Chapter 16 Chapter 16

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Lectures by Chris C. Romero, updated by Edward J. Zalisko

PowerPoint^® Lectures for

Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey

Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey

Chapter 16 Chapter 16

Plants, Fungi, and the Move

onto Land

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Biology and Society:

Will the Blight End the Chestnut?

• American chestnut trees

– Once dominated forests of the eastern United States – Were prized for their

– Rapid growth – Huge size

– Rot-resistant wood

(3)

(4)

• Around 1900, an Asian fungus was accidentally introduced from China into North America, and in just 25 years, blight caused by the fungus killed virtually all adult American chestnut trees.

(5)

• Fortunately, this type of harmful interaction between plant and fungus is unusual.

• Many plants and fungi benefit from each other’s existence.

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COLONIZING LAND

• Plants are terrestrial organisms that include forms that have returned to water, such as water lilies.

(7)

Terrestrial Adaptations of Plants Structural Adaptations

• A plant is

– A multicellular eukaryote

– A photoautotroph, making organic molecules by photosynthesis

(8)

• In terrestrial habitats, the resources that a photosynthetic organism needs are found in two very different places:

– Light and carbon dioxide are mainly available in the air – Water and mineral nutrients are found mainly in the soil

(9)

• The complex bodies of plants are specialized to take advantage of these two environments by having

– Aerial leaf-bearing organs called shoots – Subterranean organs called roots

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Reproductive structures (such as those in flowers) contain spores and gametes Leaf performs photosynthesis Cuticle reduces water loss; stomata regulate gas exchange Shoot supports plant

(and may perform photosynthesis)

Surrounding water supports the alga

Roots anchor plant;

absorb water and minerals from the Whole alga

performs

photosynthesis;

absorbs water, CO₂, and

minerals from the water

Alga

Plant

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• Most plants have mycorrhizae, symbiotic fungi associated with their roots, in which the fungi

– Absorb water and essential minerals from the soil – Provide these materials to the plant

– Are nourished by sugars produced by the plant

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Roots

Fungus

Root

surrounded by fungus

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• Leaves are the main photosynthetic organs of most plants, with

– Stomata for the exchange of carbon dioxide and oxygen with the atmosphere

– Vascular tissue for transporting vital materials

– A waxy cuticle surface that helps the plant retain water

(14)

Phloem

Xylem Vascular tissue

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• Vascular tissue in plants is also found in the

– Roots – Shoots

• Two types of vascular tissue exist in plants:

– Xylem transports water and minerals from roots to leaves – Phloem distributes sugars from leaves to the roots and other

nonphotosynthetic parts of the plant

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Reproductive Adaptations

• Plants produce their gametes in protective structures called

gametangia, which have a jacket of protective cells surrounding a moist chamber where gametes can develop without dehydrating.

(17)

• The zygote develops into an embryo while still contained within the female parent in plants but not in algae.

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Embryo Maternal

tissue

LM

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The Origin of Plants from Green Algae

• The algal ancestors of plants

– Carpeted moist fringes of lakes or coastal salt marshes – First evolved over 500 million years ago

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• Charophytes

– Are a modern-day lineage of green algae

– May resemble one of these early plant ancestors

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LM LM

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LM

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LM

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PLANT DIVERSITY

• The history of the plant kingdom is a story of adaptation to diverse terrestrial habitats.

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Highlights of Plant Evolution

• The fossil record chronicles four major periods of plant evolution.

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Ancestral green algae

Origin of first terrestrial adaptations (about 475 mya)

Origin of vascular tissue (about 425 mya)

Origin of seeds (about 360 mya)

600 500 400 300 200 100 0

Origin of flowers (about 140 mya)

Millions of years ago

Angiosperms Gymnosperms Ferns and other seedless vascular plants

Bryophytes

Charophytes (a group

of green algae) Land plants

Vascular plants

Seed plants Seedlessvascularplants Nonvascularplants(bryophytes)

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• (1) About 475 million years ago plants originated from an algal ancestor giving rise to bryophytes, nonvascular plants, including mosses, liverworts, and hornworts that are nonvascular plants

without

– Lignified walls – True roots

– True leaves

(28)

• (2) About 425 million years ago ferns evolved

– With vascular tissue hardened with lignin – But without seeds

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• (3) About 360 million years ago gymnosperms evolved with

seeds that consisted of an embryo packaged along with a store of food within a protective covering but not enclosed in any

specialized chambers.

• Today, conifers, consisting mainly of cone-bearing trees such as pines, are the most diverse and widespread gymnosperms.

(30)

• (4) About 140 million years ago angiosperms evolved with complex reproductive structures called flowers that bear seeds within protective chambers called ovaries.

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• The great majority of living plants

– Are angiosperms

– Include fruit and vegetable crops, grains, grasses, and most trees – Are represented by more than 250,000 species

Video: Flower Blooming (time lapse)

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PLANT DIVERSITY

Bryophytes (nonvascular plants)

Ferns

(seedless vascular plants)

Gymnosperms (naked-seed plants)

Angiosperms (flowering plants)

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Bryophytes

• Bryophytes, most commonly mosses

– Sprawl as low mats over acres of land

– Need water to reproduce because their sperm swim to reach eggs within the female gametangium

– Have two key terrestrial adaptations:

– A waxy cuticle that helps prevent dehydration

– The retention of developing embryos within the mother plant’s gametangium

(38)

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• Mosses have two distinct forms:

– The gametophyte, which produces gametes – The sporophyte, which produces spores

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Spores

Spore capsule

Sporophyte

Gametophytes

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• The life cycle of a moss exhibits an alternation of generations shifting between the gametophyte and sporophyte forms.

• Mosses and other bryophytes are unique in having the gametophyte as the larger, more obvious plant.

Blast Animation: Non-Flowering Plant Life Cycle Animation: Moss Life Cycle

Blast Animation: Alternation of Generations

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Gametes:

sperm and eggs

(n) Gametophyte

(n)

Key

Haploid (n) Diploid (2n)

osis Mit

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Gametes:

(n)

Zygote (2n) Gametophyte

(n)

Key

FERTILIZATION osis

Mit

(44)

Spore capsule

Gametes:

(n)

Sporophyte (2n)

Key

FERTILIZATION osis

Mit

Mito sis

(45)

Spores (n)

Gametes:

(n)

Key

MEIOSIS FERTILIZATION

osis Mit

Mito sis

(46)

Spores (n)

Gametes:

(n)

Key

MEIOSIS FERTILIZATION

osis

Mit Mitosis

Mito sis

(47)

Ferns

• Ferns are

– Seedless vascular plants

– By far the most diverse with more than 12,000 known species

• The sperm of ferns, like those of mosses

– Have flagella

– Must swim through a film of water to fertilize eggs

Animation: Fern Life Cycle

(48)

Spore capsule

“Fiddlehead”

(young leaves

(49)

(50)

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Spore capsule

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“Fiddlehead”

(young leaves ready to unfurl)

(53)

• During the Carboniferous period, from about 360 to 300 million years ago, ferns

– Were part of a great diversity of seedless plants

– Formed swampy forests over much of what is now Eurasia and North America

• As they died, these forests formed coal.

(54)

• Fossil fuels

– Include coal, oil, and natural gas

– Formed from the remains of long-dead organisms

(55)

(56)

Gymnosperms

• At the end of the Carboniferous period, the climate turned drier and colder, favoring the evolution of gymnosperms, which can

– Complete their life cycles on dry land – Withstand long, harsh winters

• The descendants of early gymnosperms include the conifers, or cone-bearing plants.

(57)

Conifers

• Conifers

– Cover much of northern Eurasia and North America

– Are usually evergreens, which retain their leaves throughout the year – Include the tallest, largest, and oldest organisms on Earth

(58)

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Terrestrial Adaptations of Seed Plants

• Conifers and most other gymnosperms have three additional terrestrial adaptations:

– Further reduction of the gametophyte – Pollen

– Seeds

(60)

• Seed plants have a greater development of the diploid sporophyte compared to the haploid gametophyte generation.

(61)

Key

Gametophyte

(n) Sporophyte (2n)

Gametophyte (n)

Gametophyte (n) Sporophyte

(2n)

(a) Sporophyte dependent on gametophyte (e.g., mosses)

(b) Large sporophyte and small, Independent gametophyte (e.g., ferns)

(c) Reduced gametophyte dependent on sporophyte (seed plants)

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• A pine tree or other conifer is actually a sporophyte with tiny gametophytes living in cones.

(63)

Scale

Ovule-producing cones; the scales contain female gametophytes

Pollen-producing cones; they

produce male gametophytes

Ponderosa pine

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Scale

Ovule-producing cones; the scales contain female gametophytes

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(67)

• A second adaptation of seed plants to dry land was the evolution of pollen.

• A pollen grain

– Is actually the much-reduced male gametophyte – Houses cells that will develop into sperm

(68)

• The third terrestrial adaptation was the development of the seed, consisting of

– A plant embryo

– A food supply packaged together within a protective coat

(69)

• Seeds

– Develop from structures called ovules, located on the scales of female cones in conifers

– Can remain dormant for long periods before they germinate, as the embryo emerges through the seed coat as a seedling

(70)

(a) Ovule

Cross section of scale

Female cone, cross section

Integument

Spore

Spore case

Egg nucleus

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(a) Ovule

(b) Fertilized ovule

Integument

Spore

Spore case Pollen tube

Spore case

Egg nucleus

Female

gametophyte

Discharged sperm nucleus Pollen grain

(male

gametophyte)

(72)

(a) Ovule

(b) Fertilized ovule

(c) Seed

Integument

Spore

Spore case Pollen tube

Spore case

Egg nucleus

Female

gametophyte

Discharged sperm nucleus Seed coat

(derived from integument)

Embryo Food supply

(derived from female

Pollen grain (male

gametophyte)

(73)

(74)

Angiosperms

• Angiosperms

– Dominate the modern landscape

– Are represented by about 250,000 species

– Supply nearly all of our food and much of our fiber for textiles

• Their success is largely due to

– A more efficient water transport – The evolution of the flower

(75)

Flowers, Fruits, and the Angiosperm Life Cycle

• Flowers help to attract pollinators who transfer pollen from the sperm-bearing organs of one flower to the egg-bearing organs of another.

Video: Bat Pollinating Agave Plant Video: Bee Pollinating

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• A flower is actually a short stem with four whorls of modified leaves:

– Sepals – Petals – Stamens – Carpels

(77)

Petal

Carpel Stamen

Sepal Ovule

Anther Filament

Stigma Style Ovary

(78)

• Flowers come in many forms.

(79)

Pansy Bleeding heart California poppy Water lily

(80)

Pansy

(81)

(82)

California poppy

(83)

Water lily

(84)

• Flowers are an essential element of the angiosperm life cycle.

Video: Flowering Plant Life Cycle (time lapse) Animation: Plant Fertilization

Animation: Fruit Development

Blast Animation: Flowering Plant Life Cycle Blast Animation: Pollination and Fertilization

(85)

Mature sporophyte plant with flowers

Key

(86)

Twosperm nuclei

Embryo sac (female

gametophyte) Egg

Key Anther at tip of stamen

Pollen tube growing down style of carpel Ovary (base of carpel) Ovule

Germinated pollen grain (male gametophyte) on stigma of carpel

(87)

Twosperm nuclei

Zygote

Endosperm Embryo sac

(female

FERTILIZATION

Key

Haploid (n) Diploid (2n) Anther at tip of stamen

(88)

Embryo (sporophyte) Twosperm

nuclei

Zygote

(female

FERTILIZATION

(89)

Seed

Seed (develops

from ovule) Fruit (develops from ovary)

nuclei

Zygote

(female

FERTILIZATION

Key

Haploid (n) Diploid (2n) Anther at tip of stamen

(90)

Sporophyte seedling

Germinating seed

Seed

nuclei

Zygote

(female

FERTILIZATION

(91)

• Although both have seeds

– Angiosperms enclose the seed within an ovary – Gymnosperms have naked seeds

(92)

• Fruit

– Is a ripened ovary – Helps protect the seed – Increases seed dispersal

– Is a major food source for animals

(93)

Wind

dispersal

Animal

transportation

Animal ingestion

(94)

Wind

dispersal

(95)

Animal transportation

(96)

(97)

Angiosperms and Agriculture

• Gymnosperms supply most of our lumber and paper.

• Angiosperms

– Provide nearly all our food

– Supply fiber, medications, perfumes, and decoration

• Agriculture is a unique kind of evolutionary relationship between plants and animals.

(98)

Plant Diversity as a Nonrenewable Resource

• The exploding human population is

– Extinguishing plant species at an unprecedented rate

– Destroying fifty million acres, an area the size of the state of Washington, every year!

(99)

(100)

• Humans depend on plants for thousands of products including

– Food

– Building materials – Medicines

(101)

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• Preserving plant diversity is important to many ecosystems and humans.

• Scientists are now rallying to

– Slow the loss of plant diversity

– Encourage management practices that use forests as resources without damaging them

(103)

FUNGI

• Fungi

– Recycle vital chemical elements back to the environment in forms other organisms can assimilate

– Form mycorrhizae, fungus-root associations that help plants absorb from the soil

– Minerals – Water

(104)

• Fungi are

– Eukaryotes

– Typically multicellular

– More closely related to animals than plants, arising from a common ancestor about 1.5 billion years ago

(105)

• Fungi

– Come in many shapes and sizes

– Represent more than 100,000 species

Video: Water Mold Zoospores Video: Water Mold Oogonium

(106)

Orange fungi

Mold

Predatory fungus Budding yeast A “fairy ring”

Bud

Roundworm Body of fungus

Colorized SEM Colorized SEMColorized SEM

(107)

(108)

A “fairy ring”

(109)

Budding yeast

Bud

Colorized SEM

(110)

(111)

Colorized SEM

(112)

Roundworm Body of fungus

(113)

Characteristics of Fungi

• Fungi have unique

– Structures

– Forms of nutrition

(114)

Fungal Nutrition

• Fungi

– Are chemoheterotrophs

– Acquire their nutrients by absorption

(115)

• A fungus

– Digests food outside its body

– Secretes powerful digestive enzymes to break down the food – Absorbs the simpler food compounds

(116)

Fungal Structure

• The bodies of most fungi are constructed of threadlike filaments called hyphae.

• Hyphae are minute threads of cytoplasm surrounded by a

– Plasma membrane

– Cell wall mainly composed of chitin

(117)

• Hyphae branch repeatedly, forming an interwoven network called a mycelium (plural, mycelia), the feeding structure of the fungus.

Animation: Fungal Reproduction and Nutrition

(118)

Reproductive structure

Mycelium Mycelium

Hyphae Spore-producing

structures

(119)

Mycelium

Spore-producing structures

Hyphae

(120)

Mycelium

(121)

Fungal Reproduction

• Mushrooms

– Arise from an underground mycelium – Mainly function in reproduction

• Fungi reproduce by releasing billions and trillions of spores that are produced either sexually or asexually.

Video: Phlyctochytrium Zoospore Release Video: Allomyces Zoospore Release

(122)

The Ecological Impact of Fungi

• Fungi have

– An enormous ecological impact – Many interactions with humans

(123)

Fungi as Decomposers

• Fungi and bacteria

– Are the principal decomposers of ecosystems

– Keep ecosystems stocked with the inorganic nutrients necessary for plant growth

• Without decomposers, carbon, nitrogen, and other elements would accumulate in nonliving organic matter.

(124)

• Molds can destroy

– Fruit – Grains – Wood

– Human-made material

(125)

Parasitic Fungi

• Parasitic fungi absorb nutrients from the cells or body fluids of living hosts.

• Of the 100,000 known species of fungi, about 30% make their living as parasites, including

– Dutch elm disease

– Deadly ergot, which infests grain

(126)

(127)

(b) Ergots

(128)

• About 50 species of fungi are known to be parasitic in humans and other animals, causing

– Lung and vaginal yeast infections – Athlete’s foot

(129)

The Process of Science:

Did a Fungus Lead to the Salem Witch Hunt?

• Observation: In 1692, eight young girls were accused of being witches and had symptoms consistent with ergot poisoning.

• Question: Did an ergot outbreak cause the witch hunt?

• Hypothesis: The girls’ symptoms were the result of ergot poisoning.

• Prediction: The historical facts would be consistent with this hypothesis.

(130)

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• Results:

– Agricultural records from 1691, before the symptoms appeared, indicated a particularly warm and wet year, in which ergot thrives.

– Records from the following year, when accusations of witchcraft died down, indicate a dry year consistent with an ergot die-off.

– This correlation is consistent with the hypothesis but not conclusive.

(132)

Commercial Uses of Fungi

• Fungi are commercially important. Humans eat them and use them to

– Produce medicines such as penicillin – Decompose wastes

– Produce bread, beer, wine, and cheeses

(133)

Truffles

(the fungal kind, not the chocolates)

Blue cheese

Chanterelle mushrooms

(134)

Truffles

(the fungal kind, not the chocolates)

(135)

Blue cheese

(136)

Chanterelle mushrooms

(137)

Penicillium Zone of inhibited growth Staphylococcus

(138)

Evolution Connection:

Mutually Beneficial Symbiosis

• Symbiosis is the term used to describe ecological relationships between organisms of different species that are in direct contact.

• Mutually beneficial symbiotic relationships benefit both species.

(139)

• Examples of mutually beneficial symbiotic relationships involving fungi include

– Mycorrhizae, the association of fungi and plant roots – Lichens, the association of fungi and algae

(140)

Algal cell

Fungal hyphae

Colorized SEM

(141)

(142)

Algal cell

Colorized SEM

(143)

Bacteria

Archaea

Eukarya

Protists

Plants

Fungi Animals

(144)

Bryophytes

Ferns

Gymnosperms

Angiosperms

(145)

Bryophytes

Ferns

Gymnosperms

Angiosperms

(146)

Bryophytes

Ferns

Gymnosperms

Angiosperms

(147)

Bryophytes

Ferns

Gymnosperms

Angiosperms

(148)

Bacteria

Archaea

Eukarya

Protists

Plants Fungi

Animals

(149)

Leaves

Gametangia

Stomata

Cuticle Lignin Shoot

Vascular tissues

Roots

(150)

Origin of gametangia

(protect gametes and embryos)

Origin of vascular

tissue (conducts water

and nutrients)

Origin of seeds (protect embryos from dessication and

other hazards)

Origin of flowers (bear ovules within protective chambers called

ovaries)

(151)

Hyphae

Mycelium