Chapter 29, 30. Diversity of Plants How Plants Colonized the Land 1
The first plants For more than 3 billion years, Earth s terrestrial surface was lifeless life evolved in the seas 1st photosynthetic organisms were aquatic green algae endosymbiosis chlorophytes & charophyceans red & green algae are closest living relatives Volvox Chlamydomonas 2
Chlorophytes 3
Charophyceans Chara Spirogyra Coleochaete 4
Land Plants 500 mya land plants evolved required special adaptations for life on dry land 5
Adaptations of Land Plants Adaptations in growth apical meristem Adaptations in reproduction alternation of generations walled spores multicellular gametangia structures for gamete production multicellular dependent embryos Adaptations against water loss cuticle 6
Apical Meristem Localized regions of cell division at the tips of shoots & roots shoots roots 7
Alternation of generations Alternating multicellular bodies sporophyte = multicellular diploid (2n) formed from fertilization produced from zygote mitosis produces haploid spores through meiosis haploid spores sprout to form gametophyte gametophyte = multicellular haploid (n) produced from sprouting spores produces egg & sperm fuse to form zygote 8
Alternation of Generations diploid haploid 9
Walled spores Spores produced in sporangia adaptation to life on dry land tough & resistant to harsh environments fossil spores fern spore 10
Multicellular Gametangia Production of gametes within multicellular organs egg in archegonium sperm in antheridium 11
Multicellular dependent embryos transfer of nutrients from maternal tissue to embryo embryo of liverwort embryo of angiosperm This is analogous to the nutrient -transferring embryo-mother interface of placental mammals. The m ulticellular, dependent embryo of land plants is such a significant adaptation that land plants are also known as embryophytes 12
Adaptations against water loss cuticle outer waxy (lipid) coating protect from desiccation 13
Land plants 4 major groups Bryophytes mosses & liverworts nonvascular Pteridophytes ferns vascular, seedless Gymnosperm conifers vascular, naked seeds Angiosperm flowering plants vascular, flower, seeds in fruit ~500 mya 14
Plant evolution cladogram ~50 million years between adaptations origin of seed plants (~360 mya) origin of vascular plants (~420 mya) origin of land plants (~500 mya) 15
Bryophytes: mosses & liverworts Characteristics non-vascular no water transport system rhizoids, no true roots motile sperm flagellated sperm lifecycle dominated by gametophyte stage fuzzy moss plant you are familiar with is haploid spores for reproduction haploid cells which sprout to form gametophyte haploid diploid Where must mosses live? 16
Bryophytes: mosses & liverworts 17
Bryophytes: Moss life cycle diploid sporophyte dependent on haploid gametophyte 18
Bryophytes: Moss life cycle 19
Pteridophytes: ferns Characteristics vascular water transport system xylem, phloem, roots, leaves motile sperm flagellated sperm life cycle dominated by sporophyte stage haploid leafy fern plant you are familiar with is diploid fragile gametophyte spores haploid cells which sprout to form gametophyte Where must mosses live? diploid 20
Pteridophytes: ferns Selaginella Psilotum Horsetails Ferns 21
diploid sporophyte diploid sporophyte sori (spore structures) sorus mature sporangium haploid gametophyte 22
Homospory bisexual gametophyte produces both male & female spores 23
Early Pteridophytes: Tree Ferns Carboniferous forest (coal & oil deposits used today) 24
Pteridophytes: tree ferns With fronds like these... 25
Pteridophytes: Fern life cycle 26