what human reproductive organ is functionally similar to this seed?

What human reproductive organ is functionally similar to this seed?

LECTURE PRESENTATIONSFor 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 byErin Barley

Kathleen Fitzpatrick

Plant Diversity II: The Evolution of Seed Plants

Chapter 30

1. Why is a flower a lazy organism’s alternative to sex?

2. How do the derived characters facilitate maximizing

adaptive radiation?

3. What are advantages of seeds over spores?

4. What is the purpose of double fertilization?

a) What are the “quirks” in the process?

Guiding questions for chapter 30

Five Derived Traits of Seed Plants

Reducedgametophytes

Heterospory

Ovules

Pollen

Seeds

Microscopic male andfemale gametophytes(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

Malegametophyte

REVIEW

Concept 30.1: Seeds and pollen grains are key adaptations for life on land

• the following are common to all seed plants– Seeds (an embryo with a connected food supply

and a protective coat)

– Reduced gametophytes

– Heterospory

– Ovules

– Pollen


Figure 30.2

PLANT GROUP

Mosses and othernonvascular plants

Gametophyte

Sporophyte

Sporophyte(2n)

Gametophyte(n)

Dominant

Reduced, dependent ongametophyte for nutrition

Dominant

Reduced, independent(photosynthetic andfree-living)

Ferns and other seedlessvascular plants

Dominant

Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition

Seed plants (gymnosperms and angiosperms)

AngiospermGymnosperm

Microscopicfemalegametophytes(n) insidethese partsof flowers

Microscopic femalegametophytes (n) insideovulate cone

Microscopicmalegametophytes(n) insidethese partsof flowers

Microscopic malegametophytes (n)inside pollencone

Sporophyte (2n)Sporophyte (2n)

Sporophyte(2n)

Gametophyte(n)

Example

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


Figure 30.3-1

Immatureovulate 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



Animation: Plant Fertilization Right-click slide / select”Play”


Animation: Seed DevelopmentRight-click slide / select”Play”

Figure 30.3-2


Integument (2n)

Spore wall

Megaspore (n)

Femalegametophyte (n)

Egg nucleus(n)

Dischargedsperm nucleus(n)

Pollen tubeMale gametophyte (n)


Megasporangium(2n)


(b) Fertilized ovule

Figure 30.3-3


Integument (2n)

Spore wall

Megaspore (n)

Femalegametophyte (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)

The Evolutionary Advantage of Seeds

• What are they?


• 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

– Protected by integuments


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

Nonvascular plants (bryophytes)

Seedless vascular plantsGymnosperms

Angiosperms

• Living seed plants can be divided into two clades: gymnosperms and angiosperms

–What is the ideal ecosystem for gymnosperms?


• 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)


Phylum Cycadophyta• Individuals have large cones and palmlike leaves• These thrived during the Mesozoic, but relatively

few species exist today


Figure 30.5a

Cycas revoluta

Phylum Cycadophyta

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 bilobaleaves andfleshy seeds

Ginkgo biloba pollen-producing tree

Figure 30.5b

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

Phylum Coniferophyta• This phylum is by far the largest of the

gymnosperm phyla• Most conifers are evergreens and can carry out

photosynthesis year round


Figure 30.5e

Douglas fir

Common juniper

European larch

Sequoia

Wollemi pine Bristlecone pine


Animation: Pine Life Cycle Right-click slide / select”Play”

Key

Haploid (n)Diploid (2n)

Maturesporophyte(2n)

Pollencone

Microsporocytes(2n)

Microsporangia

Microsporangium (2n)

Pollengrains (n)

MEIOSIS

Life cycle of a pine

Key



Ovulatecone

Pollencone

Microsporocytes(2n)

Microsporangia

Microsporangium (2n)Survivingmegaspore (n)

MEIOSIS

Megasporangium (2n)Pollengrain

Pollengrains (n)

MEIOSIS

Megasporocyte (2n)

Integument

Ovule

Figure 30.6-2

Key



Ovulatecone

Pollencone

Microsporocytes(2n)

Microsporangia


Archegonium

Survivingmegaspore (n)

MEIOSIS


Pollengrains (n)

MEIOSIS

Femalegametophyte

Megasporocyte (2n)

Integument

Spermnucleus (n) Egg nucleus (n)

Pollentube

FERTILIZATION

Ovule

Figure 30.6-3

Key



Ovulatecone

Pollencone

Microsporocytes(2n)

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

Figure 30.6-4

Concept 30.3: The reproductive adaptations of angiosperms include flowers and fruits

• Angiosperms have two key adaptations– Flowers

– Fruits

– They are the most widespread and diverse of all plants


Why is a flower a lazy organism’s alternative to

sex?

Stamen Anther

Filament

StigmaCarpel

Style

Ovary

Petal

Sepal

Ovule

Figure 30.7

What is the purpose of each part?


Video: Flower Blooming (time lapse)

Fruits

• A fruit typically consists of a mature ovary but can also include other flower parts– Fruits represent tremendous investments in a plant’s

energy and nutrient resources. – What is a fruit’s purpose? Is this purpose justifiable?



Animation: Fruit DevelopmentRight-click slide / select”Play”

TomatoRuby grapefruit

Hazelnut

Nectarine

Milkweed

Figure 30.8

Wings

Seeds within berries

Barbs

Figure 30.9


REPEAT: Plant Fertilization Right-click slide / select”Play”


REPEAT : Seed DevelopmentRight-click slide / select”Play”

• 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 triploid endosperm nourishes the developing embryo

• Within a seed, the embryo consists of a root and two seed leaves called cotyledons


AntherMature flower onsporophyte plant(2n)

Pollengrains

Tube cell

Generative cell

Microspore (n)MEIOSIS

Microsporangium

Microsporocytes (2n)

Key


Figure 30.10-1


Megasporangium (2n)

Ovary

Antipodal cellsCentral cellSynergids

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

Microsporangium


Key


Figure 30.10-2


Megasporangium (2n)

Ovary

Seed



Egg (n)

Eggnucleus (n)


Pollentube

Sperm(n)

Style

SpermPollentube

Stigma

Pollengrains

Tube cell

Generative cell

Microspore (n)


Ovule (2n)

MEIOSIS

MEIOSIS

Discharged sperm nuclei (n)

FERTILIZATION

Microsporangium


Key


Figure 30.10-3


Germinatingseed

Megasporangium (2n)

Ovary

Embryo (2n)

Endosperm (3n)

Seed coat (2n)

Seed



Egg (n)

Eggnucleus (n)


Pollentube

Sperm(n)

Style

SpermPollentube

Stigma

Pollengrains

Tube cell

Generative cell

Microspore (n)


Ovule (2n)

MEIOSIS

MEIOSIS

Discharged sperm nuclei (n)

FERTILIZATIONZygote (2n)

Microsporangium


Nucleus ofdevelopingendosperm(3n)

Key


Figure 30.10-4


Video: Flowering Plant Life Cycle (time lapse)

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


Most recent common ancestorof all living angiosperms

300

Eudicots

Monocots

Magnoliids

Star aniseand relatives

Water lilies

Amborella

Bennettitales

Livinggymnosperms

Millions of years ago

(b) Angiosperm phylogeny

250 200 150 100 50 0

Angiosperm evolutionary history

• The clade eudicot (“true” dicots) includes most dicots

• 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


Water lily

Star anise

Amborella trichopoda

Basal AngiospermsFigure 30.13a

Magnoliids• Magnoliids include magnolias,

laurels, and black pepper plants• Magnoliids are more closely

related to monocots and eudicots than basal angiosperms


Southern magnolia

Orchid

Monocots

Lily

Pygmy date palm

Anther

Filament

Stigma

Ovary

Barley, a grass

Figure 30.13c

California poppy Dog rose

Pyrenean oak

Snow pea Zucchini

Eudicots (more than 2/3 of all plant species)Figure 30.13d

Figure 30.13eMonocot

CharacteristicsEudicot

Characteristics

Embryos

One cotyledon Two cotyledons

Leafvenation

Veins usuallyparallel

Veins usuallynetlike

Stems

Vascular tissuescattered

Vascular tissueusually arranged

in ring

Roots

Root systemusually fibrous(no main root)

Taproot (main root)usually present

Pollen

Pollen grain withone opening

Pollen grain withthree openings

Flowers

Floral organsusually in

multiples of three

Floral organsusually in multiples

of four or five

Evolutionary Links Between Angiosperms and Animals

• Animals influence the evolution of plants and vice versa

– Pollinators and flowers are obviously mutualistically symbiotic

– How can herbivory also be beneficial to both?



Video: Bat Pollinating Agave Plant


Video: Bee Pollinating

A plant pollinated by flies

Clades with bilateral symmetry are more diverse than those with radial symmetry?

Concept 30.4: Human welfare depends greatly on 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 30.1

Threats to Plant Diversity

• 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 showsclear-cut areas inBrazil surroundedby dense tropicalforest.

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

4 km

Five Derived Traits of Seed Plants

Reducedgametophytes

Heterospory

Ovules

Pollen

Seeds

Microscopic male andfemale gametophytes(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

Malegametophyte

REVIEW

1. Why is a flower a lazy organism’s alternative to sex?

2. How do the derived characters facilitate maximizing

adaptive radiation?

3. What are advantages of seeds over spores?

4. What is the purpose of double fertilization?

a) What are the “quirks” in the process?

Guiding questions for chapter 30: REVIEW

what human reproductive organ is functionally similar to this seed?

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