Lesson 1 notes - Lesson 1 Evolutionary Solutions to Terrestrial Environments in Plants Green plant phylogeny Green algae and land plants share a common

Lesson 1 notes - Lesson 1 Evolutionary Solutions to...

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Lesson 1: Evolutionary Solutions to Terrestrial Environments in Plants Green plant phylogeny Green algae and land plants share a common ancestor o Collectively called green plants All green plants are photoautotrophic but not all photoautrophs are green plants o Red and brown algae are excluded Two major groups of green algae o Chlorophytes – never made it to land o Charophytes – sister group to all land plants DNA evidence points to a single common ancestor to all land plants o An ancestoral charophytes species gave rise to land plants Streptophytes include both charophytes and landplants Land plants have multicellular haploid and diploid stages and diploid embryos o These features are not found in the charophytes Challenges to terrestrial life Two major challenges to terrestrial life availability to water o Plants living in water have easy access to water for most of their cells and are protected from the evaporative demand that air imposes on body surfaces Protection from desiccation and transport of water were challenges plants faced when they moved onto land This figure shows a diagram and a micrograph of an angiosperm leaf illustrating some of the adaptations land plants evolved in response to some of these challenges Angiosperms most highly evolved land plants o Less evolved groups possess some of these adaptations To protect against desiccation: o Cuticle – waxy covering on the exposed surfaces Relatively water proof material prevents water loss but also limits gas exchange o Stomata – small openings in the leave surfaces Solve the gas exchange problem 2 nd major issue: Transport (tissues) o Only source of water of terrestrial plants comes from the soils they are anchored in o Land plants must transport the water absorbed from the soil throughout the plant body o Tracheophytes have Tracheids – specialized cells for transport of water and minerals o Xylem – water transport system in tracheids o Phloem – food conducting system in tracheids
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Haplodiplontic life cycle: Alternation of generations All plants have a haplodiplontic life cycle – one in which both haploid and diploid stages are multicellular The haploid multicellular gametophyte generation alternates with the diploid multicellular sporophyte generation Gametophyte means gamete plant – haploid o Produces gametes by mitosis Fusion of gametes – fertilization forms the zygote
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  • Spring '08
  • GEORGESIMMONS
  • Biology, land plants

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