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Chapter
30
Plant Diversity II: The
Evolution of Seed Plants
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: Feeding the
World
• Seeds changed the course of plant evolution,
enabling their bearers to become the dominant
producers in most terrestrial ecosystems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 30.1: The reduced gametophytes of
seed plants are protected in ovules and pollen
grains
• In addition to seeds, the following are common to
all seed plants:
– Reduced gametophytes
– Heterospory
– Ovules
– Pollen
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Advantages of Reduced
Gametophytes
• The gametophytes of seed plants develop within
the walls of spores retained within tissues of the
parent sporophyte
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Heterospory: The Rule Among Seed
Plants
• Seed plants evolved from plants with
megasporangia, which produce megaspores that
give rise to female gametophytes
• Seed plants evolved from plants with
microsporangia, which produce microspores that
give rise to male gametophytes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ovules and Production of
Eggs
• An ovule consists of a megasporangium,
megaspore, and one or more protective
integuments
• Gymnosperm megaspores have one integument
• Angiosperm megaspores usually have two
integuments
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pollen and Production of
Sperm
• Microspores develop into pollen grains, which
contain the male gametophytes
• Pollination is the transfer of pollen to the part of a
seed plant containing the ovules
• Pollen can be dispersed by air or animals,
eliminating the water requirement for fertilization
• If a pollen grain germinates, it gives rise to a
pollen tube that discharges two sperm into the
female gametophyte within the ovule
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Evolutionary Advantage of
Seeds
• A seed develops from the whole ovule
• A seed is a sporophyte embryo, along with its food
supply, packaged in a protective coat
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 30.2: Gymnosperms bear “naked”
seeds, typically on cones
• The gymnosperms include four phyla:
– Cycadophyta (cycads)
– Gingkophyta (one living species: Ginkgo
biloba)
– Gnetophyta (three genera: Gnetum, Ephedra,
Welwitschia)
– Coniferophyta (conifers, such as pine, fir, and
redwood)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 304aa
Cycas revoluta
LE 304ab
LE 304ac
LE 304ad
Gnetum. This genus
includes about 35
species of tropical
trees, shrubs, and
vines, mainly native
to Africa and Asia.
Their leaves look
similar to those of
flowering plants,
and their seeds look
somewhat like fruits.
LE 304ae
Ephedra. This genus includes about 40 species that inhabit arid
regions throughout the world. Known in North America as
“Mormon tea,” these desert shrubs produce the compound
ephedrine, commonly used as a decongestant.
LE 304af
Welwitschia. This genus
consists of one species
Welwitschia mirabilis, a
plant that lives only in the
deserts of southwestern
Africa. Its strap like
leaves are among the
largest known.
LE 304ag
Ovulate
cones
LE 304ba
Douglas fir. “Doug fir”
(Pseudotsuga menziesii)
provides more timber
than any other North
American tree species.
Some uses include
house framing, plywood,
pulpwood for paper,
railroad ties, and boxes
and crates.
LE 304bb
Pacific yew. The
bark of Pacific yew
(Taxa brevifolia) is a
source of taxol, a
compound used to
treat women with
ovarian cancer. The
leaves of a
European yew
species produce a
similar compound,
which can be
harvested without
destroying the plants. Pharmaceutical companies are now refining
techniques for synthesizing drugs with taxol-like properties.
LE 304bc
Bristlecone pine.
This species (Pinus
longaeva), which is
found in the White
Mountains of
California, includes
some of the oldest
living organisms,
reaching ages of
more than 4,600
years. One tree (not
shown here) is
called Methuselah
because it may be
the world’s oldest
living tree. In order
to protect the tree,
scientists keep its
location a secret.
LE 304bd
Sequoia.
This giant
sequoia (Sequoiadendron
giganteum), in California’s
Sequoia National Park
weighs about 2,500 metric
tons, equivalent to about
24 blue whales (the
largest animals), or 40,000
people. Giant sequoias
are the largest living
organisms and also some
of the most ancient, with
some estimated to be
between 1,800 and 2,700
years old. Their cousins,
the coast redwoods
(Sequoia sempervirens),
grow to heights of more
than 110 meters (taller
than the Statue of Liberty)
and are found only in a
narrow coastal strip of
northern California.
LE 304be
Common juniper.
The “berries” of
the common
juniper (Juniperus
communis), are
actually ovuleproducing cones
consisting of
fleshy sporophylls.
LE 304bf
Wollemia pine. Survivors of a confer group
once known only from fossils, living Wollemia
pines (Wollemia nobilis), were discovered in
1994 in a national park
only 150 kilometers
from Sydney, Australia.
The species consists of
just 40 known
individuals two small
groves. The inset photo
compares the leaves of
this “living fossil” with
actual fossils.
Concept 30.3: The reproductive adaptations
of angiosperms include flowers and fruits
• Angiosperms are flowering plants
• These seed plants have reproductive structures
called flowers and fruits
• They are the most widespread and diverse of all
plants
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Characteristics of
Angiosperms
• All angiosperms are classified in a single phylum,
Anthophyta
• The name comes from the Greek anthos, flower
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Flower
s
• The flower is an angiosperm structure specialized
for sexual reproduction
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 3011
Carpel
Stamen
5 cm
Archaefructus sinensis, a
125-million-year-old fossil
Artist’s reconstruction of
Archaefructus sinensis
LE 3012ba
MONOCOTS
EUDICOTS
Orchid
Monocot
(Lemboglossum
Characteristics
rossii)
Eudicot
Characteristics
Embryos
One cotyledon
Two cotyledons
California
poppy
(Eschscholzia
california)
Evolutionary Links Between Angiosperms and
Animals
• Pollination of flowers by animals and transport of
seeds by animals are two important relationships
in terrestrial ecosystems
Video: Bee Pollinating
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Video: Bat Pollinating
LE 3013
A flower pollinated by
honeybees.
A flower pollinated by
hummingbirds.
A flower pollinated by nocturnal animals.