Plant Life Cycles Plant life cycles alternate between two cycles: Producing spores and producing...

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)

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..

.

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