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22.1 Plant Life Cycles
KEY CONCEPT
All plants alternate between two phases in their life
cycles.
22.1 Plant Life Cycles
Plant life cycles alternate between producing spores and
gametes.
• A two-phase life cycle is called alternation of generations.
– haploid phase
– diploid phase
– alternates between
the two
SPOROPHYTE
PHASE
fertilization
meiosis
GAMETOPHYTE
PHASE
22.1 Plant Life Cycles
• The spore-producing plant is the mature sporophyte.
– sporophyte phase is diploid
– begins with fertilized egg
– spores produced through
meiosis
• The gamete-producing plant is
the mature gametophyte.
SPOROPHYTE
– gametophyte
PHASE
fertilization
phase is haploid
GAMETOPHYTE
– begins with spore
PHASE
– gametes
produced through
mitosis
meiosis
22.1 Plant Life Cycles
Life cycle phases look different among various plant
groups.
• 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
Through
22.1
Plant •2)
Life
Cycles
gametophy water, sperm
tes grow
from the male
near the
gametophyte
ground
will swim to the
(haploid
female
stage)
gametophyte to
create a diploid
zygote
•sporophyte
•3) Diploid
sporophyte will
grow from the
gametophyte
where the
zygote is
located
•.
•.•.
•gametophyte
•4) Sporophyte
will create and
release haploid
spores
•5)
Spores
•6) The
22.1
Plant Life Cycles
land and
process
grow into
repeats
new
. gametophy
tes
•gametophyte
•ground
22.1 Plant Life Cycles
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
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
22.1 Plant Life Cycles
• The sporophyte is the dominant phase for seedless
vascular plants.
– Fern spores form in sacs, sori, on underside of mature
sporophytes (fronds).
sporophyte (2n)
sori
22.1 Plant Life Cycles
– A fern gametophyte, or prothallus, produces sperm
and eggs.
gametophyte (1n))
rhizoid
– A zygote forms on the prothallus, growing into the
sporophyte.
•1)
Sporophyte
creates
and releases haploid spores
22.1
Plant Life
Cycles
•.
•.
•. •.
•Adult
•Sporophyte
(diploid)
•ground
•2)
Spores
landLife
in the
soil
22.1
Plant
Cycles
•ground
•3)
From
the haploid
spores, a prothallus (haploid gametophyte)
22.1
Plant
Life Cycles
grows in the soil
•
-- Rhizoids anchor
•Let’s zoom in
•ground
•4)
Sperm
swim
through
water from the antheridium to the
22.1
Plant
Life
Cycles
archegonia
•Let’s zoom back out
•5)
Diploid
sporophyte
(fiddlehead) grows from the prothallus
22.1
Plant
Life Cycles
•-- prothallus eventually dies
•ground
•6)
Fiddlehead
uncurls
into fronds of ferns.
22.1
Plant Life
Cycles
•7) Cycle repeats
• -- Sporangia creates spores to be released
•.
•.
•.
•.
•ground
22.1 Plant Life Cycles
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
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
22.1 Plant Life Cycles
Conifer Life Cycle
22.1 Plant Life Cycles
• The sporophyte is the dominant phase for seed plants.
22.1
Plant
Cycles
1) Male
and Life
female
seed cones grow in adult sporophytes
•2) Pollen grains released from the male seed cones
22.1 Plant Life Cycles
-- Pollen is the male gametophyte
•Let’s zoom into the female seed cone
22.1 Plant Life Cycles
•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)
22.1
Cycles
•7) AfterPlant
seedsLife
harden,
the cone
reopens and the seeds are released
22.1 Plant Life Cycles
•8) Seed will land
•ground
22.1 Plant Life Cycles
•9) Seedling grows into (sporophyte)…the cycle repeats
•ground
22.1 Plant Life Cycles
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
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
1/--страниц
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