SEEDLESS VASCULAR PLANTS Packet #70 Chapter #29

THE THEORY OF EVOLUTION CONNECTION Seedless vascular plants arose in the Carboniferous Period 420 – 360 mya Phylum Rhinophyta are known as the oldest seedless vascular plants These organisms left relics, fossils and coals Scientists believe that seed plants were present during this evolutionary time period but were not dominant. Seedless vascular plants became important as the swamps dried up and the global climate cooled.

TYPES OF SEEDLESS VASCULAR PLANTS There are four phyla of seedless vascular plants. Phylum Polypodiophyta Ferns Phylum Psilotophyta Whisk ferns Phylum Equisetophyta Horsetail Phylum Lycophyta Club Mosses

IMPORTANT INFORMATION FOR VASCULAR PLANTS

LEAVES OF VASCULAR PLANTS Microphylls There are two types of leaves that may be found on seedless vascular plants Microphylls Small and have a single vascular strand Club mosses Megaphylls Larger and have more than one vascular strand Plants needed a flattened blade with more stomata for gas exchange Ferns, horsetails and seed plants Microphylls are thought to have evolved as extensions of stems Megaphylls are thought to have evolved from stem branchings that filled in with an additional webbing and perhaps in response to decreases in carbon dioxide

KEYWORDS OF VASCULAR PLANTS Homospory The production of one kind of spore Bryophytes Whisk ferns Horsetails Most club mosses Most ferns Spore gives rise to gametophyte plants that produce both egg and sperm cells.

KEYWORDS OF VASCULAR PLANTS II Heterospory Production of two kinds of spores Microspores Give rise to male gametophytes that produce sperm cells Megaspores Give rise to female gametophytes that produce eggs. Occurs in Certain club mosses Certain ferns ALL SEED PLANTS. The “evolution” of heterospory was an essential step in the evolution of seeds.

SEED VASCULAR PLANTS—FERNS

PHYLUM PTEROPHYTA SUBPHYLUM POLYPOIOPHYTA THE FERNS Largest and most diverse group of seedless vascular plants. Have xylem and phloem tissue Most have true roots More than 12,000 species have been described.

PHYLUM PTEROPHYTA SUBPHYLUM POLYPOIOPHYTA THE FERNS Almost all species are homosporous All have megaphylls. Found primarily in moist tropical habitats Few are aquatic

Comparison to Bryophytes FERNS FEATURES THAT DISTINGUISH FERNS AND OTHER SEEDLESS VASCULAR PLANTS FROM ALGAE AND BRYOPHYTES. Comparison to Bryophytes Ferns have vascular tissue Ferns have a dominant sporophyte generation. As in bryophytes, reproduction in ferns depends on water as a transport medium for their motile sperm cells. What are the similarities between the bryophytes and the seedless vascular plants (ferns)?

REPRODUCTIVE CYCLE OF FERNS

PHYLUM PTEROPHYTA SUBPHYLUM POLYPOIOPHYTA THE FERNS Figure 29.12 Page 585 Ferns display alternation of generation and they have a dominant sporophyte generation Fern bodies consist of a rhizome (an underground stem), roots, and leaves (megaphylls).

PHYLUM PTEROPHYTA SUBPHYLUM POLYPOIOPHYTA THE FERNS Sprophytes have roots, rhizomes and leaves that are megaphylls. Leaves, or fronds, bear sporangia in clusters called sori. Meiosis of sporangia produces haploid spores.

PHYLUM PTEROPHYTA SUBPHYLUM POLYPOIOPHYTA THE FERNS Spore germinates and grow via mitosis into a gametophyte called haploid prothallus. Heart shaped and lacks vascular tissue Anchored by rhizoids Bears antheridia and archegonia Water is still required for transportation of the flagellated sperm to the archegonium Zygote grows into free-living sporophyte plant.

SEEDLESS VASCULAR PLANTS—WHISK FERNS

PHYLUM PTEROPHYTA SUBPHYLUM PSILOTOPHYTA THE WHISK FERNS Simplest vascular plants Lack true roots and leaves Consists of dichotomously branching rhizomes Have erect stems. Homosporous sporophylls.

SEEDLESS VASCULAR PLANTS—HORSETAILS

PHYLUM PTEROPHYTA SUBPHYLUM EQUISETOPHYTA THE HORSETAILS Sporophytes have roots Rhizomes Aerial stems Hollow and jointed Leaves that are reduced megaphylls

SEEDLESS VASCULAR PLANTS—CLUB MOSSES

PHYLUM LYCOPHYTA THE CLUB MOSSES Small plants with rhizomes and short erect branches Extant species have true roots and leaves that are microphylls.

REVIEW

REVIEW Students List potential examination questions and/or here, and on following slides, based on the packet.