Thank you to Skillshare for supporting  this episode of Journey to the Microcosmos.   If you are one of the first thousand  people to click the link in the description   you can get a free trial of  Skillshare’s Premium Membership.  There’s a lot of green in the world,  and that is thanks in no small part   to the microcosmos.

Not only did cyanobacteria  lay the foundation for an oxygenated Earth,   they laid the foundation for chloroplasts when  they were endosymbiotically consumed helping   their host take on their photosynthetic machinery. For most of us, the green we are confronted with   every day is a more macroscopic kind, the leaves  you see on trees and grass.

And if you’re on a   hike, you might notice some squishy bundles of  green flush against a tree, or low to the ground.  “Oh, a moss,” you might tell yourself. Or “oh, a  lichen!” And then, perhaps, you move on, unsure   of whether you’ve called it the right thing but  distracted by the many other sights around you.  But today we’re not going to let  that happen. We’re going to linger   on our non-vascular plant friends  and look at them a little closer,   learning more about what they are, and why  only one of those things is actually a plant.  …it’s the moss.

Moss is the plant. More specifically, moss is a member of the   plant division called Bryophyta. And when we say  that moss is a non-vascular plant, what we mean   is that it doesn’t have the vascular tissue like a  xylem and phloem to transport water and nutrients   around the plant.

This lack of vasculature keeps  mosses short so that they can still transport   nutrients and water easily. And while they don’t  technically have roots or leaves as defined for   vascular plants, you’ll see the equivalent  structures like their root-like filaments   called rhizoids and also these leafy parts. And mosses provide a lot of benefits to the   environment around them.

They help prevent  erosion, and they can provide insulation.   And we’ve seen ourselves how mosses provide a  home to some of our favorite microbial companions.  Lichen on the other hand though they are  sometimes called non-vascular plants,   they are very definitely not  plants. So what is lichen?  In a 2010 Discovery article, the lichenologist  Trevor Goward described lichen as “fungi   that have discovered agriculture.” To be more specific,   lichen is a symbiotic union between a fungus and  an algae. The fungus provides access to nutrients,   as well as protection from the elements  and UV light.

And in exchange, the algae   provides its own photosynthetic capabilities. Now that sounds straightforward enough, especially   when you consider all the symbiotic relationships  we’ve learned about in the microcosmos.   Put together the right fungus, and the  right algae, and you get a lichen…right?  Well, scientists have attempted to  create lichens in the lab by culturing   the appropriate partners together, but  with little success. And it turns out   that that might be because we’ve underestimated  the number of partners involved.

In one study,   scientists found that there was at least  one other fungal partner in their lichens.   And it could be that other species have many  many other members involved, making them   far more complex than we have understood thus far. For something so strange and complicated,   lichens are amazingly prevalent: they’re estimated  to cover up to around 6% of our planet’s surface,   whether that’s on the side of a tree or on a rock  or even on dunes. And lichens have this ability   to not only latch on to all sorts of surfaces,  but to disrupt them and convert them into a more   habitable environment by releasing minerals and  creating the early ingredients for future soil.  And so because lichens are so important to  cultivating the seemingly inhospitable parts of   our world, many have thought lichens were possibly  one of the first organisms to make it onto land.   But research from 2019 has suggested that lichens  didn’t find their way to land until well after   vascular plants did.

In fact, it could be as long  as 100 million years after, raising new questions   about how plants and our own earth evolved. Now mosses are also part of this story,   as they were likely among the earliest plants to  make it onto land. And their ancient spread may   have played an important role in raising  oxygen levels to where they are today,   allowing for the evolution of not just other plant  life, but of more complex animal bodies as well.  With that said, the trick with evolution  is to know that creating a whole world   is much more complicated than any one  step would have you believe.

Mosses and   lichens carry their own worlds in their spreading  masses, not fully invisible like the microcosmos,   but often underfoot and easy to ignore. But  maybe if you spot some on a walk, take a moment   to look a little closer, and to wonder what  other secrets they might possibly hide.  Thank you for coming on this journey with us as  we explore the unseen world that surrounds us.  And thank you again to Skillshare  for supporting this video.  After staring at all of this moss,  maybe you’re thinking, “You know,   I could use more plants around the house.” But  you might also be worried that you don’t have the   green thumb necessary to keep those plants alive. Well, with classes like Happy Houseplants,   hosted by the botanist Chris Satch, Skillshare  can make sure you have everything you need   to pot and care for your plants so that they live  long, healthy lives.

That’s right. Skillshare,   you can learn Python, you can learn  plants. This course can teach you   how to troubleshoot for your plants as well as  more specific skills like how to pot a cactus.  Skillshare is an online learning community  that offers membership with meaning.   With so much to explore, real world projects  to create, and the support of fellow-creatives,   Skillshare empowers you to accomplish real  growth.

It’s curated specifically for learning,   meaning there are no ads to distract you, and  they’re always launching new premium classes,   so you can stay focused and follow  wherever your creativity takes you.  A Premium Membership will give you  unlimited access, so you can join the   classes and communities that are right for you. And an annual subscription to Skillshare is   less than $10 a month, and if you’re one  of the first 1,000 people to click the   link in the description, you can get a free  trial of Skillshare’s Premium Membership.  Everybody whose names are on the screen  right now? They are our Patreon patrons.   If you like what we do here and you’d like to  join them check out patreon.com/journeytomicro.  If you want to see more from our  master of microscopes James Weiss,   check out Jam & Germs on Instagram.  And if you want to see more from us,   there’s always a subscribe  button somewhere nearby.