What human reproductive organ is functionally similar to this seed?

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

Chapter 30 Plant Diversity II: The Evolution of Seed Plants

Lectures by Erin Barley Kathleen Fitzpatrick

© 2011 Pearson Education, Inc.

Guiding questions for 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? What are the “quirks” in the process? 5. Are fruits a reasonable investment?

Plant FRQs: (focus on bold prompts) 2009, Form B, #2.

Discuss

the patterns of sexual reproduction in plants.

Compare

and

contrast

reproduction in nonvascular plants with that in flowering plants.

Include

the following topics in your discussion: (a) alternation of generations (b) mechanisms that bring female and male gametes together (c) mechanisms that disperse offspring to new locations

2008 #4. Flowering plants have evolved various strategies for fertilization.

(a)

Describe

the process of fertilization in flowering plants.

(b)

Discuss

TWO mechanisms of pollen transfer and the adaptations that facilitate each mechanism.

Some species of flowering plants have evolved mechanisms to prevent self-fertilization.

(c)

Discuss

an evolutionary advantage of preventing self-fertilization.

(d)

Describe

TWO mechanisms that prevent self fertilization.

REVIEW Five Derived Traits of Seed Plants Reduced gametophytes Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Male gametophyte Female gametophyte Heterospory Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovules Pollen Seeds Integument (2n) Ovule (gymnosperm) 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

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 © 2011 Pearson Education, Inc.

Figure 30.2

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

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 30.3-1

Immature ovulate cone Integument (2n) Spore wall Megaspore (n) Megasporangium (2n) Micropyle Pollen grain (n) (a) Unfertilized ovule

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.

© 2011 Pearson Education, Inc.

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

© 2011 Pearson Education, Inc.

Animation: Seed Development Right click slide / select”Play”

Figure 30.3-2

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

n

)

Figure 30.3-3

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

n

) Food supply (n) Embryo (2n) (c) Gymnosperm seed

The Evolutionary Advantage of Seeds

•

What are they?

© 2011 Pearson Education, Inc.

• 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 © 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

• Living seed plants can be divided into two clades:

gymnosperms

and

angiosperms

–

What is the ideal ecosystem for gymnosperms?

© 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

Phylum Cycadophyta

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.

Figure 30.5b

Ginkgo biloba

leaves and fleshy seeds Ginkgo biloba pollen-producing tree

• •

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

Welwitschia Gnetum 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

Common juniper Douglas fir European larch Sequoia Wollemi pine Bristlecone pine

© 2011 Pearson Education, Inc.

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

Key Haploid (n) Diploid (2n)

Life cycle of a pine

Mature sporophyte (2n) Pollen cone Microsporocytes (2n) MEIOSIS Microsporangia Microsporangium (2n) Pollen grains (n)

Figure 30.6-2

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

Figure 30.6-3

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

Figure 30.6-4

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

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 © 2011 Pearson Education, Inc.

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

Figure 30.7

Stamen Anther Filament Stigma Style Carpel Ovary Petal

What is the purpose of each part?

Ovule Sepal

© 2011 Pearson Education, Inc.

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?

© 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc.

Animation: Fruit Development Right click slide / select”Play”

Figure 30.8

Tomato Ruby grapefruit Nectarine Hazelnut Milkweed

Figure 30.9

Wings Seeds within berries Barbs

© 2011 Pearson Education, Inc.

REPEAT

: Plant Fertilization Right click slide / select”Play”

© 2011 Pearson Education, Inc.

REPEAT

: Seed Development Right 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 © 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.

Figure 30.10-1

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

Figure 30.10-2

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

Figure 30.10-3

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

Figure 30.10-4

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

© 2011 Pearson Education, Inc.

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 Dicots

(one cotyledon) (two dicots) DNA studies suggest that monocots form a clade, but dicots are polyphyletic © 2011 Pearson Education, Inc.

Angiosperm evolutionary history Most recent common ancestor of all living angiosperms 300 250 200 150 100 Millions of years ago (b) Angiosperm phylogeny 50 Living gymnosperms Bennettitales

Amborella

Water lilies Star anise and relatives Magnoliids Monocots 0 Eudicots

• 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 © 2011 Pearson Education, Inc.

Figure 30.13a

Basal Angiosperms Water lily Star anise

Amborella trichopoda

• •

Magnoliids

Magnoliids include magnolias, laurels, and black pepper plants Magnoliids are more closely related to monocots and eudicots than basal angiosperms

Southern magnolia

© 2011 Pearson Education, Inc.

Figure 30.13c

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

Figure 30.13d

Eudicots (more than 2/3 of all plant species) California poppy Dog rose Pyrenean oak Snow pea Zucchini

Figure 30.13e

Monocot Characteristics Embryos Eudicot Characteristics 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) Pollen Taproot (main root) usually present 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

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?

© 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc.

Video: Bat Pollinating Agave Plant

© 2011 Pearson Education, Inc.

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 © 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 30.16

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.

REVIEW Five Derived Traits of Seed Plants Reduced gametophytes Microscopic male and female gametophytes (n) are nourished and protected by the sporophyte (2n) Male gametophyte Female gametophyte Heterospory Microspore (gives rise to a male gametophyte) Megaspore (gives rise to a female gametophyte) Ovules Pollen Seeds Integument (2n) Ovule (gymnosperm) 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

Guiding questions for chapter 30: 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?