Plant diversity.ppt

Plant Diversity

PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

charophyceans as the closest
relatives of land plants

–  Rose-shaped complexes for cellulose
synthesis

Coleochaete

Nitella

•  There are four key traits that land plants share
only with charophyceans

Chara

30 nm

Figure 29.2

Genetic Evidence
–  Peroxisome enzymes
–  Structure of flagellated sperm
–  Formation of a phragmoplast

•  Comparisons of both nuclear and chloroplast
genes
–  Point to charophyceans as the closest living
relatives of land plants

(a) Chara,
a pond
organism

10 mm

40 µm

Figure 29.3a, b

(b) Coleochaete orbicularis, a diskshaped charophycean (LM)


1

Adaptations Enabling the Move to Land
•  In charophyceans
–  A layer of a durable polymer called
sporopollenin prevents exposed zygotes from
drying out


•  Land plants possess a set of derived terrestrial
adaptations
•  Many adaptations
–  Emerged after land plants diverged from their
charophycean relatives


Defining the Plant Kingdom
•  Systematists
–  Are currently debating the boundaries of the
plant kingdom
Viridiplantae
Streptophyta
Plantae

Red algae

Figure 29.4

Chlorophytes Charophyceans Embryophytes

Ancestral alga


Derived Traits of Plants
•  Five key traits appear in nearly all land plants
but are absent in the charophyceans

•  Apical meristems and alternation of
generations
APICAL MERISTEMS

Apical
meristem
of shoot

Developing
leaves

Apical meristems of plant shoots
and roots. The light micrographs
are longitudinal sections at the tips
of a shoot and root.

–  Apical meristems
–  Alternation of generations
Apical meristem
of root

–  Walled spores produced in sporangia
–  Multicellular gametangia

Shoot

100 µm

Haploid multicellular
organism (gametophyte)
Mitosis

ALTERNATION OF GENERATIONS

–  Multicellular dependent embryos

Root

100 µm

Mitosis

n

n
Spores

n
n

n

Gametes
MEIOSIS

FERTILIZATION

2n
Diploid multicellular
organism (sporophyte)

Figure 29.5

2n

Zygote

Mitosis

Alternation of generations: a generalized scheme



Figure 29.5

2

•  Walled spores; multicellular gametangia; and
multicellular, dependent embryos

GAMETOPHYTE
(n)
mitosis
Spores
(n)
Archegonium Antheridium
(n)
(n)
produce

meiosis
Sporocyte
(2n)

HAPLODIPLONTIC
("Alternation of
Gen erations")

Egg
(n)

Sporangium
(2n)

Sperm
(n)

} lost by reduction and modification
in the Angiosperms

WALLED SPORES PRODUCED IN SPORANGIA

and some Gnetales

Sporophyte and sporangium
of Sphagnum (a moss)

Sporophyte
Gametophyte

MULTICELLULAR GAMETANGIA

Female gametophyte
Archegonium
with egg

Embryo
(2n)

mitosis

Antheridium
with sperm

Archegonia and antheridia
of Marchantia (a liverwort)
Male
gametophyte

Zygote

mitosis

Longitudinal section of
Sphagnum sporangium (LM)

(Sperm non-flagellate in Conifers,
Gnetales, and Angiosperms)

fertilization

SPOROPHYTE
(2n )

Spores
Sporangium

MULTICELLULAR, DEPENDENT EMBRYOS

(2n)

Embryo and placental
transfer cell of Marchantia

Figure 29.5

Embryo
Maternal tissue
2 µm

10 µm
Wall ingrowths
Placental transfer cell


The Origin and Diversification of Plants
•  Additional derived units

•  Fossil evidence

–  Such as a cuticle and secondary compounds,
evolved in many plant species


–  Indicates that plants were on land at least 475
million years ago


•  Fossilized spores and tissues
–  Have been extracted from 475-million-year-old
rocks
(a) Fossilized spores.
Unlike the spores of
most living plants,
which are single
grains, these spores
found in Oman are
in groups of four
(left; one hidden)
and two (right).

•  Whatever the age
of the first land
plants
–  Those ancestral
species gave
rise to a vast
diversity of
modern plants

(b) Fossilized

Figure 29.6 a, b

sporophyte tissue.
The spores were
embedded in tissue
that appears to be
from plants.

Table 29.1


3

•  An overview of land plant evolution
Land plants
Vascular plants

Gymnosperms

Angiosperms

Seed plants

Pterophyte
(ferns, horsetails, whisk fern)

Lycophytes
(club mosses, spike mosses, quillworts)

Seedless vascular plants

Mosses

Hornworts

Charophyceans

Liverworts

Bryophytes
(nonvascular plants)

Origin of seed plants
(about 360 mya)

Origin of vascular
plants (about 420 mya)

The life cycles of mosses and other
bryophytes are dominated by the
gametophyte stage

Origin of land plants
(about 475 mya)

Ancestral
green alga



Bryophyte Gametophytes
•  Bryophytes are represented today by three
phyla of small herbaceous (nonwoody) plants
–  Liverworts, phylum Hepatophyta

•  In all three bryophyte phyla
–  Gametophytes are larger and longer-living than
sporophytes

–  Hornworts, phylum Anthocerophyta
–  Mosses, phylum Bryophyta



•  The life cycle of a moss
Raindrop
Key

Male
gametophyte

1

Spores develop into
threadlike protonemata.

•  Bryophyte diversity

Haploid (n)
Diploid (2n)

Sperm

Gametophore of
female gametophyte

“Bud”

2 The haploid
protonemata
produce “buds”
that grow into
gametophytes.
Protonemata

4 A sperm swims
through a film of
moisture to an
archegonium and
fertilizes the egg.

Antheridia

3 Most mosses have separate
male and female gametophytes,
with antheridia and archegonia,
respectively.

LIVERWORTS (PHYLUM HEPATOPHYTA)

Plagiochila
deltoidea,
a “leafy”
liverwort

Foot

“Bud”

Seta
Egg

Spores

Marchantia polymorpha,
a “thalloid” liverwort

Sporangium

MEIOSIS

Mature
Mature
sporophytes
sporophytes

Capsule
(sporangium)

Calyptra

Zygote

Marchantia sporophyte (LM)

FERTILIZATION

(within archegonium)

HORNWORTS (PHYLUM ANTHOCEROPHYTA)
An Anthoceros
hornwort species

Embryo

Sporophyte

Foot

Sporangium
500 µm

Gametophore
Female
Archegonia
Meiosis occurs and haploid
gametophyte
spores develop in the sporangium
of the sporophyte. When the
sporangium lid pops off, the
Rhizoid
peristome “teeth” regulate
6 The sporophyte grows a
gradual release of the spores.
long stalk, or seta, that emerges
Seta
from the archegonium.

8
Peristome

MOSSES (PHYLUM BRYOPHYTA)
Polytrichum commune,
hairy-cap moss
Sporophyte

Archegonium

Capsule with
peristome (LM)

Figure 29.8

Female
gametophytes

Young
5 The diploid zygote
sporophyte
develops into a
sporophyte embryo within
Attached by its foot, the
the archegonium.
sporophyte remains nutritionally
dependent on the gametophyte.

Gametophyte

7


Gametophyte

Figure 29.9

4

Ecological and Economic Importance of Mosses
•  Sphagnum, or “peat moss”

•  Ferns and other seedless vascular plants

–  Forms extensive deposits of partially decayed
organic material known as peat
–  Plays an important role in the Earth’s carbon
cycle
(a) Peat being harvested from a peat bog

(b) Closeup of Sphagnum. Note the “leafy” gametophytes
and their offspring, the sporophytes.

Gametophyte

Sporangium at
tip of sporophyte
Living
photo- Dead watersynthetic storing cells
cells
100 µm

(c) Sphagnum “leaf” (LM). The combination of living photosynthetic
cells and dead water-storing cells gives the moss its spongy quality.

Figure 29.10 a–d

(d) “Tolland Man,” a bog mummy dating from 405–100 B.C.
The acidic, oxygen-poor conditions produced by
Sphagnum canpreserve human or other animal bodies for
thousands of years.


•  Ferns and other seedless vascular
plants formed the first forests
•  Bryophytes and bryophyte-like plants


•  These early tiny plants
–  Had independent, branching sporophytes
–  Lacked other derived traits of vascular plants

–  Were the prevalent vegetation during
the first 100 million years of plant
evolution

•  Vascular plants
–  Began to evolve during the
Carboniferous period
Figure 29.11


Life Cycles with Dominant Sporophytes
•  In contrast with bryophytes

•  The life cycle of a fern

–  Sporophytes of seedless vascular plants are
the larger generation, as in the familiar leafy
fern

1 Sporangia release spores.
Most fern species produce a single
type of spore that gives rise to a
bisexual gametophyte.

Key

2 The fern spore
develops into a small,
photosynthetic gametophyte.

3 Although this illustration
shows an egg and sperm
from the same gametophyte,
a variety of mechanisms
promote cross-fertilization
between gametophytes.

Haploid (n)
Diploid (2n)

Antheridium
Spore
MEIOSIS

–  The gametophytes are tiny plants that grow on
or below the soil surface

Young
gametophyte

Sporangium
Archegonium
Mature
sporophyte

New
sporophyte

Sperm

Egg
Zygote

Sporangium

FERTILIZATION

Sorus
6 On the underside
of the sporophyte‘s
reproductive leaves
are spots called sori.
Each sorus is a
cluster of sporangia.

Gametophyte

Fiddlehead

Figure 29.12

4 Fern sperm use flagella
to swim from the antheridia
to eggs in the archegonia.

5 A zygote develops into a new
sporophyte, and the young plant
grows out from an archegonium
of its parent, the gametophyte.


5

Transport in Xylem and Phloem
•  Vascular plants have two types of vascular
tissue
–  Xylem and phloem

•  Xylem
–  Conducts most of the water and minerals
–  Includes dead cells called tracheids

•  Phloem
–  Distributes sugars, amino acids, and other
organic products
–  Consists of living cells



Evolution of Roots

Evolution of Leaves

•  Roots

•  Leaves

–  Are organs that anchor vascular plants
–  Enable vascular plants to absorb water and
nutrients from the soil

–  Are organs that increase the surface area of
vascular plants, thereby capturing more solar
energy for photosynthesis

–  May have evolved from subterranean stems


•  Leaves are categorized by two types
–  Microphylls, leaves with a single vein
–  Megaphylls, leaves with a highly branched
vascular system


•  According to one model of evolution
–  Microphylls evolved first, as outgrowths of
stems
Vascular tissue

Figure 29.13a, b


(a) Microphylls, such as those of lycophytes, may have
originated as small stem outgrowths supported by
single, unbranched strands of vascular tissue.

(b) Megaphylls, which have branched vascular
systems, may have evolved by the fusion of
branched stems.


6

Sporophylls and Spore Variations

Classification of Seedless Vascular Plants

•  Sporophylls

•  Seedless vascular plants form two phyla

–  Are modified leaves with sporangia

•  Most seedless vascular plants
–  Are homosporous, producing one type of spore
that develops into a bisexual gametophyte


–  Lycophyta, including club mosses, spike
mosses, and quillworts
–  Pterophyta, including ferns, horsetails, and
whisk ferns and their relatives


•  The general groups of seedless vascular plants
LYCOPHYTES (PHYLUM LYCOPHYTA)

Strobili
(clusters of
sporophylls)

Isoetes
gunnii,
a quillwort
Selaginella apoda,
a spike moss

Diphasiastrum tristachyum, a club moss

PTEROPHYTES (PHYLUM PTEROPHYTA)
Psilotum
nudum,
a whisk
fern

Equisetum
arvense,
field
horsetail

Athyrium
filix-femina,
lady fern

Vegetative stem
Strobilus on
fertile stem

Figure 29.14

WHISK FERNS AND RELATIVES

HORSETAILS

FERNS


Phylum Lycophyta: Club Mosses, Spike Mosses, and
Quillworts

Phylum Pterophyta: Ferns, Horsetails, and Whisk
Ferns and Relatives

•  Modern species of lycophytes

•  Ferns

–  Are relics from a far more eminent past

–  Are the most diverse seedless vascular plants

–  Are small herbaceous plants



7

The Significance of Seedless Vascular Plants
•  The ancestors of modern lycophytes,
horsetails, and ferns
–  Grew to great heights during the
Carboniferous, forming the first forests

•  The growth of these early forests
–  May have helped produce the major global
cooling that characterized the end of the
Carboniferous period
–  Decayed and eventually became coal

Figure 29.15


•  Seeds changed the course of plant evolution

The Evolution of Seed Plants

–  Enabling their bearers to become the dominant
producers in most terrestrial ecosystems

PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece

Figure 30.1


Advantages of Reduced Gametophytes
•  The reduced gametophytes of seed plants are
protected in ovules and pollen grains
•  In addition to seeds, the following are common
to all seed plants

•  The gametophytes of seed plants
–  Develop within the walls of spores retained
within tissues of the parent sporophyte

–  Reduced gametophytes
–  Heterospory
–  Ovules
–  Pollen



8

Heterospory: The Rule Among Seed Plants
•  Gametophyte/sporophyte relationships
Sporophyte
(2n)

Sporophyte
(2n)

Gametophyte
(n)

(a) Sporophyte dependent
on gametophyte
(mosses and other
bryophytes).

Gametophyte
(n)

–  Which produce megaspores that give rise to
female gametophytes

(b) Large sporophyte and

small, independent
gametophyte (ferns
and other seedless
vascular plants).

Microscopic female
gametophytes (n) in
ovulate cones
(dependent)

Microscopic female
gametophytes (n)
inside these parts
of flowers
(dependent)

Microscopic male
gametophytes (n)
inside these parts
of flowers
(dependent)
Microscopic male
gametophytes (n)
in pollen cones
(dependent)

•  Seed plants evolved from plants that had
megasporangia

•  Seed plants evolved from plants that had
microsporangia
–  Which produce microspores that give rise to
male gametophytes

Sporophyte (2n),
the flowering plant
(independent)

Sporophyte (2n)
(independent)

(c) Reduced gametophyte dependent on sporophyte
(seed plants: gymnosperms and angiosperms).

Figure 30.2a–c



Ovules and Production of Eggs

Pollen and Production of Sperm

•  An ovule consists of

•  Microspores develop into pollen grains

–  A megasporangium, megaspore, and
protective integuments
Integument
Spore wall

Megasporangium
(2n)

–  Which contain the male gametophytes of
plants

•  Pollination
–  Is the transfer of pollen to the part of a seed
plant containing the ovules

Megaspore (n)
(a) Unfertilized ovule. In this sectional
view through the ovule of a pine (a
gymnosperm), a fleshy
megasporangium is surrounded by a
protective layer of tissue called an
integument. (Angiosperms have two
integuments.)

Figure 30.3a



•  If a pollen grain germinates
–  It gives rise to a pollen tube that discharges two
sperm into the female gametophyte within the
ovule
Female
gametophyte (n)

–  Eliminated the water requirement for
fertilization

Egg nucleus (n)

Spore wall

Male gametophyte
(within germinating
pollen grain) (n)

Discharged
sperm nucleus (n)
Micropyle

Figure 30.3b

•  Pollen, which can be dispersed by air or
animals

Pollen grain (n)

(b) Fertilized ovule. A megaspore develops into a
multicellular female gametophyte. The micropyle,
the only opening through the integument, allows
entry of a pollen grain. The pollen grain contains a
male gametophyte, which develops a pollen tube
that discharges sperm.



9

The Evolutionary Advantage of Seeds
•  A seed
–  Develops from the whole ovule
–  Is a sporophyte embryo, along with its food
supply, packaged in a protective coat
Seed coat
(derived from
Integument)

•  Gymnosperms bear “naked” seeds, typically
on cones
•  Among the gymnosperms are many wellknown conifers
–  Or cone-bearing trees, including pine, fir, and
redwood

Food supply
(female
gametophyte
tissue) (n)
Embryo (2n)
(new sporophyte)
(c)

Figure 30.3c

Gymnosperm seed. Fertilization initiates
the transformation of the ovule into a seed,
which consists of a sporophyte embryo, a
food supply, and a protective seed coat
derived from the integument.



•  The gymnosperms include four plant phyla
–  Cycadophyta
–  Gingkophyta
–  Gnetophyta
–  Coniferophyta

Cycas



Cycas revoluta



10

Ginkgo biloba

Ginkgo biloba



Conifer
Diversity
Female cone

Ginkgo biloba



Araucariaceae

Cupressaceae


11

Pinaceae: Pinus





Gymnosperm Evolution
•  Fossil evidence reveals that by the late Devonian
–  Some plants, called progymnosperms, had begun
to acquire some adaptations that characterize
seed plants

Figure 30.5


12

A Closer Look at the Life Cycle of a Pine
•  Gymnosperms appear early in the fossil record
–  And dominated the Mesozoic terrestrial
ecosystems

•  Key features of the gymnosperm life cycle
include
–  Dominance of the sporophyte generation, the
pine tree

•  Living seed plants
–  Can be divided into two groups: gymnosperms
and angiosperms

–  The development of seeds from fertilized
ovules
–  The role of pollen in transferring sperm to
ovules



•  The life cycle of a pine

2
An ovulate cone scale has two
ovules, each containing a megasporangium. Only one ovule is shown.
Key

1 In most
conifer species,
each tree has
both ovulate
and pollen
cones.

Haploid (n)
Diploid (2n)

Ovule

Pollen
cone

Integument
Longitudinal
section of
ovulate cone

Microsporocytes
(2n)

Mature
sporophyte
(2n)

MEIOSIS

Seedling

3

Micropyle

Megasporangium

Longitudinal
section of
Sporophyll
pollen cone Microsporangium

Germinating
pollen
Pollen grain
grains (n)
MEIOSIS
(containing male
gametophytes)
Surviving
megaspore (n)

A pollen cone contains many microsporangia
held in sporophylls. Each microsporangium Germinating
contains microsporocytes (microspore mother pollen grain
cells). These undergo meiosis, giving rise to
Archegonium
haploid microspores that develop into
Egg (n)
Integument
pollen grains.
Female
Seeds on surface
gametophyte

A pollen grain
enters through
the micropyle
and germinates,
forming a pollen
tube that slowly
digests
through the
megasporangium.
4

Megasporocyte (2n)

Ovulate
cone

5

While the
pollen tube
develops, the
megasporocyte
(megaspore
mother cell)
undergoes meiosis,
producing four
haploid cells. One
survives as a
megaspore.

of ovulate scale

Germinating
pollen grain (n)

8 Fertilization usually occurs more
than a year after pollination. All eggs
may be fertilized, but usually only one
zygote develops into an embryo. The
ovule becomes a seed, consisting of an
embryo, food supply, and seed coat.

Figure 30.6

Embryo
(new sporophyte)
(2n)

Food reserves
(gametophyte
tissue) (n)

Seed coat
(derived from
parent
sporophyte) (2n)

Discharged
sperm nucleus (n)
Pollen
tube

FERTILIZATION

Egg nucleus (n)

The female gametophyte
6
develops within the megaspore
and contains two or three
archegonia, each with an egg.

•  The reproductive adaptations of angiosperms
include flowers and fruits
•  Angiosperms
–  Are commonly known as flowering plants
–  Are seed plants that produce the reproductive
structures called flowers and fruits
–  Are the most widespread and diverse of all
plants

7
By the time the eggs are mature,
two sperm cells have developed in the
pollen tube, which extends to the
female gametophyte. Fertilization occurs
when sperm and egg nuclei unite.



Characteristics of Angiosperms

Flowers

•  The key adaptations in the evolution of
angiosperms

•  The flower

–  Are flowers and fruits


–  Is an angiosperm structure specialized for
sexual reproduction


13

Fruits
•  A flower is a specialized shoot with modified
leaves
–  Sepals, which enclose the flower

•  Fruits
–  Typically consist of a mature ovary
(a) Tomato, a fleshy fruit with
soft outer and inner layers
of pericarp

–  Petals, which are brightly colored and attract
pollinators

(b) Ruby grapefruit, a fleshy fruit
with a hard outer layer and
soft inner layer of pericarp

–  Stamens, which produce pollen
–  Carpels, which produce ovules
(c) Nectarine, a fleshy
fruit with a soft outer
layer and hard inner
layer (pit) of pericarp

Carpel
Stigma
Anther

Stamen

Style
Ovary

Filament

Petal

Sepal

Receptacle

Figure 30.7

Ovule

Figure 30.8a–e


(d) Milkweed, a dry fruit that
splits open at maturity

(e) Walnut, a dry fruit that
remains closed at maturity


The Angiosperm Life Cycle
•  Can be carried by wind, water, or animals to new
locations, enhancing seed dispersal
(a)

Wings enable maple fruits
to be easily carried by the wind.

•  In the angiosperm life cycle
–  Double fertilization
–  One sperm fertilizes the egg, while the other
combines with two nuclei in the center cell of
the female gametophyte and initiates
development of food-storing endosperm

(b) Seeds within berries and other
edible fruits are often dispersed
in animal feces.

•  The endosperm
–  Nourishes the developing embryo
(c)

Figure 30.9a–c

The barbs of cockleburs
facilitate seed dispersal by
allowing the fruits to
“hitchhike” on animals.



Fossil Angiosperms
•  The life cycle of an angiosperm
Key
Haploid (n)
Diploid (2n)

Microsporangium

Anther

Microsporocytes (2n)

Mature flower on
sporophyte plant
(2n)

2
Microspores form
pollen grains (containing
male gametophytes). The
generative cell will divide
to form two sperm. The
tube cell will produce the
pollen tube.

–  Display both derived and primitive traits
Carpel

MEIOSIS

Microspore (n)
Ovule with
megasporangium (2n)

7 When a seed
germinates, the
embryo develops
into a mature
sporophyte.

Generative cell

Embryo (2n)
Endosperm
(food
Supply) (3n)

Seed

Pollen
grains

MEIOSIS

3 In the megasporangium
of each ovule, the
megasporocyte divides by
meiosis and produces four
megaspores. The surviving
megaspore in each ovule
forms a female gametophyte
(embryo sac).

Stamen

Tube cell

Male gametophyte
(in pollen grain)
Ovary

Germinating
Seed

6 The zygote
develops into an
embryo that is
packaged along
with food into a
seed. (The fruit
tissues surrounding the seed are
not shown).

•  Primitive fossils of 125-million-year-old
angiosperms

1
Anthers contain microsporangia.
Each microsporangium contains microsporocytes (microspore mother cells) that
divide by meiosis, producing microspores.

Stigma

Megasporangium
(n)
Surviving
megaspore
(n)

Seed coat (2n)

Pollen
tube
Sperm
Pollen
tube

5 cm

Style

Female gametophyte
(embryo sac)

Antipodal cells
Polar nuclei
Synergids
Egg (n)

Pollen
tube

(a) Archaefructus sinensis, a 125-million-yearold fossil.

Zygote (2n)
Nucleus of
developing
endosperm
(3n)

Egg
Nucleus (n)

Sperm
(n)

5

Figure 30.10

Double fertilization occurs. One sperm
fertilizes the egg, forming a zygote. The
other sperm combines with the two polar
nuclei to form the nucleus of the endosperm,
which is triploid in this example.


(b) Artist’s reconstruction of
Archaefructus sinensis

4 After pollination, eventually
two sperm nuclei
are discharged in
each ovule.

FERTILIZATION

Discharged
sperm nuclei (n)

Figure 30.11a, b

14

Angiosperm Diversity
•  The two main groups of angiosperms
–  Are monocots and eudicots

•  Basal angiosperms
–  Are less derived and include the flowering
plants belonging to the oldest lineages

•  Magnoliids
–  Share some traits with basal angiosperms but
are more closely related to monocots and
eudicots


•  Exploring Angiosperm Diversity

•  Exploring Angiosperm Diversity

BASAL ANGIOSPERMS

EUDICOTS

MONOCOTS
Monocot
Characteristics

Orchid
(Lemboglossum
fossii)

Eudicot
Characteristics

California
poppy
(Eschscholzia
californica)

Embryos
One cotyledon

Two cotyledons

Leaf
venation

Amborella trichopoda

Eudicots

Monocots

Magnoliids

Star anise
and relatives

Amborella

Water lilies

HYPOTHETICAL TREE OF FLOWERING PLANTS

Pygmy date palm
(Phoenix roebelenii)

Pyrenean oak
(Quercus
pyrenaica)
Veins usually
netlike

Veins usually
parallel

Star anise (Illicium
floridanum)

Water lily (Nymphaea
“Rene Gerard”)

Stems

Lily (Lilium
“Enchantment”)

Vascular tissue
usually arranged
in ring

Vascular tissue
scattered
Roots

Root system
Usually fibrous
(no main root)

Barley (Hordeum vulgare),
a grass

Taproot (main root)
usually present

Dog rose (Rosa canina), a wild rose
Pea (Lathyrus
nervosus,
Lord Anson’s
blue pea), a
legume

Pollen

MAGNOLIIDS

Pollen grain with
one opening

Pollen grain with
three openings

Flowers
Anther

Southern magnolia (Magnolia
grandiflora)

Stigma

Figure 30.12

Figure 30.12


Filament

Ovary

Floral organs
usually in
multiples of three

Floral organs usually
in multiples of
four or five

Zucchini
(Cucurbita
Pepo), female
(left) and
male flowers


Evolutionary Links Between Angiosperms and Animals

Products from Seed Plants

•  Pollination of flowers by animals and transport
of seeds by animals

•  Humans depend on seed plants for

–  Are two important relationships in terrestrial
ecosystems

(a) A flower pollinated by
honeybees. This honeybee is
harvesting pollen and nectar (a
sugary solution secreted by
flower glands) from a Scottish
broom flower. The flower has a
tripping mechanism that arches
the stamens over the bee
and dusts it with pollen, some of
which will rub off onto the stigma
of the next flower the bee visits.

(b) A flower pollinated by hummingbirds.
The long, thin beak and tongue of this
rufous hummingbird enable the animal to
probe flowers that secrete nectar deep
within floral tubes. Before the hummer
leaves, anthers will dust its beak and
head feathers with pollen. Many flowers
that are pollinated by birds are red or
pink, colors to which bird eyes are
especially sensitive.

Figure 30.13a–c

–  Food
–  Wood
–  Many medicines

(c) A flower pollinated by nocturnal animals. Some
angiosperms, such as this cactus, depend mainly on
nocturnal pollinators, including bats. Common
adaptations of such plants include large, light-colored,
highly fragrant flowers that nighttime pollinators can
locate.

Table 30.1

15

Plant diversity.ppt

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