Evolution of Plants

Meet the true lords of life, the plants. Life could get
along without animals and without fungi. But abolish the plants, and life would
rapidly cease. Plants sit, indispensably, at the base — the very foundation — of
nearly every food chain. They are the most noticeable creatures on our planet,
the first living things any visiting Martian would remark. By far the largest
single organisms that ever lived are plants, and an impressive percentage of the
world's biomass is locked up in plants. This doesn't just happen to be so. Some
such high proportion follows necessarily from the fact that almost* all biomass
comes ultimately from the sun via photosynthesis, most of it in green plants,
and the transaction at every link of the food chain is only about 10 per cent
efficient. The surface of the land is green because of plants, and the surface of
the sea would be green too if its floating carpet of photosynthesisers were
macroscopic plants instead of micro-organisms too small to reflect noticeable
quantities of green light. It is as though plants are going out of their way to
cover every square centimetre with green, leaving none uncovered. And that is
pretty much what they are doing, for a very sensible reason.
A finite number of photons reaches the planet's surface from the sun, and
every last photon is precious. The total number of photons that can be garnered
from its star by a planet is limited by its surface area, with the complication that
only one side is facing its star at any one time. From a plant's point of view, a
square centimetre of the Earth's surface that is anything but green amounts to a
negligently wasted opportunity to sweep up photons. Leaves are solar panels, as
flat as possible to maximise photons caught per unit expenditure. There is a
premium on placing your leaves in such a position that they are not overshadowed
by other leaves, especially somebody else's leaves. This is why forest
trees grow so tall. Tall trees that are not in a forest are out of place, probably
because of human interference. It is a complete waste of effort to grow tall if you
are the only tree around. It is much better to spread out sideways like grasses
because that way you trap more photons per unit of effort put into growing. As
for forests, it is no accident that they are so dark. Every photon that makes it to
the ground represents failure on the part of the leaves above.
With few exceptions, such as Venus flytraps, plants don't move. With few
exceptions, such as sponges, animals do. Why the difference? It must have to do
with the fact that plants eat photons while animals (ultimately) eat plants. We
need that 'ultimately', of course, because the plants are sometimes eaten at
second or third hand, via animals eating other animals. But what is it about eating photons that makes it a good idea to sit still with
roots in the ground? What is it about eating plants, as
opposed to being a plant, that makes it a good idea to
move? Well, I suppose given that plants stay still, animals
have got to move in order to eat them. But why do plants
stay still? Maybe it has something to do with the need to be
rooted in order to suck nutrients out of the soil. Maybe
there is too unbridgeable a distance between the best shape
to be if you want to move (solid and compact), and the best
shape to be if you want to expose yourself to lots of photons
(high surface area, hence straggly and unwieldy). I'm
not sure. Whatever the reason, of the three great groups of
megalife that have evolved on this planet, two of them, the
fungi and the plants, stay mostly still as statues, while the
third group, the animals, do most of the scurrying about,
most of the active go-getting. Plants even make use of
animals to do their scurrying for them, and flowers, with
their beauteous colours, shapes and scents, are the instruments
of this manipulation.

From the book The Ancestor's Tale- A pilgrimage to the dawn of life, by RICHARD DAWKINS

Category:

Education

Tags:

• botany
• evolution
• plants
• horticulture

[2missbookworm]

Why do plants stay still? :)

[ChlorophyllYourMind]

@2missbookworm

It may seem like silly question, but it appears to be valid from a strictly technical perspective.

[Craptron2000]

@2missbookworm They move but slowly. Put a pot plant on a window and after a few weeks you will see the leaves will grow to face the sun. Turn it around the opposite way and it will turn back again. I have Aloe Vera on my window now and it transforms itself like that quite quickly. Life will move towards it's energy source. If it's energy is the sun, then it doesn't need to scurry around like a mammal or reptile. Some plants can move though, like the Venus fly trap.

[Craptron2000]

@bridgegood It's "Spring" from Vivaldi's Four Seasons.

[bridgegood]

What's the name of the music at the beginning ?

[Subfightr]

AGH I LOVE RICHARD DAWKINS! Thank you for posting this. He makes everything so beautiful and amazing to discover.

[2missbookworm]

@ChlorophyllYourMind I don't think it's silly. The question actually frightened me and made me smile at the same time.