Chapter 29

 500 mya plants and fungi moved from the land to the water  All plants evolved from an aquatic green algae  In Kingdom Plantae, there are 4 main subdivisions: Bryophytes, Seedless Vascular Plants (ch 29), Gymnosperms, and Angiosperms (ch 30)

 Plants and algae share 4 key traits due to their evolutionary origins:  Rose-shaped complexes for cellulose synthesis  Peroxisome enzymes (minimize glucose loss)  Structure of flagellated sperm  Formation of a phragmoplast (helps form the cell plate during mitosis)

 Plants (and not algae) have 5 traits that allowed them to move onto land:  Apical Meristems  Alternation of Generations  Walled spores produced in sporangia  Multicellular Gametangia  Multicellular, Dependent Embryos

 An apical meristem is a localized region of cell division at the tips of roots and shoots.  Mitosis occurs rapidly here, so plants can optimize water and mineral collection from the soil and the atmosphere.

 The life cycle of land plants alternates between a diploid multicellular organism (sporophyte) and a haploid multicellular organism (gametophyte).

 Plant spores are haploid reproductive cells  Through mitosis, they can develop into gametophytes  The diploid sporophyte has multicellular organs called sporangia that produce plant spores  Spores are formed from sporocytes (inside sporangia) that go through meiosis

 Gametes are made in organs called gametangia  Female gametangia are called archegonia  Male gametangia are called antheridia

 Zygotes undergo mitosis to become multicellular embryos called embryophytes, which stay inside the female parent’s tissues  The embryo has special cells called placental transfer cells that enhance the transfer of nutrients from parent to embryo

 Vascular tissue is made up of cells that transport water and nutrients throughout a plant.  Vascular plants either are seedless (mosses, horsetails, and ferns) or have seeds (gymnosperms like pine trees, angiosperms like flowers)  Non-vascular plants include liverworts, hornworts, and mosses

 Bryophytes are non-vascular, seedless plants  Liverworts  Hornworts  Mosses

 Phylum Hepatophyta  Gametophytes are shaped like livers  Common in Northern Hemisphere tropical and subtropical regions

 Phylum Anthocerophyta  Sporophytes are shaped like blades of grass  5 cm high

 Phylum Bryophyta  Gametophytes look like carpets  Sporophytes are elongated and visible to the naked eye

 Gametophytes (the haploid stage) are larger and longer lived than sporophytes (the diploid stage)  Germinating moss spores produce a protonema, a mass of green, branched, one- cell thick filaments.  They absorb water and form buds that produce gametes called gametophores.  The protonema and the gametophore make up the moss gametophyte.

 Gametophytes are anchored by delicate rhizoids (long tubular single celled filaments).

 Bryophytes sporophytes are green and photosynthetic, but remain attached to their parental gametophytes which give them sugar, amino acids, minerals and water.  Sporophytes are simple and small, made up of a foot (absorbs nutrients), a seta (long stalk), and a sporangium (on top of the stalk, makes spores).

 Ferns are vascular plants WITHOUT seeds  They have swimming sperm and need moist environments  Ferns have a life cycle with a dominant sporophyte

 Xylem are tubes that conduct water and minerals in a plant  Xylem is made up of tracheids, tube shaped cells that carry water  Their cell walls are strengthened by ligin  Phloem are tubes that conduct sugar in a plant

 Roots are organs that anchor vascular plants and enable them to absorb water and nutrients from the soil  Leaves are organs that increase the surface area of vascular plants, capturing more solar energy for photosynthesis

 Sporophylls are leaves that bear sporangia (which make spores)  A group of sporangia are called a sorus (sori), and are shaped like cones called strobili.

 Seedless vascular plants, like ferns, lychophytes, and horsetails, formed the first forests  These removed CO2 from the atmosphere and increased levels of oxygen, causing global cooling and glacier formation.  These forests, after millions of years of decay, heat, and pressure, became coal (which now causes global warming).