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What human reproductive organ is functionally similar to this seed?
Figure 30.1 What human reproductive organ is functionally similar to this seed? 1
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Plant Diversity II: The Evolution of Seed Plants
Chapter 30 Plant Diversity II: The Evolution of Seed Plants
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Guiding questions for chapter 30
Why is a flower a lazy organism’s alternative to sex? How do the derived characters facilitate maximizing adaptive radiation? What are advantages of seeds over spores? What is the purpose of double fertilization? What are the “quirks” in the process?
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Five Derived Traits of Seed Plants
REVIEW Five Derived Traits of Seed Plants Reduced gametophytes Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Male gametophyte Female gametophyte Heterospory Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovules Integument (2n) Megaspore (n) Ovule (gymnosperm) Megasporangium (2n) Figure 30.UN04 Summary figure, Concept 30.1 Pollen Pollen grains make water unnecessary for fertilization Seeds Seeds: survive better than unprotected spores, can be transported long distances Seed coat Food supply Embryo 4
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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.
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Ferns and other seedless
Figure 30.2 PLANT GROUP Mosses and other nonvascular plants Ferns and other seedless vascular plants Seed plants (gymnosperms and angiosperms) Reduced, independent (photosynthetic and free-living) Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Gametophyte Dominant Reduced, dependent on gametophyte for nutrition Sporophyte Dominant Dominant Gymnosperm Angiosperm Sporophyte (2n) Microscopic female gametophytes (n) inside ovulate cone Sporophyte (2n) Microscopic female gametophytes (n) inside these parts of flowers Gametophyte (n) Example Figure 30.2 Gametophyte-sporophyte relationships in different plant groups. Microscopic male gametophytes (n) inside these parts of flowers Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Sporophyte (2n) Gametophyte (n) 6
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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.
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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.
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(a) Unfertilized ovule
Figure Immature ovulate cone Integument (2n) Spore wall Megaspore (n) Figure 30.3 From ovule to seed in a gymnosperm. Megasporangium (2n) Micropyle Pollen grain (n) (a) Unfertilized ovule 9
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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.
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Animation: Plant Fertilization Right-click slide / select”Play”
© 2011 Pearson Education, Inc.
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Animation: Seed Development
Right-click slide / select”Play” © 2011 Pearson Education, Inc.
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(a) Unfertilized ovule (b) Fertilized ovule
Figure Immature ovulate cone Female gametophyte (n) Integument (2n) Spore wall Egg nucleus (n) Megaspore (n) Discharged sperm nucleus (n) Figure 30.3 From ovule to seed in a gymnosperm. Megasporangium (2n) Pollen tube Micropyle Male gametophyte (n) Pollen grain (n) (a) Unfertilized ovule (b) Fertilized ovule 13
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(a) Unfertilized ovule (b) Fertilized ovule (c) Gymnosperm seed
Figure Immature ovulate cone Seed coat Female gametophyte (n) Integument (2n) Spore wall Spore wall Egg nucleus (n) Megaspore (n) Discharged sperm nucleus (n) Food supply (n) Figure 30.3 From ovule to seed in a gymnosperm. Megasporangium (2n) Pollen tube Male gametophyte (n) Embryo (2n) Micropyle Pollen grain (n) (a) Unfertilized ovule (b) Fertilized ovule (c) Gymnosperm seed 14
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The Evolutionary Advantage of Seeds
What are they? © 2011 Pearson Education, Inc.
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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.
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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.
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Nonvascular plants (bryophytes)
Figure 30.UN01 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms Figure 30.UN01 In-text figure, p. 621 18
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Living seed plants can be divided into two clades: gymnosperms and angiosperms
What is the ideal ecosystem for gymnosperms? © 2011 Pearson Education, Inc.
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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.
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Phylum Cycadophyta Individuals have large cones and palmlike leaves
These thrived during the Mesozoic, but relatively few species exist today © 2011 Pearson Education, Inc.
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Phylum Cycadophyta Cycas revoluta Figure 30.5a
Figure 30.5 Exploring: Gymnosperm Diversity Cycas revoluta 22
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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.
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Ginkgo biloba pollen-producing tree
Figure 30.5b Figure 30.5 Exploring: Gymnosperm Diversity Ginkgo biloba leaves and fleshy seeds Ginkgo biloba pollen-producing tree 24
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Phylum Gnetophyta This phylum comprises three genera
Species vary in appearance, and some are tropical whereas others live in deserts © 2011 Pearson Education, Inc.
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Ovulate cones Gnetum Welwitschia Ephedra Figure 30.5d
Figure 30.5 Exploring: Gymnosperm Diversity Welwitschia Ephedra 26
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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.
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Figure 30.5 Exploring: Gymnosperm Diversity
Common juniper Douglas fir Figure 30.5 Exploring: Gymnosperm Diversity Sequoia European larch Wollemi pine Bristlecone pine 28
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Animation: Pine Life Cycle Right-click slide / select”Play”
© 2011 Pearson Education, Inc.
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Life cycle of a pine Key Haploid (n) Diploid (2n) Pollen cone
Microsporocytes (2n) Mature sporophyte (2n) Pollen grains (n) MEIOSIS Microsporangia Microsporangium (2n) Figure 30.6 The life cycle of a pine. 30
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Key Haploid (n) Ovule Diploid (2n) Ovulate Megasporocyte (2n) cone
Figure Key Haploid (n) Diploid (2n) Ovule Ovulate cone Megasporocyte (2n) Pollen cone Integument Microsporocytes (2n) Mature sporophyte (2n) Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Surviving megaspore (n) Figure 30.6 The life cycle of a pine. 31
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Key Haploid (n) Ovule Diploid (2n) Ovulate Megasporocyte (2n) cone
Figure Key Haploid (n) Diploid (2n) Ovule Ovulate cone Megasporocyte (2n) Pollen cone Integument Microsporocytes (2n) Mature sporophyte (2n) Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Surviving megaspore (n) Archegonium Figure 30.6 The life cycle of a pine. Female gametophyte Sperm nucleus (n) Egg nucleus (n) Pollen tube FERTILIZATION 32
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Pollen grain Food reserves (n)
Figure Key Haploid (n) Diploid (2n) Ovule Ovulate cone Megasporocyte (2n) Pollen cone Integument Microsporocytes (2n) Mature sporophyte (2n) Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS MEIOSIS Microsporangia Microsporangium (2n) Surviving megaspore (n) Seedling Archegonium Figure 30.6 The life cycle of a pine. Female gametophyte Seeds Food reserves (n) Sperm nucleus (n) Egg nucleus (n) Seed coat (2n) Pollen tube Embryo (new sporophyte) (2n) FERTILIZATION 33
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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.
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Why is a flower a lazy organism’s alternative to sex?
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What is the purpose of each part?
Figure 30.7 Stigma Carpel Stamen Anther Style Filament Ovary Figure 30.7 The structure of an idealized flower. Petal Sepal Ovule What is the purpose of each part? 36
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Video: Flower Blooming (time lapse)
© 2011 Pearson Education, Inc.
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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.
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Animation: Fruit Development
Right-click slide / select”Play” © 2011 Pearson Education, Inc.
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Tomato Ruby grapefruit Nectarine Hazelnut Milkweed Figure 30.8
Figure 30.8 Some variations in fruit structure. Milkweed 40
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Wings Seeds within berries Barbs Figure 30.9
Figure 30.9 Fruit adaptations that enhance seed dispersal. Barbs 41
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REPEAT: Plant Fertilization Right-click slide / select”Play”
© 2011 Pearson Education, Inc.
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REPEAT : Seed Development
Right-click slide / select”Play” © 2011 Pearson Education, Inc.
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The ovule is entered by a pore called the micropyle
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.
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The triploid endosperm nourishes the developing embryo
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.
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Microsporangium Anther Microsporocytes (2n) Mature flower on
Figure Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Microspore (n) Generative cell Tube cell Pollen grains Figure The life cycle of an angiosperm. Key Haploid (n) Diploid (2n) 46
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Microsporangium Anther Microsporocytes (2n) Mature flower on
Figure Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Microspore (n) Generative cell Ovule (2n) Male gametophyte (in pollen grain) (n) Tube cell Ovary Pollen grains MEIOSIS Megasporangium (2n) Surviving megaspore (n) Antipodal cells Female gametophyte (embryo sac) Central cell Synergids Pollen tube Figure The life cycle of an angiosperm. Egg (n) Sperm (n) Key Haploid (n) Diploid (2n) 47
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Discharged sperm nuclei (n)
Figure Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Microspore (n) Generative cell Ovule (2n) Male gametophyte (in pollen grain) (n) Tube cell Ovary Pollen grains MEIOSIS Stigma Megasporangium (2n) Pollen tube Sperm Surviving megaspore (n) Seed Antipodal cells Female gametophyte (embryo sac) Style Central cell Figure The life cycle of an angiosperm. Synergids Pollen tube Egg (n) Sperm (n) Egg nucleus (n) FERTILIZATION Key Haploid (n) Diploid (2n) Discharged sperm nuclei (n) 48
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Discharged sperm nuclei (n)
Figure Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Microspore (n) Generative cell Ovule (2n) Male gametophyte (in pollen grain) (n) Tube cell Ovary Germinating seed Pollen grains MEIOSIS Stigma Megasporangium (2n) Pollen tube Embryo (2n) Sperm Surviving megaspore (n) Endosperm (3n) Seed Seed coat (2n) Antipodal cells Female gametophyte (embryo sac) Style Central cell Pollen tube Figure The life cycle of an angiosperm. Synergids Nucleus of developing endosperm (3n) Egg (n) Sperm (n) Egg nucleus (n) Zygote (2n) FERTILIZATION Key Haploid (n) Diploid (2n) Discharged sperm nuclei (n) 49
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Video: Flowering Plant Life Cycle (time lapse)
© 2011 Pearson Education, Inc.
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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.
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Angiosperm evolutionary history
Living gymnosperms Bennettitales Amborella Water lilies Most recent common ancestor of all living angiosperms Star anise and relatives Magnoliids Monocots Figure Angiosperm evolutionary history. Eudicots 300 250 200 150 100 50 Millions of years ago (b) Angiosperm phylogeny 52
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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.
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Basal Angiosperms Star anise Water lily Amborella trichopoda
Figure 30.13a Basal Angiosperms Star anise Water lily Figure Exploring: Angiosperm Diversity Amborella trichopoda 54
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Magnoliids Magnoliids include magnolias, laurels, and black pepper plants Magnoliids are more closely related to monocots and eudicots than basal angiosperms Southern magnolia © 2011 Pearson Education, Inc.
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Monocots Orchid Lily Pygmy date palm Anther Stigma Ovary Filament
Figure 30.13c Monocots Orchid Lily Figure Exploring: Angiosperm Diversity Pygmy date palm Anther Stigma Ovary Filament Barley, a grass 56
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Eudicots (more than 2/3 of all plant species)
Figure 30.13d Eudicots (more than 2/3 of all plant species) Dog rose California poppy Figure Exploring: Angiosperm Diversity Pyrenean oak Snow pea Zucchini 57
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Figure 30.13 Exploring: Angiosperm Diversity
Monocot Characteristics Eudicot Characteristics Embryos One cotyledon Two cotyledons Leaf venation Veins usually parallel Veins usually netlike Stems Vascular tissue usually arranged in ring Vascular tissue scattered Roots Root system usually fibrous (no main root) Taproot (main root) usually present Figure Exploring: Angiosperm Diversity Pollen Pollen grain with one opening Pollen grain with three openings Flowers Floral organs usually in multiples of three Floral organs usually in multiples of four or five 58
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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.
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Video: Bat Pollinating Agave Plant
© 2011 Pearson Education, Inc.
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Video: Bee Pollinating
© 2011 Pearson Education, Inc.
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A plant pollinated by flies
Figure A plant pollinated by flies. 62
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Clades with bilateral symmetry are more diverse than those with radial symmetry?
Figure Pollinating a bilaterally symmetrical flower. 63
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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.
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Table 30.1 Table 30.1 Examples of Plant-Derived Medicines 65
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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.
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The tropical rain forests may contain undiscovered medicinal compounds
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.
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A satellite image from 2000 shows clear-cut areas in Brazil surrounded
Figure 30.16 A satellite image from 2000 shows clear-cut areas in Brazil surrounded by dense tropical forest. By 2009, much more of this same tropical forest had been cut down. Figure Impact: Clear-Cutting of Tropical Forests 4 km 68
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Five Derived Traits of Seed Plants
REVIEW Five Derived Traits of Seed Plants Reduced gametophytes Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Male gametophyte Female gametophyte Heterospory Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovules Integument (2n) Megaspore (n) Ovule (gymnosperm) Megasporangium (2n) Figure 30.UN04 Summary figure, Concept 30.1 Pollen Pollen grains make water unnecessary for fertilization Seeds Seeds: survive better than unprotected spores, can be transported long distances Seed coat Food supply Embryo 69
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Guiding questions for chapter 30: REVIEW
Why is a flower a lazy organism’s alternative to sex? How do the derived characters facilitate maximizing adaptive radiation? What are advantages of seeds over spores? What is the purpose of double fertilization? What are the “quirks” in the process?
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