Plant Diversity I New.pptx

Plant Diversity I  Plant Diversity I I. Adaptations of Plants to Land II. Diversity of Plants III. Non-Vascular Plants IV. Vascular Plants  Learning Objectives 1. Describe the adaptations of plants to land 2. Describe the derived traits of plants 3. Explain the role of vascular tissue...

Plant Diversity I  Plant Diversity I I. Adaptations of Plants to Land II. Diversity of Plants III. Non-Vascular Plants IV. Vascular Plants  Learning Objectives 1. Describe the adaptations of plants to land 2. Describe the derived traits of plants 3. Explain the role of vascular tissues, leaves, roots and seeds in the classification of plant diversity 4. Identify the derived traits of non-vascular plants 5. Explain the gametophyte and sporophyte roles in the life cycle of bryophytes 6. Identify the derived traits of seedless vascular plants 7. Explain the meaning of sporophyte and gametophyte dominant 8. Identify the main phyla of bryophytes and seedless vascular plants  I. Adaptations of Plants to Land A. Shared Traits with Algae Many characteristics of land plants also appear in a variety of algal clades, mainly green algae However, land plants share four key traits with only charophytes – Rings of cellulose- synthesizing proteins – Peroxisome enzymes – Structure of flagellated sperm – Formation of a phragmoplast  Systematists are currently debating the boundaries of the plant kingdom Some biologists think the plant kingdom should be expanded to include some or all green algae Until this debate is resolved, we define plants as embryophytes, plants with embryos B. Derived Traits of Plants 1. Alternation of Generations Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations The gametophyte is haploid and produces haploid gametes by mitosis Fusion of the gametes gives rise to the diploid sporophyte, which produces haploid spores by meiosis  The diploid embryo is retained within the tissue of the female gametophyte Nutrients are transferred from parent to embryo through placental transfer cells Land plants are called embryophytes because of the dependency of the embryo on the parent 2. Sporangia Produces Walled Spores The sporophyte produces spores in organs called sporangia Diploid cells called sporocytes undergo meiosis to generate haploid spores Spore walls contain sporopollenin, which makes them resistant to harsh environments 3. Multicellular Gametangia Gametes are produced within organs called gametangia Female gametangia, called archegonia, produce eggs and are the site of fertilization Male gametangia, called antheridia, produce and release sperm 4. Apical Meristems Plants sustain continual growth in their apical meristems Cells from the apical meristems differentiate into various tissues 5. A waxy cuticle to prevent water loss.  II. Diversity of Plants A. Hypotheses on the Origin of Plants Fossil evidence indicates that plants were on land at least 475 million years ago Fossilized spores and tissues have been extracted from 475-million-year-old rocks B. Vascular Tissues. Land plants can be informally grouped based on the presence or absence of vascular tissue Most plants have vascular tissue; these constitute the vascular plants Nonvascular plants are commonly called bryophytes Bryophytes are not a monophyletic group; their relationships to each other and to vascular plants is unresolved  Seedless vascular plants can be divided into clades – Lycophytes (club mosses and their relatives) – Monilophytes (ferns and their relatives) Seedless vascular plants are paraphyletic, and are of the same level of biological organization, or grade C. Seeds A seed is an embryo and nutrients surrounded by a protective coat Seed plants form a clade and can be divided into further clades – Gymnosperms, the “naked seed” plants, including the conifers – Angiosperms, the flowering plants  III. Non-Vascular Plants A. Bryophytes are represented today by three phyla of small herbaceous (nonwoody) plants – Liverworts, phylum Hepatophyta – Hornworts, phylum Anthocerophyta – Mosses, phylum Bryophyta Bryophyte refers to all nonvascular plants, whereas Bryophyta refers only to the phylum of mosses B. Bryophyte Gametophytes In all three bryophyte phyla, gametophytes are larger and longer- living than sporophytes Sporophytes are typically present only part of the time  A spore germinates into a gametophyte composed of a protonema and gamete- producing gametophore The height of gametophytes is constrained by lack of vascular tissues Rhizoids anchor gametophytes to substrate Mature gametophytes produce flagellated sperm in antheridia and an egg in each archegonium Sperm swim through a film of water to reach and fertilize the egg C. Bryophyte Sporophytes Bryophyte sporophytes grow out of archegonia, and are the smallest and simplest sporophytes of all extant plant groups A sporophyte consists of a foot, a seta (stalk), and a sporangium, also called a capsule, which discharges spores through a peristome Hornwort and moss sporophytes have stomata for gas exchange; liverworts do not D. Ecologic and Economic Importance of Mosses  Some mosses might help retain nitrogen in the soil  Sphagnum, or “peat moss,” forms extensive deposits of partially decayed organic material known as peat  Peat can be used as a source of fuel  Sphagnum is an important global reservoir of organic carbon  IV. Seedless Vascular Plants Living vascular plants are characterized by Life cycles with dominant sporophytes Vascular tissues called xylem and phloem Well-developed roots and leaves and are usually restricted to moist environments Vascular tissue allowed these plants to grow tall Seedless vascular plants have flagellated sperm A. Life Cycles With Dominant Sporophytes In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in familiar ferns The gametophytes are tiny plants that grow on or below the soil surface B. Vascular Tissues Vascular plants have two types of vascular tissue: xylem and phloem Xylem conducts most of the water and minerals and includes dead cells called tracheids Water-conducting cells are strengthened by lignin and provide structural support Phloem consists of living cells and distributes sugars, amino acids, and other organic products C. Roots Roots are organs that anchor vascular plants They enable vascular plants to absorb water and nutrients from the soil Roots may have evolved from subterranean stems D. Leaves Leaves are organs that increase the surface area of vascular plants, thereby capturing more solar energy that is used for photosynthesis Leaves are categorized by two types Microphylls, leaves with a single vein Megaphylls, leaves with a highly branched vascular system E. Sporophylls Sporophylls are modified leaves with sporangia Sori are clusters of sporangia on the undersides of sporophylls Strobili are cone-like structures formed from groups of sporophylls Most seedless vascular plants are homosporous, producing one type of spore that develops into a bisexual gametophyte F. Classification 1. Phylum Lycophyta includes club mosses, spike mosses, and quillworts Club mosses and spike mosses have vascular tissues and are not true mosses 2. Phylum Pterophyta includes ferns, horsetails, and whisk ferns and their relatives They are most diverse in the tropics but also thrive in temperate forests Horsetails were diverse during the Carboniferous period, but are now restricted to the genus Equisetum Whisk ferns resemble ancestral vascular plants but are closely related to modern ferns