Transcript 30_Lectures_PPT

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
Concept 30.1: The reduced gametophytes of seed
plants are protected in ovules and pollen grains
• The following are common to all seed plants:
– Reduced gametophytes
– Embryo protected within seed
– Ovule
– Pollen
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Advantages of Reduced Gametophytes
Sporophyte
(2n)
• The gametophytes
of seed plants
develop within the
walls of spores
retained within
tissues of the parent
sporophyte
Sporophyte
(2n)
Gametophyte
(n)
Sporophyte dependent on
gametophyte (mosses
and other bryophytes)
Microscopic female
gametophytes (n) in
ovulate cones
(dependent)
Gametophyte
(n)
Large sporophyte and
small, independent gametophyte (ferns and other
seedless vascular plants)
Sporophyte (2n),
the flowering plant
(independent)
Microscopic male
gametophytes (n) in
inside these parts
of flowers
(dependent)
Microscopic male
gametophytes (n)
in pollen cones
(dependent)
Sporophyte (2n),
(independent)
Microscopic female
gametophytes (n) in
inside these parts
of flowers
(dependent)
Reduced gametophyte dependent on sporophyte (seed
plants: gymnosperms and angiosperms)
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
Integument
Female
gametophyte (n)
Seed coat
(derived from
integument)
Spore wall
Egg nucleus (n)
Megasporangium
(2n)
Megaspore (n)
Unfertilized ovule
Male gametophyte
(within germinating
pollen grain) (n)
Micropyle
Fertilized ovule
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Discharged
sperm nucleus (n)
Pollen grain (n)
Food supply
(female
gametophyte
tissue) (n)
Embryo (2n)
(new sporophyte)
Gymnosperm seed
Ovules and Production of Eggs
Diagrammatic ovules.
a, Angiosperm ovule. b, Gymnosperm ovule. i, integument (covering); ii, inner integument; m,
micropyle (opening); oi, outer integument; s, stalk.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pollen and Production of Sperm
• Microspores develop into pollen grains, which
contain the male gametophytes
• If a pollen grain germinates, it gives rise to a
pollen tube that discharges two sperm into the
female gametophyte within the ovule
Integument
Female
gametophyte (n)
Seed coat
(derived from
integument)
Spore wall
Egg nucleus (n)
Megasporangium
(2n)
Megaspore (n)
Unfertilized ovule
Male gametophyte
(within germinating
pollen grain) (n)
Micropyle
Fertilized ovule
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Discharged
sperm nucleus (n)
Pollen grain (n)
Food supply
(female
gametophyte
tissue) (n)
Embryo (2n)
(new sporophyte)
Gymnosperm seed
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 30-4aa
Cycas revoluta
LE 30-4ab
LE 30-4ac
LE 30-4ad
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 30-4ae
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 30-4af
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 30-4ag
Ovulate
cones
LE 30-4ba
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 30-4bb
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 30-4bc
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 30-4bd
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 30-4be
Common juniper.
The “berries” of
the common
juniper (Juniperus
communis), are
actually ovuleproducing cones
consisting of
fleshy sporophylls.
LE 30-4bf
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 in two small
groves. The inset photo
compares the leaves of
this “living fossil” with
actual fossils.
• Gymnosperms appear early in the fossil record
and dominated the Mesozoic terrestrial
ecosystems
• Living seed plants can be divided into two
clades: gymnosperms and angiosperms
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A Closer Look at the Life Cycle of a Pine
• Key features of the gymnosperm life cycle:
– Dominance of the sporophyte generation
– Development of seeds from fertilized ovules
– The transfer of sperm to ovules by pollen
• The life cycle of a pine is an example
Animation: Pine Life Cycle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 30-6_3
Key
Haploid (n)
Diploid (2n)
Ovule
Ovulate
cone
Pollen
cone
Megasporocyte (2n)
Integument
Longitudinal
Micropyle
section of
ovulate cone
Megasporangium
Mature
sporophyte
(2n)
Microsporocytes
(2n)
MEIOSIS
Longitudinal
section of
pollen cone
Sporophyll
Microsporangium
Germinating
Pollen pollen grain
grains (n)
MEIOSIS
(containing male
gametophytes)
Surviving
megaspore (n)
Seedling
Germinating
pollen grain
Archegonium
Egg (n)
Seeds on surface
of ovulate scale
Female
gametophyte
Germinating
pollen grain (n)
Food reserves Seed coat
(gametophyte (derived from
Discharged
tissue) (n)
sperm nucleus (n)
parent
sporophyte) (2n)
Pollen
tube
Embryo
(new sporophyte)
(2n)
FERTILIZATION
Egg nucleus (n)
Integument
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
Flowers
• The flower is an angiosperm structure specialized
for sexual reproduction
• A flower is a specialized shoot with up to four
types of modified leaves:
– Sepals, which enclose the flower
– Petals, which are brightly colored and attract
pollinators
– Stamens, which produce pollen
– Carpels, which produce ovules
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 30-7
Stigma
Stamen
Anther
Carpel
Style
Filament
Ovary
Petal
Sepal
Ovule
Receptacle
Video: Flower Blooming (time lapse)
Fruits
• A fruit typically consists of a mature ovary but
can also include other flower parts
• Fruits protect seeds and aid in their dispersal
• Mature fruits can be either fleshy or dry
Animation: Fruit Development
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 30-8
Tomato, a fleshy fruit with soft
outer and inner layers of pericarp
Ruby grapefruit, a fleshy fruit
with a hard outer layer and soft
inner layer of pericarp
Nectarine, a fleshy
fruit with a soft outer
layer and hard inner
layer (pit) of pericarp
Milkweed, a dry fruit that splits
open at maturity
Walnut, a dry fruit that remains
closed at maturity
LE 30-9
Wings enable maple
fruits to be easily
carried by the wind.
Seeds within berries
and other edible fruits
are often dispersed in
animal feces.
The barbs of cockleburs
facilitate seed dispersal
by allowing these fruits to
hitchhike on animals.
The Angiosperm Life Cycle
• In the angiosperm life cycle, double fertilization
occurs.
– ovum
– food-storing endosperm
• nourishes the developing embryo
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 30-10a
Key
Haploid (n)
Diploid (2n)
Microsporangium
Microsporocytes (2n)
Anther
Mature flower on
Sporophyte plant
(2n)
MEIOSIS
Microspore (n)
Ovule with
megasporangium (2n) Male
gametophyte
(in pollen
grain)
Ovary
MEIOSIS
Megasporangium
(n)
Surviving
megaspore
(n)
Female gametophyte
(embryo sac)
Antipodal cells
Polar nuclei
Synergids
Eggs (n)
Pollen
tube
Sperm
(n)
Generative cell
Tube cell
LE 30-10b
Key
Haploid (n)
Diploid (2n)
Microsporangium
Microsporocytes (2n)
Anther
Mature flower on
sporophyte plant
(2n)
MEIOSIS
Microspore (n)
Ovule with
megasporangium (2n) Male
gametophyte
(in pollen
grain)
Ovary
Generative cell
Pollen
grains
MEIOSIS
Stigma
Pollen
Megasporangium tube
(n)
Sperm
Surviving
megaspore
(n)
Pollen
tube
Style
Antipodal cells
Female gametophyte
Polar nuclei
(embryo sac)
Synergids
Eggs (n)
Pollen
tube
Sperm
(n)
Eggs
nucleus (n)
Discharged
sperm nuclei (n)
Tube cell
LE 30-10c
Key
Haploid (n)
Diploid (2n)
Microsporangium
Microsporocytes (2n)
Anther
Mature flower on
sporophyte plant
(2n)
MEIOSIS
Microspore (n)
Ovule with
megasporangium (2n) Male
gametophyte
(in pollen
grain)
Ovary
Germinating
seed
Generative cell
Pollen
grains
MEIOSIS
Stigma
Pollen
Megasporangium tube
(n)
Sperm
Surviving
megaspore
(n)
Embryo (2n)
Endosperm
(food
supply) (3n)
Seed
Pollen
tube
Seed coat (2n)
Style
Antipodal cells
Female gametophyte
Polar nuclei
(embryo sac)
Synergids
Eggs (n)
Pollen
tube
Sperm
(n)
Zygote (2n)
Nucleus of
developing
endosperm
(3n)
Eggs
nucleus (n)
FERTILIZATION
Discharged
sperm nuclei (n)
Tube cell
Animation: Plant Fertilization
Animation: Seed Development
Video: Flowering Plant Life Cycle (time lapse)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Angiosperm Evolution
• Clarifying the origin and diversification of
angiosperms poses fascinating challenges to
evolutionary biologists
• Angiosperms originated at least 140 million
years ago
• During the late Mesozoic, the major branches of
the clade diverged from their common ancestor
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 30-11
Carpel
Stamen
5 cm
Archaefructus sinensis, a
125-million-year-old fossil
Artist’s reconstruction of
Archaefructus sinensis
Angiosperm Diversity
• The two main groups of angiosperms are
monocots and eudicots
• Basal angiosperms are less derived and include
the flowering plants belonging to the oldest
lineages
• Magnoliids share some traits with basal
angiosperms but are more closely related to
monocots and eudicots
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 30-12aa
BASAL ANGIOSPERMS
Amborella trichopoda
Water lily (Nymphaea
“Rene Gerald”)
Star anise (Illicium
floridanum)
LE 30-12ab
MAGNOLIIDS
Southern magnolia
(Magnolia
grandiflora)
Eudicots
Monocots
Magnoliids
Star anise
and relatives
Water lilies
Amborella
HYPOTHETICAL TREE OF FLOWERING PLANTS
LE 30-12ba
MONOCOTS
EUDICOTS
Orchid
Monocot
(Lemboglossum
Characteristics
rossii)
Eudicot
Characteristics
Embryos
One cotyledon
Two cotyledons
California
poppy
(Eschscholzia
california)
LE 30-12bb
MONOCOTS
EUDICOTS
Pyrenean oak
(Quercus
pyrenaica)
Leaf
venation
Veins usually
netlike
Veins usually
parallel
Stems
Pygmy date palm (Phoenix roebelenii)
Vascular tissue
scattered
Vascular tissue
usually arranged
in ring
LE 30-12bc
MONOCOTS
EUDICOTS
Lily (Lilium
“Enchantment”)
Roots
Dog rose (Rosa canina), a wild rose
Root system
usually fibrous
(no main root)
Taproot (main root)
usually present
LE 30-12bd
MONOCOTS
EUDICOTS
Barley (Hordeum vulgare), a grass
Pea
(Lathyrusner
vosus, Lord
Anson’s
blue pea),
a legume
Pollen
Pollen grain with
one opening
Pollen grain with
three openings
Flowers
Anther
Stigma
Filament
Ovary
Floral organs
usually in
multiples of three
Floral organs usually
in multiples of
four or five
Zucchini
(Cucurbita
Pepo), female
(left), and
male flowers
Evolutionary Links Between Angiosperms and Animals
• Pollination of flowers by animals and transport of
seeds by animals are two important relationships
in terrestrial ecosystems
A flower pollinated by
honeybees.
A flower pollinated by
hummingbirds.
Video: Bee Pollinating
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A flower pollinated by nocturnal animals.
Video: Bat Pollinating