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Fig. 30-1 What human reproductive organ is functionally similar to this seed? Overview: Transforming the World • Seeds changed the course of plant evolution, enabling their bearers to become the dominant producers in most terrestrial ecosystems • A seed consists of an embryo and nutrients surrounded by a protective coat Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-1 What human reproductive organ is functionally similar to this seed? Seeds and pollen grains are key adaptations for life on land • In addition to seeds, the following are common to all seed plants – Reduced gametophytes – Heterospory – Ovules – Pollen Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Advantages of Reduced Gametophytes • The gametophytes of seed plants develop within the walls of spores that are retained within tissues of the parent sporophyte • Protect female gametophyte from UV and desiccation (good for the land life!) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-2 PLANT GROUP Mosses and other nonvascular plants Gametophyte Dominant Sporophyte 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 Reduced, dependent on Dominant gametophyte for nutrition Dominant Gymnosperm Sporophyte (2n) Microscopic female gametophytes (n) inside ovulate cone Sporophyte (2n) Gametophyte (n) Angiosperm Microscopic female gametophytes (n) inside these parts of flowers Example Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Gametophyte (n) Microscopic male gametophytes (n) inside these parts of flowers Sporophyte (2n) Fig. 30-2c Seed plants (gymnosperms and angiosperms) Reduced (usually microscopic), dependent on surrounding Gametophyte sporophyte tissue for nutrition Sporophyte Dominant Gymnosperm Microscopic female gametophytes (n) inside ovulate cone Angiosperm Microscopic male gametophytes (n) inside these parts of flowers Example Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Sporophyte (2n) Microscopic female gametophytes (n) inside these parts of flowers Heterospory: The Rule Among Seed Plants • The ancestors of seed plants were likely homosporous (one type of spore [like ferns]), while seed plants are heterosporous • Megasporangia produce megaspores that give rise to female gametophytes • Microsporangia produce microspores that give rise to male gametophytes Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-3-1 Integument Spore wall Immature female cone Megasporangium (2n) Megaspore (n) (a) Unfertilized ovule Pollen and Production of Sperm • Microspores develop into pollen grains, which contain the male gametophytes Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 eliminates the need for a film of water and can be dispersed great distances by air or animals Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 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 two sperm into the female gametophyte within the ovule Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-3-2 Female gametophyte (n) Spore wall Male gametophyte (within a germinated pollen grain) (n) Micropyle (b) Fertilized ovule Egg nucleus (n) Discharged sperm nucleus (n) Pollen grain (n) The Evolutionary Advantage of Seeds • A seed develops from the whole ovule Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 © 2008 Pearson Education, Inc., publishing as Pearson 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 • Seeds provide some evolutionary advantages over spores: – They may remain dormant for days to years, until conditions are favorable for germination Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 • Seeds provide some evolutionary advantages over spores: – They may remain dormant for days to years, until conditions are favorable for germination – They may be transported long distances by wind or animals Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-3-3 (c) Gymnosperm seed Fig. 30-3-3 Seed coat (derived from integument) Food supply (female gametophyte tissue) (n) Embryo (2n) (new sporophyte) (c) Gymnosperm seed Fig. 30-3-4 Integument Female gametophyte (n) Seed coat (derived from integument) Spore wall Egg nucleus (n) Immature female cone Megasporangium (2n) Megaspore (n) (a) Unfertilized ovule Male gametophyte (within a germinated pollen grain) (n) Micropyle (b) Fertilized ovule Discharged sperm nucleus (n) Pollen grain (n) Food supply (female gametophyte tissue) (n) Embryo (2n) (new sporophyte) (c) Gymnosperm seed Concept 30.2: Gymnosperms bear “naked” seeds, typically on cones • The gymnosperms have “naked” seeds not enclosed by ovaries and 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) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-UN1 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms Gymnosperm Evolution (fun fact) • Fossil evidence reveals that by the late Devonian period some plants, called progymnosperms, had begun to acquire some adaptations that characterize seed plants Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-4 Archaeopteris, a progymnosperm • Living seed plants can be divided into two clades: gymnosperms and angiosperms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Living seed plants can be divided into two clades: gymnosperms and angiosperms • Gymnosperms appear early in the fossil record and dominated the Mesozoic terrestrial ecosystems Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Living seed plants can be divided into two clades: gymnosperms and angiosperms • Gymnosperms appear early in the fossil record and dominated the Mesozoic terrestrial ecosystems • Gymnosperms were better suited than nonvascular plants to drier conditions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Living seed plants can be divided into two clades: gymnosperms and angiosperms • Gymnosperms appear early in the fossil record and dominated the Mesozoic terrestrial ecosystems • Gymnosperms were better suited than nonvascular plants to drier conditions • Today, cone-bearing gymnosperms called conifers dominate in the northern latitudes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phylum Cycadophyta • Individuals have large cones and palmlike leaves • These thrived during the Mesozoic, but relatively few species exist today Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-5a Cycas revoluta Very successful during Mesozoic (age of cycads) 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-5b Ginkgo biloba pollen-producing (male) tree Fig. 30-5c Ginkgo biloba leaves and fleshy seeds Phylum Gnetophyta • This phylum comprises three genera • Species vary in appearance, and some are tropical whereas others live in deserts Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-5d Gnetum Fig. 30-5e Ephedra “Morman Tea” caffeine + ephedrine! Fig. 30-5f Welwitschia SW Africa some of the biggest leaves Fig. 30-5g Ovulate cones 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-5h Douglas fir Fig. 30-5i European larch Fig. 30-5j Bristlecone pine 4,600 years! Fig. 30-5k Sequoia Fig. 30-5l Wollemi pine Fig. 30-5m Common juniper 1942 air raids ‘44-’45 balloons, deaths Result= 1. Loss of habitat! 2. Cataclysmic fires ? Fire Ecology: Longleaf Pine (Pinus) Life Stages 1. Seed – falls to ground and germinates (or dies)* 2. Grass Stage – builds root system. Meristem protected by needles. 3. Bottlebrush-Shoots up fast – vulnerable, but bark is thickening rapidly. * Other pines may release seeds only when hot (wax, etc.) Disclimax Community Thick bark, no lower limbs, no understory “staircase” vegetation, no fuel buildup (1-7 year natural fire rotation) The Life Cycle of a Pine: A Closer Look • Three key features of the gymnosperm life cycle are: – Dominance of the sporophyte generation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Life Cycle of a Pine: A Closer Look • Three key features of the gymnosperm life cycle are: – Dominance of the sporophyte generation – Development of seeds from fertilized ovules Animation: Pine Life Cycle Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Life Cycle of a Pine: A Closer Look • Three key features of the gymnosperm life cycle are: – Dominance of the sporophyte generation – Development of seeds from fertilized ovules – The transfer of sperm to ovules by pollen Animation: Pine Life Cycle Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The pine tree is the sporophyte and produces sporangia in male and female cones Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The pine tree is the sporophyte and produces sporangia in male and female cones • Small cones produce microspores called pollen grains, each of which contains a male gametophyte Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The pine tree is the sporophyte and produces sporangia in male and female cones • Small cones produce microspores called pollen grains, each of which contains a male gametophyte • The familiar larger cones contain ovules, which produce megaspores that develop into female gametophytes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The pine tree is the sporophyte and produces sporangia in male and female cones • Small cones produce microspores called pollen grains, each of which contains a male gametophyte • The familiar larger cones contain ovules, which produce megaspores that develop into female gametophytes • It takes nearly three years from cone production to mature seed Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 30.3: The reproductive adaptations of angiosperms include flowers and fruits • Angiosperms are seed plants with reproductive structures called flowers and fruits • They are the most widespread and diverse of all plants Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-UN2 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms Characteristics of Angiosperms • All angiosperms are classified in a single phylum, Anthophyta • The name comes from the Greek anthos, flower Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Flowers • The flower is an angiosperm structure specialized for sexual reproduction • Many species are pollinated by insects or animals, while some species are windpollinated Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Allergenic Pollen (poplar, alder, timothy grass, ragweed, sagebrush, scotchbroom) (SEM x1,000). This image is copyright Dennis Kunkel http://www.pbrc.hawaii.edu/~kunkel/gallery. • A flower is a specialized shoot with up to four types of modified leaves: – Sepals, which enclose the flower Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 on their terminal anthers – Carpels, which produce ovules Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-7 Stigma Stamen Anther Carpel Style Filament Ovary Petal Sepal Ovule • A carpel consists of an ovary at the base and a style leading up to a stigma, where pollen is received Video: Flower Blooming (time lapse) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-8 Tomato Ruby grapefruit Nectarine Hazelnut Milkweed • Various fruit adaptations help disperse seeds • Seeds can be carried by wind, water, or animals to new locations Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-9 Wings Seeds within berries Barbs Science 1 January 1982: Vol. 215. no. 4528, pp. 19 - 27 Neotropical Anachronisms: The Fruits the Gomphotheres Ate Daniel H. Janzen 1 and Paul S. Martin 2 Guanacaste: A victim of ice age extinctions? Gomphotheres! Other anachronistic fruits? Megalonyx jeffersonii The Angiosperm Life Cycle • The flower of the sporophyte is composed of both male and female structures Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Angiosperm Life Cycle • The flower of the sporophyte is composed of both male and female structures • Male gametophytes are contained within pollen grains produced by the microsporangia of anthers Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Angiosperm Life Cycle • The flower of the sporophyte is composed of both male and female structures • Male gametophytes are contained within pollen grains produced by the microsporangia of anthers • The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Angiosperm Life Cycle • The flower of the sporophyte is composed of both male and female structures • Male gametophytes are contained within pollen grains produced by the microsporangia of anthers • The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma • Most flowers have mechanisms to ensure cross-pollination between flowers from different plants of the same species Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Silk = style; trichomes make them sticky Long way to go, if you are a corn pollen! • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 endosperm nourishes the developing embryo (think yolk!) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 endosperm nourishes the developing embryo (think yolk!) • Within a seed, the embryo consists of a root and two seed leaves called cotyledons Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-10-1 Key Haploid (n) Diploid (2n) Mature flower on sporophyte plant (2n) Anther Microsporangium Microsporocytes (2n) MEIOSIS Microspore (n) Generative cell Tube cell Male gametophyte (in pollen grain) Pollen (n) grains Fig. 30-10-2 Key Haploid (n) Diploid (2n) Mature flower on sporophyte plant (2n) Microsporangium Microsporocytes (2n) Anther MEIOSIS Microspore Ovule (2n) (n) Ovary MEIOSIS Male gametophyte (in pollen grain) Pollen (n) grains Megasporangium (2n) Megaspore (n) Antipodal cells Female gametophyte Central cell (embryo sac) Synergids Egg (n) Generative cell Tube cell Fig. 30-10-3 Key Haploid (n) Diploid (2n) Mature flower on sporophyte plant (2n) Microsporangium Microsporocytes (2n) Anther MEIOSIS Microspore Ovule (2n) (n) Ovary MEIOSIS Megasporangium (2n) Male gametophyte (in pollen grain) Pollen (n) grains Stigma Pollen tube Megaspore (n) Antipodal cells Female gametophyte Central cell (embryo sac) Synergids Egg (n) Generative cell Tube cell Sperm Style Pollen tube Sperm (n) FERTILIZATION Egg nucleus (n) Discharged sperm nuclei (n) Fig. 30-10-4 Key Haploid (n) Diploid (2n) Mature flower on sporophyte plant (2n) Microsporangium Microsporocytes (2n) Anther MEIOSIS Microspore Ovule (2n) (n) Ovary Germinating seed MEIOSIS Megasporangium (2n) Embryo (2n) Endosperm (3n) Seed Seed coat (2n) Nucleus of developing endosperm (3n) Male gametophyte (in pollen grain) Pollen (n) grains Stigma Pollen tube Megaspore (n) Antipodal cells Female gametophyte Central cell (embryo sac) Synergids Egg (n) Generative cell Tube cell Sperm Style Pollen tube Sperm (n) FERTILIZATION Zygote (2n) Egg nucleus (n) Discharged sperm nuclei (n) Animation: Plant Fertilization Animation: Seed Development Video: Flowering Plant Life Cycle (time lapse) Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fossil Angiosperms • Primitive fossils of 125-million-year-old angiosperms display derived and primitive traits • Archaefructus sinensis, for example, has anthers and seeds but lacks petals and sepals Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-11 Carpel Stamen 5 cm (a) Archaefructus sinensis, a 125-million-year-old fossil (b) Artist s reconstruction of Archaefructus sinensis Angiosperm Phylogeny • The ancestors of angiosperms and gymnosperms diverged about 305 million years ago • Angiosperms may be closely related to Bennettitales, extinct seed plants with flowerlike structures • Amborella and water lilies are likely descended from two of the most ancient angiosperm lineages Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-12 Living gymnosperms Microsporangia (contain microspores) Bennettitales Amborella Water lilies Most recent common ancestor of all living angiosperms Star anise and relatives Monocots Magnoliids Eudicots Ovules (a) A possible ancestor of the angiosperms? 300 250 200 150 100 Millions of years ago (b) Angiosperm phylogeny 50 0 Angiosperm Diversity • The two main groups of angiosperms are monocots (one cotyledon) and eudicots (“true” dicots) • The clade eudicot includes some groups formerly assigned to the paraphyletic dicot (two cotyledons) group Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Basal Angiosperms • Three small lineages constitute the basal angiosperms • These include Amborella trichopoda, water lilies, and star anise Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-13a Amborella trichopoda Fig. 30-13b Water lily Fig. 30-13c Star anise Magnoliids • Magnoliids include magnolias, laurels, and black pepper plants • Magnoliids are more closely related to monocots and eudicots than basal angiosperms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-13d Southern magnolia Monocots • More than one-quarter of angiosperm species are monocots Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-13e Orchid Fig. 30-13e1 Pygmy date palm (Phoenix roebelenii) Fig. 30-13f Fig. 30-13g Barley Anther Stigma Filament Ovary Eudicots • More than two-thirds of angiosperm species are eudicots Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-13h California poppy Fig. 30-13i Pyrenean oak Fig. 30-13j Dog rose Fig. 30-13k Snow pea Fig. 30-13l Zucchini flowers Fig. 30-13m 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 Taproot (main root) usually present Root system usually fibrous (no main root) 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 Fig. 30-13n Monocot Characteristics Eudicot Characteristics Embryos Two cotyledons One cotyledon Leaf venation Veins usually parallel Veins usually netlike Stems Vascular tissue scattered Vascular tissue usually arranged in ring Fig. 30-13o Monocot Characteristics Eudicot Characteristics Roots Taproot (main root) usually present Root system usually fibrous (no main root) 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 Evolutionary Links Between Angiosperms and Animals • Pollination of flowers and transport of seeds by animals are two important relationships in terrestrial ecosystems • Clades with bilaterally symmetrical flowers have more species than those with radially symmetrical flowers • This is likely because bilateral symmetry affects the movement of pollinators and reduces gene flow in diverging populations Video: Bee Pollinating Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Video: Bat Pollinating Agave Plant Coevolution: Reciprocal evolution between two interacting species Ocotillo Ocotillo sex Carpenter bee = cheater Red = hummingbirds White = moths/bats (low light) Yellows = bees Stinky or perfume? Nectar is an expensive way to attract pollinators If bees can cheat, why can’t plants?!! http://www.youtube.com/watch?v=-h8I3cqpgnA&feature=related Concept 30.4: Human welfare depends greatly on seed plants • No group of plants is more important to human survival than seed plants • Plants are key sources of food, fuel, wood products, and medicine • Our reliance on seed plants makes preservation of plant diversity critical Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Products from 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Table 30-1a Table 30-1b Cinchona bark, source of quinine Threats to Plant Diversity • Destruction of habitat is causing extinction of many plant species • Loss of plant habitat is often accompanied by loss of the animal species that plants support • At the current rate of habitat loss, 50% of Earth’s species will become extinct within the next 100–200 years Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 30-UN3 Five Derived Traits of Seed Plants Reduced gametophytes Heterospory Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Male gametophyte Female gametophyte Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovules Integument (2n) Ovule (gymnosperm) Megaspore (2n) Megasporangium (2n) Pollen Pollen grains make water unnecessary for fertilization Seeds Seeds: survive better than unprotected spores, can be transported long distances Integument Food supply Embryo Fig. 30-UN4 A. Flowers B. embryos C. seeds D. vascular tissue Charophyte green algae Mosses B Ferns D C Gymnosperms A Angiosperms