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Plant Life CyclesPlant life cycles alternate between two cycles: Producing spores and producing gametes
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 OneSeedless, nonvascular plants (ex: moss)
• Characteristics:• Live in moist environments• Lack true leaves (only one cell thick)• Rhizoids anchor into soil• Early inhabitant of new ecosystems (succession)• Moss gametophytes look like green carpet • Moss sporophytes shoot up as stalk-like structures
sporophyte (2n)sporophyte (2n)
gametophyte (1n)gametophyte (1n)
Capsule
Spores
Moss Life Cycle Snapshot
• Gametophyte phase– Dominant stage– Carpet of moss growing
near ground• Archegonium:
produces female egg• Antheridium:
produces male sperm– Sperm swims through
water to fertilize egg• Sporophyte phase
– Stalk grows up from the gametophyte (zygote)
– Sporangia (capsule)houses haploid spores
– Spores land, and new gametophyte grows See appendix B in your text book for more info
Gametophyte Phase
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 zygote
4) Sporophyte will create and release haploid spores
.....Sporophyte
eggegg
egg egg
malemale male malefemalefemalefemalefemale
zygotezyg
ote
zygote
zygote
XX - ArchegoniumXY - Antheridium
5) Haploid spores land and grow into new gametophytes
groundGametophyte Phase
6) The process repeats
Plant Life Cycle ComparisonsPlant type Sporophyte Gametophyte Dominant Phase?
Moss Stalk with cup (capsule) at tip, which is where spores are produced by meiosis.
More familiar, carpet-like plant that produces specialized gametes.XX - ArchegoniumXY - Antheridium
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
Group TwoSeedless, vascular plants (ex: ferns)
• Characteristics:• Vascular system allows nutrient transport to greater heights• Rhizoids: Underground stems draw nutrients, like roots• Fiddleheads are uncurled leaves (fronds) • Fern sporophytes are the typical leaf like plant • Fern gametophytes (prothallus) look like a heart
Fern Life Cycle Snapshot• Sporophyte phase
– Dominant stage– Sporangia (spore producing
structure) creates haploid spores
• Sori are clusters of sporangia– Spores released and land
• 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
AdultSporophyte (diploid)
.
..
.
1) Sporophyte creates and releases haploid spores
Ground
Ground
2) Haploid spores land in the soil
Ground
3) From the haploid spores, gametophyte grows in the soil
Let’s zoom in…
4) Sperm swim through water from the male parts (antheridium) to the female parts (archegonia)
Let’s zoom back out…
eggegg
egg
zygote
zygote
zygote
Ground
5) Diploid sporophyte grows from the zygote
sporophyte
Ground
6) Fronds uncurls into leaves.
7) Cycle repeats -- Haploid spores created and released
.
.
..
Plant Life Cycle ComparisonsPlant type Sporophyte Gametophyte Dominant Phase?
Moss Stalk with cup at tip, which is where spores are produced.
More familiar, carpet-like plant that produces specialized gametesXX - ArchegoniumXY – Antheridium
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
Group ThreeSeeded, vascular plants (ex: gymnosperms)
• Characteristics:• Vascular system allows nutrient transport to greater heights• Seeds not enclosed in fruit (angiosperms); produced inside cones
• Advantages of seed plants• Seeds allow for reproduction without free-standing water = Pollen• Seeds nourish and protect the growing plant embryo = Endosperm , seed coat, dormancy• Seeds allow plants to disperse to new places = Wind, water, animals
• Conifer sporophyte is the typical tree like structure • Conifer gametophytes are inside the male/female cones
Cycad Ginkgo
Conifer
What are the other types of gymnosperms?
Conifer Life Cycle Snapshot• Sporophyte phase
– Dominant stage– Cones grow on tree
• Female cones produce egg & seed
• Male cones produce pollen– Pollen reaches end of female
scale and sticks to ovule• Pollen tube grows from
pollen• Sperm travels down pollen
tube (zygote/seed created)• Sporophyte stage restarts
See appendix B in your text book
The sporophyte is the dominant phase for seed plants
1) Male and female seed cones grow on 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
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)
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
9) Seedling grows into (sporophyte)…the cycle repeats
Ground
Plant Life Cycle ComparisonsPlant type Sporophyte Gametophyte Dominant Phase?
Moss Stalk with cup at tip, which is where spores are
produced.
More familiar, carpet-like plant that produces
specialized gametesXX - ArchegoniumXY - Antheridium
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
Male gametophytes are pollen grains
spermFemale gametophytes are microscopic eggs
SPOROPHYTE
Group Four Seeded, vascular plants (ex: angiosperm)
Flowers contain reproductive organs protected by specialized leaves
carpel style
stigma
ovary
stamen
filament anther
petalsepal
• Sepals and petals are modified leaves.• Sepals are outermost layer that protects
developing flower • Petals can help to attract animal pollinators
• A stamen is the male structure of the flower• anther produces pollen grains • filament supports the anther
• The innermost layer of a flower is the female carpel.• stigma is sticky tip • style is tube leading from stigma to ovary • ovary produces female gametophyte
Flowering plants can be pollinated by wind or animals
• Wind pollinated flowers have small flowers and large amounts of pollen.
• Animal pollinated flowers have larger flowers and less pollen. many flowering plants pollinated by animal pollinators
– Pollination occurs as animal feeds from flower to flower– Animal pollination more efficient than wind pollination
Fertilization takes place within the flowerMale gametophytes, or pollen grains, are produced in the anthers.
– Male spores produced inanthers by meiosis
– Each spore divides bymitosis to form twohaploid cells – Two cells form a
single pollen grainPollen grain
AntherStamen
Filament
• 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)
One female gametophyte can form in each ovule of a flower’s ovary
1. Pollen stick to animal or released into wind.
..
3. Pollen tube grows and 2 nuclei transfer into the ovule
Let’s zoom in…
2. Animal finds a new flower to feed on and pollen grains land on the stigma (pollination)
4. Flowering plants go through the process of double fertilization.
femalegametophyte
ovule
egg
spermpolar nuclei
1 sperm fuse with the polar nuclei = triploid (3n) endosperm 1 sperm fuse with the egg = zygote
Double Fertilization
endosperm
seed coat
embryo
Endosperm provides food supply for embryo
5. Each ovule becomes a seed.
The surrounding ovary grows into a fruit.
6. Seeds get dispersed
7. Seed germinates, and the cycle starts over
Ground
Plant Life Cycle ComparisonsPlant type Sporophyte Gametophyte Dominant
Phase?Moss Stalk with cup at tip,
which is where spores are produced.
More familiar, carpet-like plant that produces specialized gametes XX - ArchegoniumXY - Antheridium
GAMETOPHYTE
Fern More familiar, leafy plant with clusters of spore producing sacs (sori)
Haploid plant body 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
Male gametophytes are pollen grains spermFemale gametophytes are microscopic eggs
SPOROPHYTE
Flowers(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