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Flagellated Sperm:
Bryophytes and
Pteridophytes
Non-Flagellated Sperm:
Gymnosperms and
Angiosperms
BRYOPHYTES→ Mosses → “non-vascular” (No water tubes)
PTERIDOPHYTES → Ferns → “Vascular”…but seedless
GYMNOSPERMS → Conifers → “Vascular” with seeds
ANGIOSPERMS → Flowering Plants → “Vascular” with
seeds and flowers
First Land Plants had no
animal predators!!
Bryophytes - Mosses
Angiosperms – Flowering
Plants
Pteridophytes - Ferns
Gymnosperms
- Conifers 2
Charophyceans
-CLOSEST RELATIVE TO LAND PLANTS!
- A type of green algae most closely related to
land plants
- Exact taxonomic classification is constantly
under debate about WHERE it fits in under
plants
- Most complex traits found in land plants
(related to sexual reproduction,
photosynthesis, etc) evolved first in
charophyceans;
- Analysis of cpDNA (chloroplast DNA) shows
that many characteristics of plant
chloroplasts evolved first in charophyceans
- These organisms gave rise to land plants
Features that CONNECT Charophyceans and Land Plants:
1. Distinctive rings of cellulose-synthesizing complexes
(synthesize the cell wall – normal algae has a linear structure.)
2. Peroxisome enzymes (regular algae lacks these enzymes)
3. Flagellated sperm
4. Formation of a phragmoplast (cell plate) during division.
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Land Plants have some characteristics that differentiate them from algae, and even
from their close algal relatives – charophyceans. These characteristics are found in
LAND PLANTS ONLY:
1. Apical Meristems
2. Multi-cellular Embryos (in green algae, embryos are NOT retained in
the parental tissue)
3. Alternation of Generation
4. Sporangia produce spores
5. Gametangia produce gametes
- Archegonia = FEMALE (produces eggs)
- Antheridia = MALE (produces sperm)
Multicellular Embryo – develops from the
zygote; retained by female parent
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Alternation of Generations =
Multicellular Diploid phase
alternates with a Multicellular
Haploid phase; each generation
gives rise to the next
Gametophyte with HAPLOID
cells produces the gametes
(sperm and egg) by Mitosis
Gametes come together
(FERTILIZATION) to produce
the DIPLOID zygote
DIPLOID zygote develops into
the Sporophyte… sporophyte
gives rise to HAPLOID spores
by MEIOSIS
Mitosis in spores gives rise to a
new multicellular gametophyte
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Plant spores are haploid
reproductive cells that
grow into gametophytes by
mitosis.
Sporopollenin makes the
walls of spores very tough
and resistant to harsh
environments.
Multicellular organs called
sporangia are found on the
sporophyte and produce
spores.
Within sporangia, diploid
cells called sporocytes
undergo meiosis and
generate haploid spores.
The outer tissues of the
sporangium protect the
developing spores until
they are ready to be
released into the air.
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A female
gametangium, called
an archegonium,
produces a single egg
cell in a vase-shaped
organ and the egg is
retained within the
base.
Male gametangia,
called antheridia,
produce and release
sperm into the
environment.
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Vascular tissues distribute water and nutrients to
different regions of the plants. They are
organized in vascular bundles. The two main
components are:
-Xylem → dead cells; water and nutrients are
transported UP from the root
- Phloem → alive cells; disperse food (sugar,
amino acids, etc) from the LEAVES to the rest of
the plant
…more on xylem and phloem later
Plants are divided
into vascular and
non-vascular
plants.
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Bryophytes
-Gametophyte is the
dominant phase
-Flagellated Sperm
- The sporophyte depends
on the gametophyte for
nutrition (remains
attached!)
- Usually separate male
and female plants
- Produce many archegonia
(female) and antheridia
(male)
- 3 phyla
- Liverworts
- Hornworts
- Mosses (closest to
vascular plants)
Plants that are non-vascular
lack true roots and leaves.
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Hornworts
- Appear similar to mosses but have
distinctive conical or horn-shaped
sporophytes
- Both Hornworts and mosses appear
to have evolved from liverworts
Liverworts
- The flattened green portions of the plant represent
the non-vascular gametophyte stage, while the
stalked structures are the sporophytes
- Genetic evidence suggests that the Liverworts are
the most ancient Bryophyte group and thus
probably represent the first plants to make the
transition to life on land
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Mosses
- Most closely related to land plants
- The "leafy" green plants near the bottom of the
photo represent the gametophyte stage
-In general, mosses are limited in size to no more
than a few inches, since water must be drawn up
by simple capillary action.
The gametophyte plants produce eggs and sperm
in small sex organs near the apex of the plant
body.
- The stalked capsules represent the sporophyte
stage of the life cycle. The sporophytes grow in
attachment to the gametophytes (and are
nutritionally dependent on them).
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Vascular Plants
Pteridophytes
Gymnosperms
Angiosperms
-Use phloem (food) and xylem(water) for transport in
plants → VASCULAR TISSUE
- Organized in vascular bundles (also called veins)
- The SPOROPHYTE (diploid) is the dominant
generation!
- **Remember- diploid organisms are protected from the
effects of mutation because they have 2 sets of
chromosomes
Three main traits characterize modern
vascular plants:
1. Life cycles with dominant sporophytes,
2. Transport in vascular tissue called
xylem and phloem,
3. Well-developed roots and leaves,
including spore-bearing leaves called
sporophylls.
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- Seedless and vascular
- SPOROPHYTE is dominant phase
- Homosporous = single type of spore; can develop into
EITHER an egg or sperm
- Heterosporous = 2 kinds of spores
- Megaspores = FEMALE gametophyte (haploid)
- Microspores = MALE gametophyte (haploid)
- Produce sori (clusters of sporangia (produces spores) on the underside of leaves)
- Differ from seed plants in their mode of reproduction …they lack flowers and seeds
- Unlike the gymnosperms and angiosperms, the ferns' gametophyte is a free-living
organism
Sori
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Vascular Tissue
-Organized into veins
- Transports materials
between the roots and the
shoots
- 2 main parts:
- Xylem → transports
water “up”
- Phloem → transports
food to roots and nonphotosynthetic parts of
the plant
Phloem  transports
sugars, amino acids, and
other organic products
from the photosynthetic
parts of the plant to the rest
of the plant (source to
sink!); uses sieve tube
elements; cells alive at
functional maturity
In this
picture,
the “S”
stands for
phloem
(sieve
tube
elements)
Xylem 
transports
water and
minerals “up”
from the root;
includes
tracheids and
vessel
elements; cells
are dead at
functional
maturity
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Roots are organs that anchor
vascular plants and enable
them to absorb water and
nutrients from the soil. This
allows the shoot system to
grow taller.
So land plants (except for
bryophytes) have true roots,
stems and leaves because of
the vascular tissue.
Leaves are organs that
increase the surface area of
vascular plants to capture
light.
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 Most
seedless vascular plants are
homosporous, producing a single
type of spore.
 A heterosporous species produces
two kinds of spores:
 Megaspores = develop into
FEMALE Gametophytes
 Microspores = develop into
MALE gametophytes
Sporophylls are leaves
specialized for reproduction.
They greatly vary in structure.
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- The first forests gave rise to modern-day coal.
- In the stagnant waters of the Carboniferous period,
dead plants did not fully decay.
- The organic material turned to thick layers of peat.
Marine sediments piled up on top, and over
millions of years, heat and pressure converted the
peat to COAL.
- It forms in wetlands or peatlands, and it is
sometimes called peat bogs
- Humans still burn 6 billion tons of coal each year.
- Coal, formed from plants that contributed to
global cooling, now contributes to global warming
by returning carbon to the atmosphere.
Peat to Coal
Peat
Peat Bog
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Stomata (gas exchange)
Waxy cuticle (prevents water loss)
Vascular tissue (xylem and phloem)
Seeds
Flowers
In dry environments, larger leaf surfaces are
NOT beneficial because they can lose too much
water through the stomata
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Water conservation was an issue when plants came out of
the water to colonize land, so they had the following
structures to try to prevent dessication (drying out) and
help adapt :
Waxy cuticles  prevent water loss
Stomata  pores on the surface of leaves that function in gas
exchange; controlled by guard cells
 Vascular Tissue  xylem and phloem for transport
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Other adaptations for land existence in addition to vascular
tissue were apical meristems, seeds, and flowers.
If leaves wilt because there isn’t enough water, the stomata
close so there is a decrease in gas exchange and therefore
there is a decrease in photosynthesis
The first land plants didn’t have to deal with animal
predators
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Reproductive ADVANTAGES
of SEED PLANTS:
1. Reduction of gametophyte
2. Evolution of seed
3. Evolution of pollen
1. Reduction of
gametophyte →
The mini female
gametophyte is
retained in the
parental sporophyte
so it does not have to
deal with
environmental stress;
the gametophyte is
NOT free living in
seed plants
(gymnosperms and
angiosperms)
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Most seedless vascular plants are
homosporous, producing a single type
of spore.
 A heterosporous species produces two
kinds of spores:
 Megasporangium produces
Megaspores = develop into
FEMALE Gametophytes
 Microsporangium produces
Microspores = develop into MALE
gametophytes
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Sporophylls are leaves
specialized for reproduction.
They greatly vary in structure.
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2. Evolution of seed →
Spores = single-celled; can be dormant;
develop into gametophytes
Seeds = multicellular; sporophyte (diploid)
embryo and food supply contained in the seed; may
be dormant for years; desiccation resistant, aids in
dispersal of plant;
megasporangium → ovule → seed
3. Evolution of pollen →
Pollen = immature male gametophyte
NO Water required (No flagellated sperm)
Pollen grains are covered with a tough outer
coat containing sporopollenin
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Mature Ovary = FRUIT
-Pollination →
hormonal changes →
Seeds are an important means Ovarian growth into the
of dispersing offspring.
fruit
- The ovary wall
The female part of the plant (carpal/ pistil) becomes a pericarp
(thickened wall of the
contains the style that leads to the ovary.
fruit)
- The ovule/seeds are protected by the
-Helps in dispersal by
ovary
wind and animals
- SEED forms from the OVULE
- FRUIT forms from the OVARY
Definition of Fruit:
- Angiosperm structure that
protects dormant seeds and aids in
dispersal
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Microspores = male gametophytes (form pollen)
Megaspores = female gametophyte (form
embryo sac)
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Seed Plants
-Vascular plants that produce seeds
-Sporophyte = dominant phase
- Two groups:
-Gymnosperms → NO
FLOWERS OR FRUITS; conifers,
cone-bearing (ex. pines); showed
earlier in the fossil record; use
wind-blown seeds for dispersal
- Angiosperms → flowering
plants (Produce flowers and
fruit); most diverse and
geographically widespread;
250,000 known species
Gymnosperms
Windblown
seeds help
with
dispersal!
Angiosperms
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Gymnosperms bear “naked” seeds,
typically on cones. They do NOT have
fruits or flowers
Sprorphyte = Dominant Phase
The Seed is a resistant, dispersible stage
in the life cycle
Pollen brings gametes together (nonflagellated sperm)
Have needle-shaped leaves, which
have thick cuticles and relatively small
surface areas
Conifers belong to the largest
gymnosperm phylum, phylum
Coniferophyta
Coniferous trees are among the largest
and oldest organisms on Earth
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Angiosperms, commonly known as
flowering plants, are seed plants
that produce flowers and fruits.
All angiosperms are placed in a
single phylum, Anthophyta
The flower is the defining
reproductive adaptation of
angiosperms.
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-Flowers are the reproductive
structures in angiosperms
- There are 4 main parts:
- Sepals → at base of flower
before it opens
- Petals → inside the ring of
sepals; bright colors can attract
insects (spread pollen)
- Stamens → MALE reproductive
part; produces microspores (male
gametophytes); consist of
filament (stalk) and anther (makes
pollen)
-Carpals → FEMALE
reproductive part; also called the
PISTILS; produces the
megaspores (female
Sporophylls – leaves specialized for
gametophytes); at the tip they
reproduction; pistils and stamens are
have a sticky stigma that receives
modified sporophylls
the pollen; the style leads to the
ovary at the base
Microspores = male gametophytes (forms pollen)
- SEED forms from the OVULE
Megaspores = female gametophyte (forms
- FRUIT forms from the OVARY
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embryo sac)
Steps of the Cycle:
Male Parts =
1. Anthers produce
microspores
2. Microspores form
pollen
Female Parts =
1. Ovules produce
megaspores
2. Megaspores form
embryo sac
Pollen gets on the
sticky stigma of the
carpal and fertilization
results
Angiosperms are HETEROSPOROUS (they produce both male and female gametes)
Male = Pollen grain (sporopollenin and male gametophyte make up the
pollen grain; the male gametophyte has two haploid cells: generative
cell (divides to form 2 sperm) and a tube cell (produces a pollen
tube))
Female = Embryo sac in the ovule
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Double Fertilization
-Angiosperms do double fertilization
- Creates a triploid central cell
- Function → synchronizes development of food
storage with development of the embryo
-Details →
- 1 pollen grain = 2 sperm
- 1 sperm fertilizes egg → 2n zygote
- 1 sperm fuses with 2 nuclei to form 3n
endosperm (develops into the food supply
for the zygote in the seed)
The pollen is released from the anther
and carried to the sticky stigma at the
Notes:
tip of the carpel.
-Monocots store
The pollen grain absorbs water and
most food in
germinates after adhering to the
endosperm (ex.
stigma of a carpel.
corn)
The tube cell produces a pollen tube
-Dicots transfer their
that grows down within the style of
nutrients from the
the carpel.
endosperm to the
After reaching the ovary, the pollen
cotyledons (seed
tube penetrates the ovule.
leaves) (Ex. beans)
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Humans depend greatly on seed plants as key
sources of food, fuel, wood products, and
medicine.
Angiosperms provide nearly all our food.
Just six crops—maize, rice, wheat, potatoes,
cassava, and sweet potatoes—yield 80% of all
calories consumed by humans.
Many seed plants are sources of wood, which is
absent in all living seedless plants and consists of
tough-walled secondary xylem cells.
Humans depend on seed plants for medicines.
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Although plants are a renewable
resource, plant diversity is not.
The demand for space and natural
resources resulting from the
exploding human population is
extinguishing plant species at a
rapid rate.
This extinction is especially severe
in the tropics, where more than
two-thirds of the human
population lives and where
population growth is fastest.
The loss of plant species is often
accompanied by the loss of insects
and other rain forest animals.
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Relationship between angiosperms and
animals was a mutualistic one – animals got
food and plants got dispersed! 
COEVOLUTION!!
Fossil Record:
Single celled Green Algae  Charophyceans 
Bryophytes  Pteridophytes  Gymnosperms
 Angiosperms
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