic sequences
to what they've found, there are differences.
The question is how big do those differences have to be
to make the organism itself different?
Do they define a new species, an entirely new genus?
At what point do we decide
something is too different to be the same or even just similar?
That's not necessarily a
problem that DNA in computers will be able to solve for us.
There's still going to be a person who has to decide, a person who has to make
a subjective call based on the data presented and the questions asked.
And their definition will probably have exceptions
to leaving blanks, in our understanding.
But blanks are exciting.
They leave us room for new ways of seeing things, of asking things,
because our definitions are an attempt to bring the expansiveness of biology
into something we can understand, something we can speak and read.
But life expands beyond those constraints in ways
we know, in ways we have yet to find out.
Thank you for coming on this journey with us.
As we explore the unseen world that surrounds us.
This episode has been brought to you by CuriosityStream.
a subscription streaming service that offers thousands of documentaries
and nonfiction TV shows from some of the world's best filmmakers,
including award winning exclusives and originals.
They cover topics like history, nature,
science, food technology, travel and more.
And since we're already on the topic of long necked creatures,
why not check out the documentary The Woman Who Loves Giraffes?
It's the story of Anne Dagg, a zoologist who in 1956 took a solo journey
to South Africa to study giraffes
in the wild and helped pioneer the field of giraffe biology.
And you can find it right now on CuriosityStream.
You can stream CuriosityStream’s Library, including their collections
of curated programs hand-picked by their experts
to any device for viewing any time anywhere.
And if you go to curiositystream.com/microcosmos
and use the code “Microcosmos” to sign up.
It will only cost you $14.99 for an entire year.
The names you're seeing on the screen
right now, they are people who are supporting us on Patreon.
Patreon is a place where you can go and give a little bit of money
to the things that you really think should exist in the world.
And all of those people really think that Journey to the Microcosmos should exist.
And we agree with them.
And we're so thankful to them.
If you want to see more from our master microscopes, James Wieiss,
you can check out Jam & Germs on Instagram.
And if you want to see more from us,
there's always a subscribe button somewhere nearby.