Gymnosperms

Seed vs Spore

• Seed←reproductive body consisting of a young, multicellular plant and food reserves, enclosed by a seed coat

• Spores←single cell with minimal food reserves

Seed, Ovule, and Integuments

• Ovule↔Structure in seed plants that develops into a seed following fertilization

• Integument↔Outer layer of an ovule that develops into a seed coat following fertilization

Gymnosperm vs Seedless Vascular plants

• Seed

  • Gymnosperm←Any of a group of seed plants in which the seeds are not enclosed in an ovary

  • Gymnosperm seeds are either totally exposed or borne on scales of cones

    • True

    • False

  • radicle→first root that emerges from the seed (embryonic root)

  • Testa→outer most covering of the seed

  • cotyledon→emryonic leaves

  • aril→fleshy structure found in gymnosperms

• Pollen

  • Which of these produce pollen grains.

    • Seedless Vascular Plants

    • Gymnosperms

    • Ferns

    • All of the above

    • None

  • Pollen grain←Structure in seed plants that develops from a microspore into a male gametophyte

Three layers of angiosperm fruit

• exocarp→peel or skin

• mesocarp→flesh

• endocarp→skin of seed

• pericarp→fusion of 3 fruit layers

Examples by Sir Dex

• Yew→Taxus brevifolia

• Example of diciduous tree (angiosperm) Tectona philippinensis→Philippine teak

4 Phyla of Gymnosperms

• Conifers

  • Woody trees and shrubs with needlelike, mostly evergreen tree, and seeds in cones

  • Bristlecone pine→Pinus longevea

• Cycads

  • palmlike of fernlike in appearance

  • pollen and seeds in conelike structures

• Ginkgo

  • Gingko biloba→only surviving species in the phyla

  • deciduous tree

  • female ginkgos produce produce fleshy seeds directly on branches

• Gnetophytes

  • Share traits with angiosperms

  • More efficient water-conducting cells (vessel elements) in xylem

Monoecious vs. Dioecious

• Monoecious↔Having male and female reproductive parts in separate flowers or cones on the same plant

• Dioecious↔Having male and female reproductive structures on separate plants

• Most conifers are {{8521122802526248::monoecious}}

• Cycads, ginkgo, and most gnetophytes are {{4342448362750244::dioecious}}

Life Cycle of Pine

• A pine tree is a mature {{884063769441085::sporophyte}}

• Pine gametophytes←extremely small and nutritionally dependent on sporophyte generation

• Pine is {{9863652457869461::heterosporous}} (spore)

• Produces microspores and megaspores in

  • separate cones

  • the same cone

• Each cone has a {{0852212934776766::sporophyll}}→a leaflike structure that bears spores within a{{46727372789080834:: sporangium (or sporangia)}}

• Pine Spores

  • Male cones produce {{5631909074906845::microspores}} which↔develops into pollen grains, carried by air currents to female cones

  • Female cones produce {{9751881486674977::megaspores}}

    • {{00971580828187324::One of four}} megaspores produced by meiosis develops into a female {{9726926984202936::gametophyte}} within an ovule (megasporangium)

• Pollination

  • Pollination←The transfer of pollen to female cones

  • After pollination a {{8912986702851395::pollen tube}} grows through the {{5479256470891479::megasporangium}} to the egg within the {{5360488244556649::archegonium}}

  • pollen tube←In seed plants, a tube that forms after the germination of a pollen grain and through which male gametes (sperm cells) pass into the ovule

  • After fertilization→The zygote develops into an embryo encased in a seed adapted for wind dispersal

Ecological and Economic Significance of Gymnosperms

• Ecology

  • Conifers are the predominant trees in about 35% of the world’s forests

  • Their roots hold soil in place, reducing soil erosion

  • Conifer forests are important watersheds and provide habitat for many organism

• Economy

  • Recreational uses of forests

    • Camping, backpacking, picnicking, observing nature

  • Products

    • Lumber, medicinal products, turpentine, resins

  • Conifers grown commercially

    • Landscape design, Christmas trees

• Commercially Important Conifers

Evolution of Gymnosperms from Seedless Vascular Plants

• Evolution 1

  • Seed plants evolved from→seedless vascular plants

  • {{4342772522680516::Progymnosperms}} were seedless vascular plants that had megaphylls and “modern” woody tissue

• Evolution 2

  • Progymnosperms probably gave rise to→conifers and seed ferns

    • Which likely gave rise to→cycads and ginkgo

  • Evolution of gnetophytes is unclear

    • Molecular data indicate they are closely related to→conifers