LECTURE PRESENTATIONS For 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 by Erin Barley Kathleen Fitzpatrick Plant Diversity II: The Evolution of Seed Plants Chapter 30

Overview: Transforming the World Seeds changed the course of plant evolution, enabling their bearers to become the dominant producers in most terrestrial ecosystems Seed plants originated about 360 million years ago A seed consists of an embryo and nutrients surrounded by a protective coat Domestication of seed plants had begun by 8,000 years ago and allowed for permanent settlements © 2011 Pearson Education, Inc.

Figure 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 © 2011 Pearson Education, Inc.

Advantages of Reduced Gametophytes The gametophytes of seed plants develop within the walls of spores that are retained within tissues of the parent sporophyte © 2011 Pearson Education, Inc.

Figure 30.2 PLANT GROUP Mosses and other nonvascular plants Gametophyte Sporophyte (2n) Gametophyte (n) Dominant Reduced, dependent on gametophyte for nutrition Dominant Reduced, independent (photosynthetic and free-living) Ferns and other seedless vascular plants Dominant Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Seed plants (gymnosperms and angiosperms) AngiospermGymnosperm Microscopic female gametophytes (n) inside these parts of flowers Microscopic female gametophytes (n) inside ovulate cone Microscopic male gametophytes (n) inside these parts of flowers Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Sporophyte (2n) Gametophyte (n) Example

Figure 30.2a Mosses and other nonvascular plants Gametophyte Sporophyte (2n) Gametophyte (n) Dominant Reduced, dependent on gametophyte for nutrition Example

Figure 30.2b Dominant Reduced, independent (photosynthetic and free-living) Ferns and other seedless vascular plants Sporophyte (2n) Gametophyte (n) Gametophyte Sporophyte Example

Dominant Reduced (usually microscopic), dependent on surrounding sporophyte tissue for nutrition Seed plants (gymnosperms and angiosperms) Angiosperm Gymnosperm Microscopic female gametophytes (n) inside these parts of flowers Microscopic female gametophytes (n) inside ovulate cone Microscopic male gametophytes (n) inside these parts of flowers Microscopic male gametophytes (n) inside pollen cone Sporophyte (2n) Sporophyte (2n) Gametophyte Sporophyte Example Figure 30.2c

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 Immature ovulate 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.

Figure Immature ovulate cone Integument (2n) Spore wall Megaspore (n) Female gametophyte (n) Egg nucleus (n) Discharged sperm nucleus (n) Pollen tube Male gametophyte ( n ) (a) Unfertilized ovule Megasporangium (2n) Pollen grain (n) Micropyle (b) Fertilized ovule

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 © 2011 Pearson Education, Inc.

Figure Immature ovulate cone Integument (2n) Spore wall Megaspore (n) Female gametophyte (n) Egg nucleus (n) Discharged sperm nucleus (n) Pollen tube Male gametophyte ( n ) (a) Unfertilized ovule Megasporangium (2n) Pollen grain (n) Micropyle (b) Fertilized ovule (c) Gymnosperm seed Seed coat Spore wall Food supply (n) Embryo (2n)

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 © 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 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 © 2011 Pearson Education, Inc.

Figure 30.4

Living seed plants can be divided into two clades: gymnosperms and angiosperms Gymnosperms appear early in the fossil record about 305 million years ago and dominated Mesozoic (251–65 million years ago) terrestrial ecosystems Gymnosperms were better suited than nonvascular plants to drier conditions © 2011 Pearson Education, Inc.

Angiosperms began to replace gymnosperms near the end of the Mesozoic Angiosperms now dominate more terrestrial ecosystems Today, cone-bearing gymnosperms called conifers dominate in the northern latitudes © 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 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 biloba leaves and fleshy seeds Ginkgo biloba pollen-producing tree Figure 30.5b

Figure 30.5ba Ginkgo biloba pollen-producing tree

Figure 30.5bb 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 © 2011 Pearson Education, Inc.

Figure 30.5d Ovulate cones Gnetum Ephedra Welwitschia

Figure 30.5da Welwitschia

Figure 30.5db Ovulate cones Welwitschia

Figure 30.5dc Gnetum

Figure 30.5dd Ephedra

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

Figure 30.5ea Douglas fir

Figure 30.5eb European larch

Figure 30.5ec Sequoia

Figure 30.5ed Common juniper

Figure 30.5ee Wollemi pine

Figure 30.5ef Wollemi pine

Figure 30.5eg Bristlecone pine

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 © 2011 Pearson Education, Inc. 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 © 2011 Pearson Education, Inc.

Key Haploid (n) Diploid (2n) Mature sporophyte (2n) Pollen cone Microsporocytes (2n) Microsporangia Microsporangium (2n) Pollen grains (n) MEIOSIS Figure

Key Haploid (n) Diploid (2n) Mature sporophyte (2n) Ovulate cone Pollen cone Microsporocytes (2n) Microsporangia Microsporangium (2n) Surviving megaspore (n) MEIOSIS Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS Megasporocyte (2n) Integument Ovule Figure

Key Haploid (n) Diploid (2n) Mature sporophyte (2n) Ovulate cone Pollen cone Microsporocytes (2n) Microsporangia Microsporangium (2n) Archegonium Surviving megaspore (n) MEIOSIS Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS Female gametophyte Megasporocyte (2n) Integument Sperm nucleus (n) Egg nucleus (n) Pollen tube FERTILIZATION Ovule Figure

Key Haploid (n) Diploid (2n) Mature sporophyte (2n) Ovulate cone Pollen cone Microsporocytes (2n) Microsporangia Microsporangium (2n) Seedling Archegonium Surviving megaspore (n) MEIOSIS Megasporangium (2n) Pollen grain Pollen grains (n) MEIOSIS Female gametophyte Megasporocyte (2n) Integument Sperm nucleus (n) Egg nucleus (n) Pollen tube Seed coat (2n) FERTILIZATION Food reserves (n) Seeds Embryo (new sporophyte) (2n) Ovule Figure

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 © 2011 Pearson Education, Inc.

Figure 30.UN02 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms

Characteristics of Angiosperms All angiosperms are classified in a single phylum, Anthophyta, from the Greek anthos for flower Angiosperms have two key adaptations –Flowers –Fruits © 2011 Pearson Education, Inc.

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 © 2011 Pearson Education, Inc.

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 –Carpels, which produce ovules © 2011 Pearson Education, Inc.

A stamen consists of a stalk called a filament, with a sac called an anther where the pollen is produced A carpel consists of an ovary at the base and a style leading up to a stigma, where pollen is received © 2011 Pearson Education, Inc. Video: Flower Blooming (time lapse)

Stamen Anther Filament Stigma Carpel Style Ovary Petal Sepal Ovule Figure 30.7

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 © 2011 Pearson Education, Inc. Animation: Fruit Development

Tomato Ruby grapefruit Hazelnut Nectarine Milkweed Figure 30.8

Figure 30.8a Tomato

Figure 30.8b Ruby grapefruit

Figure 30.8c Nectarine

Figure 30.8d Hazelnut

Figure 30.8e Milkweed

Various fruit adaptations help disperse seeds Seeds can be carried by wind, water, or animals to new locations © 2011 Pearson Education, Inc.

Wings Seeds within berries Barbs Figure 30.9

Figure 30.9a Wings

Figure 30.9b Seeds within berries

Figure 30.9c Barbs

Figure 30.9d 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 © 2011 Pearson Education, Inc.

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.

Anther Mature flower on sporophyte plant (2n) Pollen grains Tube cell Generative cell Microspore (n) MEIOSIS Microsporangium Microsporocytes (2n) Key Haploid (n) Diploid (2n) Figure

Anther Mature flower on sporophyte plant (2n) Megasporangium (2n) Ovary Antipodal cells Central cell Synergids Female gametophyte (embryo sac) Egg (n) Surviving megaspore (n) Pollen tube Sperm (n) Pollen grains Tube cell Generative cell Microspore (n) Male gametophyte (in pollen grain) (n) Ovule (2n) MEIOSIS Microsporangium Microsporocytes (2n) Key Haploid (n) Diploid (2n) Figure

Anther Mature flower on sporophyte plant (2n) Megasporangium (2n) Ovary Seed Antipodal cells Central cell Synergids Female gametophyte (embryo sac) Egg (n) Egg nucleus (n) Surviving megaspore (n) Pollen tube Sperm (n) Style Sperm Pollen tube Stigma Pollen grains Tube cell Generative cell Microspore (n) Male gametophyte (in pollen grain) (n) Ovule (2n) MEIOSIS Discharged sperm nuclei (n) FERTILIZATION Microsporangium Microsporocytes (2n) Key Haploid (n) Diploid (2n) Figure

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

© 2011 Pearson Education, Inc. Video: Flowering Plant Life Cycle (time lapse) Animation: Seed Development Animation: Plant Fertilization

Angiosperm Evolution Darwin called the origin of angiosperms an “abominable mystery” Angiosperms originated at least 140 million years ago During the late Mesozoic, the major branches of the clade diverged from their common ancestor Scientists are studying fossils, refining phylogenies, and investigating developmental patterns to resolve the mystery © 2011 Pearson Education, Inc.

Fossil Angiosperms Chinese fossils of 125-million-year-old angiosperms share some traits with living angiosperms but lack others Archaefructus sinensis, for example, has anthers and seeds but lacks petals and sepals © 2011 Pearson Education, Inc.

(a) Archaefructus sinensis, a 125- million-year-old fossil (b) Artist’s reconstruction of Archaefructus sinensis Carpel Stamen 5 cm Figure 30.11

Figure 30.11a (a) Archaefructus sinensis, a 125- million-year-old fossil 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 © 2011 Pearson Education, Inc.

Microsporangia (contain microspores) Ovules Most recent common ancestor of all living angiosperms Eudicots Monocots Magnoliids Star anise and relatives Water lilies Amborella Bennettitales Living gymnosperms Millions of years ago (b) Angiosperm phylogeny (a) A possible ancestor of the angiosperms? Figure 30.12

Microsporangia (contain microspores) Ovules (a) A possible ancestor of the angiosperms? Figure 30.12a

Most recent common ancestor of all living angiosperms 300 Eudicots Monocots Magnoliids Star anise and relatives Water lilies Amborella Bennettitales Living gymnosperms Millions of years ago (b) Angiosperm phylogeny Figure 30.12b

Developmental Patterns in Angiosperms Egg formation in the angiosperm Amborella resembles that of the gymnosperms In early angiosperms, the two integuments appear to originate separately Researchers are currently studying expression of flower development genes in gymnosperm and angiosperm species © 2011 Pearson Education, Inc.

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.

The clade eudicot (“true” dicots) includes most dicots The rest of the former dicots form several small lineages 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.

Basal Angiosperms Three small lineages constitute the basal angiosperms These include Amborella trichopoda, water lilies, and star anise © 2011 Pearson Education, Inc.

Water lily Star anise Amborella trichopoda Basal Angiosperms Figure 30.13a

Water lily Figure 30.13aa

Figure 30.13ab Star anise

Figure 30.13ac Amborella trichopoda

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.

Figure 30.13b Magnoliids Southern magnolia

Monocots More than one-quarter of angiosperm species are monocots © 2011 Pearson Education, Inc.

Orchid Monocots Lily Pygmy date palm Anther Filament Stigma Ovary Barley, a grass Figure 30.13c

Figure 30.13ca Orchid

Figure 30.13cb Pygmy date palm

Figure 30.13cc Lily

Figure 30.13cd Anther Filament Stigma Ovary Barley, a grass

Figure 30.13ce

Eudicots More than two-thirds of angiosperm species are eudicots © 2011 Pearson Education, Inc.

California poppy Dog rose Pyrenean oak Snow peaZucchini Eudicots Figure 30.13d

Figure 30.13da California poppy

Figure 30.13db Pyrenean oak

Figure 30.13dc Dog rose

Figure 30.13dd Snow pea

Figure 30.13de Zucchini

Figure 30.13e Monocot Characteristics Eudicot Characteristics Embryos One cotyledonTwo cotyledons Leaf venation Veins usually parallel Veins usually netlike Stems Vascular tissue scattered Vascular tissue usually arranged in ring Roots Root system usually fibrous (no main root) Taproot (main root) usually present 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

Figure 30.13ea Monocot Characteristics Eudicot Characteristics Embryos One cotyledon Two cotyledons Leaf venation Veins usually parallel Veins usually netlike Stems Vascular tissue scattered Vascular tissue usually arranged in ring

Figure 30.13eb Roots Root system usually fibrous (no main root) Taproot (main root) usually present 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 Monocot Characteristics Eudicot Characteristics

Evolutionary Links Between Angiosperms and Animals Animals influence the evolution of plants and vice versa –For example, animal herbivory selects for plant defenses –For example, interactions between pollinators and flowering plants select for mutually beneficial adaptations © 2011 Pearson Education, Inc. Video: Bee Pollinating Video: Bat Pollinating Agave Plant

Figure 30.14

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 © 2011 Pearson Education, Inc.

Figure 30.15

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 © 2011 Pearson Education, Inc.

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 © 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 km 2 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 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. 4 km

Figure 30.16a A satellite image from 2000 shows clear-cut areas in Brazil surrounded by dense tropical forest. 4 km

Figure 30.16b 4 km By 2009, much more of this same tropical forest had been cut down.

Figure 30.UN03 Time since divergence from common ancestor Common ancestor “Bilateral” clade “Radial” clade Compare numbers of species

Five Derived Traits of Seed Plants Reduced gametophytes Heterospory Ovules Pollen Seeds Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovule (gymnosperm) Integument (2n) Megaspore (n) Megasporangium (2n) Pollen grains make water unnecessary for fertilization Seeds: survive better than unprotected spores, can be transported long distances Seed coat Food supply Embryo Female gametophyte Male gametophyte Figure 30.UN04

Figure 30.UN05 Charophyte green algae Mosses Ferns Gymnosperms Angiosperms

Figure 30.UN06 Charophyte green algae Mosses Ferns Gymnosperms Angiosperms

Figure 30.UN07