Transcript SHOW-5-2005
Page 518, Figure 25.9 Photosynthesis by Purple Bacteria Protists: •Domain Eukarya •Some Autotrophic (photosynthetic), some not •Aquatic •Greater part of life cycle as Haploid Bryophytes Sporophyte ↑ Liverwort Moss → Gametophyte Ferns & Fern Allies: Fossil 230 million years old China Horsetail The Seed Plants All plants that produce seeds are either Gymnosperm = “naked seed” or Angiosperm = “covered seed” Most gymnosperms occur in areas that are: very cold (like the forests of Canada or Alaska) or very dry (like deserts). There aren’t many gymnosperms in tropical regions (which have warm temperatures, and plenty of moisture). Gymnosperm leaves are usually tough and leathery and shaped like: Needles or Scales or Fronds But there are some exceptions! Gnetum Ginkgo Gymnosperms are usually perennials (live many years)…so are trees or shrubs. Gymnosperms tend to be evergreen. Although the leaves (be they needles, scales, etc.) do fall off, they do so continuously instead of on any set schedule like you see with many deciduous (Angiosperm) trees and shrubs. In Gymnosperms, the reproductive structures are not called “flowers” They are “cones” Cones are usually unisex.... Either male or female Cones are often tough, and not very colorful, and can be: papery or woody or berry-like Most gymnosperms are wind-pollinated (and can cause allergies for some people). …females produce a “pollination droplet” which catches pollen grains to increase odds of fertilization. Insect pollinators are not required. Gymnosperms are generally considered to be more ancient than Angiosperms ...this primarily comes from fossil evidence Gymnosperms were the most common plants during the “Age of the Dinosaurs” (65 to 250 million years ago) ....although there were some Angiosperms during this period they didn’t become real abundant until about 60 million years ago. Mostly Cycads at that time What advantage do Angiosperms have that Gymnosperms don’t have? Angiosperms often have shorter life spans so they can grow faster, and reproduce more (before being eaten by animals). This shorter life cycle would allow faster evolution, because there are more generations. Plus, when insect pollination came on the scene there was more opportunity for plants to evolve different mechanisms for attracting insects …..not only to pollinate them, but also to eat and disseminate the fruit This may help explain why there are only 760 species of Gymnosperms while there are about 250,000 species of Angiosperms currently on the planet. There are 4 phyla of Gymnosperm: 1) the Conifers 2) the Cycads 3) Ginkgo biloba (a single species) 4) the Gnetophytes CONIFERS: Juniper Cypress Fir Cedar Sequoia Redwood Pine Hemlock Larch Arborvitae Yew CYCADS: the palm-like gymnosperms Ginkgo biloba Gnetophytes: Ephedra Welwitschia Gnetum Only 1 species...it grows only in the desert of Namibia...can live 1000 years...gets its water mostly from fog Welwitschia mirabilis Durio zibethinus An Angiosperm Native to Borneo