Plant Diversity Chapters 29 & 30 Biology – Campbell Reece

Background  Charophytes are the green algae most closely related to land plants  4 main groups of land plants : Bryophytes – mosses Pteridophytes – ferns Gymnosperms – conifers Angiosperms – flowering plants

Classification of Plants

Evolutionary Adaptations  Vascular tissue – transports water & nutrients throughout the plant  Apical meristems – regions of cell division at the tips of shoots and roots  Multicellular, dependent embryos – the developing embryos are retained within tissues of the female parent

Evolutionary Adaptations cont.  Alternation of generations: Gametophyte – haploid generation during which gametes are formed Sporophyte – diploid generation during which spores are formed

Evolutionary Adaptations cont.  Spores produced in sporangia  Multicellular gametangia where gametes are produced (archegonia – female; antheridia – male)  Cuticle – waxy layer to prevent water loss  Stomata – pores used for gas exchange

Bryophytes  Nonvascular plants – do not contain xylem and phloem  3 phyla: Hepatophyta (liverworts) Anthocerophyta (hornworts) Bryophyta (mosses)  Most grow close to the ground, anchored by rhizoids

Bryophytes

 Gametophyte is the dominant generation  Sporophytes disperse enormous numbers of spores  The sperm are flagellated and must swim through a film of water to reach the eggs  Found in moist alpine, boreal, temperate, tropical forests, and wetlands

Pteridophytes  Seedless vascular plants  Two phyla: Lycophyta (club mosses) Pterophyta (ferns, whisk ferns, & horsetails)  Have true roots with lignified vascular tissue  Microphylls – small leaves with a single unbranched vein  Sporophyte is the dominant life cycle  Formed “coal forests” during the Carboniferous period

Pteridophytes

Homosporous vs. Heterosporous  Homosporous Sporophyte → single type of spore → bisexual gametophyte → eggs and sperm  Heterosporous Sporophyte → megaspore → female gametophyte → eggs Sporophyte → microspore → male gametophyte → sperm  Sperm are still flagellated and must swim in water to reach the eggs

Life Cycle of a Fern

Seed plants  Vascular plants that produce seeds  Includes the gymnosperms & angiosperms  Three important reproductive adaptations: Continued reduction of the gametophyte (microscopic)  All seed plants are heterosporous Development of seeds for dispersing offspring Pollen eliminated the liquid-water requirement for fertilization

Gymnosperms  “naked seeds” Seeds develop on the surface of specialized leaves called sporophylls  Most familiar are the conifers – the cone- bearing plants such as pines  Dominant plant life in the Mesozoic era  There are four phyla of gymnosperms

The 3 Small Gymnosperm Phyla  Ginkgophyta Includes only Ginkgo biloba  Cycadophyta Includes the cycads, which resemble palms  Gnetophyta Consists of 3 genera that are very different in appearance

The 3 Small Gymnosperm Phyla

Phylum Coniferophyta  The largest of the gymnosperm phyla  The cone is the reproductive structure  Examples: pines, firs, spruces, junipers, cedars, and redwoods  Most are evergreens  Where we get much of our lumber and paper pulp  Among the largest & oldest organisms on Earth

Phylum Coniferophyta

Life Cycle of a Pine

Angiosperms  Flowering plants  Vascular seed plants that produce flowers and fruits (as reproductive structures)  All are in a single phylum, Anthophyta  Are the most diverse and geographically widespread of all plants  Marks the transition from the Mesozoic era to the Cenozoic era

Flower  Four types of modified leaves: Sepals – enclose the flower before it opens Petals – brightly colored to attract pollinators Stamens – male reproductive organs  Anther – where pollen is produced  Filament – stalk Carpels (pistils) – female reproductive organs  Stigma – sticky, receives the pollen  Style – stalk that leads to the ovary  Ovary – where the ovules are located

Flower

Fruits  A mature ovary  Protect dormant seeds and aid in their dispersal

Life Cycle of an Angiosperm

 Double fertilization – one sperm unites with the egg forming the zygote; the other sperm fuses with 2 nuclei in the ovule to form the endosperm (food supply)