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Chapter 19 Plants

Man: ©G. R. "Dick" Roberts/Natural Sciences Image Library

Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

Plants Have Changed the World

Section 19.1 Figure 19.1

Members of kingdom Plantae are nearly everywhere.

Snow: ©Design Pics/Carson Ganci/Getty Images RF; Prairie: ©Tetra Images/Tetra Images/Corbis RF; Forest: ©Ted

Mead/Getty Images RF

Plants Have Changed the World


Plants harness the energy that sustains ecosystems. They also release O2, which consumers use for respiration.

Snow: ©Design Pics/Carson Ganci/Getty Images RF; Prairie: ©Tetra Images/Tetra Images/Corbis RF; Forest: ©Ted

Mead/Getty Images RF

Highlights in the History of Plants

Section 19.1

Plants arose about 475 million years ago from ancestors resembling green algae.

Cotton: © S. Solum/PhotoLink/Getty Images RF

Section 19.1


Plants arose about 475 million years ago.

Section 19.1


Major evolutionary events in plants include the origins of vascular tissue, pollen and seeds, and flowers.

Section 19.1


The presence or absence of vascular tissue, pollen and seeds, and flowers defines each plant group.

Section 19.1


Figure 19.3

The presence or absence of vascular tissue, pollen and seeds, and flowers defines each plant group.

Section 19.1


Figure 19.3

Bryophytes have no vascular tissue, seeds, or flowers. Mosses are bryophytes.

Section 19.1


Figure 19.3

The origin of vascular tissue, which transports water and nutrients in the plant, allowed plants to grow taller. Taller plants reach above

their neighbors in the struggle for sunlight.

Section 19.1

Vascular tissue consists of phloem and xylem. Phloem transports sugars. Xylem transports water.


Figures 19.3, 19.4Stem cross section: © Dr. John D. Cunningham/Visuals Unlimited

Section 19.1

Lignin is a complex polymer that strengthens cell walls in vascular tissue.


Figures 19.3, 19.4Stem cross section: © Dr. John D. Cunningham/Visuals Unlimited

Section 19.1


Figure 19.3

Modifications in vascular tissue led to the evolution of seedless vascular plants, like ferns.

Section 19.1


Figure 19.3

The origin of seeds—dormant, protected plant embryos with a nutrient supply—was also adaptive. Seeds might travel far from the parent and only germinate when conditions are favorable.

Section 19.1


Cone scale

Seed

Gymnosperms are plants with vascular tissue and seeds, such as pine trees.

Pine cones: © Westend61/Alamy RF Figures 19.3, 19.4

Section 19.1


Figure 19.3

More recently, the origin of flowers and fruits introduced new reproductive adaptations. Angiosperms are flowering plants.

Section 19.1


More recently, the origin of flowers and fruits introduced new reproductive adaptations. Angiosperms are flowering plants.

Seed contains

embryo and its

food supply

Fertilized flowers develop

into fruits that protect and

disperse seeds

Figures 19.3, 19.4Pea pods: ©Corbis RF

Clicker Question #1

A newly discovered plant in the rain forest has xylem and seeds, but no flowers. What is it?

A. a bryophyteB. a seedless vascular plantC. a gymnospermD. an angiosperm

Flower: © Doug Sherman/Geofile/RF

Section 19.1

The similarity among plant life cycles is evidence that all plants share a common ancestor.

All Plants Have Similar Life Cycles

Figure 19.5

Section 19.1

The plant life cycle is called alternation of generations, in which a multicellular diploid stage alternates with a multicellular haploid stage.


Figure 19.5

Section 19.1


Figure 19.5

Diploid stage


Section 19.1


Figure 19.5

Haploid stage


Section 19.1

A zygote develops by mitotic cell division into a multicellular, diploid sporophyte.


Figure 19.5

Section 19.1

The sporophyte produces haploid spores by meiosis.


Figure 19.5

Section 19.1

Haploid spores divide by mitosis into a multicellular, haploid gametophyte.


Figure 19.5

Section 19.1

The haploidgametophyte produces gametes by mitotic cell division.


Figure 19.5

Section 19.1

These sex cells fuse at fertilization, forming a diploid zygote and starting the cycle anew.


Figure 19.5

Section 19.1

The sporophyte and gametophyte shown in this generalized plant life cycle are those of a seedless vascular plant.


Figure 19.5

Section 19.1

Substituting images in the alternation of generations produces diagrams of other plant life cycles.


Figure 19.21

Section 19.1

Note that the size of the sporophyte relative to the gametophyte varies through plant groups.


Sporophyte

Gametophyte

Figure 19.21

Clicker Question #2

How many of the items in the following list are haploid?

zygote, gamete, sporophyte, spore, gametophyte

A. oneB. twoC. threeD. fourE. five


19.1 Mastering Concepts

What features differentiate the four major groups of plants?


Section 19.2

Bryophytes Are the Simplest Plants

Figure 19.3

Section 19.2


Bryophytes are seedless plants that lack vascular tissue. They also lack true leaves and roots.

Figure 19.7Liverwort: ©Edward S. Ross; Hornwort: ©William E. Ferguson; Moss: ©Steven P. Lynch/The Mcgraw-Hill Companies

Section 19.2


Materials move from cell to cell within the plant by diffusion and osmosis.

Figure 19.7Liverwort: ©Edward S. Ross; Hornwort: ©William E. Ferguson; Moss: ©Steven P. Lynch/The Mcgraw-Hill Companies

Section 19.2


Examples of bryophytes include:

LiverwortsHornwortsMosses

Figure 19.7Liverwort: ©Edward S. Ross; Hornwort: ©William E. Ferguson; Moss: ©Steven P. Lynch/The McGraw-Hill Companies

Section 19.2


The bryophyte life cycle is an alternation of generations.

Section 19.2


Figure 19.9

Sporophyte

Haploid spores form by meiosis in the sporophyte tip.

Section 19.2


Figure 19.9

Sporophyte

Spores are released from the sporophyte.

Section 19.2


Figure 19.9

Sporophyte

Young gametophyte

Each spore might develop by mitosis into a gametophyte.

Section 19.2


Figure 19.9

Sporophyte

Male

Female

A mature gametophyte is either male or female.

Section 19.2


Figure 19.9

Sporophyte

Sperm cells

Egg

cell

Male

Female

Gametophytes produce gametes by mitosis.

Section 19.2


Figure 19.9

Sporophyte

Sperm cells

Egg

cell

Male

Female

Gametes travel from male to female gametophytes in water.

Section 19.2


Figure 19.9

Sporophyte

Sperm cells

Egg

cell

Zygote

Male

Female

When sperm meets egg, a zygote forms within the female gametophyte.

Section 19.2


Figure 19.9

Sporophyte

Sperm cells

Egg

cell

Zygote

Male

Female

The zygote develops by mitosis into a sporophyte, and the cycle begins again.

Section 19.2


Figure 19.9

Bryophyte life cycle overview

Bryophytes: ©Ed Reschke

Clicker Question #3

Meiosis occurs in the structure indicated by the arrow. What will the structure produce?

A. sporesB. phloemC. gametesD. pollen

Flower: © Doug Sherman/Geofile/RF; Moss: ©Steven P. Lynch/The McGraw-Hill Companies


Name two reasons mosses usually live in moist, shady habitats.


Section 19.3

Seedless Vascular Plants

Figure 19.3

Section 19.3

Seedless vascular plants have xylem and phloem but not seeds. These plants typically have true roots, stems, and leaves.

Figure 19.10


Whisk fern: ©W. Ormerod/Visuals Unlimited; Horsetail: ©Ed Reschke; Beech fern: ©Rod Planck/Science Source



Examples of seedless vascular plants include:

Lycopods (not shown)Whisk fernsTrue fernsHorsetails

Whisk fern: ©W. Ormerod/Visuals Unlimited; Horsetail: ©Ed Reschke; Beech fern: ©Rod Planck/Science Source

Section 19.3

The seedless vascular plant life cycle is an alternation of generations.


Section 19.3

Haploid spores form by meiosis in sporangia on sporophyte leaves.

Sporophyte


Figure 19.11

Section 19.3

Sporophyte

Spores are released from the sporangia.

Spores

Sporangium


Figure 19.11

Section 19.3

Gametophyte

Each spore might develop by mitosis into a gametophyte.

Sporophyte

Spores

Sporangium


Figure 19.11

Section 19.3

Gametophyte

Sporophyte

Spores

Sporangium


Gametophytes produce gametes by mitosis. Egg

cell

Sperm

cell

Figure 19.11

Section 19.3

Gametophyte

Sporophyte

Spores

Sporangium


Egg

cell

Sperm

cell

Gametes travel from male to female gametophytes in water.

Figure 19.11

Section 19.3

Gametophyte

Sporophyte

Spores

Sporangium


Egg

cell

Sperm

cell

When sperm meets egg, a zygote forms within the gametophyte tissue.

Zygote

Figure 19.11

Section 19.3

Gametophyte

Sporophyte

Spores

Sporangium


Egg

cell

Sperm

cell

Zygote

The zygote develops by mitosis into a sporophyte, and the cycle begins again.

Figure 19.11

Section 19.3


Seedless vascular plant life cycle overview

Figure 19.11Spores: ©Ed Reschke/Peter Arnold/Getty Images; Fern gametophyte: ©Les Hickok and Thomas Warne, C-Fern


How are seedless vascular plants similar to and different from bryophytes?


Section 19.4

Gymnosperms Are “Naked Seed” Plants

Figure 19.3

Section 19.4

The sporophytes of most gymnosperms are woody trees or shrubs. Reproductive structures and leaf types are diverse.

Figure 19.12


Cycad tree: ©Alena Brozova/Alamy; cycad seed: ©Pat Pendarvis; ginko tree: ©Light of Peace/Flickr/Getty Images RF; ginko

seed: ©G. R. "Dick" Roberts/Natural Sciences Image Library; conifer tree: ©Jack Dykinga/Nature Picture Library; pine cone:

©Ed Reschke/Peter Arnold/Getty Images; ephedra: ©Gerald & Buff Corsi/Visuals Unlimited; ephedra reproductive structures:

©Edward S. Ross

Section 19.4

Gymnosperms are divided into four groups:

Figure 19.12


CycadsGinkgo

Conifers Gnetophytes

Cycad tree: ©Alena Brozova/Alamy; cycad seed: ©Pat Pendarvis; ginko tree: ©Light of Peace/Flickr/Getty Images RF; ginko

seed: ©G. R. "Dick" Roberts/Natural Sciences Image Library; conifer tree: ©Jack Dykinga/Nature Picture Library; pine cone:

©Ed Reschke/Peter Arnold/Getty Images; ephedra: ©Gerald & Buff Corsi/Visuals Unlimited; ephedra reproductive structures:

©Edward S. Ross

Section 19.4

Gymnosperm life cycle is an alternation of generations.


Section 19.4

Haploid spores form by meiosis in sporophyte cones.

Sporophyte

Figure 19.13

Female cones

Male cones


Section 19.4

Male cones produce microspores by meiosis on cone scales.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores

Section 19.4

Ovules on female cone scales produce megaspores by meiosis.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores

Megaspores (three will degenerate)

Section 19.4

Spores develop by mitosis into microscopic gametophytes.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores


Egg cells

Pollen grain

Section 19.4

Gametophytes unite at pollination.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores


Egg cells

Pollen grain

Section 19.4

A pollen grain germinates, producing a pollen tube.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores


Egg cells

Pollen grainSperm

nuclei

Pollen

tube

Section 19.4

Sperm nuclei travel through the pollen tube to the egg cells. Fertilization occurs.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores


Egg cells

Pollen grainSperm

nuclei

Pollen

tube

Section 19.4

The resulting zygote grows mitotically into an embryo, inside a seed, on a female cone scale.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores


Egg cells

Pollen grainSperm

nuclei

Pollen

tube

Zygote

Seeds

Section 19.4

The seed germinates and grows mitotically into a mature sporophyte.

Sporophyte

Figure 19.13

Female cones

Male cones


Microspores


Egg cells

Pollen grainSperm

nuclei

Pollen

tube

Zygote

Seeds



Gymnosperm life cycle overview

Clicker Question #4

How is gymnosperm reproduction different from that of ferns?

A. Gymnosperms produce seeds; ferns don’t.B. Gymnosperms produce swimming sperm; ferns don’t.C. Gymnosperms produce zygotes; ferns don’t.D. Gymnosperms don’t produce spores; ferns do.



What happens during and after pollination in gymnosperms?


Section 19.5

Angiosperms Produce Seeds in Fruits

Figure 19.3

Section 19.5

Today, most plant species have reproductive structures called flowers, which develop into seed-toting fruits.

Figure 19.16


Red maple flower: ©Dwight Kuhn; cattails: ©Hans Reinhard/Okapia/Science Source;

bee: ©McGraw-Hill Education; banana flower: ©Igor Prahin/Flickr Open/Getty Images RF

Section 19.5

Flowers produce pollen and eggs; wind or animals usually carry pollen from plant to plant. Fruits protect the seeds and disperse them to new habitats.

Figure 19.16




Section 19.5

Variation in flowers and fruits is the result of millions of years of evolution.

Figure 19.16






Scientists classify the diverse angiosperms into several taxa, notably the eudicots and monocots.

Section 19.5

The angiosperm life cycle is an alternation of generations.


Section 19.5

Haploid spores form by meiosis in flowers.

Sporophyte

Figure 19.15

Pollen sacOvule


Section 19.5

Each mother cell in a pollen sac divides into four microspores.

Sporophyte

Figure 19.15

Pollen sacOvule


Microspores

Section 19.5

Each mother cell in an ovule divides into four megaspores. Only one persists.

Sporophyte

Figure 19.15

Pollen sacOvule


Megaspores (three degenerate)

Microspores

Section 19.5

Spores divide mitotically into microscopic gametophytes.

Sporophyte

Figure 19.15

Pollen sacOvule



Microspores

Ovule Polar nucleiEgg

Pollen grains

Section 19.5

During pollination, a pollen grain lands on a stigma. The pollen grain germinates, producing a pollen tube.

Sporophyte

Figure 19.15

Pollen sacOvule



Microspores


Pollen grains

Section 19.5

Sperm nuclei travel through the pollen tube and fertilize the egg and polar nuclei.

Sporophyte

Figure 19.15

Pollen sacOvule



Microspores


Pollen grains

Endosperm

nucleus (3n)

Zygote (2n)

Pollen tube

Section 19.5

The zygote develops into an embryo, and the endosperm provides its food.

Sporophyte

Figure 19.15

Pollen sacOvule



Microspores


Pollen grains

Endosperm

nucleus (3n)

Zygote (2n)

Pollen tube

Section 19.5

Seeds contain the embryo and endosperm; part of the flower develops into an enclosing fruit.

Sporophyte

Figure 19.15

Pollen sacOvule



Microspores


Pollen grains

Endosperm

nucleus (3n)

Zygote (2n)

Pollen tube

Section 19.5

Seeds germinate into young sporophytes, and the cycle begins again.

Sporophyte

Figure 19.15

Pollen sacOvule



Microspores


Pollen grains

Endosperm

nucleus (3n)

Zygote (2n)

Pollen tube

Section 19.5

Angiosperm life cycle overview

Figure 19.15


Clicker Question #5

In the angiosperm life cycle, the seed is analogous to the ____ in the human life cycle.

A. male reproductive organsB. female reproductive organsC. fetusD. sperm cellE. egg cell



In what ways are the life cycles of angiosperms similar to and different from those of conifers?


Section 19.6

Frozen soils preserve DNA from organisms that lived long ago.

Figure 19.17

Investigating Life: Genetic Messages From Ancient Ecosystems

Drilling: Courtesy of K. Schaefer

Section 19.6

Researchers drill through the permafrost to collect DNA that will help them learn about ancient ecosystems.

Figure 19.17


Drilling: Courtesy of K. Schaefer

Section 19.6

Their data reveal how a plant community changed over many thousands of years.

Figure 19.18


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