Plant Diversity What to know from Ch 29, 30, 35

General Characteristics of Plants All plants are: Eukaryotic Autotrophic Multicellular Cell Walls with cellulose Chloroplasts w/ chlorophyll a, b, and carotenoids May have waxy cuticle to prevent water loss. Stomata allow gas exchange. Plants probably evolved from charophytes (which evolved after green algae: See cladogram at end of PPt) Chloroplast similarity Biochemical similarities Cell Wall similarities

Charophytes vs. Plants No alternation of generations No cuticle needed Jacketed gametes No protection of embryos Alternation of generations Cuticle (prevents water loss/dessication) Jacketed gametes (protects from dessication) Protected embryo (protects from dessication)

Alternation of Generations Sporophyte (2N) Mitosis Meiosis Zygote (2N) Spores (N) fertilization Gametes (egg & sperm Gametophyte (N)

Evolutionary Trend zygote SPOROPHYTE (2n) GAMETOPHYTE (n) GREEN ALGA BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM

Classifying Plants Plants can be divided into 2 major categories based on their characteristics: Nonvascular Plants Do NOT have specialized tissues to transport water and nutrients Instead, these plants transport water from cell-to-cell by osmosis Vascular Plants Have specialized tissues to transport water and nutrients in plants Xylem – carries water upward from roots in angiosperms. Tracheids (smaller tubes) in Pteridophytes (ferns) and Gymnosperms Phloem – carries nutrients and carbohydrates produced by photosynthesis

Nonvascular Plants (Bryophytes) Again, these plants do not have specialized tissues to transport water and nutrients and instead rely on osmosis Thus, these plants must be small Why? Major types of bryophytes (nonvascular plants): Mosses Liverworts Hornworts

Nonvascular Plants/ Bryophytes Mosses Have rhizoids that anchor them to the ground (instead of roots) Depend on water for fertilization The sperm must swim to the egg Therefore, nonvascular plants must live in MOIST environments Gametophyte is the dominant phase of the life cycle

Moss/ Bryophyte Life Cycle Zygote grows, develops into a sporophyte while still attached to gametophyte. mature sporophyte zygote Diploid Stage Fertilization Meiosis Haploid Stage Spores germinate. sperm-producing structure male gametophyte egg-producing structure female gametophyte

Vascular Plants/Tracheophytes Reminder: Vascular plants have specialized tissues to transport water and nutrients in plants Xylem & phloem Vascular plants (tracheophytes) can be divided into 2 categories: Seedless vascular plants Seed (vascular) plants

Seedless Vascular Plants Have true roots, leaves, and stems Consist of ferns, club mosses, and horsetails

Seedless Vascular Plants (Pteridophytes) Ferns – A Close Up Diploid sporophyte is the dominant stage (gametophyte is underground and inconspicuous) Have rhizomes, which are underground stems Fronds: large “leaves” where spores develop Develop spores in sporangia on underside of fronds Reproduce using spores A sorus (plural: sori) is a cluster of sporangia

Fern Life Cycle Sporophyte still attached to gametophyte sorus zygote rhizome Diploid Stage fertilization meiosis Haploid Stage Spores are released Spores develop egg sperm mature gametophyte Spore germinates

Seed (Vascular) Plants Have true roots, leaves, and stems Have the ability to form seeds, which are used for reproduction Seed plants are the most dominant group of photosynthetic organisms on land There are 2 types of seed (vascular) plants: 1. gymnosperms 2. angiosperms

Seed (Vascular) Plants Gymnosperms = “cone bearers” “naked seeds” – not enclosed in ovaries Bear seeds directly on the surfaces of cones Cones = sporophyte structures that produce gametophytes (gametes). Seed (diploid) is the result of fertilization Coniferous trees are the major example Pines, junipers, spruces, etc.

Pine Life Cycle section through one ovule surface view of one cone scale (houses two ovules) Pine Life Cycle ovule surface view of one cone scale (houses a pollen-producing sac) mature sporophyte section through a pollen-producing sac seed coat zygote seeding embryo Diploid seed fertilization meiosis pollen tube Haploid microspores form eggs sperm-producing cell megaspores form pollination female gametophyte

Seed (Vascular) Plants Angiosperms = flowering plants Seeds are enclosed by an ovary Flowers are reproductive organs Evolutionary advantage  attract pollinators Flowering plants contain ovaries Ovaries surround and protect seeds Ovary develops into a fruit after fertilization & helps with seed dispersal when eaten Examples: Maple trees, tulips, grass

Flowering Plant Life Cycle (more detail in later chapter) sporophyte Flowering Plant Life Cycle (more detail in later chapter) Diploid Double fertilization Meiosis Meiosis Haploid mitosis without cytoplasmic division microspores pollination two sperm enter ovule female gametophyte

Plant Cell Types- NO (except mesophyll/parenchyme) parenchyma (aka mesophyll) Least differentiated & most abundant Photosynthetic Ex. leaf tissue sclerenchyma reinforced, tough cell walls No longer growing Ex. Wood, nutshells collenchyma support Ex. Celery strings

zygophytes, related groups Evolutionary Tree for Plants Nested monophyletic groups flowering plants green algae zygophytes, related groups charophytes bryophytes lycophytes horsetails ferns cycads ginkgos conifers gnetophytes seed plants euphyllophytes embryophytes (land plants) vascular plants (closely related groups)

*NOTE: Mesophyll aka parenchyme LEAVE STRUCTURE