Ch 30 Plants 11 19 2012 All green algae and the land plants shared a common ancestor a little over 1 BYA Kingdom viridiplantae Not all photoautotrophs are plants o Red and brown algae is excluded from plants A single species of freshwater geen algae gave rise to the entire population of land plants The green algae split into 2 major clades Chlorophytes never made it to land Protista Charophytes did make it to land sister to all land plants Land plants Have multicellular haploid and diploid stages Trend toward more diploid embryo protection Trend toward smaller haploid stage Haplodiplontic life cycle Multicellular diploid stage sporophyte o Produces haploid spores by meiosis o Diploid spore mother cells sporocytes undergo meiosis in sporangia Produce 4 haploid spores Mirst cells of gametophyte generation o Multicellular haploid stage gametophyte Spores divide by mitosis Produces gametes by meiosis Gametes fuse to form diploid zygote All land plants are haplodiplontic Relative sizes of generations ary Moss o Large gametophyte o Small dependent sporophyte Angiosperm o Small dependent gametophyte o Large sporophyte o Individuals are microscopic o 2 anterior flagella o most individuals are haploid o reproduces asesually and sexually o not haplodiplontic always unicellular Ulva o Multicellular chlorophyte o Haplodiplontic life cycle Chlorophytes Early green algae probably resembled Chlamydomonas reinhardtiii o Gametophyte and sporophyte have identical appearance o No ancestral chlorophytes gave rise to land plants Charophytes Clade of streptophytes Alo green algae Distinguished from What is a plant Multicellular Autotrophic Dominate the land Land plants Share a fresh water algal ancestor Evolved over a 470 million year period Common traits Features needed to exploit terrestrial world Vascular system o Transport of nutrients organic compounds water Water proofing o Prevent desiccation Growth habit supportive structures access to light Reproductive adaptations o Pollen seeds flowers fruit Adaptations to terrestrial life Protection from desiccation Waxy cuticle and stomata o Specialized cells that open small pores through plant through which gas exchange happens Moving water using vascular tissue o Vascular plants have conductive tissues in their stems Xylem conducts water from roots to leaves provides support bark wood for changes in growth habit Phloem conducts food from leaves to roots Haplodiplontic life cycle o Multicellular haploid and diploid life stages Shift to a dominant diploid generation over the evolution of land plants Features evolved gradually o Origin of land plants from green algae o Cuticle to stop desiccation allowed to enter land o Vascular plants arose o Origin of the seed to protect the plant embryo o Emergence of flowering plants Bryophytes Lack vascular tissue non vascular Some adaptations for terrestrial life but not highly adapted Lack true roots leaves and stems Largely confined to moist habitats Small Paraphyletic group no common ancestor Mosses liverworts and Hornworts o Gametophytes are photosynthetic dominant portion of life cycle o Multicellular portion represents a gametophyte formed at the tips of leafy gametophytes Archegonia female gametangia egg Antheridia male gametangia sperm o Lack vascular tissue limited in size o Sporophytes are attached to and nutritionally dependent on gametophytes o Require water to reproduce sexually o Tracheophytes land plants with a vascular system Vascular tissues specialized cylindrical or elongated cells that form a network throughout plant o Xylem conducts water dissolved minerals upward from o Phloem conducts sucrose and hormone signals throughout roots the plant Sporophyte dominates the life cycle o Two main types of Tracheophytes Seedless Vascular Plants Seed Plants gymnosperms angiosperms Division Pterophyta of Tracheophytes Ferns are the most common seedless vascular plants o Most abundant group of seedless vascular plants o About 11 000 living species 75 in the tropics o Life cycle differs from a moss Fern Reproduction Greater development independent and dominance of o Fern sporophytes typically have a horizontal underground fern s sporophyte stem the rhizome Fronds leaves usually develop at the tip of the rhizomes as tightly rolled up coils fiddle heads Roots emerge from the sides of the rhizome o Homosporous most reproducing sporangia in clusters sori o Motile sperm o Water needed for fertilization not spores o Sporophyte dominant portion o Gametophyte photosynthetic small heart or ribbon shaped structure in the soil lack vascular tissue Usually have both archegonia and antheridia o Diploid spore mother cells in each sporangium produces haploid gametophyte cells 2n n Seed Plants Seed plants first appeared about 360 mya o Drought protection o Enhanced dispersal o Dormant phase of the embryo Growth ceases and seed dehydrates can survive better Increase embryo survival by waiting for favorable environmental conditions Dominate the land Main reproductive adaptations o Reduction in size of gametophytes o Protected inside reproductive organs of sporophyte o Not an independent generation o Pollination allows for efficient reproduction Pollen grain male gametophyte Does not need water to reproduce o Seed embryonic plant food protective coat Type of Seed Plants o Gymnosperms Lack flowers naked seeds o Angiosperms Flowering plants covered seeds within the fruit The evolution of Seed Plants First appeared 305 465 mya o Evolved from spore bearing plants known as progymnopserms Success attributed to evolution of seed o Protects and provides food for embryo o Allows the clock to be stopped to survive harsh periods before germinating o Later development of fruits enhanced dispersal Seed o Embryo protected by integument An extra layer or 2 of sporophyte tissue Hardens into seed coat o Megasporangium divides meiotically inside ovule to produce haploid megaspores o Seed plants produce 2 kinds of gametophytes Male pollen grains Not sperm cells multicellular organism that produces sperm Dispersed by wind pollinator no need for water Female develop within an ovule enclosed within diploid sporophyte tissue in angiosperms Gymnosperms Naked seed not packed in sporophyte tissue No flowers or fruit Three divisions in textbook Conifers o Lots of species o Dominant gymnosperm o Did well and spread as Earth became dryer o Do particularly well in cold climates high altitudes Evergreen grow slowly even when cold o Small leaves with waxy
View Full Document
Unlocking...