Chapter 16 Plants, Fungi, and the Move onto Land

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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
• 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.
• Fortunately, this type of harmful interaction
  between plant and fungus is unusual.
• Many plants and fungi benefit from each others
  existence.

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Bacteria
Archaea
Protists
Eukarya
Plants
Fungi
Animals
Figure 16.UN01
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Terrestrial Adaptations of Plants Structural
Adaptations

• Plants are terrestrial organisms that include
  forms that have returned to water, such as water
  lilies.
• A plant is
• A multicellular eukaryote
• A photoautotroph, making organic molecules by
  photosynthesis
• 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

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Terrestrial Adaptations of Plants Structural
Adaptations

• 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
• 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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Reproductive structures (such as those in
flowers) contain spores and gametes
Plant
Leaf performs photosynthesis
Cuticle reduces water loss stomata regulate gas
exchange
Shoot supports plant (and may perform photosynthes
is)
Alga
Whole alga performs photosynthesis absorbs
water, CO2, and minerals from the water
Surrounding water supports the alga
Roots anchor plant absorb water and minerals
from the soil (aided by fungi)
Figure 16.1
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Roots
Fungus
Root surrounded by fungus
Figure 16.2
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Plant Structures

• 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
• 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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Leaves
Gametangia
Stomata
Cuticle
Lignin
Shoot
Vascular tissues
Roots
Figure 16.UN07
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Phloem
Vascular tissue
Xylem
Oak leaf
Figure 16.3
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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.
• The zygote develops into an embryo while still
  contained within the female parent in plants but
  not in algae.

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LM
Embryo
Maternal tissue
Figure 16.4
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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
• Charophytes
• Are a modern-day lineage of green algae
• May resemble one of these early plant ancestors

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LM
LM
Figure 16.5
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PLANT DIVERSITY EVOLUTION

• The history of the plant kingdom is a story of
  adaptation to diverse terrestrial habitats.
• The fossil record chronicles four major periods
  of plant evolution.
• (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

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Charophytes (a group of green algae)
Origin of first terrestrial adaptations (about
475 mya)
Ancestral green algae
Nonvascular plants (bryophytes)
Bryophytes
Land plants
Origin of vascular tissue (about 425 mya)
Ferns and other seedless vascular plants
Seedless vascular plants
Origin of seeds (about 360 mya)
Vascular plants
Gymnosperms
Origin of flowers (about 140 mya)
Seed plants
Angiosperms
600
500
400
300
200
100
0
Millions of years ago
Figure 16.6
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Bryophytes
Ferns
Gymnosperms
Angiosperms
Figure 16.UN02
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PLANT EVOLUTION

• (2) About 425 million years ago ferns evolved
• With vascular tissue hardened with lignin
• But without seeds
• (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.
• (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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Plant Diversity

• 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

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PLANT DIVERSITY
Bryophytes (nonvascular plants)
Ferns (seedless vascular plants)
Gymnosperms (naked-seed plants)
Angiosperms (flowering plants)
Figure 16.7
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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 plants gametangium

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Figure 16.8
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Spores
Spore capsule
Sporophyte
Gametophytes
Figure 16.9
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Mosses

• Mosses have two distinct forms
• The gametophyte, which produces gametes
• The sporophyte, which produces spores
• 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.

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Gametes sperm and eggs (n)
Spores (n)
Gametophyte (n)
FERTILIZATION
MEIOSIS
Spore capsule
Zygote (2n)
Sporophyte (2n)
Key
Haploid (n) Diploid (2n)
Figure 16.10-5
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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

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Spore capsule
Fiddlehead (young leaves ready to unfurl)
Figure 16.11
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Carboniferous Period

• 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.
• Fossil fuels
• Include coal, oil, and natural gas
• Formed from the remains of long-dead organisms

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Figure 16.12
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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.

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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

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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
• Seed plants have a greater development of the
  diploid sporophyte compared to the haploid
  gametophyte generation.
• A pine tree or other conifer is actually a
  sporophyte with tiny gametophytes living in
  cones.

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Gametophyte (n)
Sporophyte (2n)
Sporophyte (2n)
Sporophyte (2n)
Gametophyte (n)
Gametophyte (n)
(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)
Key
Haploid (n) Diploid (2n)
Figure 16.14
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Scale
Ovule-producing cones the scales contain
female gametophytes
Pollen-producing cones they produce
male gametophytes
Ponderosa pine
Figure 16.15
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Terrestrial Adaptations of Seed Plants

• 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
• The third terrestrial adaptation was the
  development of the seed, consisting of
• A plant embryo
• A food supply packaged together within a
  protective coat

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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

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Haploid (n) Diploid (2n)
Cross section of scale
Female cone, cross section
Integument
Spore case
(a) Ovule
Spore
Egg nucleus
Female gametophyte
Spore case
(b) Fertilized ovule
Pollen tube
Discharged sperm nucleus
Pollen grain (male gametophyte)
Seed coat (derived from integument)
(c) Seed
Food supply (derived from female gametophyte tissu
e)
Embryo (new sporophyte)
Figure 16.16-3
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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

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Flowers, Fruits, 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.
• A flower is actually a short stem with four
  whorls of modified leaves
• Sepals
• Petals
• Stamens
• Carpels
• Flowers are an essential element of the
  angiosperm life cycle come in many forms

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Petal
Stigma
Anther
Carpel
Stamen
Style
Filament
Ovary
Ovule
Sepal
Figure 16.17
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Pansy
Bleeding heart
California poppy
Water lily
Figure 16.18
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Germinated pollen grain (male gametophyte)
on stigma of carpel
Anther at tip of stamen
Pollen tube growing down style of carpel
Mature sporophyte plant with flowers
Ovary (base of carpel)
Ovule
FERTILIZATION
Endosperm
Embryo sac (female gametophyte)
Egg
Zygote
Two sperm nuclei
Sporophyte seedling
Embryo (sporophyte)
Seed
Germinating seed
Key
Haploid (n) Diploid (2n)
Seed (develops from ovule)
Fruit (develops from ovary)
Figure 16.19-6
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Seed Types

• Although both have seeds
• Angiosperms enclose the seed within an ovary
• Gymnosperms have naked seeds
• Fruit
• Is a ripened ovary
• Helps protect the seed
• Increases seed dispersal
• Is a major food source for animals

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Wind dispersal
Animal transportation
Animal ingestion
Figure 16.20
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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.

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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!
• Humans depend on plants for thousands of products
  including
• Food
• Building materials
• Medicines

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Figure 16.21
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Table 16.1
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Plant Preservation

• 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

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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
• Eukaryotes
• Typically multicellular
• More closely related to animals than plants,
  arising from a common ancestor about 1.5 billion
  years ago
• Come in many shapes and sizes
• Represent more than 100,000 species

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Bud
Colorized SEM
Budding yeast
A fairy ring
Roundworm
Body of fungus
Mold
Colorized SEM
Orange fungi
Colorized SEM
Predatory fungus
Figure 16.22
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Roundworm
Body of fungus
Colorized SEM
Predatory fungus
Figure 16.22f
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Characteristics of Fungi

• Fungi have unique
• Structures
• Forms of nutrition is chemoheterotrophs
• Acquire their nutrients by absorption
• A fungus
• Digests food outside its body
• Secretes powerful digestive enzymes to break down
  the food
• Absorbs the simpler food compounds

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

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Reproductive structure
Spore-producing structures
Hyphae
Mycelium
Mycelium
Figure 16.23
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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.

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The Ecological Impact of Fungi

• Fungi have
• An enormous ecological impact
• Many interactions with humans
• 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.
• Molds can destroy Fruit, Grains, Wood,
  Human-made material

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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
• About 50 species of fungi are known to be
  parasitic in humans and other animals, causing
• Lung and vaginal yeast infections
• Athletes foot

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Parasitic Fungi
(a) American elm trees killed by Dutch elm
disease fungus
(b) Ergots
Figure 16.24a
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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.

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Figure 16.25
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The Process of Science Did a Fungus Lead to the
Salem Witch Hunt?

• 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.

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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

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Truffles (the fungal kind, not the chocolates)
Blue cheese
Chanterelle mushrooms
Figure 16.26
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Penicillium
Zone of inhibited growth
Staphylococcus
Figure 16.27
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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.
• Examples of mutually beneficial symbiotic
  relationships involving fungi include
• Mycorrhizae, the association of fungi and plant
  roots
• Lichens, the association of fungi and algae

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Algal cell
Colorized SEM
Fungal hyphae
Figure 16.28