Plant Diversity Chapter 33

PHYLOGENY OF LAND PLANTS 33.1 Plant diversity is dominated by angiosperms, which make up about 90% of all extant plant species. 90% of all plants Over 400,000 extant species Over 90% are angiosperms Land plants date back to 465 mya Angiosperms are newest from140 mya Evolution of angiosperms resulted in rapid plant diversity Moist tropical rain forests dominated by angiosperms provided new types of habitats into which other plants could evolve

PLANT DIVERSITY THROUGH TIME

BRYOPHYTES 33.2 Bryophytes diverged before the evolution of vascular plants, and they grow in environments where the ability to obtain water from the soil does not provide a disadvantage. Paraphyletic group; 3 types of bryophytes:;Mosses, Liverworts, Hornworts Small, simple and tough plants; Have either a flattened thallus or upright leafy Bryophytes Seed Vasc Seedless vasc

BRYOPHYTE DIVERSITY “Bryon” means moss; small and tough plants; cannot retain water and cannot deliver water to other plant parts since they do not have vasculature Therefore, need moist environment Main component of life cycle ….the mat of moss….is gametophyte (haploid multicellular generation that produces gametes). Sporophytes are dependent on gametophyte. They live in all temperatures and altitudes, only plant to live in Antarctica. They do not need roots or soil for water; so they live on rocks and tree trunks/branches

BRYOPHYTE SPECIALIZATION Peat moss covers large regions known as peat-lands, and has many practical uses, including fuel

SPHAGNUM MOSS Dominant plant of peat bogs Produces water-holding cells that allow it to soak up water and to acidify environment Helps slow decomposition, so much carbon build-up Bryophytes are epiphytes: a plant that grows high in the canopy of other plants, or on branches or trunks of trees, without contact with the soil

FOSSIL RECORD OF EARLIEST VASCULAR PLANTS 33.3 Spore-dispersing vascular plants are small, often epiphytic plants that grow in moist environments. Seedless vascular plants: Lycophytes Ferns and horsetails First plants to grow tall Have tubes; xylem for water and phloem for food Dominant lifecycle is diploid sporophyte, with a tiny independent gametophye Seedless vascular plants dominated early forests Their growth helped global cooling at end of Carboniferous period Decaying remnants of ferns/first forests eventually became coal

EARLY LYCOPHYTE Early lycophytes: 300 mya Large trees that dominated swamp forests Todays lycophytes: Small plants that grow in forest as epiphytes Occur in shallow ponds

LYCOPHYTE DIVERSITY – LYCOPODIUM

LYCOPHYTE DIVERSITY –SELAGINELLA

LYCOPHYTE DIVERSITY – ISOETES

GIANT LYCOPHYTES

WOODY PLANT EVOLUTION

FERNS AND HORSETAIL DIVERSITY Ferns and horsetails are morphologically diverse Ferns produce large leaves that uncoil as they grow Horsetails have tiny leaves Whisk ferns have no leaves at all

FIDDLEHEAD

TREE FERN AND AQUATIC FERN

STAGHORN FERNS

GYMNOSPERMS 33.4 Gymnosperms produce seeds and woody stems, and are most common in seasonably cool or dry regions. Only 2 extant seed plants: Gymnosperms (with less than 1,000 species) 4 groups of woody plants Cycads Gingkos Conifers Gnetophytes Angiosperms (with more than 380,000 species) Produce seeds (naked or enclosed) and woody stems Common in cool or dry regions

CYCADS Produce large leaves on stout, unbranched stems They now occur in small, fragmented populations….primarily in tropics and subtropics Insect pollinated All form symbiotic relationships with nitrogen-fixing bacteria

GINKGOS Single living species of a group distributed globally before evolution of angiosperms Wind pollinated Produces tall, branched trees

CONIFERS Tallest and oldest trees on Earth Wind-pollinated Mainly evergreen Found primarily in cool to cold environments

GNETOPHYTES Small group Contains only 3 genera and few species Independently evolved xylem vessels

ANGIOSPERMS 33.4 Angiosperm diversity is partly explained by animal pollination.

EARLY-BRANCHING ANGIOSPERM

ANGIOSPERM HISTORY Angiosperm diversity: Low rates of extinction High rates of species formation Plants having flowers can reproduce even if far apart Allows rare species to persist and reproduce Xylem vessels make it possible for angiosperms to have a diversity of form, and to grow toward light 2 diverse groups

MONOCOTS Single cotyledon: embryonic seed leaf Do not form a vascular cambrium i,.r. grasses, coconut palms, bananas, ginger and orchids

 What may have influenced the monocot body?  Creeping, horizontal stems  Loose substrates  Flowing water  Fluctuating water levels MONOCOT BODY

EUDICOTS Pollen grains with 3 openings through which the pollen tube can grow Diverse; legumes, roses, coffee, tea, cacao