30 Lecture Plant Diversity II

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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 by8,000 years ago and allowed for permanent

settlements




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




Advantages of Reduced Gametophytes

• The gametophytes of seed plants develop withinthe walls of spores that are retained within

tissues of the parent sporophyte




Figure 30.2

PLANT GROUP

Mosses and other

nonvascular plants

Gametophyte

Sporophyte

Sporophyte

(2n )

Gametophyte

(n )

Dominant

Reduced, dependent on

gametophyte for nutritionDominant

Reduced, independent

(photosynthetic andfree-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

femalegametophytes(n ) inside

these parts

of flowers

Microscopic female

gametophytes (n ) inside

ovulate cone

Microscopic

male

gametophytes(n ) inside

these parts

of flowers

Microscopic malegametophytes (n )

inside pollen

cone

Sporophyte (2n )Sporophyte (2n )

Sporophyte

(2n )

Gametophyte

(n )

Example



Figure 30.2a

Mosses and other

nonvascular plants

Gametophyte

Sporophyte

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 seedlessvascular plants

Sporophyte

(2n )

Gametophyte

(n )

Gametophyte

Sporophyte

Example



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 ) insidethese parts

of flowers

Microscopic malegametophytes (n )

inside pollen

coneSporophyte

(2n )Sporophyte

(2n )

Gametophyte

Sporophyte

Example

Figure 30.2c



Heterospory: The Rule Among Seed Plants

• The ancestors of seed plants were likelyhomosporous, 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




Figure 30.3-1

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, whichcontain the male gametophytes

• Pollination is the transfer of pollen to the part ofa seed plant containing the ovules

• Pollen eliminates the need for a film of water andcan be dispersed great distances by air oranimals

•

If a pollen grain germinates, it gives rise to apollen tube that discharges sperm into the femalegametophyte within the ovule


Fi 30 3 2



Figure 30.3-2

Immature

ovulate cone

Integument (2n )

Spore wall

Megaspore (n )

Female

gametophyte (n )

Egg nucleus

(n )

Dischargedsperm nucleus(n )

Pollen tubeMale gametophyte (n )


Megasporangium

(2n )


(b) Fertilized ovule



Figure 30 3 3



Figure 30.3-3

Immature

ovulate cone

Integument (2n )

Spore wall

Megaspore (n )

Female

gametophyte (n )

Egg nucleus

(n )

Dischargedsperm nucleus(n )

Pollen tubeMale gametophyte (n )


Megasporangium

(2n )


(b) Fertilized ovule (c) Gymnosperm seed

Seedcoat

Sporewall

Foodsupply (n )

Embryo (2n )



• Seeds provide some evolutionary advantagesover 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




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


Figure 30 UN01



Figure 30.UN01

Nonvascular plants (bryophytes)

Seedless vascular plantsGymnosperms

Angiosperms



Gymnosperm Evolution

• Fossil evidence reveals that by the late Devonianperiod some plants, called progymnosperms,

had begun to acquire some adaptations that

characterize seed plants


Figure 30 4



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




• Angiosperms began to replace gymnospermsnear the end of the Mesozoic

• Angiosperms now dominate more terrestrial

ecosystems

• Today, cone-bearing gymnosperms called

conifers dominate in the northern latitudes




• The gymnosperm 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


Figure 30.5a



g

Cycas revoluta



Phylum Ginkgophyta • This phylum consists of a single living species,

Ginkgo biloba

•

It has a high tolerance to air pollution and is apopular ornamental tree


Figure 30.5b



Ginkgo bi lobaleaves and

fleshy seeds

Ginkgo bi loba pollen-producing tree

g

Figure 30.5ba



Ginkgo bi loba pollen-producing tree

Figure 30.5bb



Ginkgo b i loba leavesand fleshy seeds



Phylum Gnetophyta• This phylum comprises three genera

• Species vary in appearance, and some are

tropical whereas others live in deserts


Figure 30.5d



Ovulate conesGnetum

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 outphotosynthesis year round


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 cycleare

– 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

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_06PineLifeCycle_A.html



•The pine tree is the sporophyte and producessporangia in male and female cones

• Small cones produce microspores called pollengrains, each of which contains a male

gametophyte• The familiar larger cones contain ovules, which

produce megaspores that develop into femalegametophytes

• It takes nearly three years from cone productionto mature seed


Key

Figure 30.6-1



Key

Haploid (n )

Diploid (2n )

Maturesporophyte(2n )

Pollencone

Microsporocytes(2n )

Microsporangia

Microsporangium (2n )

Pollengrains (n )

MEIOSIS

Key

Figure 30.6-2



Key

Haploid (n )

Diploid (2n )


Ovulatecone

Pollencone


Microsporangia

Microsporangium (2n )Survivingmegaspore (n )

MEIOSIS

Megasporangium (2n )Pollengrain

Pollengrains (n )

MEIOSIS

Megasporocyte (2n )

Integument

Ovule

Key

Figure 30.6-3



Key

Haploid (n )

Diploid (2n )


Ovulatecone

Pollencone


Microsporangia


Archegonium

Survivingmegaspore (n )

MEIOSIS


Pollengrains (n )

MEIOSIS

Femalegametophyte

Megasporocyte (2n )

Integument

Spermnucleus (n ) Egg nucleus (n )

Pollentube

FERTILIZATION

Ovule

Key

Figure 30.6-4



Key

Haploid (n )

Diploid (2n )


Ovulatecone

Pollencone


Microsporangia


Seedling

Archegonium

Survivingmegaspore (n )

MEIOSIS


Pollengrains (n )

MEIOSIS

Femalegametophyte

Megasporocyte (2n )

Integument

Spermnucleus (n ) Egg nucleus (n )

Pollentube

Seed coat (2n )

FERTILIZATION

Foodreserves (n )

Seeds

Embryo(new sporophyte)

(2n

)

Ovule



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


Figure 30.UN02



Nonvascular plants (bryophytes)

Seedless vascular plantsGymnosperms

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




Flowers

•

The flower is an angiosperm structurespecialized 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 fourtypes of modified leaves

– Sepals, which enclose the flower

– Petals, which are brightly colored and attract

pollinators

– Stamens, which produce pollen

– Carpels, which produce ovules




•

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 isreceived


Video: Flower Blooming (time lapse)

Figure 30.7

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_07FlowerTimeLapse_SV.mpg



Stamen Anther

Filament

StigmaCarpel

Style

Ovary

Petal

Sepal

Ovule



Fruits

•

A fruit typically consists of a mature ovary butcan also include other flower parts

• Fruits protect seeds and aid in their dispersal

• Mature fruits can be either fleshy or dry


Animation: Fruit Development

TomatoRuby grapefruit

Figure 30.8

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_08FruitDevelopment_A.html



Ruby grapefruit

Hazelnut

Nectarine

Milkweed

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


WingsFigure 30.9



Seeds within berries

Barbs

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 bothmale and female structures

• Male gametophytes are contained within pollengrains produced by the microsporangia of anthers

• The female gametophyte, or embryo sac,develops within an ovule contained within anovary at the base of a stigma

• Most flowers have mechanisms to ensure cross-pollination between flowers from different plantsof the same species




•

A pollen grain that has landed on a stigmagerminates 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 othercombines with two nuclei in the central cell of the

female gametophyte and initiates development of

food-storing endosperm

• The triploid endosperm nourishes the developingembryo

• Within a seed, the embryo consists of a root and

two seed leaves called cotyledons


AntherMature flower on

h t l t

Microsporangium

Microsporocytes (2n )

Figure 30.10-1



sporophyte plant(2n )

Pollengrains

Tube cell

Generative cell

Microspore (n )MEIOSIS

Key

Haploid (n )

Diploid (2n )


h t l t

Microsporangium


Figure 30.10-2




Megasporangium (2n )

Ovary

Antipodal cells

Central cell

Synergids

Femalegametophyte

(embryo sac)Egg (n )

Survivingmegaspore(n )

Pollentube

Sperm(n )

Pollengrains

Tube cell

Generative cell

Microspore (n )

Malegametophyte(in pollengrain) (n )

Ovule (2n )

MEIOSIS

MEIOSIS

Key

Haploid (n )

Diploid (2n )


h t l t

Microsporangium


Figure 30.10-3





Ovary

Seed

Antipodal cells

Central cell

Synergids

Femalegametophyte


Eggnucleus (n )


Pollentube

Sperm(n )

Style

SpermPollentube

Stigma

Pollengrains

Tube cell

Generative cell

Microspore (n )

Male

gametophyte(in pollengrain) (n )

Ovule (2n )

MEIOSIS

MEIOSIS

Discharged sperm nuclei (n )

FERTILIZATION

Key

Haploid (n )

Diploid (2n )


h t l t

Microsporangium


Figure 30.10-4




Germinatingseed


Ovary

Embryo (2n )

Endosperm (3n )Seed coat (2n )

Seed

Antipodal cells

Central cell

Synergids

Femalegametophyte


Eggnucleus (n )


Pollentube

Sperm(n )

Style

SpermPollentube

Stigma

Pollengrains

Tube cell

Generative cell

Microspore (n )

Male

gametophyte(in pollengrain) (n )

Ovule (2n )

MEIOSIS

MEIOSIS

Discharged sperm nuclei (n )

FERTILIZATIONZygote (2n )

Nucleus ofdevelopingendosperm(3n )

Key

Haploid (n )

Diploid (2n )




Video: Flowering Plant Life Cycle (time lapse)

Animation: Seed Development

Animation: Plant Fertilization

A i E l ti

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_10PlantFertilization_A.html

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_10SeedDevelopment_A.html

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_10PlantTimeLapse_SV.mpg



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 developmentalpatterns to resolve the mystery


F il A i



Fossi l Angiosperms

•

Chinese fossils of 125-million-year-oldangiosperms share some traits with living

angiosperms but lack others

• Archaefructus sinensis, for example, has anthers

and seeds but lacks petals and sepals


Carpel

Figure 30.11



(a) Archaefructus s inens is , a 125-million-year-old fossil

(b) Artist s reconstruction ofArchaefructus s inens is

Stamen

5 cm

Figure 30.11a



(a) Archaefructus sinensis , a 125-million-year-old fossil

5 cm

A i Ph l



Angiosperm Phylogeny

•

The ancestors of angiosperms and gymnospermsdiverged 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


Figure 30.12



Microsporangia

(contain

microspores)

Ovules

Most recent common ancestor

of all living angiosperms

300 250 200 150 100 50 0

Eudicots

Monocots

Magnoliids

Star anise

and relatives

Water lilies

Amborel la

Bennettitales

Living

gymnosperms

Millions of years ago

(b) Angiosperm phylogeny

(a) A possible ancestor of the angiosperms?

Figure 30.12a



Microsporangia(containmicrospores)

Ovules

(a) A possible ancestor of the angiosperms?



Developmental Patterns in Angiosperms



Developmental Patterns in Angiosperms

•

Egg formation in the angiosperm Amborellaresembles that of the gymnosperms

• In early angiosperms, the two integuments

appear to originate separately

• Researchers are currently studying expression offlower development genes in gymnosperm and

angiosperm species


Angiosperm Diversity



Angiosperm Diversity

•

Angiosperms comprise more than 250,000 livingspecies

• Previously, angiosperms were divided into twomain groups

–Monocots (one cotyledon)

– Dicots (two dicots)

• DNA studies suggest that monocots form aclade, but dicots are polyphyletic




•

The clade eudicot (“true

” dicots) includes mostdicots

• 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 basalangiosperms but evolved later




Basal Angiosperms• Three small lineages constitute the basal

angiosperms

• These include Amborella trichopoda, water lilies,

and star anise


Basal AngiospermsFigure 30.13a



Water lily

Star anise

Amborel la t r ichopoda

Figure 30.13aa



Water lily

Figure 30.13ab



Star anise

Figure 30.13ac



Ambore l la t r ichopoda



Magnoliids • Magnoliids include magnolias, laurels, and black

pepper plants

• Magnoliids are more closely related to monocots

and eudicots than basal angiosperms






Monocots • More than one-quarter of angiosperm species

are monocots


Orchid

Monocots

Lily

Figure 30.13c



Pygmy date palm

Anther

Filament

Stigma

Ovary

Barley, a grass

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



Barley, a grass



Eudicots • More than two-thirds of angiosperm species are

eudicots


EudicotsFigure 30.13d



California poppy Dog rose

Pyrenean oak

Snow pea Zucchini

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 30.13eMonocot

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

Roots

Root system

usually fibrous

(no main root)

Taproot (main root)

usually present

Pollen

Pollen grain with

one openingPollen 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

MonocotCharacteristics

EudicotCharacteristics



Roots

Root system

usually fibrous

(no main root)

Taproot (main root)

usually present

Pollen

Pollen grain with

one openingPollen 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



y g p

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


Video: Bee Pollinating

Video: Bat Pollinating Agave Plant

Figure 30.14

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_04BatPollinating_SV.mpg

http://localhost/var/www/apps/conversion/tmp/scratch_5/30_04BeePollinating_SV.mpg





•

Clades with bilaterally symmetrical flowers havemore species than those with radially

symmetrical flowers

• This is likely because bilateral symmetry affects

the movement of pollinators and reduces geneflow in diverging populations


Figure 30.15



Concept 30.4: Human welfare depends



p p

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 caloriesconsumed by humans

•

Modern crops are products of relatively recentgenetic change resulting from artificial selection

• Many seed plants provide wood

• Secondary compounds of seed plants are used

in medicines


Table 30.1



Threats to Plant Diversity



y

• 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




• 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


Figure 30.16

A satellite imagefrom 2000 shows



from 2000 showsclear-cut areas in

Brazil surroundedby dense tropicalforest.

By 2009, muchmore of this sametropical forest hadbeen cut down.

4 k m

Figure 30.16a



A satellite image

from 2000 shows

clear-cut areas in

Brazil surrounded by

dense tropical forest.

4 k m

Figure 30.16b



4 k m

By 2009, muchmore of this sametropical forest hadbeen cut down.

Figure 30.UN03



Time since divergencefrom common ancestor

Common

ancestor Bilateral”

clade

Radial” clade

Comparenumbersof species

Five Derived Traits of Seed Plants

Reducedgametophytes

Microscopic male andfemale gametophytes

Malegametophyte

Figure 30.UN04



g p y

Heterospory

Ovules

Pollen

Seeds

g p y(n ) are nourished andprotected by thesporophyte (2n )

Microspore (gives rise toa male gametophyte)

Megaspore (gives rise toa female gametophyte)

Ovule(gymnosperm)

Integument (2n )Megaspore (n )

Megasporangium(2n )

Pollen grains make waterunnecessary for fertilization

Seeds: survivebetter thanunprotectedspores, can betransportedlong distances

Seed coat

Food supply

Embryo

Femalegametophyte

g p y

Figure 30.UN05



Charophyte green algae

Mosses

Ferns

Gymnosperms

Angiosperms

Figure 30.UN06



Charophyte green algae

Mosses

Ferns

Gymnosperms

Angiosperms

Figure 30.UN07



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30 Lecture Plant Diversity II