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What human reproductive organ is functionally similar to this seed?
LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
© 2011 Pearson Education, Inc.
Lectures byErin Barley
Kathleen Fitzpatrick
Plant Diversity II: The Evolution of Seed Plants
Chapter 30
1. Why is a flower a lazy organism’s alternative to sex?
2. How do the derived characters facilitate maximizing
adaptive radiation?
3. What are advantages of seeds over spores?
4. What is the purpose of double fertilization?
a) What are the “quirks” in the process?
Guiding questions for chapter 30
Five Derived Traits of Seed Plants
Reducedgametophytes
Heterospory
Ovules
Pollen
Seeds
Microscopic male andfemale gametophytes(n) are nourished andprotected by thesporophyte (2n)
Microspore (gives rise toa male gametophyte)
Megaspore (gives rise toa female gametophyte)
Ovule(gymnosperm)
Integument (2n)
Megaspore (n)
Megasporangium(2n)
Pollen grains make waterunnecessary for fertilization
Seeds: survivebetter thanunprotectedspores, can betransportedlong distances
Seed coat
Food supply
Embryo
Femalegametophyte
Malegametophyte
REVIEW
Concept 30.1: Seeds and pollen grains are key adaptations for life on land
• the following are common to all seed plants– Seeds (an embryo with a connected food supply
and a protective coat)
– Reduced gametophytes
– Heterospory
– Ovules
– Pollen
© 2011 Pearson Education, Inc.
Figure 30.2
PLANT GROUP
Mosses and othernonvascular plants
Gametophyte
Sporophyte
Sporophyte(2n)
Gametophyte(n)
Dominant
Reduced, dependent ongametophyte for nutrition
Dominant
Reduced, independent(photosynthetic andfree-living)
Ferns and other seedlessvascular plants
Dominant
Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition
Seed plants (gymnosperms and angiosperms)
AngiospermGymnosperm
Microscopicfemalegametophytes(n) insidethese partsof flowers
Microscopic femalegametophytes (n) insideovulate cone
Microscopicmalegametophytes(n) insidethese partsof flowers
Microscopic malegametophytes (n)inside pollencone
Sporophyte (2n)Sporophyte (2n)
Sporophyte(2n)
Gametophyte(n)
Example
Heterospory: The Rule Among Seed Plants
• The ancestors of seed plants were likely homosporous, while seed plants are heterosporous– Megasporangia produce megaspores that give rise to
female gametophytes– Microsporangia produce microspores that give rise to
male gametophytes
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
Figure 30.3-1
Immatureovulate cone
Integument (2n)
Spore wall
Megaspore (n)
(a) Unfertilized ovule
Megasporangium(2n)
Pollen grain (n)Micropyle
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 eliminates the need for a film of water and can be dispersed great distances by air or animals– If a pollen grain germinates, it gives rise to a pollen
tube that discharges sperm into the female gametophyte within the ovule
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Animation: Plant Fertilization Right-click slide / select”Play”
© 2011 Pearson Education, Inc.
Animation: Seed DevelopmentRight-click slide / select”Play”
Figure 30.3-2
Immatureovulate cone
Integument (2n)
Spore wall
Megaspore (n)
Femalegametophyte (n)
Egg nucleus(n)
Dischargedsperm nucleus(n)
Pollen tubeMale gametophyte (n)
(a) Unfertilized ovule
Megasporangium(2n)
Pollen grain (n)Micropyle
(b) Fertilized ovule
Figure 30.3-3
Immatureovulate cone
Integument (2n)
Spore wall
Megaspore (n)
Femalegametophyte (n)
Egg nucleus(n)
Dischargedsperm nucleus(n)
Pollen tubeMale gametophyte (n)
(a) Unfertilized ovule
Megasporangium(2n)
Pollen grain (n)Micropyle
(b) Fertilized ovule (c) Gymnosperm seed
Seedcoat
Sporewall
Foodsupply (n)
Embryo (2n)
The Evolutionary Advantage of Seeds
• What are they?
© 2011 Pearson Education, Inc.
• Seeds provide some evolutionary advantages over spores
– They may remain dormant for days to years, until conditions are favorable for germination
– Seeds have a supply of stored food
– They may be transported long distances by wind or animals
– Protected by integuments
© 2011 Pearson Education, Inc.
Concept 30.2: Gymnosperms bear “naked” seeds, typically on cones
• Gymnosperms means “naked seeds”• The seeds are exposed on sporophylls that form
cones
• Angiosperm seeds are found in fruits, which are mature ovaries
© 2011 Pearson Education, Inc.
Figure 30.UN01
Nonvascular plants (bryophytes)
Seedless vascular plantsGymnosperms
Angiosperms
• Living seed plants can be divided into two clades: gymnosperms and angiosperms
–What is the ideal ecosystem for gymnosperms?
© 2011 Pearson Education, Inc.
• The gymnosperms consist of four phyla– Cycadophyta (cycads)
– Gingkophyta (one living species: Ginkgo biloba)
– Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia)
– Coniferophyta (conifers, such as pine, fir, and redwood)
© 2011 Pearson Education, Inc.
Phylum Cycadophyta• Individuals have large cones and palmlike leaves• These thrived during the Mesozoic, but relatively
few species exist today
© 2011 Pearson Education, Inc.
Figure 30.5a
Cycas revoluta
Phylum Cycadophyta
Phylum Ginkgophyta• This phylum consists of a single living species,
Ginkgo biloba• It has a high tolerance to air pollution and is a
popular ornamental tree
© 2011 Pearson Education, Inc.
Ginkgo bilobaleaves andfleshy seeds
Ginkgo biloba pollen-producing tree
Figure 30.5b
Phylum Gnetophyta• This phylum comprises three genera• Species vary in appearance, and some are
tropical whereas others live in deserts
© 2011 Pearson Education, Inc.
Figure 30.5d
Ovulate conesGnetum
Ephedra
Welwitschia
Phylum Coniferophyta• This phylum is by far the largest of the
gymnosperm phyla• Most conifers are evergreens and can carry out
photosynthesis year round
© 2011 Pearson Education, Inc.
Figure 30.5e
Douglas fir
Common juniper
European larch
Sequoia
Wollemi pine Bristlecone pine
© 2011 Pearson Education, Inc.
Animation: Pine Life Cycle Right-click slide / select”Play”
Key
Haploid (n)Diploid (2n)
Maturesporophyte(2n)
Pollencone
Microsporocytes(2n)
Microsporangia
Microsporangium (2n)
Pollengrains (n)
MEIOSIS
Life cycle of a pine
Key
Haploid (n)Diploid (2n)
Maturesporophyte(2n)
Ovulatecone
Pollencone
Microsporocytes(2n)
Microsporangia
Microsporangium (2n)Survivingmegaspore (n)
MEIOSIS
Megasporangium (2n)Pollengrain
Pollengrains (n)
MEIOSIS
Megasporocyte (2n)
Integument
Ovule
Figure 30.6-2
Key
Haploid (n)Diploid (2n)
Maturesporophyte(2n)
Ovulatecone
Pollencone
Microsporocytes(2n)
Microsporangia
Microsporangium (2n)
Archegonium
Survivingmegaspore (n)
MEIOSIS
Megasporangium (2n)Pollengrain
Pollengrains (n)
MEIOSIS
Femalegametophyte
Megasporocyte (2n)
Integument
Spermnucleus (n) Egg nucleus (n)
Pollentube
FERTILIZATION
Ovule
Figure 30.6-3
Key
Haploid (n)Diploid (2n)
Maturesporophyte(2n)
Ovulatecone
Pollencone
Microsporocytes(2n)
Microsporangia
Microsporangium (2n)
Seedling
Archegonium
Survivingmegaspore (n)
MEIOSIS
Megasporangium (2n)Pollengrain
Pollengrains (n)
MEIOSIS
Femalegametophyte
Megasporocyte (2n)
Integument
Spermnucleus (n) Egg nucleus (n)
Pollentube
Seed coat (2n)
FERTILIZATION
Foodreserves (n)
Seeds
Embryo(new sporophyte)(2n)
Ovule
Figure 30.6-4
Concept 30.3: The reproductive adaptations of angiosperms include flowers and fruits
• Angiosperms have two key adaptations– Flowers
– Fruits
– They are the most widespread and diverse of all plants
© 2011 Pearson Education, Inc.
Why is a flower a lazy organism’s alternative to
sex?
Stamen Anther
Filament
StigmaCarpel
Style
Ovary
Petal
Sepal
Ovule
Figure 30.7
What is the purpose of each part?
© 2011 Pearson Education, Inc.
Video: Flower Blooming (time lapse)
Fruits
• A fruit typically consists of a mature ovary but can also include other flower parts– Fruits represent tremendous investments in a plant’s
energy and nutrient resources. – What is a fruit’s purpose? Is this purpose justifiable?
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Animation: Fruit DevelopmentRight-click slide / select”Play”
TomatoRuby grapefruit
Hazelnut
Nectarine
Milkweed
Figure 30.8
Wings
Seeds within berries
Barbs
Figure 30.9
© 2011 Pearson Education, Inc.
REPEAT: Plant Fertilization Right-click slide / select”Play”
© 2011 Pearson Education, Inc.
REPEAT : Seed DevelopmentRight-click slide / select”Play”
• A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary
• The ovule is entered by a pore called the micropyle
• Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within an ovule
© 2011 Pearson Education, Inc.
• One sperm fertilizes the egg, while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm
• The triploid endosperm nourishes the developing embryo
• Within a seed, the embryo consists of a root and two seed leaves called cotyledons
© 2011 Pearson Education, Inc.
AntherMature flower onsporophyte plant(2n)
Pollengrains
Tube cell
Generative cell
Microspore (n)MEIOSIS
Microsporangium
Microsporocytes (2n)
Key
Haploid (n)Diploid (2n)
Figure 30.10-1
AntherMature flower onsporophyte plant(2n)
Megasporangium (2n)
Ovary
Antipodal cellsCentral cellSynergids
Femalegametophyte(embryo sac)
Egg (n)
Survivingmegaspore(n)
Pollentube
Sperm(n)
Pollengrains
Tube cell
Generative cell
Microspore (n)
Malegametophyte(in pollengrain) (n)
Ovule (2n)
MEIOSIS
MEIOSIS
Microsporangium
Microsporocytes (2n)
Key
Haploid (n)Diploid (2n)
Figure 30.10-2
AntherMature flower onsporophyte plant(2n)
Megasporangium (2n)
Ovary
Seed
Antipodal cellsCentral cellSynergids
Femalegametophyte(embryo sac)
Egg (n)
Eggnucleus (n)
Survivingmegaspore(n)
Pollentube
Sperm(n)
Style
SpermPollentube
Stigma
Pollengrains
Tube cell
Generative cell
Microspore (n)
Malegametophyte(in pollengrain) (n)
Ovule (2n)
MEIOSIS
MEIOSIS
Discharged sperm nuclei (n)
FERTILIZATION
Microsporangium
Microsporocytes (2n)
Key
Haploid (n)Diploid (2n)
Figure 30.10-3
AntherMature flower onsporophyte plant(2n)
Germinatingseed
Megasporangium (2n)
Ovary
Embryo (2n)
Endosperm (3n)
Seed coat (2n)
Seed
Antipodal cellsCentral cellSynergids
Femalegametophyte(embryo sac)
Egg (n)
Eggnucleus (n)
Survivingmegaspore(n)
Pollentube
Sperm(n)
Style
SpermPollentube
Stigma
Pollengrains
Tube cell
Generative cell
Microspore (n)
Malegametophyte(in pollengrain) (n)
Ovule (2n)
MEIOSIS
MEIOSIS
Discharged sperm nuclei (n)
FERTILIZATIONZygote (2n)
Microsporangium
Microsporocytes (2n)
Nucleus ofdevelopingendosperm(3n)
Key
Haploid (n)Diploid (2n)
Figure 30.10-4
© 2011 Pearson Education, Inc.
Video: Flowering Plant Life Cycle (time lapse)
Angiosperm Diversity
• Angiosperms comprise more than 250,000 living species
• Previously, angiosperms were divided into two main groups
– Monocots (one cotyledon)– Dicots (two dicots)
• DNA studies suggest that monocots form a clade, but dicots are polyphyletic
© 2011 Pearson Education, Inc.
Most recent common ancestorof all living angiosperms
300
Eudicots
Monocots
Magnoliids
Star aniseand relatives
Water lilies
Amborella
Bennettitales
Livinggymnosperms
Millions of years ago
(b) Angiosperm phylogeny
250 200 150 100 50 0
Angiosperm evolutionary history
• The clade eudicot (“true” dicots) includes most dicots
• Basal angiosperms are less derived and include the flowering plants belonging to the oldest lineages
• Magnoliids share some traits with basal angiosperms but evolved later
© 2011 Pearson Education, Inc.
Water lily
Star anise
Amborella trichopoda
Basal AngiospermsFigure 30.13a
Magnoliids• Magnoliids include magnolias,
laurels, and black pepper plants• Magnoliids are more closely
related to monocots and eudicots than basal angiosperms
© 2011 Pearson Education, Inc.
Southern magnolia
Orchid
Monocots
Lily
Pygmy date palm
Anther
Filament
Stigma
Ovary
Barley, a grass
Figure 30.13c
California poppy Dog rose
Pyrenean oak
Snow pea Zucchini
Eudicots (more than 2/3 of all plant species)Figure 30.13d
Figure 30.13eMonocot
CharacteristicsEudicot
Characteristics
Embryos
One cotyledon Two cotyledons
Leafvenation
Veins usuallyparallel
Veins usuallynetlike
Stems
Vascular tissuescattered
Vascular tissueusually arranged
in ring
Roots
Root systemusually fibrous(no main root)
Taproot (main root)usually present
Pollen
Pollen grain withone opening
Pollen grain withthree openings
Flowers
Floral organsusually in
multiples of three
Floral organsusually in multiples
of four or five
Evolutionary Links Between Angiosperms and Animals
• Animals influence the evolution of plants and vice versa
– Pollinators and flowers are obviously mutualistically symbiotic
– How can herbivory also be beneficial to both?
© 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
Video: Bat Pollinating Agave Plant
© 2011 Pearson Education, Inc.
Video: Bee Pollinating
A plant pollinated by flies
Clades with bilateral symmetry are more diverse than those with radial symmetry?
Concept 30.4: Human welfare depends greatly on seed plants
• Most of our food comes from angiosperms• Six crops (wheat, rice, maize, potatoes, cassava,
and sweet potatoes) yield 80% of the calories consumed by humans
• Modern crops are products of relatively recent genetic change resulting from artificial selection
• Many seed plants provide wood• Secondary compounds of seed plants are used
in medicines
© 2011 Pearson Education, Inc.
Table 30.1
Threats to Plant Diversity
• Destruction of habitat is causing extinction of many plant species
• In the tropics 55,000 km2 are cleared each year• At this rate, the remaining tropical forests will be
eliminated in 200 years • Loss of plant habitat is often accompanied by
loss of the animal species that plants support
© 2011 Pearson Education, Inc.
• At the current rate of habitat loss, 50% of Earth’s species will become extinct within the next 100–200 years
• The tropical rain forests may contain undiscovered medicinal compounds
© 2011 Pearson Education, Inc.
Figure 30.16
A satellite imagefrom 2000 showsclear-cut areas inBrazil surroundedby dense tropicalforest.
By 2009, muchmore of this sametropical forest hadbeen cut down.
4 km
Five Derived Traits of Seed Plants
Reducedgametophytes
Heterospory
Ovules
Pollen
Seeds
Microscopic male andfemale gametophytes(n) are nourished andprotected by thesporophyte (2n)
Microspore (gives rise toa male gametophyte)
Megaspore (gives rise toa female gametophyte)
Ovule(gymnosperm)
Integument (2n)
Megaspore (n)
Megasporangium(2n)
Pollen grains make waterunnecessary for fertilization
Seeds: survivebetter thanunprotectedspores, can betransportedlong distances
Seed coat
Food supply
Embryo
Femalegametophyte
Malegametophyte
REVIEW
1. Why is a flower a lazy organism’s alternative to sex?
2. How do the derived characters facilitate maximizing
adaptive radiation?
3. What are advantages of seeds over spores?
4. What is the purpose of double fertilization?
a) What are the “quirks” in the process?
Guiding questions for chapter 30: REVIEW