16 lecture presentation

© 2010 Pearson Education, Inc.
COLONIZING LAND
• Plants are terrestrial organisms that include forms that have
returned to water, such as water lilies.

Terrestrial Adaptations of Plants
Structural Adaptations
• 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

• 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

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
soil (aided by fungi)
Whole alga
performs
photosynthesis;
absorbs water,
CO2, and
minerals from
the water
Alga
Plant
Figure 16.1

• 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

• 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

• 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

Phloem
Xylem
Oak leaf
Vascular
tissue
Figure 16.3

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.

Embryo
Maternal
tissue
LM
Figure 16.4

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

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

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

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)
Landplants
Vascularplants
Seedplants
Seedless
vascular
plants
Nonvascular
plants
(bryophytes)
Figure 16.6

• (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
– True roots
– True leaves

• (2) About 425 million years ago ferns evolved
– With vascular tissue
– 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.

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

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

• The great majority of living plants
– Are angiosperms
– Include fruit and vegetable crops, grains, grasses, and most trees
Video: Flower Blooming (time lapse)

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

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

Spores
Spore capsule
Sporophyte
Gametophytes
Figure 16.9

• 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

Gametes:
sperm
and eggs
(n)
Gametophyte
(n)
Key
Haploid (n)
Diploid (2n)
osis
Mit
Figure 16.10-1

Gametes:
sperm
and eggs
(n)
Zygote
(2n)
Gametophyte
(n)
Key
Haploid (n)
Diploid (2n)
FERTILIZATION
osis
Mit
Figure 16.10-2

Spore
capsule
Gametes:
sperm
and eggs
(n)
Zygote
(2n)
Gametophyte
(n)
Sporophyte
(2n)
Key
Haploid (n)
Diploid (2n)
FERTILIZATION
osis
Mit
to
Mi
sis
Figure 16.10-3

Spores
(n)
Spore
capsule
Gametes:
sperm
and eggs
(n)
Zygote
(2n)
Gametophyte
(n)
Sporophyte
(2n)
Key
Haploid (n)
Diploid (2n)
MEIOSIS FERTILIZATION
osis
Mit
to
Mi
sis
Figure 16.10-4

Spores
(n)
Spore
capsule
Gametes:
sperm
and eggs
(n)
Zygote
(2n)
Gametophyte
(n)
Sporophyte
(2n)
Key
Haploid (n)
Diploid (2n)
MEIOSIS FERTILIZATION
osis
M
it
osis
Mit
to
Mi
sis
Figure 16.10-5

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

Spore capsule
“Fiddlehead”
(young leaves
ready to unfurl)
Figure 16.11

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.

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

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.
Animation: Pine Life Cycle

• 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

• 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

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

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

• A flower has;
– Sepals
– Petals
– Stamens
– Carpels
Blast Animation: Flower Structure

Petal
CarpelStamen
SepalOvule
Anther
Filament
Stigma
Style
Ovary
Figure 16.17

• Flowers come in many forms.

Pansy Bleeding heart California poppy Water lily
Figure 16.18

California
poppy
Figure 16.18c

• Flowers are an essential element of the angiosperm life cycle.
Animation: Seed Development
Video: Flowering Plant Life Cycle (time lapse)
Animation: Plant Fertilization
Animation: Fruit Development
Blast Animation: Flowering Plant Life Cycle
Blast Animation: Pollination and Fertilization

Mature
sporophyte
plant with
flowers
Sporophyte
seedling
Germinating
seed
Seed
Seed (develops
from ovule)
Fruit (develops
from ovary)
Embryo
(sporophyte)
Two
sperm
nuclei
Zygote
Endosperm
Embryo sac
(female
gametophyte)
Egg
FERTILIZATION
Key
Haploid (n)
Diploid (2n)
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
Figure 16.19-6

• 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

Wind
dispersal
Animal
transportation
Animal
ingestion
Figure 16.20

Animal transportation
Figure 16.20b

Animal ingestion
Figure 16.20c

Angiosperms and Agriculture
• Gymnosperms supply most of our lumber and paper.
• Angiosperms
– Provide nearly all our food
– Supply fiber, medications, perfumes, and decoration

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

• 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

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

• Fungi are
– Eukaryotes
– Typically multicellular

• Fungi
– Come in many shapes and sizes
– Represent more than 100,000 species
Video: Water Mold Zoospores
Video: Water Mold Oogonium

Orange fungi
Mold
Predatory fungus
Budding yeast
A “fairy ring”
Bud
Roundworm Body of fungus
ColorizedSEM
ColorizedSEMColorizedSEM
Figure 16.22

Characteristics of Fungi
• Fungi have unique
– Structures
– Forms of nutrition

Fungal Nutrition
• Fungi
– 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

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

• Hyphae branch repeatedly, forming an interwoven network called
a mycelium (plural, mycelia), the feeding structure of the fungus.
Animation: Fungal Reproduction and Nutrition

Reproductive
structure
Mycelium
Mycelium
Hyphae Spore-producing
structures
Figure 16.23

Mycelium
Spore-producing
structures
Reproductive
structure
Hyphae
Figure 16.23a

The Ecological Impact of Fungi
• Fungi have
– An enormous ecological impact
– Many interactions with humans

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.

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

(a) American elm trees killed by Dutch
elm disease fungus
Figure 16.24a

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

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

Truffles
(the fungal kind, not the chocolates)
Blue cheese
Chanterelle
mushrooms
Figure 16.26

Truffles
(the fungal kind,
not the chocolates)
Figure 16.26a

Chanterelle
mushrooms
Figure 16.26c

Penicillium Zone of inhibited growth
Staphylococcus
Figure 16.27

16 lecture presentation

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