Plants Chapter Summary PDF

Manoa Falls Trail, Oahu, Roy V. Rea Plants Chapter Word “Embryophyte” 23/32 Lecture Outline Plant evolution and the plant family tree Derived traits of plants An introduction to the major divisions of plants with some life cycles An introduction to seed plan...

Manoa Falls Trail, Oahu, Roy V. Rea Plants Chapter Word “Embryophyte” 23/32 Lecture Outline Plant evolution and the plant family tree Derived traits of plants An introduction to the major divisions of plants with some life cycles An introduction to seed plants Gymnosperms and the life cycle Angiosperms and the life cycle Sexual and Asexual reproduction *Below ground mass can = above ground Tehandon.com Overview: The Greening of Earth For more than the first 3 billion years of Earth’s history, the terrestrial surface was lifeless Since colonizing land, plants have diversified into roughly 300,000 living species Plants supply oxygen and are the ultimate source of most food eaten by land animals R. Dalhquist Land plants evolved from green algae Green algae called charophytes (Charophyceans) are Archaeplastids and related to land plants Comparisons of both nuclear and chloroplast genes point to charophytes as the closest living relatives of land plants Note that land plants are not descended from charophytes, but share a common ancestor with modern charophytes (probably ~450mya) Chara vulgaris, a Stonewort has flagellated sperm Adaptations Enabling the Move to Land In charophytes, a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out as ponds dry. This polymer also encases spores of land plants The movement onto land by ancient plant ancestors provided unfiltered sun, more plentiful CO2, nutrient-rich soil, and few herbivores or pathogens Land presented challenges: a scarcity of water and lack of structural support; intense UV Embryophytes The accumulation of traits that facilitated survival on land may have opened the way for plants to colonize land 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 (but we keep them separate here…next page) Derived Traits of Plants Four key traits appear in nearly all land plants (embryophytes) but are absent in the charophytes: Alternation of generations (with multicellular, dependent embryos) Walled spores produced in sporangia Multicellular gametangia Apical meristems Many plants have cuticles and mycorrhizae  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  Alternation of Generations 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 that develops from the zygote on the parent plant Furled frond (fiddlehead) Edible fiddleheads J. Herschell A Hawaiian fiddlehead Roy V. Rea Walled Spores Produced in Sporangia 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 Multicellular Gametangia Gametes are produced within organs called gametangia S. Blue Female gametangia, called archegonia, produce eggs and are the site of fertilization Male gametangia, called antheridia, are the site of sperm production and release sperm Apical Meristems Plants sustain continual growth in their apical meristems (at shoot and root tips) Cells from the apical meristems differentiate into various tissues The Origin and Diversification of Plants Fossilized spores Fossilized spores and tissues have been extracted from 475-million-year-old rocks Those ancestral species gave rise to a vast diversity of modern plants Land plants can be informally grouped as vascular plants (tracheophytes with vessels) and non-vascular plants (bryophytes) Please at least know what is in this box here Nonvascular plants – a life dominated by gametophytes Bryophytes are represented today by 3 phyla of small herbaceous (nonwoody) plants: Liverworts, phylum Hepatophyta Hornworts, phylum Anthocerotophyta Mosses, phylum Bryophyta Mosses are most closely related to vascular plants (maybe?) Nonvascular plants – a life dominated by gametophytes, but occasionally a sporophyte shows up Figure 23.11 Colin Chisholm The Ecological and Economic Importance of Mosses Moses are capable of inhabiting diverse and sometimes extreme environments, but are especially common in moist forests and wetlands Sphagnum, or “peat moss,” forms extensive deposits of partially decayed organic material known as peat Sphagnum (and peat) is an important global reservoir of organic carbon  https://www.youtube.com/watch?v=ufwvFOXUCnc Peat Sphagnum moss Freshly cored peat May 2022, Prince Rupert The dark secret of the bog bodies | Tollund man bog body - YouTube Peat “Tollund Man,” a bog mummy A Peat Fire A.E. Hasse Vascular Plants: Origins and Traits Fossils of the forerunners of vascular plants date back about 420 million years These early tiny plants had independent, branching sporophytes Living vascular plants are characterized by: Life cycles with dominant sporophytes Vascular tissues called xylem and phloem Well-developed roots to anchor plants and absorb nutrients and leaves for photosynthesis Life Cycles with Dominant Sporophytes In contrast with bryophytes, sporophytes of seedless vascular plants are the larger generation, as in the familiar leafy fern The gametophytes are tiny plants that grow on or below the soil surface Roy V. Rea Reproductive frond of the Ostrich fern The Fern Life Cycle Roy Rea Roy Rea Classification of Seedless Vascular Plants There are two phyla of seedless vascular plants: – Phylum Lycophyta includes club mosses, spike mosses (neither are true mosses), and quillworts – Phylum Pterophyta includes ferns, horsetails, and whisk ferns and their relatives – These grew to great heights during the Carboniferous Lycophytes Surviving Lycophytes are small herbaceous plants Phylum Pterophyta: Ferns, Horsetails, and Whisk Ferns and Relatives Ferns are the most diverse seedless vascular plants, with more than 12,000 species They are most diverse in the tropics but also thrive in temperate forests Temperate Fern Tropical Fern Pterophytes – Horsetails and Whisk Ferns Horsetails were diverse during the Carboniferous period, but now comprise the genus Equisetum Whisk ferns resemble ancestral vascular plants but are closely related to modern ferns The Significance of Seedless Vascular Plants Ancient Lycophytes and Pterophytes proliferated and grew large during the Devonian and Carboniferous, forming the first forests Increased photosynthesis may have helped produce the global cooling at the end of the Carboniferous period The decaying plants of these Carboniferous forests eventually became coal The Significance of Seedless Vascular Plants 300-360 mya Today at Otway slough  Seed Plants – here we lose the flagellated sperm!! Seeds changed the course of plant evolution, Sunrise seeds enabling their bearers to A 380 myo progymnosperm become the dominant That produced spores, not seeds producers in most terrestrial ecosystems A seed consists of an embryo and nutrients surrounded by a protective coat Seeds came on the scene about 360 mya – 60 million years before gymnosperms and 200 million years before angiosperms Seeds and pollen grains are key adaptations for life on land In addition to seeds, the following are common to all seed plants (i.e., these are derived traits) – Reduced (small) gametophytes – Heterospory (male and female spores) – Ovules – Pollen The gametophytes of seed plants develop within the walls of spores that are retained within tissues of the parent sporophyte Trends in Dominance of Generations Heterospory: The Rule Among Seed Plants The ancestors of seed plants were likely homosporous, while seed plants are heterosporous (for next 3 slides see Fig 23.24) Megasporangia produce megaspores that give rise to female gametophytes (produces and houses the egg/ovum) Microsporangia produce microspores that give rise to male gametophytes (pollen grains) Pollination is the transfer of pollen to the part of a seed plant containing the ovules via air or animals (a film of water is not needed) The Evolutionary Advantage of Seeds A seed develops from the whole ovule which contains a fertilized ovum A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat Seeds provide some evolutionary advantages over spores: – They may remain dormant for days to years, until conditions are favorable for germination (some germinate on parent) – They may be transported long distances by wind or A red mangrove propagule, a live embryo. R.V. Rea animals or water The Life Cycle of a Pine: A Closer Look Staminate (male) cones of lodgepole pine The pine tree is the sporophyte and produces sporangia in male and female cones Small cones produce microspores called pollen grains, each contains a male gametophyte The familiar larger cones contain ovules, which produce megaspores that develop into female gametophytes R. Rea It takes nearly 3 years from cone production to mature seed Clip of pollen fall Germinating radicles (roots) of western red cedar Roy V. Rea Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gymnosperm Evolution Living seed plants can be divided into two clades: gymnosperms and angiosperms Gymnosperms appeared early Bing Cherries, an angiosperm California, R. Rea in the fossil record and domi- nated the Mesozoic terrestrial ecosystems (250-66 mya) Gymnosperms were better suited than nonvascular plants to drier conditions Pollen for dry conditions rather than sperm Mugho Pine, a gymnosperm which need moisture Prince George, R. Rea Gymnosperms bear “naked” seeds, typically on cones The gymnosperms have “naked” seeds not enclosed by ovaries and consist of four phyla: – Cycadophyta (cycads) – Ginkgophyta (one living species: Ginkgo biloba) – Gnetophyta (three genera: Gnetum, Ephedra, Welwitschia) – Coniferophyta (conifers, such as pine, fir, and redwood) Phylum Cycadophyta Cycads have large cones and palm-like leaves These thrived during the Mesozoic, but relatively few (~ 130) species exist today Phylum Ginkgophyta This phylum consists of a single living species, Ginkgo biloba Lived in Driftwood Canyon 50 mya!! It has a high tolerance to air pollution and is a popular ornamental Phylum Gnetophyta This phylum contains 3 genera Species vary in appearance, and some are tropical whereas others live in deserts File:Welwitschia mirabilis00.jpg Gnetum Fig. 23.27  Australia firefighters save rare trees from ruin - YouTube Phylum Coniferophyta Wollemi pine This phylum is by far the largest of the gymnosperm phyla Most conifers are evergreens and can carry out photosynthesis Jane Plaza year round Western juniper Douglas fir Bristlecone pine James Bouldin Roy Rea Angiosperms came on the scene 130-150 mya means seeds in containers (ovaries) Angiosperms are seed plants with reproductive structures called flowers and fruits They are the most widespread and diverse of all Male flowers plants Some are monocots: Fig. 23.29a Female flowers Typha latifolia (Cattail) Roy V. Rea Characteristics of Angiosperms Some are eudicots: Fig. 23.29b All angiosperms are classified in a single phylum, Anthophyta The name comes from the Greek anthos, flower Pollination Pollination is the transfer of pollen from an anther of one flower to the stigma of another Pollination can be by wind, water, bee, moth, butterfly, fly, beetle, bird, lizard, or bat Lizard pollination: the stigma of having food on your face - Moldowan - 2019 - Frontiers in Ecology and the Environment - Wiley Online Library Bumblebee, Aleza Lake Research Forest, R.V. Rea P. Moldowan B. Formed http://www.youtube.com/watch?v=-h8I3cqpgnA&feature=PlayList&p=1CBD5C92C2DF4CF1&playnext=1&playnext_from=PL&index=19 Angiosperm Life Cycle and the 3Fs Ovules enclosed in ovary (container) Angiosperms flower, double- fertilize and fruit Embryo sac = Female gametophyte Figure 32.6 Figure 32.4 http://www.youtube.com/watch?v=H_UyDtaa8Ow Fruit Form and Function A fruit develops from the ovary It protects the enclosed seeds Dry (samara) fruits of Ash R. Rea and aids in seed dispersal by wind or animals A fruit may be classified as dry, if the ovary dries out at maturity, or fleshy, if the ovary becomes thick, soft, and sweet at maturity Fleshy (berry) fruits of huckleberry R. Rea  Fruit dispersal mechanisms include: -Wind -Water -Animals M Parode Roy V. Rea Wonderful Video | Fish eating fruits | Think Big - YouTube Roy V. Rea Plants reproduce sexually, asexually, or both Many angiosperm species reproduce both asexually and sexually Sexual reproduction results in offspring that are genetically different from their parents Asexual reproduction results in a clone of genetically identical organisms Mechanisms of Asexual Reproduction Fragmentation, separation of a parent plant into parts that develop into whole plants, is a very common type of asexual reproduction Beaver-gnawed willow twig, John Prince Research Forest, R.V. Rea Mechanisms of Asexual Reproduction In some species, a parent plant’s root system gives rise to adventitious shoots that become separate shoot systems 3 different aspen clones, Bobtail Lake, R.V., Rea AspenOverview0172.JPG Fig. 38-12 Pando: ~80,000 years old 6000 tones over 100 acres -Burton Barnes who first mapped Pando said it may be a million yrs. old Asexual vs Sexual: Advantages and Disadvantages Asexual reproduction is also called vegetative reproduction and can be beneficial to a successful plant in a stable environment Young Clone Creosote Bushes, Mojave Desert – Probably less than 1,000 yrs old. King Clone Creosote Bush, Mojave Desert – 12,000 yrs old. K. Keid Asexual vs Sexual: Advantages and Disadvantages However, a clone of plants is vulnerable to local extinction if there is an environmental change (e.g., the Lumper potato of Ireland) Sexual Reproduction Sexual reproduction generates genetic variation that makes evolutionary adaptation possible, particularly in unstable environments Offspring are dispersed away from parents However, it is energetically expensive, seedlings are susceptible and only a fraction survive A. Right