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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)
- Recall seed plants are heterosporous
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
Microsporocytes
(2n)
Mature
sporophyte
(2n)
MEIOSIS
Longitudinal
section of
pollen cone
Sporophyll
Microsporangium
Micropyle
Germinating
pollen grain
Pollen
grains (n)
(containing male
gametophytes)
Megasporangium
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
Germinating
pollen grain
Archegonium
Egg (n)
Integument
Female
gametophyte
Germinating
pollen grain (n)
Discharged
sperm nucleus (n)
Pollen
tube
Egg nucleus (n)
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)
Male gametophyte
(in pollen grain)
Ovary
MEIOSIS
Megasporangium
(n)
Surviving
megaspore
(n)
Female gametophyte
(embryo sac)
Antipodal cells
Polar nuclei
Synergids
Egg (n)
Pollen
tube
Sperm
(n)
Generative cell
Tube cell
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
Stigma
Megasporangium
(n)
Pollen
tube
Sperm
Surviving
megaspore
(n)
Female gametophyte
(embryo sac)
Antipodal cells
Polar nuclei
Synergids
Egg (n)
Egg
nucleus (n)
Pollen
tube
Sperm
(n)
Discharged
sperm nuclei (n)
Pollen
tube
Style
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