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  • Figure 30.1 What human reproductive organ is functionally similar to this seed?
  • Figure 30.2 Gametophyte/sporophyte relationships in different plant groups
  • Figure 30.2 Gametophyte/sporophyte relationships in different plant groups
  • Figure 30.2 Gametophyte/sporophyte relationships in different plant groups
  • Figure 30.2 Gametophyte/sporophyte relationships in different plant groups
  • Figure 30.3a From ovule to seed in a gymnosperm
  • Figure 30.3b From ovule to seed in a gymnosperm
  • Figure 30.3c From ovule to seed in a gymnosperm
  • Figure 30.3 From ovule to seed in a gymnosperm
  • Figure 30.4 A progymnosperm
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.5 Gymnosperm diversity
  • Figure 30.6 The life cycle of a pine
  • Figure 30.6 The life cycle of a pine
  • Figure 30.6 The life cycle of a pine
  • Figure 30.6 The life cycle of a pine
  • Figure 30.7 The structure of an idealized flower
  • Figure 30.8 Some variations in fruit structure
  • Figure 30.9 Fruit adaptations that enhance seed dispersal
  • Figure 30.10 The life cycle of an angiosperm
  • Figure 30.10 The life cycle of an angiosperm
  • Figure 30.10 The life cycle of an angiosperm
  • Figure 30.10 The life cycle of an angiosperm
  • Figure 30.11 A primitive flowering plant?
  • Figure 30.12 Angiosperm evolutionary history
  • Figure 30.12 Angiosperm evolutionary history
  • Figure 30.12 Angiosperm evolutionary history
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.13 Angiosperm diversity
  • Figure 30.14 Can flower shape influence speciation rate?
  • Figure 30.14 Can flower shape influence speciation rate?
  • Figure 30.14 Can flower shape influence speciation rate?
  • Table 30.1
  • Table 30.1

Chapter 30 Presentation Chapter 30 Presentation Presentation Transcript

  • Chapter 30 Plant Diversity II: The Evolution of Seed Plants
  • 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
  • Fig. 30-1
  • Concept 30.1: 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
  • Advantages of Reduced Gametophytes
    • The gametophytes of seed plants develop within the walls of spores that are retained within tissues of the parent sporophyte
  • Fig. 30-2 Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Reduced, independent (photosynthetic and free-living) Gametophyte Sporophyte (2 n ) Sporophyte (2 n ) Gametophyte ( n ) Sporophyte Example Gametophyte ( n ) Dominant Dominant Dominant Reduced, dependent on gametophyte for nutrition Mosses and other nonvascular plants Ferns and other seedless vascular plants Seed plants (gymnosperms and angiosperms) PLANT GROUP Gymnosperm Angiosperm Microscopic female gametophytes ( n ) inside ovulate cone Microscopic male gametophytes ( n ) inside pollen cone Sporophyte (2 n ) Sporophyte (2 n ) Microscopic female gametophytes ( n ) inside these parts of flowers Microscopic male gametophytes ( n ) inside these parts of flowers
  • Fig. 30-2a Gametophyte Sporophyte (2 n ) Gametophyte ( n ) Sporophyte Example Dominant Reduced, dependent on gametophyte for nutrition Mosses and other nonvascular plants
  • Fig. 30-2b Reduced, independent (photosynthetic and free-living) Sporophyte (2 n ) Gametophyte ( n ) Dominant Ferns and other seedless vascular plants Example Gametophyte Sporophyte
  • Fig. 30-2c Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Dominant Seed plants (gymnosperms and angiosperms) Gymnosperm Angiosperm Microscopic female gametophytes ( n ) inside ovulate cone Microscopic male gametophytes ( n ) inside pollen cone Sporophyte (2 n ) Sporophyte (2 n ) Microscopic female gametophytes ( n ) inside these parts of flowers Microscopic male gametophytes ( n ) inside these parts of flowers Example Gametophyte Sporophyte
  • 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
  • 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
  • Fig. 30-3-1 Megasporangium (2 n ) Megaspore ( n ) (a) Unfertilized ovule Integument Spore wall Immature female cone
  • 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
  • Fig. 30-3-2 Male gametophyte (within a germinated pollen grain) ( n ) Female gametophyte ( n ) (b) Fertilized ovule Micropyle Pollen grain ( n ) Spore wall Discharged sperm nucleus ( n ) Egg nucleus ( n )
  • 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
  • Fig. 30-3-3 Seed coat (derived from integument) (c) Gymnosperm seed Embryo (2 n ) (new sporophyte) Food supply (female gametophyte tissue) ( n )
  • Fig. 30-3-4 Seed coat (derived from integument) (c) Gymnosperm seed Embryo (2 n ) (new sporophyte) Food supply (female gametophyte tissue) ( n ) (b) Fertilized ovule (a) Unfertilized ovule Integument Immature female cone Spore wall Megasporangium (2 n ) Male gametophyte (within a germinated pollen grain) ( n ) Megaspore ( n ) Micropyle Pollen grain ( n ) Egg nucleus ( n ) Discharged sperm nucleus ( n ) Female gametophyte ( n )
  • 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)
  • Fig. 30-UN1 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms
  • Gymnosperm Evolution
    • Fossil evidence reveals that by the late Devonian period some plants, called progymnosperms , had begun to acquire some adaptations that characterize seed plants
  • Fig. 30-4 Archaeopteris , a progymnosperm
    • 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
  • Phylum Cycadophyta
    • Individuals have large cones and palmlike leaves
    • These thrived during the Mesozoic, but relatively few species exist today
  • Fig. 30-5a Cycas revoluta
  • 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
  • Fig. 30-5b Ginkgo biloba pollen-producing 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
  • Fig. 30-5d Gnetum
  • Fig. 30-5e Ephedra
  • Fig. 30-5f Welwitschia
  • Fig. 30-5g Welwitschia Ovulate cones
  • Phylum Coniferophyta
    • This phylum is by far the largest of the gymnosperm phyla
    • Most conifers are evergreens and can carry out photosynthesis year round
  • Fig. 30-5h Douglas fir
  • Fig. 30-5i European larch
  • Fig. 30-5j Bristlecone pine
  • Fig. 30-5k Sequoia
  • Fig. 30-5l Wollemi pine
  • Fig. 30-5m Common juniper
  • 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
    • The life cycle of a pine provides an example
    Animation: Pine Life Cycle
    • 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
  • Fig. 30-6-1 Microsporangium (2 n ) Microsporocytes (2 n ) Pollen grains ( n ) Pollen cone Microsporangia MEIOSIS Mature sporophyte (2 n ) Haploid ( n ) Diploid (2 n ) Key Ovulate cone
  • Fig. 30-6-2 Microsporangium (2 n ) Microsporocytes (2 n ) Pollen grains ( n ) Pollen cone Microsporangia MEIOSIS Mature sporophyte (2 n ) Haploid ( n ) Diploid (2 n ) Key MEIOSIS Surviving megaspore ( n ) Pollen grain Megasporangium (2 n ) Megasporocyte (2 n ) Ovule Integument Ovulate cone
  • Fig. 30-6-3 Microsporangium (2 n ) Microsporocytes (2 n ) Pollen grains ( n ) Pollen cone Microsporangia MEIOSIS Mature sporophyte (2 n ) Haploid ( n ) Diploid (2 n ) Key MEIOSIS Surviving megaspore ( n ) Pollen grain Megasporocyte (2 n ) Ovule Integument Ovulate cone FERTILIZATION Pollen tube Female gametophyte Sperm nucleus ( n ) Egg nucleus ( n ) Archegonium Megasporangium (2 n )
  • Fig. 30-6-4 Microsporangium (2 n ) Microsporocytes (2 n ) Pollen grains ( n ) Pollen cone Microsporangia MEIOSIS Mature sporophyte (2 n ) Haploid ( n ) Diploid (2 n ) Key MEIOSIS Surviving megaspore ( n ) Pollen grain Megasporocyte (2 n ) Ovule Integument Ovulate cone FERTILIZATION Pollen tube Female gametophyte Sperm nucleus ( n ) Egg nucleus ( n ) Archegonium Seedling Seeds Seed coat (2 n ) Food reserves ( n ) Embryo (2 n ) Megasporangium (2 n )
  • 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
  • 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
  • Flowers
    • The flower is an angiosperm structure specialized for sexual reproduction
    • Many species are pollinated by insects or animals, while some species are wind-pollinated
    • 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
  • Fig. 30-7 Carpel Ovule Sepal Petal Stigma Style Ovary Stamen Anther Filament
    • 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)
  • 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
  • Fig. 30-8 Hazelnut Ruby grapefruit Tomato Nectarine Milkweed
    • Various fruit adaptations help disperse seeds
    • Seeds can be carried by wind, water, or animals to new locations
  • Fig. 30-9 Barbs Seeds within berries Wings
  • 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
    • 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
    • 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
    • Within a seed, the embryo consists of a root and two seed leaves called cotyledons
  • Fig. 30-10-1 MEIOSIS Key Microsporangium Microsporocytes (2 n ) Generative cell Anther Tube cell Pollen grains Microspore ( n ) Male gametophyte (in pollen grain) ( n ) Mature flower on sporophyte plant (2 n ) Haploid ( n ) Diploid (2 n )
  • Fig. 30-10-2 MEIOSIS Key Microsporangium Microsporocytes (2 n ) Generative cell Anther Tube cell Pollen grains Microspore ( n ) Male gametophyte (in pollen grain) ( n ) Mature flower on sporophyte plant (2 n ) Haploid ( n ) Diploid (2 n ) MEIOSIS Ovule (2 n ) Ovary Megasporangium (2 n ) Megaspore ( n ) Female gametophyte (embryo sac) Antipodal cells Central cell Synergids Egg ( n )
  • Fig. 30-10-3 MEIOSIS Key Microsporangium Microsporocytes (2 n ) Generative cell Anther Tube cell Pollen grains Microspore ( n ) Male gametophyte (in pollen grain) ( n ) Mature flower on sporophyte plant (2 n ) Haploid ( n ) Diploid (2 n ) MEIOSIS Ovule (2 n ) Ovary Megasporangium (2 n ) Megaspore ( n ) Female gametophyte (embryo sac) Antipodal cells Central cell Synergids Egg ( n ) Pollen tube Pollen tube Stigma Sperm ( n ) Discharged sperm nuclei ( n ) FERTILIZATION Egg nucleus ( n ) Style Sperm
  • Fig. 30-10-4 MEIOSIS Key Microsporangium Microsporocytes (2 n ) Generative cell Anther Tube cell Pollen grains Microspore ( n ) Male gametophyte (in pollen grain) ( n ) Mature flower on sporophyte plant (2 n ) Haploid ( n ) Diploid (2 n ) MEIOSIS Ovule (2 n ) Ovary Megasporangium (2 n ) Megaspore ( n ) Female gametophyte (embryo sac) Antipodal cells Central cell Synergids Egg ( n ) Pollen tube Pollen tube Stigma Sperm ( n ) Discharged sperm nuclei ( n ) FERTILIZATION Germinating seed Embryo (2 n ) Endosperm (3 n ) Seed coat (2 n ) Seed Nucleus of developing endosperm (3 n ) Zygote (2 n ) Egg nucleus ( n ) Style Sperm
  • Video: Flowering Plant Life Cycle (time lapse) Animation: Seed Development Animation: Plant Fertilization
  • 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
  • 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
  • Fig. 30-11 Carpel Stamen Archaefructus sinensis , a 125-million-year-old fossil (a) (b) Artist’s reconstruction of Archaefructus sinensis 5 cm
  • 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
  • Fig. 30-12 Microsporangia (contain microspores) Ovules A possible ancestor of the angiosperms? (a) (b) Angiosperm phylogeny Most recent common ancestor of all living angiosperms Millions of years ago 300 250 200 150 100 50 0 Living gymnosperms Bennettitales Amborella Star anise and relatives Water lilies Monocots Magnoliids Eudicots
  • Fig. 30-12a Microsporangia (contain microspores) Ovules A possible ancestor of the angiosperms? (a)
  • Fig. 30-12b (b) Angiosperm phylogeny Most recent common ancestor of all living angiosperms Millions of years ago 300 250 200 150 100 50 0 Living gymnosperms Bennettitales Amborella Star anise and relatives Water lilies Monocots Magnoliids Eudicots
  • Developmental Patterns in Angiosperms
    • Egg formation in the angiosperm Amborella resembles that of the gymnosperms
    • Researchers are currently studying expression of flower development genes in gymnosperm and angiosperm species
  • 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
    • 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
  • Basal Angiosperms
    • Three small lineages constitute the basal angiosperms
    • These include Amborella trichopoda , water lilies, and star anise
  • 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
  • Fig. 30-13d Southern magnolia
  • Monocots
    • More than one-quarter of angiosperm species are monocots
  • Fig. 30-13e Orchid
  • Fig. 30-13e1 Pygmy date palm ( Phoenix roebelenii )
  • Fig. 30-13f
  • Fig. 30-13g Anther Barley Stigma Ovary Filament
  • Eudicots
    • More than two-thirds of angiosperm species are eudicots
  • 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 Vascular tissue usually arranged in ring Veins usually parallel Veins usually netlike Vascular tissue scattered Leaf venation One cotyledon Embryos Two cotyledons Stems Roots Pollen Root system usually fibrous (no main root) Pollen grain with three openings Taproot (main root) usually present Pollen grain with one opening Floral organs usually in multiples of three Flowers Floral organs usually in multiples of four or five
  • Fig. 30-13n Monocot Characteristics Eudicot Characteristics Vascular tissue usually arranged in ring Veins usually parallel Vascular tissue scattered Leaf venation One cotyledon Embryos Two cotyledons Stems Veins usually netlike
  • Fig. 30-13o Roots Pollen Root system usually fibrous (no main root) Pollen grain with three openings Pollen grain with one opening Floral organs usually in multiples of three Flowers Floral organs usually in multiples of four or five Monocot Characteristics Eudicot Characteristics Taproot (main root) usually present
  • 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: Bat Pollinating Agave Plant Video: Bee Pollinating
  • Fig. 30-14 Common ancestor Radial symmetry (N = 4) Bilateral symmetry (N = 15) Compare numbers of species Time since divergence from common ancestor “ Radial” clade “ Bilateral” clade 3,000 2,000 1,000 0 EXPERIMENT RESULTS Mean difference in number of species
  • Fig. 30-14a Common ancestor Compare numbers of species Time since divergence from common ancestor “ Radial” clade “ Bilateral” clade EXPERIMENT
  • Fig. 30-14b Radial symmetry (N = 4) Bilateral symmetry (N = 15) 3,000 2,000 1,000 0 RESULTS Mean difference in number of species
  • 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
  • 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
  • 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
  • Fig. 30-UN3 Reduced gametophytes Microscopic male and female gametophytes ( n ) are nourished and protected by the sporophyte (2 n ) Five Derived Traits of Seed Plants Male gametophyte Female gametophyte Heterospory Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovules Ovule (gymnosperm) Pollen Pollen grains make water unnecessary for fertilization Integument (2 n ) Megaspore (2 n ) Megasporangium (2 n ) Seeds Seeds: survive better than unprotected spores, can be transported long distances Integument Food supply Embryo
  • Fig. 30-UN4 Charophyte green algae Mosses Ferns Gymnosperms Angiosperms
  • Fig. 30-UN5
  • Fig. 30-UN6
  • You should now be able to:
    • Explain why pollen grains were an important adaptation for successful reproduction on land
    • List and distinguish among the four phyla of gymnosperms
    • Describe the life history of a pine; indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation
  • You should now be able to:
    • Identify and describe the function of the following floral structures: sepals, petals, stamens, carpels, filament, anther, stigma, style, ovary, and ovule
    • Explain how fruits may be adapted to disperse seeds
    • Diagram the generalized life cycle of an angiosperm; indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation
    • Explain the significance of Archaefructus and Amborella
    • Describe the current threat to plant diversity caused by human population growth