1. KEY CONCEPT All plants alternate between two phases in their life cycles.

2. 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
fertilization
meiosis
SPOROPHYTE
PHASE
GAMETOPHYTE

3. 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.
gametophyte phase is haploid
begins with spore
gametes produced through mitosis
fertilization
meiosis
SPOROPHYTE
PHASE
GAMETOPHYTE

4. 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)
gametophyte (1n)
capsule
spores (1n)

5. 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
gametophyte

6. 5) Spores land and grow into new gametophytes 6) The process repeats. . . . .
ground
gametophyte

7. 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

8. A fern gametophyte, or prothallus, produces sperm and eggs.
gametophyte (1n))
rhizoid
A zygote forms on the prothallus, growing into the sporophyte.

9. . . . . 1) Sporophyte creates and releases haploid spores ground Adult
Sporophyte (diploid)
ground

10. 2) Spores land in the soil. . . .
ground

11. 3) From the haploid spores, a prothallus (haploid gametophyte) grows in the soil
-- Rhizoids anchor
Let’s zoom in
ground

12. 4) Sperm swim through water from the antheridium to the archegonia
Let’s zoom back out

13. 5) Diploid sporophyte (fiddlehead) grows from the prothallus
-- prothallus eventually dies
ground

14. 6) Fiddlehead uncurls into fronds of ferns.
7) Cycle repeats
-- Sporangia creates spores to be released . . . .
ground

15. The sporophyte is the dominant phase for seed plants.
pine trees are typical seed plant sporophytes
female spores produced in female cones
male spores produced in male cones
male spores develop into pollen grains, the male gametophytes
female spores develop into female gametophytes that produce eggs
sperm from pollen travel down pollen tube toward egg
fertilized egg develops into embryo
ovule develops into protective pine seed

16. The sporophyte is the dominant phase for seed plants.

17. 1) Male and female seed cones grow in adult sporophytes

18. 2) Pollen grains released from the male seed cones
2) Pollen grains released from the male seed cones -- Pollen is the male gametophyte
Let’s zoom into the female seed cone

19. 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)

20. 7) After seeds harden, the cone reopens and the seeds are released

21. 8) Seed will land
ground

22. 9) Seedling grows into (sporophyte)…the cycle repeats
ground