Lab 6 Green Algae & Seedless Plants

Green algae (protists) and land plants are ____ that share a common ancestor.

photosynthetic eukaryotes

Similarities of green algae (protists) and land plants

• Photosynthetic eukaryotes

• cells walls made of cellulose

• sugar stored as starch

• chlorophyll as green pigment

What are the 2 evolutionary lineages of green algae

Chlorophytes and charophytes

Charophytes (Chara)

more closely related to land plants because they both have gametangia

• makes and protects gametes

• allows transition from water → land

  • antheridia: make sperm which has flagella

  • archegonia: makes eggs

• Has sterile jacket: protects gametes from drying (water needed to fertilize)

Alternation of generation

Algae, moss, and fern switch between haploid (gametophyte) and diploid (sporophyte)

• for survival and evolution

• importance: helped plants go from water → land

Alternation of generation in algae

• default reproduction is asexual (diploid, 2n)

• switch to sexual reproduction (haploid, n) when in unfavorable conditions → making zygospores which break into spores

What is Spirogyra?

Filamentous, colonial green algae

Contains ribbon chloroplasts 

Asexual Reproduction in Spirogyra

Good conditions (warm, sunlight, nutrients)

• haploid (n) and divide through mitosis/fragmentation → filaments elongate and attach to each other by the cell wall

Bad conditions

• Conjugation: haploid (n) cells come tg to make diploid (2n) zygotes = zygospores

• filaments line up (n) → forming conjugation tube in order to condense (n) (-) strain into (+) strain → zygospore (2n)

• Zygospores does meiosis to make haploid cells (n)

What is this a picture of?

Asexual reproduction in spirogyra

Land plant evolution

• diploid phase as sporophyte

• haploid phase as gametophyte

• terrestrial, primary producer

Mosses: Nonvascular Land Plants

• no vascular tissue, therefore no tissue to transport water and nutrients → make plants grow tall

• Also considered bryophytes

Moss (alternation and generation)

• dominant stage when just leafy (gametophyte)

• Non dominant stage when produces stalks

Moss asexual reproduction

Gamete producing parts: archegonium(egg), antheridium (sperm)

Spore producing parts: capsule which the sporangium (filled with spores) consist inside of the capsule

• spores burst out of capsule

• sporophyte attached to gametophyte

Vascular Land Plants

• sporophyte: dominant stage

• Has vascular tissue (true roots, stems, leaves) to transport water (xylem) and nutrients for plant growth

What is this image of?

gamete producing parts in moss

Ferns (vascular seedless land plant)

• dominant phase: sporophyte (2n) → grows on gametophyte

• Non dominant phase: gametophyte (n) → VERY small/almost microscopic

Ferns Reproduction

Gametophyte (n) - haploid

• antheridia: sperms that has flagella

• archegonia: eggs waiting for sperm for fertilization

• rhizoids: hair like projections for anchoring

Sporophyte (2n) - diploid

• Sorus: cluster of sporangia (found underside of leaf)

• purplish looking cross-sections