How did the first plant grow?

0:46 Welcome to Science Is Not Boring by Kidopoly.com. I'm Mira. And I'm Finn. Before we start, a big hello to almost seven-year-old twins, Essie and Hayes from New Jersey.

0:59 And we hear you're listening with your dog, Julep. Essie and Hayes actually asked how the very first plant grew on Earth. Awesome pick, guys.

1:09 If you haven't already, tap follow wherever you're listening so you never miss an episode. Now, Finn, picture this. Imagine stepping outside and seeing absolutely zero green. No trees, no grass, no bushes, no weeds peeking through the sidewalk. Just endless, bare, jagged rock everywhere you look.

1:32 Whoa! Like standing on the surface of Mars or the Moon.

1:36 Exactly like that. 500 million years ago, Earth's land was completely bald. The wind howled across naked continents, and the sun baked the rocky ground. If you wanted to find a plant, you had to hold your breath and dive into a freshwater pool. Wait, all the plants were underwater? What kind of plants were they?

1:59 They weren't even plants like we know them today. They were simple green algae, just floating and swaying in shallow freshwater pools alongside strange early aquatic creatures.

2:12 So, if everything was super happy floating in the water, why did they ever leave? And how did they even get onto the dry, scary land?

2:21 That is one of the greatest survival stories in the history of our planet, Finn. And it all started with a very brave, very sticky green blob. Around 470 million years ago, during a time scientists call the Ordovician period, the waters were teeming with life. But the land was a total ghost town.

2:41 So how did the algae actually get out of the water? Did it just crawl up the beach like a turtle?

2:47 Not quite. It was more like an accident. They lived in shallow freshwater lakes and pools that would sometimes dry up. As the water evaporated, some of that green algae got left behind, stranded on the damp rocks. Oh no! Wouldn't they just instantly dry out in the sun and turn to dust? Yes, that was the absolute biggest danger.

3:09 The sun would beat down mercilessly, and without a thick ozone layer back then, the radiation was intense. It was a massive survival test.

3:19 So they were getting sunburnt and dried out at the exact same time. Exactly.

3:25 Most of them didn't make it. But over millions of years, some of these pioneer plants evolved tough, waxy outer skins to hold their water in.

3:35 Phew. So the waxy skin trapped their moisture inside, like wearing a little spacesuit.

3:40 Exactly! It acted like a protective shield. These brave little survivors were the very first land plants. But Finn, get this, they were nothing like the plants we have today. They had no flowers, no leaves, and absolutely no seeds. No seeds? Then how did they make baby plants? They used tiny microscopic dust particles called spores.

4:05 They would release millions of them into the wind. And if a spore landed on a wet rock, a new plant would grow.

4:12 Okay, no seeds, no leaves. But they must have had giant roots to dig into the rock and drink, right? Nope, no roots either. Wait, wait, wait. You're telling me the first land plants didn't have roots? How on earth did they drink water?

4:30 They drank by soaking it up directly through their skin, like a bunch of tiny green sponges. Whenever it rained or the morning dew settled on the shore, they just absorbed the water straight into their bodies.

4:44 But without roots, how did they stay attached to the rocks? Wouldn't a strong wind just blow them away like a tumbleweed?

4:50 They had a clever trick for that too. They grew tiny hair-like threads called rhizoids. These acted like sticky little velcro straps to grip the stone, and also helped draw in water like a paper towel. Sticky velcro hairs? That's genius! What did these plants look like? Were they big? Not even close.

5:12 They looked a lot like modern mosses or liverwarts, which kind of looked like flat green rubbery ribbons. Why were they so flat? Because they didn't have any internal tubes to pump water upward. They had to rely on a super slow process called osmosis to pass water from one single tiny cell to the next.

5:32 That meant they had to stay completely flat, hugging the wet ground. So how tall are we talking?

5:38 Like a pancake?

5:40 Even smaller. They only grew a few centimetres tall. That's roughly one single inch. Imagine a plant so small it could easily hide under a quarter.

5:52 Oh, a tiny one-inch pancake plant. It's kind of cute.

5:56 It was very cute, but it was also incredibly tough. These tiny plants ruled the shores for tens of millions of years. But eventually, a plant was born that figured out how to reach for the sky. Fast forward to about 430 million years ago, during a time called the Silurian period. A new superstar plant appears on the scene.

6:20 Scientists call it Cooksonia.

6:22 Cooksonia? That sounds like a cool superhero name. What was its superpower?

6:28 Cooksonia developed a superpower that changed the world forever. It grew tiny, microscopic tubes inside its stem. Tubes? Like plumbing? Exactly like plumbing. Scientists call these tubes vascular tissue, specifically xylem and phloem. The xylem acted like little water pumps, pulling water from the ground, while the phloem distributed food.

6:57 Oh, so because it had an internal pump, it didn't have to lay flat like a pancake anymore.

7:02 Bingo! Cooksonia could actually stand upright. Scientists actually found the very first Kuxonia fossils hidden in ancient rocks in a quarry in England back in 1937. When they looked under a microscope, they saw those dark little water tubes perfectly preserved in the stone. So what did this upright plant actually look like?

7:26 Did it have branches? It had smooth green stems that split like a letter Y. And at the very top of each branch, it had a little trumpet-shaped cap where it kept its spores. And how tall did this giant grow? Was it the size of a tree? Well, to the little flat mosses it was a giant. But Cooksonia only grew to be about two inches tall.

7:50 Two inches? That's barely taller than a golf ball. I know. It sounds tiny to us, but back then, a two-inch plant was an absolute skyscraper. It was the tallest living thing on dry land. And standing tall meant it could catch more sunlight, and the wind could blow its spores much further.

8:11 Okay, so Cooksonia is a two-inch skyscraper. But why do these tiny motors and tubes matter so much in the big picture?

8:19 Because, Finn, they literally paved the way for every single land animal that exists today, including us. Remember how they were clinging to bare rocks?

8:31 Yeah, using the sticky Velcro rhizoids.

8:34 Right, well, as these tiny pioneer plants clung to the rocks, they released special acids. Over millions of years, these acids slowly dissolved the solid stone, breaking it down into tiny, crumbly pieces.

8:50 Wait, you're saying there was no dirt before plants? They made the soil.

8:56 They made the soil! Without those one-inch plants, we wouldn't have dirt for farms, giant ancient forests, or gardens today. But it gets even wilder. How could it get wilder than literally inventing dirt? As these plants spread, they sucked massive amounts of carbon dioxide out of the air to make their food.

9:18 They pulled out so much carbon that the Earth's temperature actually plummeted.

9:23 Whoa! A bunch of tiny plants literally froze the entire planet.

9:28 They sure did. It completely changed the climate and caused a global ice age known as the Ordovician Glaciation. Oh, and fun fact, that little two-inch giant, Cooksonia, is named after Isabel Cookson. Who was she? She was a brilliant Australian paleobotanist who spent her life studying fossilised plants.

9:51 She helped map out the amazing history of exactly how these tiny green heroes evolved.

9:58 Shout out to Isabel Cookson! Imagine your name belonging to the first skyscraper plant on Earth. Alright, Finn, time for the quiz! Are you ready? Okay, I'm ready. Let's see how much I remember about these tiny titans. First question.

10:14 How many millions of years ago did the very first algae creep onto the land? Next one. Did the very first land plants have any roots, flowers, or seeds? Question three. What was the name of the superhero plant that first grew little tubes to stand upright? Right. Here's number four. What did these pioneer plants break solid rocks down to create?

10:53 Last question. Who was the plant Cooksonia named after? Great job! Let's go through the answers and see how you did. The first answer is, it happened around 470 million years ago during the Ordovician period. For question two, nope, they had zero roots, zero flowers, and zero seeds. Number three, the answer is it was Cooksonia.

11:26 Question four, they created the very first dirt or soil on Earth. And the final answer is, it was named after the brilliant Australian scientist Isabel Cookson.

11:39 I still can't believe that before those tiny mosses, the whole planet was just bare shiny rock. It's like they completely redecorated the earth.

11:48 They really did. A two-inch tall plant with microscopic tubes literally built the foundation for every single forest, jungle, and farm we have today. Nature is just amazing.

12:02 The biggest changes really do come from the smallest things.

12:06 So true! Hey, if you loved learning about Cuxonia and the very first pioneer plants, please leave us a five-star review. Just scroll down and tap the stars. It really helps the show.

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12:40 See you next time on Science Is Not Boring. Bye everyone.