HOW PLANTS COLONIZED LAND Plant Diversity I

Fungi EUKARYA Trypanosomes Green algae Land plants Red algae Forams Ciliates Dinoflagellates Diatoms Animals Amoebas Cellular slime molds Leishmania Euglena Green nonsulfur bacteria Thermophiles Halophiles Methanobacterium Sulfolobus ARCHAEA COMMON ANCESTOR OF ALL LIFE BACTERIA (Plastids, including chloroplasts) Green sulfur bacteria (Mitochondrion) Cyanobacteria Chlamydia Spirochetes

Plant Origins Land Plants evolved from green algae more than 500 million years ago. Charophytes: green algae (closest plant ancestor) Evolutionary Lines of Evidence 1. Biochemical similarity 1. Cellulose composition 2. Peroxisomes 2. Both produce cell plates in the same way during cell division 3. Sperm similarity 4. Nuclear and chloroplast genes are similar

Advantages of Land Increased sunlight unfiltered by water More carbon dioxide Fewer predators Soil rich in nutrients

Challenges of Land Lack of water Lack of structural support

Life Cycle of Plants

Gametangia

Plant Evolution

Four Main Groups of Land Plants Non-vascular – mosses, liverworts, hornworts Seedless vascular – ferns, club mosses, horsetails, whisk ferns Gymnosperm – conifers, ginkgo Angiosperms – flowering plants (monocot & dicot)

Bryophytes Mosses, liverworts, and hornworts 1st to exhibit the embryonic condition (male = antheridium; female = archegonium) Flagellated (water) sperm No vascular tissue No lignin (short stature) Haploid gametophyte is the dominant generation

Bryophytes Liverworts Hornworts Mosses Gametophyte is dominant stage of life cycle Non-vascular

Moss Life Cycle Gametophyte  dominant generation  has both sexes and produces gametes  archegonia (eggs)  antheridia (sperm) Fertilization  sperm move along moss to find archegonia Sporophyte  grows on top of gametophyte  sporangia is where spores are produced by meiosis

Evolution of vascular tissue allowed taller growth Lycophytes – club mosses Ferns and horsetails Still require water for sperm to reach the egg Sporophyte-dominant life cycle Meiosis occurs in sporophyte stage termed Sporangea Produce haploid bisexual spores that grow into gametophytes Formed great forests during the Carboniferous period Pterophytes: seedless vascular plants

Life Cycle of Seedless Vascular Plants

Ferns

Fern Life Cycle Sporophyte  produce spores via meiosis  spores develop into young gametophyte Gametophyte  has both sexes and produces gametes  archegonia (eggs)  antheridia (sperm) Fertilization  similar to mosses