Layman D. Biology Demystified: A Self-Teaching Guide

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(d) Is a typical club fungus

10. A lichen:

(a) Is a type of green plant (roughly the same thing as moss)

(b) Exists as a symbiotic combination of fungi with algae or bacteria

(d) Basically is the fruiting body of an alga

The Giraﬀe ORDER TABLE for Chapter 8

(Key Text Facts About Biological Order Within An Organism)

1. ____________________________________________________________

The Dead Giraﬀe DISORDER TABLE for Chapter 8

(Key Text Facts About Biological Disorder Within An Organism)

1. ____________________________________________________________

2. ____________________________________________________________

3. ____________________________________________________________

CHAPTER 8 Fungi: Not Just Mushrooms 137

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The Spider Web ORDER TABLE for Chapter 8

(Key Text Facts About Biological Order Beyond The Individual

Organism)

1. ____________________________________________________________

2. ____________________________________________________________

The Broken Spider Web DISORDER TABLE for Chapter 8

(Key Text Facts About Biological Disorder Beyond The Individual

Organism)

1. ____________________________________________________________

2. ____________________________________________________________

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139

CHAPTER

The Plants: ‘‘Kings

and Queens’’ of the

World of Green

Chapter 7 considered the protists, including the algae – primitive, plant-like

protists. And Chapter 8 took a look at the lichens as mixtures of fungi with

either algae or bluish-green bacteria. Both algae alone, and in combination

with fungi as lichens, have in common the presence of chlorophyll. This

pigment, of course, is the main molecule responsible for photosynthesis,

and for producing the greenish color of these organisms.

The Human Sole–Plant Connection

Recall (Chapter 3) that the word plant literally means ‘‘a sprout.’’ It comes

from the Ancient Latin term planta, which also translates to mean ‘‘sole of

the foot’’! Quite fascinating is the connection to another term plantigrade

(PLAN-tuh-grade) – ‘‘walking’’ (-grade) on the ‘‘sole of the foot’’ (planti).

Human beings, bears, and raccoons are all mammals that share the common

trait of being plantigrade. Speciﬁcally, these mammals all walk with the entire

sole of each foot ﬁrmly ‘‘planted’’ upon the ground! It seems likely that the

early Greek botanists (BAHT-uh-nists), or ‘‘those who specialize in’’ (-ists)

‘‘plants’’ (botan), were the ones who made this connection. Thus, we have

humans who walk in a plantigrade manner, sole of the feet placed ﬂat upon

the ground. And from this same ground, up sprout the green plants!

This close anatomic and naming connection between the sole of the human

foot and the plants springing up from the ground has also been extended to

the names of some individual plants. Consider, for instance, the plant genus

called plantain (PLAN-tun). As Figure 9.1 shows, the common or broad-

leaved plantain is a low-lying weed with large, light-green leaves growing

from its base. Often invading lawns, the common plantain gets its name

from the shape of its leaves, which are ﬂat and broad like the sole of a

human foot! One can say, then, that the ﬂat leaves of the plantain have a

very plantar (PLAN-ter) or ‘‘sole of the foot-like’’ appearance. These leaves

can be crushed underfoot by a walking human, as well as eaten by them

(blanched and saute

ed in butter and garlic).

Here Come the Land Plants!

Most botanists believe that modern land plants are the ancestors of primi-

tive green algae that lived along the edges of lakes or oceans. Gradually

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Fig. 9.1 Feet, soles, and plantains: A human–plant connection.

(about 450 million years ago), the land plants emerged completely from the

water, and spread across the Continents. As they evolved, they became

more and more diﬀerent from their primitive algae ancestors. Technically

speaking, a plant is a multicellular organism that carries out photosynth-

esis, contains chlorophyll, and develops from an embryo (EM-bree-oh). An

embryo is literally ‘‘a sweller.’’ In general, then, an embryo represents the

earliest stages of development of any organism. A plant embryo is a partial,

undeveloped plant contained within a seed, that eventually ‘‘swells’’ into a

full plant.

There are more than 300,000 diﬀerent species of plants in the world, and

the vast majority are land plants (rather than algae). A few land-based species

have apparently returned to the aquatic environment, including the slender

sea grasses. But there are so many more species of land plants compared to

algae that we have entitled this chapter The Plants: ‘‘Kings and Queens’’ of the

World of Green.

THE TWO MAJOR GROUPS OF LAND PLANTS:

CONTAINING ‘‘VESSELS,’’ OR NOT?

Land plants have a huge amount of diversity (duh-VER-suh-tee) or ‘‘turning

aside’’ (divers) from common traits. Nevertheless, a broad classiﬁcation into

two main groups of plants is possible. The great majority of species make up

the vascular (VAS-kyoo-lar) plants, while a relatively few species comprise the

nonvascular (NAHN-vas-kyoo-lar) plants.

Vascular literally ‘‘pertains to’’ (-ar) ‘‘little vessels’’ (vascul). The vascular

plants are also called the tracheophytes (TRAY-kee-oh-ﬁghts) – ‘‘plants’’

(-phytes) containing ‘‘rough arteries or windpipes’’ (trache). The vascular

plants (tracheophytes) are the plants whose bodies contain many small hol-

low tubes that resemble blood vessels or windpipes (Figure 9.2, A). The

hollow tubes create a vascular (vessel-rich) tissue, which runs up and down

throughout the plant. The vascular tissue also branches outward to create

dense patterns of leaf veins along the sides of the plant.

In direct contrast to the vascular plants or tracheophytes are the nonvas-

cular plants. Their alternate name is the bryophytes (BRY-uh-ﬁghts), or ‘‘tree

moss’’ (bry-) ‘‘plants’’ (-phytes). The nonvascular plants (bryophytes) have no

internal vessels or leaf veins (Figure 9.2, B). They also lack true leaves, stems,

or roots. This nonvascular type is called bryophytes (from Latin) because the

mosses and other moss-like plants are the main examples.

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1, Order

1, Web

An Overview of the Bryophytes (Nonvascular

Plants)

The two most familiar types of bryophytes are the mosses and the liverworts

(LIV-er-werts). The word, moss, descends from the Old English for ‘‘bog’’ – a

marsh or swamp consisting of soft, wet, spongy ground. A moss is a very

small, soft, brown or green plant that grows closely together with others of its

kind, forming a living carpet on rocks, trees, or ground. Mosses have short

stems and many slender leaves. Decaying sphagnum (SFAG-num) moss (also

called peat moss) is especially common in bogs. Peat (PEET) is heavy turf

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Fig. 9.2 Two major groups of plants: (A) Vascular plants (tracheophytes) – often tall and

large. (B) Nonvascular plants (bryophytes) – short and small.

made of tightly packed mounds of partially rotted sphagnum (peat moss) and

various other plants. Peat is used as a fertilizer and is commonly burned as

fuel in Scotland, Ireland, and England, where there are many peat-containing

bogs.

Liverworts are given two alternate names – liverleaf and hepatica

(hih-PAT-uh-kuh). In humans and animals, the shorter word, hepatic

(hih-PAT-ik), literally ‘‘pertains to’’ (-ic) the ‘‘liver’’ (hepat). Obviously, the

words, liverwort and liverleaf, actually contain the smaller word, liver, while

hepatica contains the Latin word for liver. A glance at Figure 9.3 will reveal

the reason. The liverwort (liverleaf, hepatica) is a low-lying plant with brown-

ish-green, three-lobed leaves that resemble the human liver, which also has a

number of lobes. The resemblance of the hepatica plant leaves to the liver,

created the ancient belief that eating this plant cures jaundice (JAWN-dis)

and a number of other liver diseases!

LIVING HABITS AND REPRODUCTION OF THE

BRYOPHYTES

Because both mosses and liverworts are bryophytes (nonvascular plants),

they can live only in free-standing pools of water. Having no vascular

(vessel-bearing) system or roots to transport ﬂuid, nutrients, and waste pro-

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Fig. 9.3 The liverwort, liverleaf, or hepatica plant: Lobed leaves like the human liver.

ducts, they must grow upon pools of water (however tiny and shallow). Such

a tiny pool might even occur in a shadowy cleft on the sun-baked face of a

desert rock. A pool even this small may be just enough to allow the bryo-

phyte plant to absorb water and nutrients into its nonvascular tissues, and

survive.

A water pool is also needed as a ﬂuid medium, so that sperm cells can

travel from the male bryophyte plants and fertilize the female plants.

An Overview of the Tracheophytes

(Vascular Plants)

Figure 9.2 (A) showed some of the most basic anatomic features of the

tracheophytes (vascular plants). In addition to their inner system of hollow

passageways for transporting wastes and nutrients, this group of plants has

true stems and roots. The two types of vascular tissue within tracheophytes

are xylem (ZEYE-lem) and phloem (FLOW-em). Xylem comes from the

Greek for ‘‘wood,’’ because it often contains woody ﬁbers that form the

harder part of a plant vessel system. Xylem is stiﬀ enough to provide support

for vessel walls, and it also carries water and dissolved minerals upward into

the plant after they have been absorbed by the roots. Phloem derives from the

Greek for ‘‘bark.’’ While the outer bark of most vascular plants is tough and

dead, the phloem forms a softer inner bark composed of living tissue. The

phloem (living inner bark) contains vessels which carry sugars and proteins

synthesized in the leaves down towards the stem and roots.

Although all tracheophytes are vascular plants, some species produce

seeds, while the simpler types lack seeds.

The Ferns: Vascular Plants without Seeds

Ferns are the main group of seedless vascular plants. A fern is a slender plant

with feathery fronds (FRAHNDS) – split ‘‘leaves’’ that grow out along either

side of a central stem. Ferns reproduce by means of spores. The spores grow

in small brownish clusters on the back of the feathery frond leaﬂets. Ferns,

huge fern-like trees, and their close relatives grew and reproduced by the

billions in ancient tropical forests. Such forests of ferns covered vast stretches

of the Earth during the Carboniferous (car-buh-NIF-er-us) Period of the

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2, Order

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Paleozoic Era, 500 to 200 million years ago. Carboniferous literally ‘‘pertains

to carbon-carrying.’’ But it also has been nicknamed the ‘‘Age of Ferns.’’ The

Carboniferous Period gets its name from the great forests of ferns and related

plants that grew during this time, died out, and were compressed into massive

layers. After millions of years, the great pressure formed deep natural depos-

its of coal, oil, and natural gas. Because all of these ‘‘fossil fuels’’ are rich in

carbon atoms, naming their time of origin the Carboniferous Period or ‘‘Age

of Ferns’’ is very ﬁtting.

Gymnosperms: Vascular Plants with ‘‘Naked

Seeds’’

The great majority of vascular plants (other than ferns and their fern-like

relatives) reproduce by means of seeds. One important group are the gym-

nosperms (JIM-nuh-sperms) or vascular plants with ‘‘naked’’ (gymno-)

‘‘seeds’’ (sperms). By naked, it is meant that the seeds of the gymnosperms

are exposed, and not enclosed within fruits.

As the Ancient World’s climate became cooler and drier, many of the vast

fern swamps of the Carboniferous Period died and dried up. Arising in their

place were the conifers (KAHN-uh-fers) or ‘‘cone-bearers.’’ The conifers, as

their name suggests, produce cones that hold their naked seeds. Most of the

conifers are evergreen trees or shrubs that bear cones. These conifers are truly

‘‘ever-green,’’ because they keep their green, needle-like leaves all year. The

thin leaves are an adaptation to cold, dry conditions in that their needle

shape gives them a small surface area exposed to the air, thus reducing

evaporation or drying of the conifer plant.

The conifers include pine trees, ﬁr trees, spruce, larch, hemlock, and yew

bushes. Today, much of the still-natural land of the Northern Hemisphere is

covered by beautiful coniferous (kuh-NIF-er-us) forests, graced with tall

spruce, ﬁr, and pine trees.

THE LIFE CYCLE OF A PINE TREE

Since pine trees and other conifers are called gymnosperms, it is important to

examine their typical life cycle, wherein their ‘‘naked seeds’’ play an impor-

tant role. Each of the major steps are described below. (Consult Figure 9.4

for a summary.)

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3, Web

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Fig. 9.4 The life cycle of a pine tree.