Plants Part 2 - Life Cycles

what are the functions of life cycles of sexually reproducing eukaryotes?

• increasing genetic variability & the # of individuals

• dispersing individuals

what are the 3 innovations of plant reproduction in dry conditions

1. spores resist drying b/c of sporopollenin

2. gametes produced in complex, multi-cellular structures

3. embryos retained & nourished by the parent plant

sporopollenin

tough coat that prevents dessication

gametangia

specialized structures for producing gametes

antheridium

sperm-producing gametangia

archegonium

egg-producing gametangia

what was a key event in land plant evolution

the retention of embryos

what do all land plants that undergo alternation of generations have?

gametophyte & sporophyte

gametophyte

multicellular haploid phase

sporophyte

multicellular diploid phase

what are the types of reproductive cells that connect two phases of the life cycle

gametes & spores

what is the first event of alternation of generations

sporophyte produces haploid spores by meiosis

what is the second event of alternation of generations

spores germinate & divide by mitosis & develop into multicellular, haploid gametophytes

what is the third event of alternation of generations

gametophytes produce unicellular haploid gametes by mitosis

what is the fourth event of alternation of generations

two gametes unite during fertilization forming a diploid stage

what is the fifth event of alternation of generations

zygote divides by mitosis & develops into a multicellular, diploid sporophyte

what are zygotes & spores

single cells that divide by mitosis to form a multicellular individual

zygotes

• diploids that develop into sporophytes

• produced by the fusion of 2 haploid cells (gametes)

spores

• haploids that develop into gametophytes

• produced by meiosis inside sporangia

how is the life cycle in nonvascular plants

gametophyte-dominant life cycle

how is the life cycle in ferns & other vascular plants

sporophyte-dominant life cycle

• gametophytes of gymnosperms & angiosperms are microscopic

heterospory

production of 2 distinct types of spores by different structures called homosporous & heterosporous

homosporous

• producing a single type of spore that develops into bisexual gametophyte

• all nonvascular & most seedless vascular plants

bisexual gametophyte

• can self-fertilize & produce offspring

• produces egg & sperm

heterosporous

• has 2 distinct types of spore-producing structures called microsporangia and megasporangia

• seed plants

microsporangia

produce microspores that develop into male gametophytes that produce sperm

megasporangia

produce megaspores that develop into female gametophytes that produce eggs