alternation of generations

oogamous

Gametes are of different sizes One is small and motile (male) One is large and non-motile (female)

gametic meiosis

The organism is basically diploid, only producing haploid gametes for reproduction. These gametes come together, restoring the diploid state. characteristic of animals (us!) and some protists. In gametic meosis, gametes are the only haploid cells. Now in several different lineages - the zygote began dividing mitotically rather than meotically - giving rise to an organism composed of diploid cells that underwent meiosis later.

gametangia

a cell or multicellular structure where gametes are made

ulva

a green algae genus containing the "sea lettuces" an example of isomorphic generations each cell contains one nucleus and one chloroplast thallus is 2 cell layers thick Gametophyte produces haploid gametes via mitosis in structures called gametangia (note the gametes have flagella) Gametes unite to form a zygote, which divides by mitosis to produce the sporophyte Sporophyte makes flagellated spores ("zoospores") via meosis in structures called sporangia Spores divide by mitosis to produce new gametophytes

gametangia

a structure found on the gametophyte where gametes are made; it shares 1n ploidy with the gametophytye - the gametes it makes by mitosis are 1n

sporangia

a structure found on the sporophyte where spores are made; it shares 2n ploidy with the sporophyte - the spores it makes by meosis are 1n

sporic meiosis

alternation of generations an alternation of multicellular forms - one generation is diploid, the other is haploid. One produces haploid spores, the other haploid gametes. meosis doesn't produce gametes straight away. Instead it produces haploid spores, which divide and grow into multicellular haploid organisms that eventually produce gametes characteristic of plants and many algae.

sporophyte

diploid generation in alternation of generations makes spores (haploid) by meiosis dominant in vascular plants

anisogamous

motile gametes are of different sizes

isogamous

motile gametes are of identical sizes

oogonium

produces female gametes in many algae, fungi, bryophytes, ferns, and primitive vascular plants

antheridium

produces male gametes in many algae, fungi, bryophytes, ferns, and primitive vascular plants

zygotic meosis

the zygote is the only diploid cell. used by fungi and some algae The multicellular stage, if present, is HAPLOID.

spore

Haploid (1n) Divide by mitosis to produce a haploid organism Produced from diploid organism by meiosis

gamete

Haploid (1n) Fuse to produce a diploid zygote Produced by haploid organism by mitosis

gametophyte

haploid generation in alt of generations makes gametes (haploid) by mitosis dominant in nonvascular plants

isomorphic generations

sporophyte and gametophyte look the same (ex: many algae).

heteromorphic generations

the generations (sporophyte and gameophyte) look different characteristic of land plants and some algae In Bryophytes, the gametophyte generation is dominant, while in vascular plants that sporophyte generation is dominant

life cycle in the first eukaryotes

they were probably haploid and reproduced asexually but one day two fused and underwent meiosis to restore the haploid condition