Algaelution with Zack and Noor

The early morning air felt pleasantly cool on Noor’s face as she strolled along Sarsa Beach with Zack. Quiet time was even harder to come by than usual, lately, so neither of them was saying much. Just enjoying each other’s company and the sand between their toes. It wouldn’t be long before droves of wannabe pirates started to wake up and resume their preparations, so they had to enjoy the solitude while it lasted.

They didn’t get far, though. Not even ten minutes into their stroll, they stumbled across a forlorn-looking sea turtle flipping futilely through the ruined pages of a soggy book. The two mothcats glanced at each other and silently agreed to approach the huge reptile.

“What’s wrong?” Noor asked gently as they approached.

The turtle sniffled and looked up at them through a somewhat comical pair of reading glasses, “Oh, it’s nothing. It’s just… I found this book and I was so looking forward to learning something new! But it looks like it’s ruined…”

Zack’s eyes lit up, “Well, we can’t fix your book, but we can teach you something new! Just last night I was reading a really great book about seaweed.”

Noor nodded enthusiastically, “Its true! Would you like us to teach you about endosymbiosis?”

The turtle seemed to perk up almost immediately, “Endosymbi-what?! I’ve never even heard of that! How exciting!”

“Well then, get ready to learn some incredibly bizarre things about algal evolution,” Zack announced, then mumbled under his breath, “Algaelution? Algaelution!”

Noor rolled her eyes and chuckled under her breath at the pun, then sat down in the sand and looked towards the turtle, “So tell me, do you know the different types of algae?”

“Sure!” the turtle replied, “Green, red and brown, right? Green is the tastiest.”

“Yep, exactly!” said Zack, “And there’s also a group of photosynthetic bacteria called cyanobacteria, also known as blue-green algae. That’s where this story begins. You see, as far as we know, cyanobacteria were the very first photosynthetic organisms. But they’re more than just that. You know how all photosynthetic eukaryotes have chloroplasts?”

“Eukaryotes?” the turtle interjected.

“Organisms with nuclei and organelles in their cells. We’re eukaryotes. Plants are eukaryotes. Bacteria aren’t,” Noor clarified.

“Ohh, gotcha. And chloroplasts are the organelles that convert sunlight into energy, right? Photosynthesis?” said the turtle.

“Exactly!” Zack nodded, “except in cyanobacteria, which were the very first photosynthesizers. But you know what scientists believe? They believe chloroplasts are cyanobacteria!”

“Whoa, what?!” the turtle’s eyes twinkled.

 

“It’s true!” Noor confirmed, “They believe the first photosynthetic eukaryote ate some cyanobacteria, but instead of digesting them they trapped them in a membrane and harnessed their photosynthetic abilities to get energy for themselves.”

“This worked out so well for them that eventually, they evolved a way to reproduce the cyanobacteria whenever they reproduced, so future generations would be born with cyanobacteria – chloroplasts – already in them!” Zack chimed in, “Scientists call the phenomenon endosymbiosis. It was such a successful strategy that before long, a whole bunch of different photosynthetic eukaryotes had evolved from that first one. Scientists believe that all red and green algae are descendants of that first photosynthetic eukaryote.”

“Land plants, too,” added Noor, “since those are descendants of green algae.”

“Okay, but what about brown algae,” asked the turtle, perplexed.

“Ohoho, that’s the best part,” said Zack, exchanging a delighted grin with Noor.

“You see,” Noor explained, “The chloroplasts in red and green algae have two membranes – one is the cyanobacteria’s original cell membrane, and the other is the bubble the eukaryote put around them to make them an organelle. But brown algal choloroplasts have four membranes! Can you guess why?”

“That’s too many!” exclaimed the turtle, gleaming with curiosity.

Zack could barely contain his grin, “It turns out that brown algae isn’t closely related to red and green algae at all. Heck, we’re more closely related to mushrooms than brown and red algae are to each other. Except for one part… their chloroplasts.”

The turtle squinted, “Brown algae is weird.”

“You’re telling me!” Zack laughed, “so, do you have any guesses how brown algae got their chloroplasts?”

The turtle sat in contemplative silence for some time before cautiously whispering, “Did they… eat another kind of algae.”

“Wow, you’re good!” Noor praised, “That’s exactly what happened. Scientists believe brown algal chloroplasts are descended from red algae! That’s why they have four membranes – in addition to the original cyanobacteria and organelle membranes, they also have the red alga’s cell membrane and the brown alga’s organelle membrane.”

“Wow!” the turtle exclaimed, “That’s so cool. Hey, thanks for sharing your weird algae facts. I never knew seaweed was as interesting as it is tasty.”

“No problem!” Zack replied, “We’re always happy to provide fun science facts.”

“It was very nice meeting you,” said Noor with a gentle smile, “If you ever need more food for thought, you can find us by the blue propeller boat with ‘S.S. Boaty McBoatface’ pained on the side for the next few weeks.”

“If you stop by our boat at the right time, you can learn everything there is to know about dirt, rocks and eggs,” added Zack with a chuckle.