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Chapter 29 Plant Diversity
1. What are the characteristics of plants?
- Photosynthetic autotrophs
Algae also
- Cellulose in cell walls
- Starch as storage polysaccharide
- PROBLEM – light, CO2 & O2 are above ground
- water & minerals are below ground
- SOLUTION – evolution of specialized structures
2. What adaptations do plants have for survival on land?
- Stomata – pores used for gas exchange
- Roots – absorb water & minerals from underground
- Apical meristems – tips of shoots & roots where growth occurs
- Cuticle – waxy covering to prevent water loss thru leaves
- Jacketed gametangia – gamete producing organ with protective jacket
of cells to prevent dehydration
- Sporopollenin – polymer that formed around exposed zygotes & forms
walls of plant spores preventing dehydration
- Lignin – structural polymer that provides strength for woody tissues of
vascular plants
Chapter 29: Plant Diversity
1. What are the characteristics of plants?
2. What adaptations do plants have for survival on land?
3. What were the adaptations/highlights of plant evolution?
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Plants likely evolved from Charophytes (green algae)
- similar peroxisome enzymes
- similar %age of cellulose found in plants & charophytes
- nuclear & chloroplast genes have similar DNA
Movement to land led to Bryophytes (mosses & worts)
- Tougher spores (sporopollenin)
- Jacketed gametangia
Vascular tissue (ferns)
- Cells joined to transport water & nutrients
- Lacked seeds
Development of seeds (Gymnosperms, e.g. pine tree)
- More protection of embryo
- Embryo w/ food
Development of flowers (Angiosperms, e.g. oak tree)
- Complex reproductive structure
Figure 29.7 Highlights of plant evolution
Land plants
Vascular plants
Angiosperms
Origin of seed plants
(about 360 mya)
Origin of vascular
plants (about 420 mya)
Origin of land plants
(about 475 mya)
Ancestral
green alga
Seed plants
Gymnosperms
Pterophytes
(ferns, horsetails, whisk ferns)
Lycophytes
(club mosses, spike mosses, quillworts)
Seedless vascular plants
Mosses
Hornworts
Liverworts
Charophyceans
Bryophytes
(nonvascular plants)
Chapter 29 Plant Diversity
1.
2.
3.
4.
What are the characteristics of plants?
What adaptations do plants have for survival on land?
What were the adaptations/highlights of plant evolution?
Describe alternation of generations
- Alternates between sexual
& asexual reproduction
- Gametophyte (n) make gametes
by mitosis
- Sporophyte (2n) makes spores
by meiosis
Haploid multicellular
organism (gametophyte)
Mitosis
Mitosis
n
n
n
Spores
n
n
Gametes
MEIOSIS
FERTILIZATION
2n
2n
Zygote
Mitosis
Diploid multicellular
organism (sporophyte)
Alternation of generations: a generalized scheme
Figure 29.8 The life cycle of a Polytrichum moss
Raindrop
Key
Male
gametophyte
Sperm
“Bud”
Haploid (n)
Diploid (2n)
Antheridia
Protonemata
“Bud”
Egg
Spores
Gametophore
Female
gametophyte
Peristome
Archegonia
Rhizoid
Sporangium
MEIOSIS
Mature
Mature
sporophytes
sporophytes
Seta
FERTILIZATION
Capsule
(sporangium)
Calyptra
Zygote
(within archegonium)
Embryo
Foot
Archegonium
Young
sporophytes
Capsule with
peristome (LM)
Female
gametophytes
Figure 29.9 Bryophyte Diversity
Gametophore of
female gametophyte
LIVERWORTS (PHYLUM HEPATOPHYTA)
Plagiochila
deltoidea,
a “leafy”
liverwort
Foot
Seta
Marchantia sporophyte (LM)
HORNWORTS (PHYLUM ANTHOCEROPHYTA)
An Anthoceros
hornwort species
Sporophyte
Sporangium
500 µm
Marchantia polymorpha,
a “thalloid” liverwort
MOSSES (PHYLUM BRYOPHYTA)
Polytrichum commune,
hairy-cap moss
Sporophyte
Gametophyte
Gametophyte
Figure 29.12 The life cycle of a fern
1 Sporangia release spores.
Most fern species produce a single
type of spore that gives rise to a
bisexual gametophyte.
Key
3 Although this illustration
shows an egg and sperm
from the same gametophyte,
a variety of mechanisms
promote cross-fertilization
between gametophytes.
2 The fern spore
develops into a small,
photosynthetic gametophyte.
Haploid (n)
Diploid (2n)
Antheridium
Spore
Young
gametophyte
MEIOSIS
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
5 A zygote develops into a new
sporophyte, and the young plant
grows out from an archegonium
of its parent, the gametophyte.
4 Fern sperm use flagella
to swim from the antheridia
to eggs in the archegonia.
Figure 29.14 Seedless Vascular Plant Diversity
LYCOPHYTES (PHYLUM LYCOPHYTA)
Strobili
(clusters of
sporophylls)
Isoetes
gunnii,
a quillwort
Selaginella apoda,
a spike moss
Diphasiastrum tristachyum, a club moss
Psilotum
nudum,
a whisk
fern
PTEROPHYTES (PHYLUM PTEROPHYTA)
Equisetum
arvense,
field
horsetail
Vegetative stem
Athyrium
filix-femina,
lady fern
Strobilus on
fertile stem
WHISK FERNS AND RELATIVES
HORSETAILS
FERNS
Chapter 30: The Evolution of Seed Plants
1. What are the 3 most important reproductive adaptations?
- Reduction of the gametophyte
- Advent of the seed – replaced spore
- Evolution of pollen – male gametophyte
- Air dispersal instead of sperm swimming
Figure 30.2 Gametophyte/sporophyte relationships
Sporophyte
(2n)
Sporophyte
(2n)
Gametophyte
(n)
(a) Sporophyte dependent
on gametophyte
(mosses and other
bryophytes).
Gametophyte
(n)
(b) Large sporophyte and
small, independent
gametophyte (ferns
and other seedless
vascular plants).
Microscopic female
gametophytes (n) in
ovulate cones
(dependent)
Microscopic male
gametophytes (n)
inside these parts
of flowers
(dependent)
Microscopic male
gametophytes (n)
in pollen cones
(dependent)
Sporophyte (2n)
(independent)
(c) Reduced gametophyte dependent on sporophyte
(seed plants: gymnosperms and angiosperms).
Microscopic female
gametophytes (n)
inside these parts
of flowers
(dependent)
Sporophyte (2n),
the flowering plant
(independent)
Chapter 30: The Evolution of Seed Plants
1. What are the 3 most important reproductive adaptations?
- Reduction of the gametophyte
- Advent of the seed – replaced spore as
- Evolution of pollen – male gametophyte
2. How does an ovule become a seed?
- Fertilization
- Growth of the embryo
Figure 30.3 From ovule to seed
Female
gametophyte (n)
Integument
Seed coat
(derived from
integument)
Egg nucleus (n)
Spore wall
Food supply
(female
gametophyte
tissue) (n)
Megasporangium
(2n)
Male gametophyte
(within germinating
pollen grain) (n)
Discharged
sperm nucleus (n)
Megaspore (n)
Micropyle
(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.)
(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.
Pollen grain (n)
Embryo (2n)
(new sporophyte)
(c) 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.
Chapter 30: The Evolution of Seed Plants
1. What are the 3 most important reproductive adaptations?
2. How does an ovule become a seed?
3. What’s the difference between a megaspore & a microspore?
- Megasporangia  megaspores  female gametophytes (eggs)
- Microsporangia  microspores  male gametophytes (sperm)
4. What are gymnosperms?
- “naked seed” plants
- Pines, spruce, fir, sequoia, yews, junipers, ginkgo
- Most lumber & paper products
- The gymnosperm life cycle…
Figure 30.6 The life cycle of a pine
Key
Haploid (n)
Diploid (2n)
Ovule
Megasporocyte (2n)
Ovulate
cone
Pollen
cone
Integument
Longitudinal
section of
ovulate cone
Micropyle
Microsporocytes
(2n)
Mature
sporophyte
(2n)
Germinating
pollen grain
MEIOSIS
Longitudinal
section of
pollen cone
Megasporangium
Pollen
MEIOSIS
grains (n)
(containing male
gametophytes)
Surviving
Sporophyll megaspore (n)
Microsporangium
Seedling
Germinating
pollen grain
Archegonium
Egg (n)
Integument
Female
gametophyte
Seeds on surface
of ovulate scale
Germinating
pollen grain (n)
Food reserves Seed coat
(gametophyte (derived from
tissue) (n)
parent
sporophyte) (2n)
Discharged
sperm nucleus (n)
Pollen
tube
Embryo
(new sporophyte)
(2n)
FERTILIZATION
Egg nucleus (n)
Chapter 30: The Evolution of Seed Plants
1.
2.
3.
4.
What are the 3 most important reproductive adaptations?
How does an ovule become a seed?
What’s the difference between a megaspore & a microspore?
What are gymnosperms?
- “naked seed” plants
- Pines, spruce, fir, sequoia, yews, junipers, ginkgo
- Most lumber & paper products
- The gymnosperm life cycle…
5. What are angiosperms?
- Flowering plants
6. What is a flower?
- Reproductive structure of an angiosperm
Figure 30.7 The structure of an idealized flower
Carpel
Stigma
Male structures
Anther
Stamen
Style
Ovary
Filament
Petal
Sepal
Receptacle
Ovule
Female structures
Chapter 30: The Evolution of Seed Plants
1.
2.
3.
4.
5.
6.
What are the 3 most important reproductive adaptations?
How does an ovule become a seed?
What’s the difference between a megaspore & a microspore?
What are gymnosperms?
What are angiosperms?
What is a flower?
- Reproductive structure of an angiosperm
7. What is a fruit?
- Mature ovary
- Helps seed dispersal
Figure 30.8 Some variations in fruit structure
(a) Tomato, a fleshy fruit with
soft outer and inner layers
of pericarp
(b) Ruby grapefruit, a fleshy fruit
with a hard outer layer and
soft inner layer of pericarp
(c) Nectarine, a fleshy
fruit with a soft outer
layer and hard inner
layer (pit) of pericarp
(d) Milkweed, a dry fruit that
splits open at maturity
(e) Walnut, a dry fruit that
remains closed at maturity
Figure 30.9 Fruit adaptations that enhance seed dispersal
(a) Wings enable maple fruits
to be easily carried by the wind.
(b) Seeds within berries and other
edible fruits are often dispersed
in animal feces.
(c) The barbs of cockleburs
facilitate seed dispersal by
allowing the fruits to
“hitchhike” on animals.
Chapter 30: The Evolution of Seed Plants
1.
2.
3.
4.
5.
6.
7.
8.
What are the 3 most important reproductive adaptations?
How does an ovule become a seed?
What’s the difference between a megaspore & a microspore?
What are gymnosperms?
What are angiosperms?
What is a flower?
What is a fruit?
The angiosperm life cycle….
Figure 30.10 The life cycle of an angiosperm
Key
Haploid (n)
Diploid (2n)
Anther
Microsporangium
Microsporocytes (2n)
Mature flower on
sporophyte plant
(2n)
MEIOSIS
Microspore (n)
Ovule with
megasporangium (2n)
Generative cell
Tube cell
Male gametophyte
(in pollen grain)
Ovary
Pollen
grains
MEIOSIS
Germinating
seed
Stigma
Megasporangium
(n)
Embryo (2n)
Endosperm
(food
supply) (3n)
Sperm
Surviving
megaspore
(n)
Seed
Seed coat (2n)
Female gametophyte
(embryo sac)
Nucleus of
developing
endosperm
(3n)
Pollen
tube
Antipodal cells
Polar nuclei
Synergids
Egg (n)
Zygote (2n)
Egg
nucleus (n)
Pollen
tube
Sperm
(n)
FERTILIZATION
Double fertilization
Discharged
sperm nuclei (n)
Pollen
tube
Style
Chapter 30: The Evolution of Seed Plants
1.
2.
3.
4.
5.
6.
7.
8.
9.
What are the 3 most important reproductive adaptations?
How does an ovule become a seed?
What’s the difference between a megaspore & a microspore?
What are gymnosperms?
What are angiosperms?
What is a flower?
What is a fruit?
The angiosperm life cycle….
Why is double fertilization important?
- Synchronizes food development with embryo development
- Prevents angiosperms from wasting nutrients on unfertilized ovules
10. What are the 2 general types of angiosperms?
- Monocots
- Eudicots
MONOCOTS
EUDICOTS
Monocot
Characteristics
Orchid
(Lemboglossum
rossii)
Eudicot
Characteristics
California
poppy
(Eschscholzia
californica)
Embryos
One cotyledon
Two cotyledons
Leaf
venation
Veins usually
parallel
Pygmy date palm
(Phoenix roebelenii)
Pyrenean oak
(Quercus
pyrenaica)
Veins usually
netlike
Stems
Lily (Lilium
“Enchantment”)
Vascular tissue
usually arranged
in ring
Vascular tissue
scattered
Root
Barley (Hordeum vulgare),
a grass
Root system
Usually fibrous
(no main root)
Dog rose (Rosa canina), a wild rose
Taproot (main root)
usually present
Pollen
Pollen grain with
one opening
Pea (Lathyrus nervosus,
Lord Anson’s blue pea),
a legume
Pollen grain with
three openings
Flowers
Anther
Stigma
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
Table 29.1 Ten Phyla of Extant Plants