Chapter 30 Plant Diversity II

Chapter 30: Plant Diversity II Fig. 29-7 Chapter 30: Plant Diversity II 1 Origin of land plants (about 475 mya) 2 Origin of vascular plants (about 420 mya) 3 Origin of extant seed plants (about 305 mya) Liverworts Nonvascular plants (bryophytes) Land plants ANCES- TRAL GREEN ALGA 1 Hornworts Mosses Lycophytes (club mosses, spike mosses, quillworts) Seedless vascular plants 2 Vascular plants Pterophytes (ferns, horsetails, whisk ferns) Figure 29.7 Highlights of plant evolution Gymnosperms 3 Seed plants Angiosperms 500 450 400 350 300 50 Millions of years ago (mya)

What are five crucial adaptations that led the success of seed Plants? Seeds Reduced gametophytes Heterospory Ovules Pollen

Seeds 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

Reduced Gametophyte: protection of antheridia and archegonia Fig. 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 Microscopic female gametophytes (n) inside these parts of flowers Sporophyte (2n) 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) Reduced Gametophyte: protection of antheridia and archegonia Gametophyte (n)

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 Immature female cone Integument Spore wall Megasporangium (2n) Megaspore (n) (a) Unfertilized ovule

Pollen and Production of Sperm Microspores develop into pollen grains, which contain the male gametophytes Pollination 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 Seed coat (derived from integument) Integument Female gametophyte (n) Spore wall Egg nucleus (n) Immature female cone Food supply (female gametophyte tissue) (n) Male gametophyte (within a germinated pollen grain) (n) Megasporangium (2n) Discharged sperm nucleus (n) Embryo (2n) (new sporophyte) Megaspore (n) Micropyle Pollen grain (n) (a) Unfertilized ovule (b) Fertilized ovule (c) 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 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

Gymnosperms What are the four phyla of gymnosperms? Fig. 30-UN1 Gymnosperms Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms What are the four phyla of gymnosperms? Which phyla is the most biologically significant?

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)

Phylum Cycadophyta Individuals have large cones and palmlike leaves These thrived during the Mesozoic, but relatively few species exist today

Fig. 30-5a Figure 30.5 Gymnosperm diversity 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

Ginkgo biloba pollen-producing tree Fig. 30-5b Figure 30.5 Gymnosperm diversity Ginkgo biloba pollen-producing tree

Ginkgo biloba leaves and fleshy seeds Fig. 30-5c Figure 30.5 Gymnosperm diversity 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. 30-5e Figure 30.5 Gymnosperm diversity Ephedra

Fig. 30-5f Figure 30.5 Gymnosperm diversity Welwitschia

Fig. 30-5g Ovulate cones Figure 30.5 Gymnosperm diversity 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

Fig. 30-5i Figure 30.5 Gymnosperm diversity European larch

Fig. 30-5j Figure 30.5 Gymnosperm diversity Bristlecone pine

Fig. 30-5k Figure 30.5 Gymnosperm diversity Sequoia

Fig. 30-5m Figure 30.5 Gymnosperm diversity 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

Surviving megaspore (n) Seedling Fig. 30-6-4 Key Haploid (n) Ovule Diploid (2n) Ovulate cone Megasporocyte (2n) Integument Pollen cone 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 Seeds Female gametophyte Food reserves (n) Sperm nucleus (n) Seed coat (2n) Pollen tube Embryo (2n) FERTILIZATION Egg nucleus (n)

Angiosperms Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms Angiosperms are seed plants with reproductive structures called flowers and fruits They are the most widespread and diverse of all plants

Video: Flower Blooming (time lapse) Fig. 30-7 Stigma Carpel Stamen Anther Style Filament Ovary Figure 30.7 The structure of an idealized flower Petal Sepal Ovule Video: Flower Blooming (time lapse)

Animation: Fruit Development 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

Tomato Ruby grapefruit Nectarine Hazelnut Milkweed Fig. 30-8 Figure 30.8 Some variations in fruit structure Hazelnut Milkweed

Wings Seeds within berries Barbs Fig. 30-9 Figure 30.9 Fruit adaptations that enhance seed dispersal Barbs

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

Mature flower on sporophyte plant (2n) Microsporocytes (2n) Fig. 30-10-4 Key Haploid (n) Diploid (2n) Microsporangium Anther Mature flower on sporophyte plant (2n) Microsporocytes (2n) MEIOSIS Generative cell Microspore (n) Ovule (2n) Tube cell Male gametophyte (in pollen grain) (n) Ovary Pollen grains MEIOSIS Germinating seed Stigma Megasporangium (2n) Pollen tube Embryo (2n) Endosperm (3n) Seed coat (2n) Sperm Seed Megaspore (n) Style Antipodal cells Central cell Synergids Egg (n) Figure 30.10 The life cycle of an angiosperm Female gametophyte (embryo sac) Pollen tube Sperm (n) Nucleus of developing endosperm (3n) FERTILIZATION Zygote (2n) Egg nucleus (n) Discharged sperm nuclei (n)

Animation: Plant Fertilization Animation: Seed Development Video: Flowering Plant Life Cycle (time lapse)

Monocot Characteristics Eudicot Characteristics Fig. 30-13n Monocot Characteristics Eudicot Characteristics Embryos One cotyledon Two cotyledons Leaf venation Veins usually parallel Veins usually netlike Figure 30.13 Angiosperm diversity Stems Vascular tissue usually arranged in ring Vascular tissue scattered

Monocot Characteristics Eudicot Characteristics Fig. 30-13o Monocot Characteristics Eudicot Characteristics Roots Root system usually fibrous (no main root) Taproot (main root) usually present Pollen Pollen grain with one opening Pollen grain with three openings Figure 30.13 Angiosperm diversity Flowers Floral organs usually in multiples of three Floral organs usually in multiples of four or five

Basal Angiosperms Three small lineages constitute the basal angiosperms These include Amborella trichopoda, water lilies, and star anise

Fig. 30-13b Figure 30.13 Angiosperm diversity Water lily

Fig. 30-13c Figure 30.13 Angiosperm diversity 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 Figure 30.13 Angiosperm diversity Southern magnolia

Monocots More than one-quarter of angiosperm species are monocots

Fig. 30-13e Figure 30.13 Angiosperm diversity Orchid

Fig. 30-13f Figure 30.13 Angiosperm diversity

Barley Anther Stigma Ovary Filament Fig. 30-13g Figure 30.13 Angiosperm diversity Anther Stigma Ovary Filament

Eudicots More than two-thirds of angiosperm species are eudicots

Fig. 30-13h Figure 30.13 Angiosperm diversity California poppy

Fig. 30-13j Figure 30.13 Angiosperm diversity Dog rose

Fig. 30-13l Figure 30.13 Angiosperm diversity Zucchini flowers