UNIT I
C H A P T E R
1
Plants in
Our Lives
The botanical connections to our lives are many:
food, medicines, materials, and beverages are just a
few of the ways plants serve humanity.
KEY CONCEPTS
1. Green plants, especially flowering plants, are
more than just landscaping for the planet,
since they supply humanity with all the
essentials of life: food and oxygen as well
as other products that have shaped modern
society.
2. The algae are an extremely diverse group
of photosynthetic organisms that are key
producers in aquatic food chains, a valuable
source of human food, and the base for
a number of commercial and industrial
products.
3. Fungi are also an economically important
group of organisms that affect society in
CHAPTER OUTLINE Molecules of Life 8 numerous ways, from fermentation in the
Carbohydrates 8 brewing process to the use of antibiotics in
Plants and Human Society 2 Proteins 9 medicine to their role as decomposers in the
The Flowering Plants 2 Lipids 11 environment and as the cause of many plant
The Non-Flowering Plants 2 Nucleic Acids 12 and animal diseases.
The Algae 3
The Fungi 4 A CLOSER LOOK 1.2 Perfumes 4. All living organisms share certain
characteristics: growth and reproduction,
Plant Sciences 4 to Poisons: Plants as Chemical
ability to respond, ability to evolve and adapt,
Scientific Method 5 Factories 14
metabolism, organized structure, and organic
Fundamental Properties of Life 6 Chapter Summary 13 composition.
A CLOSER LOOK 1.1 Biological Review Questions 15 5. The processes of life are based on the
Mimics 6 chemical nature and interactions of
carbohydrates, lipids, proteins, and
nucleic@acids.
1
,2 UNIT I Plants and Society: The Botanical Connections to Our Lives
M
uch of modern society is estranged from the houseplant. Although there are many different types of plants,
natural world; people living in large cities often the most abundant and diverse plants in the environment are the
spend over 90% of their time indoors and have flowering plants, or angiosperms. These are also the most eco-
little contact with nature. Urbanized society is far removed nomically important members of the Plant Kingdom and are the
from the source of many of the products that make civilization primary focus of this book. From the more than 350,000 known
possible: most food is purchased in large supermarkets, most species* of angiosperms, an overwhelming diversity of prod-
medicines are purchased at pharmacies, and most building ucts has been obtained and utilized by society. The food staples
supplies are purchased at lumber yards. Society’s dependence of civilization—wheat, rice, and corn—are all angiosperms; in
on nature, especially plants, is forgotten (table 1.1). fact, with minor exceptions, all food crops are angiosperms.
In less urbanized environments, lifestyles are more attu- The list of other products from angiosperms is considerable and
ned to nature. The farmer’s existence is dependent on crop includes cloth, hardwood, herbs and spices, beverages, many
survival, and the farmer’s work cycle is timed to the growing drugs, perfumes, vegetable oils, gums, and rubber.
season of the crops. The few hunter-gatherer cultures that All angiosperms are characterized by flowers and fruits.
remain in isolated areas of the world are even more depen- A typical angiosperm flower consists of four whorls of parts:
dent on nature as they forage for wild plants and hunt wild sepals, petals, stamens, and one or more carpels (fig. 1.1).
animals. These foragers know that without grains there would The stamens and carpels are the sexual reproductive struc-
be no flour or bread; without plant fibers there would be no tures. It is from the carpels that the fruit and its seeds will
cloth, baskets, or rope; without medicinal herbs there would develop. The angiosperms traditionally have been divided
be no relief from pain; without wood there would be no shel- into two groups, the monocots and the dicots, on the basis of
ter; without firewood there would be no fuel for cooking or structural and anatomical differences. Among the most famil-
heat; and without vegetation there would be no wild game. iar monocots are lilies, grasses, palms, and orchids. A few
common dicots are geraniums, roses, tomatoes, dandelions,
and most broad-leaved trees. The structure and reproduction
PLANTS AND HUMAN SOCIETY of the angiosperms will be described in detail in later chapters.
Whether forager, farmer, or city dweller, humans have four
great necessities in life: food, clothing, shelter, and fuel. Of The Non-Flowering Plants
the four, an adequate food supply is the most pressing need, In the Plant Kingdom, several distinct groups of non flowering
and, directly or indirectly, plants and algae are the source plants can be found; these range from green algae (fig. 1.2a)
of virtually all food through the process of photosynthesis. to mosses and ferns to giant redwood trees, which are the
Through photosynthesis, plants and algae use solar energy to largest organisms on Earth. Redwoods belong to a group of
convert carbon dioxide and water into sugars and, as such, are plants called gymnosperms. Like angiosperms, gymnosperms
the producers in the food chain. They are the base of most
food chains, whether eaten by humans directly as primary Carpels
consumers or indirectly as secondary consumers when eat-
ing beef (which comes from grain-fed or pasture-fed cattle).
In addition to the food produced by photosynthesis, the@oxy-
gen given off as a by-product is Earth’s only continuous
supply of oxygen. As sources of food, oxygen, lumber, fuel, Petal
paper, rope, fabrics, beverages, medicines, and spices, plants
support and enhance life on the planet.
Stamen Sepal
Thinking Critically
Plants are crucial to the existence of many organisms,
including human beings.
Figure 1.1 A flower, one of the defining characteristics of
Could life on Earth exist without plants? Explain. angiosperms.
*Each kind of organism, or species, has a two-part scientific name consisting of a
genus name and a specific epithet; for example, white oak is known scientifically as
Quercus alba. After the first mention of a scientific name, the genus name can be
The Flowering Plants abbreviated, Q. alba. When referring to oaks in general, it is acceptable to use the
The word plant means different things to different people: to genus name, Quercus, alone. Sometimes an abbreviation for species, “sp.” or plural
“spp.,” stands in for the specific epithet—e.g., Quercus sp. or Quercus spp. Both
an ecologist, a plant is a producer; to a forester, it is a tree; to common and scientific names are used throughout this book; details on this topic are
a home gardener, a vegetable; and to an apartment dweller, a found in Chapter 8.
, CHAPTER 1 Plants in Our Lives 3
are seed-bearing plants, but the seeds are not formed in fruits.
Gymnosperm seeds are generally produced in cones. One
group of gymnosperms consists of conifers, such as pines,
cedars, and redwoods. Among the non-flowering plants, the
conifers have the greatest impact on society as a source of
wood for construction, fuel, and paper. Non-flowering land
plants are presented in Chapter 9, and additional material on
conifer wood is presented in Chapter 18.
The Algae
Algae are a diverse group of photosynthetic organisms that
are found in marine and freshwater habitats where they serve
as the base of food chains. They range from microscopic
organisms to large seaweeds and kelp that form extensive
(a)
underwater forests. All algae were once considered the most
primitive members of the Plant Kingdom, but today most
types of algae are classified in separate kingdoms along with
other simple organisms. Only the green algae (fig. 1.2a) are
considered part of the Plant Kingdom. Many species of algae
are recognized as important and nutritious food for people
throughout the world; however, the widespread uses of algal
extracts for industrial applications and as food additives gen-
erally go unrecognized.
A negative aspect of the algae is related to environmental
damage caused by algal blooms, which are sudden popula-
tion explosions of certain algal species. In recent years, the
occurrence of algal blooms has increased throughout the
world. Although these blooms sometimes occur naturally,
the increase is believed to be related to nutrient pollution,
especially from agricultural runoff, human sewage, and (b)
animal wastes. Blooms are particularly dangerous when the
algae are capable of producing toxins that can cause massive Figure 1.2 (a) Boulder covered in a green alga known as sea
fish kills or human poisoning. The algae and their connec- lettuce, Ulva sp., on a beach in Cornwall, England. (b) Cluster
tions to society will be examined in Chapter 22. of deer mushrooms, Pluteus cervinus, growing on mulch in an
Oklahoma garden.
Table 1.1
How Much Do Plants Affect Society?
_________ 1. True or False—Plants provide most of the calories and protein for the human diet.
_________ 2. True or False—Today plant extracts are widely used in herbal remedies and alternative medicine, but they are no
longer important in prescription drugs.
_________ 3. True or False—The search for cinnamon led to the discovery of North America.
_________ 4. True or False—New varieties of plants are being created through genetic engineering; these provide enormous
profits for large agrotechnology companies but have no practical value.
_________ 5. True or False—The introduction of the potato to Europe in the sixteenth century initiated events that led to a
devastating famine in Ireland.
_________ 6. True or False—Trees are the only source of pulp for papermaking.
_________ 7. True or False—The estimated number of genes in Arabidopsis thaliana, the first plant genome sequenced, has about
one-fourth the number of genes estimated for the human genome.
_________ 8. True or False—The Salem Witchcraft Trials in the 1690s might have resulted from a case of fungal poisoning.
_________ 9. True or False—Tomatoes were once considered to be an aphrodisiac.
_________ 10. True or False—A poisonous plant is one of the most important dietary staples in the tropics.
(continued)
