Plants Characteristics Plant evolution Lower plants Hornwort Orchid

Plants • • • Characteristics Plant evolution Lower plants Hornwort Orchid

Characteristics of Kingdom • • • Photosynthetic autotrophs Eukaryotic Chemistry same as for green algae * Cell walls * Pigments • Multicellular * Tissues & organs * Embryos

Characteristics of Kingdom • Life cycle – alternation of generations Diploid sporophyte meiosis zygote fertilization gametes Haploid gametophyte spores

The Plant Life cycle • • Asexual reproduction common Sexual cycle involves alternation of two generations * Gametophyte – gametes, dependent on water (at first) * Sporophyte – spores, adapted to dry condition • Trend in evolution – reduction of the gametophyte (increased importance of sporophyte)

Plant spores • • Produced by meiosis from sporophytes Haploid reproductive (dispersive) cells Grow into a gametophyte by mitosis Covered by sporopollenin

Plant gametes • • • Produced by gametophytes by mitosis Eggs & sperm Fertilized egg (zygote) grows into sporophyte Fern egg & sperm

Plant Development • Embryos * Young sporophytes develop from zygotes * Protected and nurtured by parent

• • Plant Body Root / Shoot Meristems * growing points * root/shoot tips * (woody plants) – sideways to form wood * indeterminate growth

Evolved from Charophycean Green Algae • • • Mid Paleozoic Strong similarities Differences A Coleochaete B Parka (Ordovician) From Berkeley Time Machine Chara Coleochaete

Plant classification • Bryophytes – no seeds, no roots, no vascular * Mosses, liverworts, hornworts • Seedless, vascular plants – no seeds * Ferns, horsetails, club mosses, whisk ferns • Gymnosperms - seeds & cones * Conifers, cycads, ginkgo, gnetophytes • Flowering plants – seeds, flowers & fruits * Primitive, Monocots, Dicots

Non-vascular plants “Bryophytes” • • • Mosses, liverworts, hornworts Gametophyte dominant No roots – rhizoids Often dependent on available moisture Occupy ecological niches no other plants do Represent first plants Moss Liverwort Hornwort

Phylum Bryophyta – Mosses • • • Leafy gametophytes Sporophytes with complex teeth Evolutionarily distinct group from other bryophytes

Moss Life Cycle • Sporophyte * Zygote * Embryo nurtured by gametophyte * Mature sporophyte with sporangium • Gametophyte * * Spore Protonema Leafy gametophyte Gametes eggs & sperm

Moss Life Cycle Protonema Male leafy gametophyte Female leafy gametophyte Spores Gametophyte

Moss Life Cycle Sperm from antheridia Leafy gametophytes Egg in archegonium

Moss Life Cycle Meiosis to form spores within sporangium i on i t liza rt e F Young sporophyte Zygote Spore dispersal by wind Embryo

Moss Life Cycle Sperm from antheridia Egg in archegonium Gametophyte n tio a z i il t r e F “First thread” stage Sporophyte M eio Zygote sis Spores Embryo

Moss links • • UBC Moss Class Microscopy UK

Phylum Hepatophyta Liverworts • • • Sporophyte simpler than mosses Leafy Thallose

Phylum Anthocerophyta Hornworts • • • Sporophyte linear tube with meristem at base Thalloid Closest bryophyte to ancestor of other plants

Moss, Rhizomnium

Moss, Tortula, whole leaf

Sphagnum bog

Sphagnum = Peat Moss

Thallose liverwort Marchantia

Leafy liverwort Lophocolea

Hornwort, Anthoceros