Download Plant Life Cycles

Plant Life Cycles
-All plants alternate between two phases in
their life cycles.
Alternation of generations
• Sporophyte (diploid)
– Begins when sperm
fertilizes egg (zygote)
– Diploid zygote
divides by mitosis to
create a mature
sporophyte
– Meiosis produces
haploid cells called
spores
– Haploid spores
released
Alternation of generations
• Gametophyte (haploid)
– Begins with spores
created by meiosis
– Spore grows into
gametophyte
• Male gametophyte
creates sperms
• Female gametophyte
creates eggs
– Sperm & egg create
diploid zygote
(process repeats)
Group 1: Seedless, nonvascular plants
ex: moss
• Nonvascular plants have a dominant gametophyte phase.
– moss gametophytes look like green carpet
– moss sporophytes shoot up as stalklike structures
sporophyte (2n)
capsule
spores (1n)
gametophyte (1n)
1) Moss
gametophytes
grow near the
ground (haploid
stage)
2) Through water,
sperm from the male
gametophyte will swim
to the female
gametophyte to create
a diploid zygote
3) Diploid sporophyte
will grow from the
gametophyte where
the zygote is located
.. .
sporophyte
gametophyte
4) Sporophyte will
create and release
haploid spores
5) Spores land
and grow into
new
gametophytes
6) The process
repeats
gametophyte
ground
Plant Life Cycle Comparisons
Plant type
Sporophyte
Gametophyte
Dominant?
Moss
Stalk with cup
(capsule) at tip,
which is where
spores are
produced.
More familiar,
GAMETOPHYTE
carpet-like plant
that produces
specialized gametes
Fern
More familiar, leafy
plant with clusters
of spore producing
sacs (sori)
Haploid plant body SPOROPHYTE
(prothallus) is size
of a finger nail,
produces both male
and female parts
Conifer
More familiar- like
pine trees,
produces male and
female cones that
produce spores
Pollen grains are
male
gametophytes
sperm, female
gameotphytes are
microscopic eggs
SPOROPHYTE
Group 2: Seedless, Vascular Plants
• Ex: Ferns
Ferns
• Seedless, vascular plants
– Vascular: allows taller growth
• Rhizoids: underground stems draw nutrients
• Fronds: leaves uncurl
– sporangia on underside
• Sori: clusters of sporangia
Fern Life Cycle
• Sporophyte phase
– Dominant stage
– Sporangia produces haploid
spores
– Spores released into air
• Gametophyte phase
– Spore grows into prothallus
• Archegonium: produces
female egg
• Antheridium: produces male
sperm
– Sperm swims to egg
– Zygote begins sporophyte
stage
See appendix B in your text book
1) Sporophyte creates and releases haploid spores
.
.
. .
Adult
Sporophyte
(diploid)
ground
3) From the haploid spores, a prothallus (haploid gametophyte) grows in the soil
-- Rhizoids anchor
Let’s zoom in
ground
4) Sperm swim through water from the antheridium to the archegonia
Let’s zoom back out
5) Diploid sporophyte (fiddlehead) grows from the prothallus
-- prothallus eventually dies
ground
6) Fiddlehead uncurls into fronds of ferns.
7) Cycle repeats
-- Sporangia creates spores to be released
.
.
.
ground
.
Plant Life Cycle Comparisons
Plant type
Sporophyte
Gametophyte
Dominant?
Moss
Stalk with cup
(capsule) at tip,
which is where
spores are
produced.
More familiar,
GAMETOPHYTE
carpet-like plant
that produces
specialized gametes
Fern
More familiar, leafy
plant (fronds)with
clusters of spore
producing sacs
(sori)
Haploid plant body SPOROPHYTE
(prothallus) is size
of a finger nail,
produces both male
and female parts
Conifer
More familiar- like
pine trees,
produces male and
female cones that
produce spores
Pollen grains are
male
gametophytes
sperm, female
gameotphytes are
microscopic eggs
SPOROPHYTE
Group 3: Seed producing, Vascular Plants
• 1) Seed plants don’t depend
on water to reproduce
– Pollen (contains sperm)
combines with egg
– Egg hardens into a seed
• 2) Nourishment and
protection
– Nourish: Nutrients inside seed
for the embryo
– Protection: Hard shell
• 3) Allow dispersal
– Carried by wind, water, animals
Group 3: Seed producing, Vascular Plants
• Type 1: Gymnosperms
• Seeds not enclosed in a
fruit
– produced inside cones
• Cone = reproductive
structure
• Male cones: produce
pollen
• Female cones: produce
eggs and seeds
Group 3: Seed producing, Vascular Plants
• Gymnosperm example:
Conifers
– Cone plants
– Needle-like leaves
– Common to lumber
industry
– Evergreen, Pine,
Redwood, Cedar
• The sporophyte is the dominant phase for seed plants.
1) Male and female seed cones grow in adult sporophytes
2) Pollen grains released from the male seed cones
-- Pollen is the male gametophyte
Let’s zoom into the female seed cone
3) Pollen grain sticks to the female ovule
4) Pollen tube grows from the male spore
5) Two nuclei transfer into female spore
- one fertilizes the egg
6) Diploid embryo develops (sporophyte stage restarts)
7) After seeds harden, the cone
reopens and the seeds are released
8) Seed will land
ground
9) Seedling grows into (sporophyte)…the cycle repeats
ground
Plant Life Cycle Comparisons
Plant type
Sporophyte
Gametophyte
Dominant?
Moss
Stalk with cup
(capsule) at tip,
which is where
spores are
produced.
More familiar,
GAMETOPHYTE
carpet-like plant
that produces
specialized gametes
Fern
More familiar, leafy
plant with clusters
of spore producing
sacs (sori)
Haploid plant body SPOROPHYTE
(prothallus) is size
of a finger nail,
produces both male
and female parts
Conifer
More familiar- like
pine trees,
produces male and
female cones that
produce spores
Pollen grains are
male
gametophytes
sperm, female
gameotphytes are
microscopic eggs
SPOROPHYTE
Angiosperm Life Cycle
Flowering plants are pollinated when
pollen grains land on stigma
• Wind pollinated flowers- small flowers and large
amounts of pollen.
• Animal pollinated flowers- larger flowers and
less pollen (more efficient).
Fertilization takes place within the
flower.
Male gametophytes, or pollen grains, are produced in
the anthers.
– male spores produced in
anthers by meiosis
– each spore divides by
mitosis to form two
pollen grain
haploid cells= pollen grain
stamen
anther
One female gametophyte can form in each
ovule of a flower’s ovary.
o Many cells can be made in the ovule
• one cell becomes the egg
• one cell becomes 2 polar nuclei
the rest die
Polar nuclei (2n)
1. Pollen grains are released
• Wind or animals
2. Pollen grains land on the stigma (pollination)
3. Pollen tube grows and 2 sperm nuclei
transfer into the ovule
..
Let’s zoom in…
22.2 Flower Life Cycle
4. Flowering plants go through the process of
double fertilization.
female
gametophyte
Double
Fertilization
egg
sperm
polar nuclei
ovule
1 sperm fuse with the polar nuclei = triploid (3n) endosperm
1 sperm fuse with the egg = zygote
22.2 Flower Life Cycle
5. Each ovule becomes a seed.
endosperm
seed coat
Endosperm provides food
supply for embryo
embryo
The surrounding ovary grows into a fruit.
6. Seeds get dispersed
7. Seed germinates(sporophyte), and the cycle
starts over
ground
22.2 Flower Life Cycle
Plant Life Cycle Comparisons
Plant type
Sporophyte
Gametophyte
Dominant?
Moss
Stalk with cup (capsule) at
tip, which is where spores
are produced.
More familiar, carpet-like plant
that produces specialized
gametes
GAMETOPHYTE
Fern
More familiar, leafy plant
with clusters of spore
producing sacs (sori)
Haploid plant body (prothallus)
is size of a finger nail,
produces both male and
female parts
SPOROPHYTE
Conifer
(gymnosperm)
More familiar- like pine
trees, produces male and
female cones that
produce spores
Pollen grains are male
SPOROPHYTE
gametophytes sperm, female
gameotphytes are
microscopic eggs
Flower
(angiosperm)
More familiar- apple tree,
peach tree, zucchini,
berries, etc. Contain
flowers that produce male
and female spores
Pollen grains are male
gametophytes  2 haploid
cells = pollen tube + sperm,
Female gametophyte in ovule
 egg + 2 polar nuclei
SPOROPHYTE