Chapter 26: Seed Plants Flashcards
What are seed plants, and what evolutionary advantages do seeds provide over spores?
Seed plants (spermatophytes) reproduce via seeds, which contain an embryo, stored nutrients, and a protective coat.
Advantages of seeds:
- Enhanced survival (protect embryos from desiccation/predators).
- Dormancy allows delayed germination until conditions are favorable.
- Facilitate dispersal (e.g., wind, animals).
Name the two major groups of seed plants and their defining traits.
Gymnosperms (‘naked seeds’):
- Seeds exposed on cones (e.g., conifers, ginkgo, cycads).
- No flowers/fruits.
Angiosperms (flowering plants):
- Seeds enclosed in fruits.
- Flowers for reproduction.
Describe the structure and function of a seed.
Seed components:
- Embryo: Young sporophyte (diploid).
- Seed coat: Protective outer layer (from ovule integuments).
- Endosperm (in angiosperms): Nutrient-rich tissue (triploid).
- Cotyledons: Seed leaves (store/transfer nutrients).
Function: Ensure embryo survival and dispersal.
Compare gymnosperms and angiosperms.
Trait Gymnosperms Angiosperms
Seeds Exposed on cones Enclosed in fruits
Reproduction Wind pollination Animal/wind pollination
Vascular Tissue Tracheids (no vessel elements) Vessel elements in xylem
Examples Pine, spruce, ginkgo Roses, oak trees, grasses
What are the key adaptations that made seed plants dominant on land?
Seeds for embryo protection/dispersal.
Pollen grains (male gametophytes) enable wind/animal pollination (no water required).
Vascular tissues (xylem/phloem) for efficient transport.
Secondary growth (wood) in trees/shrubs.
Explain the life cycle of a gymnosperm (e.g., pine tree).
Sporophyte phase (dominant): Produces male (pollen cones) and female (seed cones).
Pollination: Wind carries pollen to female cones.
Fertilization: Pollen tube delivers sperm to egg (no water needed).
Seed development: Embryo forms inside seed on cone scales.
Dispersal: Seeds released when cones open.
What are flowers, and how do their structures enhance angiosperm reproduction?
Flowers: Reproductive structures of angiosperms.
Key parts:
- Sepals: Protect bud.
- Petals: Attract pollinators.
- Stamens (male): Anther (produces pollen) + filament.
- Carpels (female): Stigma (catches pollen), style, ovary (contains ovules).
Function: Facilitate efficient pollination (animal/wind) and seed protection.
Define double fertilization in angiosperms. Why is it unique?
Double fertilization:
One sperm fertilizes the egg → diploid zygote.
Second sperm fuses with two polar nuclei → triploid endosperm (nutrient storage).
Significance: Ensures endosperm forms only if fertilization occurs, conserving resources.
Compare monocots and eudicots (dicots).
Trait Monocots Eudicots
Cotyledons 1 2
Leaf veins Parallel Netted
Vascular bundles Scattered Ring arrangement
Flower parts Multiples of 3 Multiples of 4 or 5
Examples Grasses, lilies, orchids Beans, roses, sunflowers
What are fruits, and how do they aid seed dispersal?
Fruits: Mature ovaries containing seeds.
Dispersal mechanisms:
- Fleshy fruits (e.g., apples): Eaten by animals, seeds excreted.
- Dry fruits (e.g., dandelions): Wind dispersal.
- Burrs: Attach to animal fur.
How do seed plants interact with pollinators? Provide examples of coevolution.
Coevolution: Mutual adaptation between plants and pollinators.
Bees: Attracted to blue/yellow flowers with UV guides (e.g., sunflowers).
Bats: Pollinate night-blooming flowers with strong scent (e.g., agave).
Hummingbirds: Long beaks for tubular red flowers (e.g., honeysuckle).
What ecological and economic roles do seed plants play?
Ecological:
- Primary producers in food webs.
- Carbon sequestration (forests).
Economic:
- Agriculture: Crops (wheat, rice).
- Forestry: Timber, paper.
- Medicine: Aspirin (from willow bark), taxol (from yew trees).
Why are conifers (gymnosperms) dominant in cold/dry environments?
Adaptations:
- Needle-like leaves reduce water loss.
- Thick cuticle and sunken stomata.
- Resin protects against insects/fungi.
Example: Boreal forests (taiga) dominated by spruce, fir, and pine.
What is secondary growth, and which seed plants exhibit it?
Secondary growth: Increase in stem/root width via vascular cambium (produces wood) and cork cambium (produces bark).
Exhibited by:
- Gymnosperms (e.g., conifers).
- Woody angiosperms (e.g., oak, maple).
How do humans threaten seed plant biodiversity?
Deforestation: Habitat loss (e.g., Amazon rainforest).
Climate change: Alters growth conditions.
Invasive species: Outcompete natives (e.g., kudzu).
Overharvesting: Rare plants (e.g., orchids, ginkgo).
