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Transcript
Chapter 12: Diversification of the
Eukaryotes: Plants and Fungi
Where did all the plants and fungi come from?
Lectures by Mark Manteuffel, St. Louis Community College; Clicker Questions by Kristen Curran, University of Wisconsin, Whitewater
• Some giant sequoia
trees weigh more than
a dozen space
shuttles.
• A mushroom is
probably more closely
related to animals than
it is to any plant.
Plant Diversity as a Nonrenewable Resource
• Humans depend
on plants for
thousands of
products
including food,
building
materials, and
medicines.
• The exploding
human
population is
eliminating plant
species at an
alarming rate.
Every 2 seconds humans destroy an area of tropical rain forest
equal to the area of 3 football fields
Learning Objectives
• Know the distinguishing characteristics of the
plant kingdom and 4 major plant phyla.
• Describe the evolutionary innovations that
allowed plants to colonize land.
• Understand the alternation of generations in the
life cycle of plants.
• Describe various relationships between plants
and other organisms
• Know the distinguishing characteristics of
Kingdom Fungi.
12.1 What makes you a plant?
Nitrogen, phosphorus, and salts
Roots and shoots
Dodder: a parasitic plant with “intelligence”
4 Major Plant Phyla
Bryophytes
12.2 Colonizing land brings new
opportunities and challenges for plants.
The First Land Plants Appeared
About 475 Million Years Ago
Early plants transitioned from
algae to moss…
 The
first land plants were small and had
no leaves, roots or flowers and could grow
only at the water’s edge.
 Nevertheless,
these plants set the stage
for the enormous diversity of terrestrial
plants and animals on earth today.
Living on land
poses very different
problems from living
in water.
Cuticle
Stomata
Vascular tissue
(xylem and phloem)
Lignin
12.3 Mosses and other non-vascular plants
lack vessels for transporting nutrients and
water.
The
Bryophytes
include:
mosses,
liverworts, and
hornworts
Alternation of Generations
• A life cycle of alternating diploid (2n – the
sporophyte) and haploid (n gametophyte) generations.
• Both generations are multicellular.
• Gametophytes produce haploid gametes
via mitosis.
• Sporophytes produce haploid spores via
meiosis.
• The Gametophyte generation dominates
only in the Bryophyte plant group.
A life cycle of alternating
haploid and diploid
generations in which the
diploid embryo is
protected by the haploid
female
Bryophyte Characteristics
Non-vascular plants—mosses, liverworts, and
hornworts—have scarcely evolved beyond the
stage of the earliest land plants.
 They lack roots and vessels to move water and
nutrients from the soil into the plant.
 They reproduce with spores that form when a
sperm from a male reproductive structure
“swims” through a drop of rainwater to the egg
in a female reproductive structure.
 Gametophyte generation dominates.

12.4 The evolution of vascular
tissue made larger plants possible.
Like a circulatory
system, vessels are an
effective way to carry
water and nutrients up
from the soil to the
leaves.
Now the sporophyte
generation (diploid adult)
dominates: is more
conspicuous, is present for a
longer period of time in the life
cycle, and is responsible for
photosynthesis.
Seedless Vascular Plant
Characteristics
• Seedless Vascular plants include ferns and
horsetails.
• Vascular tissues transport water and
nutrients and allow plants to move farther
away from water and to grow taller.
• Reproduction by haploid spores dispersed
by wind or water.
• Sprorophyte generation dominates.
Seed plants include both Angiosperms and
Gymnosperms. Gymnosperms were the first plants
to evolve both seeds and pollen.
12.5 What is a seed?
Seed = embryo + energy source +
protective seed coat
Seed Dispersal
 Only
opportunity most plants have to send
their offspring away from home
 Seeds
and seed pods have many ways to
do this:
• forceful send-off of exploding seed pods
• seeds that hitch rides on passing animals
• seeds that float in water or float through the
air
Seed dispersal in Angiosperms is aided by delicious fruits.
12.6 With the evolution of the seed,
gymnosperms became the dominant
plants on Earth.
Why would the
male cones be on
the bottom instead
of the top of the
pine tree?
Now the sporophyte
generation is even more
dominant.
The gametophytes are
smaller but are still
multicellular.
Rigidity, an
exterior layer of
bark, and the
production of
sticky sap
protects
conifers, helping
make it possible
for conifers to
grow taller and
reach older ages
than any other
plants.
Gynmosperm Characteristics
Gymnosperms include conifers, cycads,
gnetophytes, and Ginko.
 Gymnosperms were the earliest plants to
produce seeds and pollen, and this mode of
reproduction offers advantages over the
spores of earlier plants.
 The sporophyte generation
dominates and in some
species can live thousands
of years and grow
hundreds of feet tall.

95 % of the world’s plants are Angiosperms,
which diversified with the mass extinction of the
dinosaurs.
12.8 Angiosperms are the dominant
plants today.
12.9 A flower is nothing without a
pollinator. Most Angiosperms rely in
animal pollinators.
Why are flowers so flashy?
Trickery and Bribery
 Plant
deceit!
 Recall
Orchid species (wasp mimic)
• flowers that resemble female wasps
• Male wasps are tricked into pollination
2) Bribery

Plants offer something of value for pollen
transport.
Requires:
a)
b)
c)
a sticky pollen
a flower that catches the attention of the
pollinator
something of value to the pollinator.
Angiosperm
reproduction
more closely
resembles
the life cycle
of animals: a
diploid adult
and haploid
gametes.
Angiosperm characteristics
• Angiosperms are the dominant plants
today and include all flowering and fruiting
plants.
• Most angiosperms rely on animals for
pollination and seed dispersal.
• Reproduction includes double fertilization.
• Angiosperm reproduction more closely
resembles the life cycle of animals: a
diploid sporophyte generation dominates
and produces haploid gametes.
12.11 Fleshy fruits are bribes that
flowering plants pay animals to
disperse seeds.
How does this system work?
 Fruits
are colorful
 Fruits taste good.
 Fruit is good for animals.
Can seeds still sprout after
being eaten by an animal?
Test it yourself!
In fact, dung is a good place for a seed to germinate.
12.12 Unable to escape, plants must
resist predation in other ways.
Powerful
plant
alkaloids
include
caffeine,
nicotine,
and
morphine
Some plants enlist the help of friendly insects.
Predatory plant: Sundew
12.13 Fungi are closer to animals
than they are to plants.
Symbionts most often include parasitism or
mutualism.
3 Types of Symbioses
Symbiosis – an intimate living situation
between two or more different species
1. Parasitism – parasite/host relationship
where the parasite benefits at the host’s
expense
2. Mutualism – both partners benefit
3. Commensalism – one partner benefits,
while the other is neither harmed nor
benefitted.
Examples?
A parasite’s commensalistic relationship with the shotgun
fungus
Some fungi, called yeasts, live as
individual cells; most others are
multicellular.
• 12.14 Fungi have common structures, but
exploit an enormous diversity of habitats.
Most of the
fungal body is
underground,
secreting
enzymes and
absorbing food.
The mushroom
is the aboveground
reproductive
structure.
Fungal Hyphae
Mushroom Delicacies
 Portobello
 The
and shitake mushrooms
white button mushroom on pizza
 Truffles
• sell for $1750 to $3500 per pound!
How can fungi grow in so many
habitats?
 Advantages
of being a decomposer
 Saprotroph
= excretes digestive enzymes
outside the body and reabsorbs nutrients.
 Fungi
don’t need light
 Hyphae have a strong cell wall to
penetrate hard substances.
 Enormously
important ecological role!
Fungal Parasites
• Of the 100,000 known species of fungi,
about 30% make their living as parasites
• About 50 species of fungi are known to be
parasitic in humans and other animals
– Yeast infections
– Skin disease (Ringworm)
– Athlete’s foot
• Highly contagious
• easily treated
• Some fungi produce antibiotics
 Plants
and fungi have
a close mutualism.
 Mycorrhizal fungi
grow in intimate
association with the
roots of most plants,
receiving sugar from
the plant and
transferring nitrogen
and phosphorus to
the plant.
Some plants have
turned this
relationship into
parasitism—these
plants lack
chlorophyll so they
contribute nothing
to the fungus, but
they receive
nutrients from the
fungus and sugar
from other plants
that is delivered via
the fungus.
Lichens
 Fungi
and chlorophyll-containing bacteria
and algae as photosynthetic “partners”
Lichens are a
pioneer organism.
• Through the power
of mutualism, the
lichen can grow on
bare rock, slowly
turning that rock
into soil.
• Soil allows
colonization by
plants and animals.
Characteristics of Fungi
• Shared a protist ancestor with animals.
• Decomposers/saprotrophs
• Composed of hyphae with cell walls of
chitin
• Are sessile and reproduce by dispersing
spores
• Some are pathogens of animals and plants.
• Some are edible or useful as medicines.
• Many have mutualistic partnerships with
photosynthetic partners.