22.1 Plant Life Cycles KEY CONCEPT All plants alternate between two phases in their life cycles.
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Transcript of 22.1 Plant Life Cycles KEY CONCEPT All plants alternate between two phases in their life cycles.
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22.1 Plant Life Cycles
KEY CONCEPT All plants alternate between two phases in their life cycles.
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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
fertilizationfertilization
meiosismeiosis
SPOROPHYTE PHASE
GAMETOPHYTE PHASE
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22.1 Plant Life Cycles
– sporophyte phase is diploid – begins with fertilized egg – spores produced through
meiosis
• The gamete-producing plant is the mature gametophyte.
• The spore-producing plant is the mature sporophyte.
– gametophyte phase is haploid– begins with spore – gametes produced through
mitosis
fertilizationfertilization
meiosismeiosis
SPOROPHYTE PHASE
GAMETOPHYTE PHASE
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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)sporophyte (2n)
gametophyte (1n)gametophyte (1n)
capsule
spores (1n)
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22.1 Plant Life Cycles
•gametophyte
•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
•4) Sporophyte will create and release haploid spores
•.•.•.•.•.•sporophyte
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22.1 Plant Life Cycles •5) Spores land and grow into new gametophytes
•.
•ground•gametophyte
•6) The process repeats
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22.1 Plant Life Cycles
Plant Life Cycle ComparisonsPlant 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
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22.1 Plant Life Cycles
sporophyte (2n)sporophyte (2n)
sori
• The sporophyte is the dominant phase for seedless vascular plants. – Fern spores form in sacs, sori, on underside of mature
sporophytes (fronds).
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22.1 Plant Life Cycles
– A fern gametophyte, or prothallus, produces sperm and eggs.
gametophyte (1n))gametophyte (1n))
rhizoid
– A zygote forms on the prothallus, growing into the sporophyte.
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22.1 Plant Life Cycles
•Adult
•Sporophyte
(diploid)
•.
•.•.
•.
•1) Sporophyte creates and releases haploid spores
•ground
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22.1 Plant Life Cycles •.•.
•.
•.
•ground
•2) Spores land in the soil
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22.1 Plant Life Cycles
•ground
•3) From the haploid spores, a prothallus (haploid gametophyte) grows in the soil• -- Rhizoids anchor•Let’s zoom in
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22.1 Plant Life Cycles •4) Sperm swim through water from the antheridium to the archegonia•Let’s zoom back out
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22.1 Plant Life Cycles
•ground
•5) Diploid sporophyte (fiddlehead) grows from the prothallus•-- prothallus eventually dies
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22.1 Plant Life Cycles •6) Fiddlehead uncurls into fronds of ferns.
•ground
•7) Cycle repeats• -- Sporangia creates spores to be released
•.
•.
•.•.
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22.1 Plant Life Cycles
Plant Life Cycle ComparisonsPlant 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
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22.1 Plant Life Cycles
Gymnosperm Life Cycle
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22.1 Plant Life Cycles
• The sporophyte is the dominant phase for seed plants.
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22.1 Plant Life Cycles 1) Male and female seed cones grow in adult sporophytes
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22.1 Plant Life Cycles •2) Pollen grains released from the male seed cones-- Pollen is the male gametophyte
•Let’s zoom into the female seed cone
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22.1 Plant Life Cycles
•3) Pollen grain sticks to the female ovule
•5) Two nuclei transfer into female spore- one fertilizes the egg
•4) Pollen tube grows from the male spore
•6) Diploid embryo develops (sporophyte stage restarts)
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22.1 Plant Life Cycles •7) After seeds harden, the cone reopens and the seeds are released
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22.1 Plant Life Cycles •8) Seed will land
•ground
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22.1 Plant Life Cycles •9) Seedling grows into (sporophyte)…the cycle repeats
•ground
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22.1 Plant Life Cycles
Plant Life Cycle ComparisonsPlant 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
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22.1 Plant Life Cycles
Angiosperm Life Cycle
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
• Wind pollinated flowers- small flowers and large amounts of pollen.
• Animal pollinated flowers- larger flowers and less pollen (more efficient). – many flowering plants pollinated by animal pollinators
Flowering plants are pollinated when pollen grains land on stigma
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
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 twohaploid cells
– two cells form asingle pollen grain
•pollen grain
antherstamen
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
• 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)
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
1. Pollen grains are released
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
2. Pollen grains land on the stigma (pollination)
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
..
3. Pollen tube grows and 2 nuclei transfer into the ovule
Let’s zoom in…
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
3. Flowering plants go through the process of double fertilization. female
gametophyte
ovule
egg
sperm
polar nuclei
• 1 sperm fuse with the polar nuclei = triploid (3n) endosperm• 1 sperm fuse with the egg = zygote
22.2 Flower Life Cycle
Double Fertilization
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22.1 Plant Life Cycles
•endosperm
•seed coat
•embryo
• Endosperm provides food supply for embryo
4. Each ovule becomes a seed.
• The surrounding ovary grows into a fruit.
22.2 Flower Life Cycle
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22.1 Plant Life Cycles
5. Seeds get dispersed
6. Seed germinates, and the cycle starts over
ground
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22.1 Plant Life Cycles
Plant Life Cycle ComparisonsPlant 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 gametophytes sperm, female gameotphytes are microscopic eggs
SPOROPHYTE
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
22.2 Flower Life Cycle