360 likes | 372 Views
Explore the fascinating world of plants, from Purple Bacteria Protists to Gymnosperms and Angiosperms. Learn about their unique characteristics, life cycles, and reproductive structures, with a focus on Gymnosperms like Conifers and Cycads. Discover the advantages of Angiosperms, the most diverse group of plants, and delve into the taxonomy of Ginkgo biloba and Gnetophytes. Uncover the ancient history and evolutionary adaptations that have shaped plant diversity over millions of years.
E N D
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
Fossil 230 million years old China Horsetail
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.
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
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