Download The Plants

The Plants
293,000 species. made of eukaryotic cells; all plants are multicellular; most are large with distinct tissues
(dermal, vascular & ground tissues) and organs; some of the major organs are roots, stems, leaves,
flowers and fruits; they are nonmotile, usually anchored in the ground but some attach to other plants;
have fairly thick, rigid cell walls of cellulose giving most individual cells a square or rectangular shape;
almost all are green; contain the pigment chlorophyll inside organelles called chloroplasts that carry out
photosynthesis. Plants are classified into 4 major groups.
Mosses & Allies
(~23,600 species)
most ancient plants and simplest surviving plants, most are small, inconspicuous and live in moist
habitats; generally poorly adapted to life on land: no vascular tissue, no true organs; distinctive
alternation of generations with asexual sporophyte and sexual gametophyte producing sperm and egg.
Mosses (Phylum Bryophyta) 16,000 species
generally poorly adapted to land, live in dense beds on moist soil, rocks or bark; each individual
plant has tiny rootlike rhizoids for attachment (not to absorb nutrients for the plant); slender
stemlike structure bears leaflike blades; no vascular tissue, therefore no true roots stems or leaves;
gametophyte is the dominant form:
Liverworts (Phylum Hepaticophyta) 9,000 species
small inconspicuous plants; grow on moist soil, rocks, stumps and tree bark; especially common
in coniferous forests; gametophyte body is flattened, branching thallus with umbrella shaped
clusters of antheridia or archegonia; life cycle is similar to mosses
Hornworts (Phylum Anthocerotophyta) 100 species
gametophyte superficially resembles liverwort thallus; found in “disturbed” habitats (eg. fallow
fields, roadsides); after fertilization a spikelike “horn” grows out of thallus
Ferns & Allies
(11,000 species)
mostly terrestrial, a few are aquatic; in temperate regions they typically inhabit swamps and moist areas;
have true vascular tissueshave true roots, stems and leaves; still require water for sexual reproduction;
sporophyte and gametophyte are completely separate plants
Ferns (Phylum Pterophyta) 10,000 species
mostly terrestrial, a few are aquatic; range from tropics to arctic but most are tropical
epiphytes; spore production occurs on underside of leaf in clusters of sporangia called sori
spores germinate into a gametophyte called a prothallium
Whisk Ferns (Phylum Psilotophyta) 12 species
mainly tropical; simple dichotomously branching stems with underground rhizome; small
scalelike leaves; distinctive sporangia producing spores which germinate into prothallium.
Horsetails (Phylum Sphenophyta) 40 species
today consists of a single genus; grow mostly in wet marshy habitats; up to 4 feet tall; on every
continent except Australia; hollow jointed stems are impregnated with silica giving stem a gritty
texture (=scouring rushes); at each joint is whorl of small nonfunctional leaves (megaphylls)
Club Mosses (Phylum Lycophyta) 501 species
ancient group that once were the dominant forests on land; today, common in temperate forests;
many are epiphytic; distinctive alternation of generations; some with two different kinds of spores
Conifers & Allies
(760 species)
have much more efficient vascular tissue than ferns can grow larger, taller; most are trees or shrubs
with needle-like leaves; sexual reproduction only by male and female cones; male cone produces pollen
that is blown by wind to female cone; fertilized egg becomes a naked seed borne on the female cone
Conifers (Phylum Coniferophyta) 590 species
conifers group contains one of world’s most massive organisms & world’s tallest organism:
Coastal Redwood; nearly all are perennial trees & shrubs; in most conifers, leaves are needle or
scale; nearly all conifers are evergreen; many conifers produce resin; no asexual reproductive
organs; greatly reduced alternation of generationsSexual reproduction becomes the main means
of reproduction; sexual reproductive organs are cones; male cones produce pollen; zygote
develops into seed; the seeds are exposed usually on a cone
Cycads (Phylum Cycadophyta) 100 species
cone bearing palmlike plants of tropics and subtropics; living fossils from age of dinosaurs;
similar to conifers but seed structure is more primitive
Ginkgoes (Phylum Ginkgophyta) 1 species
consists of a single species that was once thought to be extinct; today is widely cultivated; with
distinctive fan shaped leaves; as seed matures on female tree the outer fleshy covering gives off a
foul odor
Gnetophytes (Phylum Gnetophyta) 70 species
group of unusual, highly adapted plants in three genera; most efficient vascular tissue of the
conifer group; in some the cone clusters resemble flowers of flowering plants
Flowering Plants
(235,000 species, 90% all plants)
dominant plants in world today90% of all living plant species; highly adaptable vegetative organs;
complex symbioses with fungi, bacteria and animals enhance survival and efficiency; much more efficient
transport tissues; no asexual reproductive organs or spores produced; sexual reproductive organ is the
flower; seeds protected within a fruit
Monocots (Class Monocotyledons) 65,000 species
floral parts in 3’s; leaves are long tapered blades with veins; stems with scattered vascular
bundles; seeds with 1 cotyledon
Dicots (Class Dicotyledons) 165,000 species
floral parts in 4’s and 5’s; leaves broad with netted veins; stems with vascular bundles in
one large circle; seeds with 2 cotyledons