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28
The Plant Kingdom: Seed Plants
Magnolia fruit with protruding seeds. Magnolia (Magnolia
grandiflora) is a flowering plant,
and its seeds are enclosed within
a fruit.
M. F. Merlet /Science Photo Library/Photo Researchers, Inc.
C
hapter 27 focused on plants that reproduce by means of
spores, haploid reproductive units that give rise to gameto-
phytes. Although the most successful and widespread plants also
produce spores, their primary means of reproduction and dispersal
is by seeds, which represent an important adaptation for life on
land (see photograph). Each seed consists of an embryonic sporophyte, nutritive tissue, and a protective coat. Seeds develop from
the fertilized egg cell, the female gametophyte, and its associated
tissues. The two groups of seed plants, gymnosperms and angiosperms (flowering plants), exhibit the greatest evolutionary complexity in the plant kingdom and are the dominant plants in most
terrestrial environments.
Seeds are reproductively superior to spores for three main rea-
KEY C ON CEP TS
sons. First, a seed contains a multicellular young plant with embry-
Seed plants include gymnosperms and angiosperms.
onic root, stem, and one or more leaves already formed, whereas
Gymnosperms produce exposed seeds, usually in cones
borne on the sporophytes.
a spore is a single cell. Second, a seed contains an abundant food
supply. After germination, food stored in the seed nourishes the
Conifers are the most diverse and numerous of the four
living gymnosperm phyla.
plant embryo until it becomes self-sufficient. Because a spore is a
Angiosperms produce ovules enclosed within carpels; following fertilization, seeds develop from the ovules, and the
ovaries of carpels become fruits.
a spore. Third, a seed is protected by a multicellular seed coat that
Angiosperms, which compose a single phylum, dominate
the land and exhibit great diversity in both vegetative and
reproductive structures.
metabolism and germinate when conditions become favorable.
Gymnosperms and angiosperms evolved from ancestral
seedless vascular plants.
single cell, few food reserves exist for the plant that develops from
is very thick and hard in some plants, as, for example, in lima beans.
Like spores, seeds live for extended periods at reduced rates of
Seeds and seed plants are intimately connected with the development of human civilization. From prehistoric times, early humans
collected and used seeds for food. The food stored in seeds is a
concentrated source of proteins, oils, carbohydrates, and vitamins,
600
which are nourishing for humans as well as for germinating plants.
are stored as conveniently or for as long. Although flowering plants
Seeds are easy to store (if kept dry), so humans can collect them
produce most seeds that humans consume, the seeds of certain
during times of plenty to save for times of need. Few other foods
gymnosperms—the piñon pine, for example—are edible.
■
AN INTRODUCTION TO SEED PLANTS
Learning Objective
1
Compare the features of gymnosperms and angiosperms.
In Chapter 27, you learned that some seedless vascular plants are
heterosporous. However, all seed plants are heterosporous and
produce two types of spores: microspores and megaspores. In
fact, heterospory is a requirement of seed production.
Following fertilization in seed plants, an ovule, which is a
megasporangium and its enclosed structures, develops into a seed.
Seed plants also have integuments, layers of sporophyte tissue
that surround and enclose the megasporangium. After fertilization takes place, the seed coat develops from the integuments.
Botanists divide seed plants into two groups based on
whether or not an ovary wall surrounds their ovules (an ovary is
a structure that contains one or more ovules). The two groups of
seed plants are the gymnosperms and the angiosperms (❚ Table
28-1). The word gymnosperm is derived from the Greek for “naked seed.” Gymnosperms produce seeds that are totally exposed
or borne on the scales of cones. In other words, an ovary wall
does not surround the ovules of gymnosperms. Pine, spruce, fir,
phyte stage and part in the multicellular haploid gametophyte
stage. The sporophyte generation is the dominant stage in each
group, and the gametophyte generation is significantly reduced
in size and entirely dependent on the sporophyte generation.
Unlike the plants we have considered so far (bryophytes and
ferns; see Chapter 27), gymnosperms and flowering plants do not
have free-living gametophytes. Instead, the female gametophyte
is attached to and nutritionally dependent on the sporophyte
generation.
Review
❚
❚
GYMNOSPERMS
Learning Objectives
2
that means “seed enclosed in a vessel or case.” Angiosperms are
flowering plants that produce their seeds within a fruit (a mature
ovary). Thus, the ovules of angiosperms are protected. Flowering
plants, which are extremely diverse, include corn, oaks, water lilies, cacti, apples, grasses, palms, and buttercups.
Both gymnosperms and flowering plants have vascular tissues: xylem, for conducting water and dissolved minerals (inorganic nutrients); and phloem, for conducting dissolved sugar.
Both have life cycles with an alternation of generations, that is,
they spend part of their lives in the multicellular diploid sporo-
What is an ovule?
How do gymnosperm and angiosperm seeds differ?
3
4
Trace the steps in the life cycle of a pine, and compare its
sporophyte and gametophyte generations.
Summarize the features that distinguish gymnosperms from
bryophytes and ferns.
Name and briefly describe the four phyla of gymnosperms.
The gymnosperms include some of the most interesting members
of the plant kingdom. For example, a giant sequoia (Sequoiadendron giganteum) known as the General Sherman Tree, in Sequoia
National Park in California, is one of the world’s most massive
organisms. It is 82 m (267 ft) tall and has a girth of 23.7 m (77 ft)
measured 1.5 m (5 ft) above ground level. Another gymnosperm,
a coast redwood (Sequoia sempervirens) known as the Mendocino
TABLE 28-1
A Comparison of Gymnosperms and Angiosperms
Characteristic
Gymnosperms
Angiosperms
Growth habit
Woody trees and shrubs
Woody or herbaceous
Conducting cells in xylem
Tracheids
Vessel elements and tracheids
Reproductive structures
Cones (usually)
Flowers
Pollen grain transfer
Wind (usually)
Animals or wind
Fertilization
Egg and sperm ¡ zygote; double fertilization
in gnetophytes
Double fertilization: egg and sperm ¡ zygote;
two polar nuclei and sperm ¡ endosperm
Seeds
Exposed or borne on scales of cones
Enclosed within fruit derived from ovary
Number of species
About 840
More than 300,000
Geographic distribution
Worldwide
Worldwide
The Plant Kingdom: Seed Plants
601
Key Point
Keith Kent /Science Photo Library/Photo Researchers, Inc.
Seed plants include four gymnosperm phyla and one phylum
of flowering plants (angiosperms).
Figure 28-1
Bristlecone pine at sunrise
Conifers are woody plants
that produce seeds in cones
The conifers (phylum Coniferophyta), which include pines,
spruces, hemlocks, and firs, are the most familiar group of gymnosperms (❚ Fig. 28-3a). These woody trees or shrubs produce
annual additions of secondary tissues (wood and bark; see Chapter 34); there are no herbaceous (nonwoody) conifers. The wood
(secondary xylem) consists of tracheids, which are long, tapering
cells with pits through which water and dissolved minerals move
from one cell to another.
Many conifers produce resin, a viscous, clear or translucent
substance consisting of several organic compounds that may protect the plant from attack by fungi or insects. The resin collects
in resin ducts, tubelike cavities that extend throughout the roots,
stems, and leaves. Cells lining the resin ducts produce and secrete
resin.
Most conifers have leaves called needles that are commonly
long and narrow, tough, and leathery (❚ Fig. 28-3b). Pines bear
clusters of two to five needles, depending on the species. In a few
conifers, such as American arborvitae, the leaves are scalelike and
602
Chapter 28
Angiosperms
Evolution
of flowering
plants
Bristlecone pines (Pinus aristata), found in mountainous parts of California, Nevada, and Utah, are the world’s longest-lived trees.
tree, is among the world’s tallest trees, measuring 112 m (364 ft)
in the year 2000. Botanists using tree-ring analysis determined
that one of the oldest living trees, a bristlecone pine (Pinus aristata) in the White Mountains of California, is 4900 years old
(❚ Fig. 28-1).
Gymnosperms are usually classified into four phyla, which
represent four different evolutionary lines (❚ Fig. 28-2). Numbering 630 species, the largest phylum of gymnosperms is Coniferophyta, commonly called conifers. Two phyla of gymnosperms,
Ginkgophyta (the ginkgoes) and Cycadophyta (the cycads), are
evolutionary remnants of groups that were more significant in
the past. The fourth phylum, Gnetophyta (gnetophytes), is a collection of some unusual plants that share certain traits not found
in other gymnosperms.
Gnetophytes
Conifers
Ginkgoes
Cycads
Gymnosperms
Evolution
of seeds
Figure 28-2
Gymnosperm and angiosperm evolution
This cladogram shows one hypothesis of phylogenetic relationships
among living seed plants, based on structural evidence and molecular
comparisons. The arrangement of the phyla shown here may change as
future analyses help clarify relationships.
cover the stem (❚ Fig. 28-3c). Most conifers are evergreen and
bear their leaves throughout the year. Only a few, such as the
dawn redwood, larch, and bald cypress, are deciduous and shed
their needles at the end of each growing season.
Most conifers are monoecious: they have separate male and
female reproductive parts in different locations on the same
plant. These reproductive parts are generally borne in strobili
(commonly called cones), hence the name conifer, which means
“cone-bearing.”
Conifers occupy extensive areas, ranging from the Arctic to
the tropics, and are the dominant vegetation in the forested regions of Alaska, Canada, northern Europe, and Siberia. In addition, they are important in the Southern Hemisphere, particularly in wet, mountainous areas of temperate and tropical regions
in South America, Australia, New Zealand, and Malaysia. Southwestern China, with more than 60 species of conifers, has the
greatest regional diversity of conifer species in the world. California, New Caledonia (an island east of Australia), southeastern China, and Japan also have considerable diversity of conifer
species.
Ecologically, conifers contribute food and shelter to animals
and other organisms, and their roots hold the soil in place and
help prevent soil erosion. Humans use conifers for their wood
(for building materials as well as paper products), medicinal
www.thomsonedu.com/biology/solomon
Angiosperms
Gnetophytes
Conifers
Ginkgoes
Cycads
Gymnosperms
Michael P. Godomski /Photo Researchers, Inc.
(b)
(a)
Figure 28-3
Conifers
(a) Colorado blue spruce (Picea pungens ) is a coniferous evergreen
tree native to Colorado, Wyoming, Utah, and New Mexico. Spruces
are important ornamental plants, as shown in this New Jersey garden.
value (such as the anticancer drug Taxol from the Pacific yew),
turpentine, and resins. Because of their attractive appearance, conifers such as firs, spruces, pines, and cedars are grown for landscape design and decorative holiday trees and wreaths.
Pines represent a typical conifer life cycle
The genus Pinus, by far the largest genus in the conifers, consists
1 , a pine tree is
of about 100 species. As shown in ❚ Figure 28-4 ●
a mature sporophyte. Pine is heterosporous and therefore produces microspores and megaspores in separate cones.1 Male cones,
usually 1 cm or less in length, are smaller than female cones
and are generally produced on the lower branches each spring
(❚ Fig. 28-5). The more familiar, woody female cones, which are
on the tree year-round, are usually found on the upper branches
of the tree and bear seeds after reproduction. Female cones vary
considerably in size. The sugar pine (P. lambertiana) that grows
in California produces the world’s longest female cones, which
reach lengths of 60 cm (2 ft).
Each male cone, also called a pollen cone, consists of sporophylls, leaflike scales that bear sporangia on the underside. At the
base of each sporophyll are two microsporangia, which contain
numerous microsporocytes, also called microspore mother cells.
1
(c)
It may be helpful to review alternation of generations in Chapter 27,
including Figure 27-16, which depicts a heterosporous life cycle, before
studying the pine life cycle.
(b, c) Leaf variation in conifers. (b) Needles of white pine (Pinus strobus). (c) Small, scalelike leaves of American arborvitae
(Thuja occidentalis).
2 , each microsporocyte undergoes meiosis to
In Figure 28-4 ●
form four haploid microspores. Microspores then develop into
extremely reduced male gametophytes. Each immature male gametophyte, also called a pollen grain, consists of four cells, two of
which — a generative cell and a tube cell — are involved in reproduction. The other two cells soon degenerate. Two large air sacs
on each pollen grain provide buoyancy for wind dissemination.
3 , male cones shed pollen grains in great numbers, and wind
In ●
currents carry some to the immature female cones.
Many botanists think that the female cones (also called
4 , each
seed cones) are modified branch systems. As shown in ●
cone scale bears two ovules, or megasporangia, on its upper surface. Within each megasporangium, meiosis of a megasporocyte,
or megaspore mother cell, produces four haploid megaspores.
One of these divides mitotically, developing into the female gametophyte, which produces an egg within each of several archegonia. The other three megaspores are nonfunctional and soon
degenerate.
When the ovule is ready to receive pollen, it produces a sticky
droplet at the opening where the pollen grains land. Pollination,
the transfer of pollen to the female cones, occurs in the spring
for a week or 10 days, after which the pollen cones wither and
drop off the tree. One of the many pollen grains that adhere to
the sticky female cone grows a pollen tube, an outgrowth that
digests its way through the megasporangium to the egg within the
archegonium. The germinated pollen grain with its pollen tube
is the mature male gametophyte. The tube cell, which is involved
The Plant Kingdom: Seed Plants
603
David Cavagnaro
John D. Cunningham / Visuals Unlimited
Angiosperms
Gnetophytes
Conifers
Cycads
Ginkgoes
Gymnosperms
(a) The leaves of Gnetum gnemon
resemble those of flowering plants. Note
the exposed seeds.
Gnetophytes
over the counter in weight-control medications and herbal energy boosters; several deaths have been reported from chronic use
or overdose of products containing ephedrine.
The third gnetophyte genus, Welwitschia, contains a single
species found in deserts of southwestern Africa (❚ Fig. 28-8c).
Most of Welwitschia’s body — a long taproot — grows underground. Its short, wide stem forms a shallow disc, up to 0.9 m
(3 ft) in diameter, from which two ribbonlike leaves extend. These
two leaves continue to grow from the stem throughout the plant’s
life, but their ends are usually broken and torn by the wind, giving the appearance of numerous leaves. Each leaf grows to about
2 m (6.5 ft) in length. When Welwitschia reproduces, cones form
around the edge of its disclike stem.
Review
❚
❚
❚
❚
What is the dominant generation in the pine life cycle? How
does pollination occur in gymnosperms?
What features distinguish gymnosperms from other plants?
What are the four groups of gymnosperms?
What features distinguish cycads from ginkgo? From
gnetophytes?
FLOWERING PLANTS
Learning Objectives
5
6
7
8
Summarize the features that distinguish flowering plants from
other plants.
Briefly explain the life cycle of a flowering plant, and describe
double fertilization.
Contrast eudicots and monocots, the two largest classes of
flowering plants.
Discuss the evolutionary adaptations of flowering plants.
Robert and Linda Mitchell
Figure 28-8
(b) A male joint fir (Ephedra) has pollen
cones clustered at the nodes. In the 19th
century, European pioneers used species
native to the American Southwest to make
a beverage, Mormon tea.
(c) Welwitschia mirabilis is native to deserts in southwestern Africa.
It survives on moisture-laden fogs that drift inland from the ocean.
Photographed in the Namib Desert, Namibia.
Flowering plants, or angiosperms (phylum Anthophyta), are the
most successful plants today, surpassing even the gymnosperms
in importance. They have adapted to almost every habitat and,
with at least 300,000 species, are Earth’s dominant plants. Flowering plants come in a wide variety of sizes and forms, from
herbaceous violets to massive eucalyptus trees. Some flowering
plants — tulips and roses, for example —have large, conspicuous
flowers; others, such as grasses and oaks, produce small, inconspicuous flowers.
Flowering plants are vascular plants that reproduce sexually
by forming flowers and, after a unique double fertilization process
(discussed later), seeds within fruits. The fruit protects the developing seeds and often aids in their dispersal (see Chapter 36).
Flowering plants have efficient water-conducting cells called vesThe Plant Kingdom: Seed Plants
607
sel elements in their xylem, and efficient sugar-conducting cells
called sieve tube elements in their phloem (see Chapter 32).
Flowering plants are extremely important to humans because
our survival as a species literally depends on them. All our major
food crops are flowering plants, including cereal crops such as
rice, wheat, corn, and barley. Woody flowering plants such as oak,
cherry, and walnut provide valuable lumber. Flowering plants
give us fibers such as cotton and linen and medicines such as digitalis and codeine. Products as diverse as rubber, tobacco, coffee,
chocolate, and aromatic oils for perfumes come from flowering
plants. Economic botany is the subdiscipline of botany that deals
with plants of economic importance.
Monocots and eudicots are the two
largest classes of flowering plants
Phylum Anthophyta is divided into several classes with only
a few members each and two very large classes: the monocots
(class Monocotyledones) and the eudicots (class Eudicotyledones) (❚ Fig. 28-9). The smaller classes will be discussed later in
the chapter in the context of their evolutionary significance; for
now, we restrict our discussion of flowering plants to the monocots and eudicots, which collectively represent about 97% of all
flowering plant species. Eudicots are more diverse and include
many more species (at least 200,000) than the monocots (at least
90,000). ❚ Table 28-2 provides a comparison of some of the general features of the two classes.
Monocots include palms, grasses, orchids, irises, onions, and
lilies. Monocots are mostly herbaceous plants with long, narrow
leaves that have parallel veins (the main leaf veins run parallel
to one another). The parts of monocot flowers usually occur in
threes. For example, a flower may have three sepals, three petals, six stamens, and a compound pistil consisting of three fused
carpels (these flower parts are discussed shortly). Monocot seeds
have a single cotyledon, or embryonic seed leaf; endosperm, a
nutritive tissue, is usually present in the mature seed.
Eudicots include oaks, roses, mustards, cacti, blueberries,
and sunflowers. Eudicots are either herbaceous (such as a tomato plant) or woody (such as a hickory tree). Their leaves vary
in shape but usually are broader than monocot leaves, with netted veins (branched veins resembling a net). Flower parts usually
occur in fours or fives or multiples thereof. Two cotyledons are
present in eudicot seeds, and endosperm is usually absent in the
mature seed, having been absorbed by the two cotyledons during
seed development.
Flowers are involved in sexual reproduction
Flowers are reproductive shoots usually composed of four parts
— sepals, petals, stamens, and carpels — arranged in whorls (circles) on the end of a flower stalk, or peduncle (❚ Fig. 28-10). The
peduncle may terminate in a single flower or a cluster of flowers
known as an inflorescence. The tip of the flower stalk that bears
the flower parts is known as the receptacle.
All four floral parts are important in the reproductive process, but only the stamens (the “male” organs) and carpels (the
“female” organs) produce gametes. A flower that has all four
parts is complete, whereas an incomplete flower lacks one or
more of these four parts. A flower with both stamens and carpels
is perfect, whereas an imperfect flower has stamens or carpels,
but not both.
Angiosperms
Richard H. Gross
Gnetophytes
Flowering plants
John Gerlach / Tom Stack & Associates
Figure 28-9
Conifers
Cycads
Ginkgoes
Gymnosperms
(a) Monocot. Trillium erectum, like most
monocots, has floral parts in threes. Note
the three green sepals, three red petals,
six stamens, and three stigmas (the compound pistil consists of three fused carpels).
608
Chapter 28
(b) Eudicot. Most eudicots, such as this
Tacitus, have floral parts in fours or fives.
Note the five petals, 10 stamens, and five
separate pistils. Five sepals are also present
but barely visible against the background.
www.thomsonedu.com/biology/solomon
S U M M ARY WI T H K EY TERMS
Learning Objectives
1
Compare the features of gymnosperms and angiosperms
(page 601).
6
❚ The two groups of seed plants are the gymnosperms
and the angiosperms. Gymnosperms produce seeds that
are totally exposed or borne on the scales of cones; an
ovary wall does not surround the ovules of gymnosperms.
Angiosperms are flowering plants that produce their seeds
within a fruit (a mature ovary).
2
❚ The sporophyte generation is dominant in flowering
plants; gametophytes are extremely reduced in size and
nutritionally dependent on the sporophyte generation.
Flowering plants are heterosporous and produce microspores and megaspores within the flower.
❚ Each microspore develops into a pollen grain (immature
male gametophyte). One of each four megaspores produced by meiosis develops into an embryo sac (female
gametophyte). The embryo sac contains seven cells with
eight nuclei; the egg cell and the central cell with two
polar nuclei participate in fertilization.
Trace the steps in the life cycle of a pine, and compare its
sporophyte and gametophyte generations (page 601).
❚ A pine tree is a mature sporophyte; pine gametophytes
are extremely small and nutritionally dependent on the
sporophyte generation. Pine is heterosporous and produces microspores and megaspores in separate cones.
❚ Double fertilization, which results in the formation of a
diploid zygote and triploid endosperm, is characteristic of
flowering plants.
❚ Male cones produce microspores that develop into pollen
grains (immature male gametophytes) that are carried by
air currents to female cones.
❚ Female cones produce megaspores. One of each four
megaspores produced by meiosis develops into a female
gametophyte within an ovule (megasporangium).
❚ After pollination, the transfer of pollen to the female
cones, a pollen tube grows through the megasporangium
to the egg within the archegonium. After fertilization, the
zygote develops into an embryo encased inside a seed
adapted for wind dispersal.
3
4
Explore plant life cycles by clicking on the
figures in ThomsonNOW.
7
❚ Eudicots (class Eudicotyledones) usually have floral parts
in fours or fives or multiples thereof, and their seeds
each contain two cotyledons. The nutritive organs in their
mature seeds are usually the cotyledons, which have absorbed the nutrients in the endosperm.
8
Name and briefly describe the four phyla of gymnosperms
(page 601).
❚ Ginkgo biloba, the only surviving species in phylum
Ginkgophyta, is a deciduous, dioecious tree. The female ginkgo produces fleshy seeds directly on branches.
❚ Gnetophytes (phylum Gnetophyta) share a number of
traits with angiosperms.
5
Summarize the features that distinguish flowering plants from
other plants (page 607).
❚ Flowering plants, or angiosperms (phylum Anthophyta),
constitute the phylum of vascular plants that produce flowers and seeds enclosed within a fruit. They are the most
diverse and most successful group of plants.
❚ The flower, which may contain sepals, petals, stamens,
and carpels, functions in sexual reproduction. Unlike
those of gymnosperms, the ovules of flowering plants are
enclosed within an ovary. After fertilization, the ovules
become seeds, and the ovary develops into a fruit.
Discuss the evolutionary adaptations of flowering plants
(page 607).
❚ Flowering plants reproduce sexually by forming flowers.
After double fertilization, seeds form within fruits. Flowering plants have efficient water-conducting vessel
elements in their xylem and efficient carbohydrateconducting sieve tube elements in their phloem. Wind,
water, insects, or other animals transfer pollen grains in
various flowering plants.
❚ Conifers (phylum Coniferophyta), the largest phylum of
gymnosperms, are woody plants that bear needles (leaves
that are usually evergreen) and produce seeds in cones.
Most conifers are monoecious and have male and female
reproductive parts in separate cones on the same plant.
❚ Cycads (phylum Cycadophyta) are palmlike or fernlike in
appearance. They are dioecious—they have male and
female reproductive structures on separate plants—but
reproduce with pollen and seeds in conelike structures.
Contrast eudicots and monocots, the two largest classes of
flowering plants (page 607).
❚ Most monocots (class Monocotyledones) have floral parts
in threes, and their seeds each contain one cotyledon.
The nutritive tissue in their mature seeds is endosperm.
Summarize the features that distinguish gymnosperms from
bryophytes and ferns (page 601).
❚ Unlike bryophytes, gymnosperms are vascular plants. Unlike bryophytes and ferns, gymnosperms produce seeds.
Gymnosperms also produce wind-borne pollen grains, a
feature that ferns and other seedless vascular plants lack.
Briefly explain the life cycle of a flowering plant, and describe
double fertilization (page 607).
Learn more about flower structure by clicking
on the figure in ThomsonNOW.
9
Summarize the evolution of gymnosperms from seedless vascular plants, and trace the evolution of flowering plants from
gymnosperms (page 614).
❚ Seed plants arose from seedless vascular plants. Progymnosperms were seedless vascular plants that had
megaphylls and “modern” woody tissue. Progymnosperms probably gave rise to conifers as well as to seed
ferns, which in turn likely gave rise to cycads and possibly
ginkgo.
❚ The evolution of the gnetophytes, particularly their relationship to flowering plants, is unclear.
❚ Flowering plants probably descended from ancient gymnosperms that had specialized features, such as leaves
with broad, expanded blades and closed carpels. Flowering plants likely arose only once.
The Plant Kingdom: Seed Plants
617
T E S T Y O U R U N DE R S TAND ING
1. Seed plants lack which of the following structure(s)?
(a) ovules surrounded by integuments (b) microspores
and megaspores (c) vascular tissues (d) a large, nutritionally independent sporophyte (e) a large, nutritionally independent gametophyte
2. Conifers, cycads, ginkgo, and gnetophytes are collectively
called (a) club mosses (b) gymnosperms (c) angiosperms
(d) eudicots (e) seedless vascular plants
3. Most conifers are
, having male and female
reproductive parts at different locations on the same plant.
(a) incomplete (b) imperfect (c) monoecious (d) dioecious
(e) perfect
4. The immature male gametophytes of pine are called
(a) ovules (b) stamens (c) seed cones (d) pollen grains
(e) polar nuclei
5. The transfer of pollen grains from the male to the female reproductive structure is known as (a) pollination (b) fertilization (c) embryo sac development (d) seed development
(e) fruit development
6. Motile sperm cells are found as vestiges in these two gymnosperm groups: (a) monocots, eudicots (b) gnetophytes,
conifers (c) gnetophytes, flowering plants (d) cycads, conifers
(e) cycads, ginkgo
7. There are at least
species of flowering
plants. (a) 235 (b) 3000 (c) 30,000 (d) 300,000 (e) 3,000,000
8. This class of flowering plants includes the palms, grasses, and
orchids. (a) eudicots (b) gnetophytes (c) cycads (d) monocots
(e) conifers
9. The pistil has three sections: (a) stigma, style, and anther
(b) anther, filament, and ovule (c) stigma, style, and ovary
(d) ovary, ovule, and sepal (e) corolla, stamen, and sepal
10. A simple pistil consists of a single (a) calyx (b) carpel
(c) ovule (d) filament (e) petal
11. A flower that lacks stamens is both
and
. (a) complete; imperfect (b) incomplete;
perfect (c) complete; perfect (d) incomplete; imperfect
12. After fertilization, the
develop(s) into
a fruit and the
develop(s) into a seed.
(a) ovary; ovule (b) polar nuclei; ovule (c) ovary; endosperm
(d) ovule; ovary (e) ovule; polar nuclei
13. The female gametophyte in flowering plants is also called the
(a) polar nuclei (b) anther (c) embryo sac (d) endosperm
(e) sporophyll
14. This flowering plant may be the nearest living relative to the
ancestor of all flowering plants. (a) Amborella (b) Archaeopteris (c) Gnetum (d) water lily (e) Archaeanthus
15.
This cross section through an ovary reveals that
the pistil is (a) simple, with one carpel (b) compound, with two fused carpels (c) compound, with
three fused carpels (d) compound, with six separate carpels
(e) compound, with six fused carpels
C R I TI C AL TH I N KI N G
1. How are cones and flowers alike? How are they different?
(Hint: Your answer should consider microspores /megaspores
and seeds.)
5. Analyzing Data. According to the cladogram in Figure
28-19, which plant(s) is /are the outgroup? Which feature does
the outgroup lack that all other angiosperms possess?
2. How do the life cycles of seedless plants (see Chapter 27) and
seed plants differ? In what fundamental way are they alike?
3. Evolution Link. Most flowers contain both male and female
reproductive structures, in contrast to the cones of gymnosperms, which are either male or female. Explain how bisexual
flowers might be an advantageous evolutionary adaptation to
the flowering plants that possess them.
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4. Evolution Link. Contrast the algae, mosses, ferns, gymnosperms, and angiosperms with respect to their dependence on
water as a transport medium for reproductive cells. Suggest a
hypothesis to explain how the differences might be adaptive
to living on land.
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Chapter 28
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