Chapter 25: Seedless Plants Flashcards
What are seedless plants, and what are their two main groups?
Seedless plants reproduce via spores instead of seeds.
Two main groups:
- Non-vascular plants (Bryophytes): Lack vascular tissues (e.g., mosses, liverworts, hornworts).
- Vascular plants (Pteridophytes): Have xylem and phloem (e.g., ferns, horsetails, club mosses).
Describe the alternation of generations in seedless plants.
Life cycle alternates between two stages:
- Gametophyte (haploid): Produces gametes (sperm and eggs) via mitosis. Dominant in non-vascular plants.
- Sporophyte (diploid): Produces spores via meiosis. Dominant in vascular plants (e.g., ferns).
Compare non-vascular and vascular seedless plants in structure and habitat.
Trait Non-vascular (Bryophytes) Vascular (Pteridophytes)
Vascular Tissue Absent (rely on diffusion) Present (xylem and phloem)
Size Small (e.g., mosses < 20 cm) Larger (e.g., ferns up to 15 meters)
Habitat Moist environments (prevent drying out) Diverse (forest understory, wetlands)
Name three non-vascular plant groups with examples.
Mosses (Bryophyta): Sphagnum (peat moss), used in gardening.
Liverworts (Marchantiophyta): Marchantia (umbrella-shaped gametophytes).
Hornworts (Anthocerotophyta): Anthoceros (sporophytes resemble horns).
What are fern allies, and name three examples.
Fern allies: Vascular seedless plants closely related to ferns.
Horsetails (Equisetum): Hollow stems with silica; used for scrubbing.
Club mosses (Lycopodiophyta): Resemble mosses but have vascular tissue.
Whisk ferns (Psilotum): Lack true roots/leaves; symbiotic with fungi.
Explain the ecological roles of mosses.
Soil formation: Pioneer species on bare rock/soil.
Erosion control: Stabilize soil with dense mats.
Carbon storage: Peat moss (Sphagnum) stores ~30% of Earth’s soil carbon.
Habitat: Provide microhabitats for insects and microorganisms.
How do ferns reproduce? Describe their life cycle.
Sporophyte phase: Dominant; produces spores via sporangia (often clustered in sori on fronds).
Spore dispersal: Spores germinate into gametophytes (heart-shaped prothallus).
Gamete production: Gametophytes produce sperm (antheridia) and eggs (archegonia).
Fertilization: Requires water for sperm to swim to egg.
New sporophyte: Grows from the gametophyte.
What is peat, and why is it ecologically significant?
Peat: Partially decayed organic material from Sphagnum moss in waterlogged environments.
Significance:
- Stores carbon, mitigating climate change.
- Used as fuel and soil conditioner.
- Forms unique ecosystems (peat bogs).
Why do non-vascular plants require water for reproduction?
Sperm must swim through water to reach eggs (no pollen or seeds).
Limits their distribution to moist habitats (e.g., damp soil, rainforests).
What are rhizoids, and how do they differ from roots?
Rhizoids: Hair-like structures in non-vascular plants (e.g., mosses) that anchor the plant.
Difference: Rhizoids lack vascular tissues and do not absorb water/nutrients like true roots.
How do vascular tissues enable ferns to grow larger than mosses?
Xylem: Transports water/minerals upward.
Phloem: Distributes sugars/organic nutrients.
Allows ferns to grow taller and colonize drier habitats than non-vascular plants.
What human uses do seedless plants have?
Mosses: Peat for fuel/gardening; Sphagnum as surgical dressing.
Ferns: Ornamental plants (e.g., Boston fern); some edible (fiddleheads).
Horsetails: Used in traditional medicine and polishing tools.
What challenges do seedless plants face in dry environments?
Dependence on water for fertilization (sperm motility).
Non-vascular plants risk desiccation without constant moisture.
Vascular plants (ferns) mitigate this with waxy cuticles and stomata.
Why are ferns considered more advanced than mosses?
Ferns have vascular tissues (xylem/phloem) and true roots/leaves, enabling larger size and greater habitat diversity.
Dominant sporophyte stage reduces reliance on gametophytes.
