THE GREEN ALGAE HIT THE LAND
by Arthur W. Siebens, Ph.D., Copyright 2000

Algae Sergeant: Come on algae! Let’s hit the land!
But there’s some things ‘bout land, you’ve got to understand
It’s dry, it’s dirty, you must support your weight
Reproduction’s a problem, but you’ll adaptively radiate
You freshwater green algae (division Chlorophyta, class Chlorophceae) have got what you need
The rest’ll stay behind – and “cover” the sea.
Green algae: But why us? Algae Sergeant: You’ve got cellulose cell walls
A little lignin in those walls, and you can stand tall
You’ve got chlorophyll a and b, and beta carotene
You store starch in plastids – you’re part of the future scene.
If you get out of the water, you can be plants!
Some day (in 440 million years) they’ll write raps, ‘bout how you took that chance.
Green algae: But we can’t stand up! Algae Sergeant: You’ll grow some roots
They’ll anchor you, and you’ll grow aerial shoots.
Green algae: But we can’t transport water! Algae Sergeant: You’ll get vessels
You’ll be tracheophytes (gymnosperms and angiosperms) – you’ll be special!
Xylem’ll move water up, phloem’ll move sugar water down
From the roots to the leaves, you’ll move solutes all around
From tracheids, fibers and vessel elements (also called vessel members) will evolve
With secondary growth and wood, the strength problem’s solved.
Seaweed spokesperson: I speak for the seaweeds, I thought we were plants.
Algae Sergeant: No, there’s analogies not homologies, that look the same at first glance
You’ve got a holdfast not roots, a stipe not a stem
Your blades are not true leaves, your thallus (body) just ain’t like them.
You don’t use starch for storage, if you’re red (Rhodophyta) or brown (Phaeophyta)
But don’t worry, in evolution, you’ll stick around (literally—some holdfasts attach using a natural glue).
Green algae: What’s all this talk about leaves? Algae Sergeant: You’ve got to make more food!
To support a big body, you need that aptitude
Got to increase surface area, develop veins
Make a waxy cuticle, so water can be retained
To get that CO2 in, you’ll evolve stomata
With guard cells to close them so you don’t waste water.
Green algae: How do leaves get their water? Algae Sergeant: Through cohesion-tension
That’s controlled by transpiration, through those stomata I just mentioned.
Then you’ll need another process, called translocation
So all the cells in your body, can get their rations
Sucrose will be actively transported (by H+-sucrose cotransport), into the phloem
Into sieve-tube members – it’s called pressure-flow
Sucrose’ll move through the phloem, from the source to the sink
You’ll be sophisticated, no more rinky-dink.
Green algae: But what about sex? What’ll we do without water?
Algae Sergeant In mosses and ferns you’ll keep swimming sperm for starters
You’ll re-evolve alternation, of generations
It’s a theme that keeps coming back with new variations
But what’ll make plants unique – and highly respected
They’ll use the parent plant’s tissues to keep their embryos protected
Now, with swimming sperm you can only, live where it’s wet
So you’ll evolve pollen and seeds – you ain’t seen nothin’ yet
There’ll be flowers, insects, nuts – you think I’m berserk?
You’ll take over the world – hit the land! GET TO WORK!
But, as you conquer the land, remember your roots
You reap what you sow, so let’s bear some fruits!