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Chapter 28: Microbiology Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prokaryotes Prokaryotes The Prokaryotes • The bacteria (domain Bacteria) and archaea (domain Archaea) are prokaryotes. • Prokaryotes (“before nucleus”) lack a membrane bounded nucleus. Instead, the chromosome is in a nucleoid (false nucleus) that lacks an envelope. • There are no membranous organelles but they do have ribosomes; prokaryotes have a cell wall that may be surrounded by a capsule. • Some prokaryotes move by flagella, and some adhere to surfaces by means of small, hairlike appendages called fimbriae. Generalized structure of a prokaryote DNA motility Gram + or - stain Generalized reproduction of a prokaryote • Prokaryotes reproduce asexually by binary fission, and some can form endospores (anthrax). • In order to accomplish genetic recombination (but not sexual reproduction) bacteria can also reproduce by: conjugation, transformation, and transduction. 1 binary fission 2 conjugation One cell passes DNA to another through a sex “pilus” 3 transformation A bacteria takes up DNA from its liquid surroundings 4 transduction Bacterial viruses carry portions of DNA from one bacteria to another Endospore formation by a prokaryote • Bacteria can “hibernate” to avoid unfavorable environmental conditons. • Hibernation is accomplished by saving a small portion of their cytoplasm and a copy of their DNA, and letting the rest of the cell dry out. They are then encased by three layers of spore coats. When conditions are favorable they rehydrate and form a full bacterial cell again! Prokaryotes, In General • Most bacteria are aerobic, requiring a constant oxygen supply for cellular respiration. • Obligate anaerobes are unable to grow in the presence of oxygen; facultative anaerobes are able to grow in the presence or absence of oxygen. • Bacteria are saprotrophs which externally digest organic compounds and absorb nutrients. Prokaryotes, In General • Bacteria are the decomposers in ecosystems. • Some bacteria are symbiotic and live in association with other organisms. • The bacteria that reside in the human intestinal tract are mutualistic (both benefit); commensalistic (no harm, no benefit) bacteria reside on our skin; and parasitic (only they benefit, we suffer) bacteria cause a wide variety of diseases. • The cyanobacteria are photosynthetic in the same manner as plants. Your Basic Bacteria: • Bacteria occur in three basic shapes: rod (bacillus), round (coccus), or spiral (spirillum). • Based on a dye test, bacteria are either Gram-positive or Gramnegative: Gram-positive bacteria have a thick layer of peptidoglycan on their cell wall; Gram-negative bacteria have a thin layer. Prokaryotes Domain Archaea: The Extremophiles Domain Archaea Adapted to extreme conditions: 1. Plasma membrane contains special lipids to tolerate super high temperatures, as well as modified cell walls compositions. 2. Archaea are NOT photosynthetic. Most gain nutrition through “chemosynthesis”. That is, they can “eat” sulfur. Some excrete methane gas, which is a large contributor to the greenhouse effect (global warming). 3. Archaea have been found living in the great salt lake and dead sea (WAY HYPERTONIC!), hot springs or even submarine thermal vents ( over 200 degrees F!) Chapter 29: Plants Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prokaryotes MONERA ANIMALS PLANTS FUNGI PROTISTA Characteristics of Plants • Plants are multicellular, photosynthetic organisms adapted to a land existence with features such as a waxy cuticle. • Plants resemble algae in using chlorophylls(green) a and b and carotenoid(red) pigments for photosynthesis. • But unlike algae, land must plants protect the developing embryo from drying out by creating a protective coat around them…... (ahhhh, the beginning of seeds and fruit!) • The many divisions of plants can be grouped into three main groups: Nonvascular plants Seedless vascular plants Vascular plants with seeds “Vascular” refers to the tissues and structures that transport water and minerals from the roots to all the tissues. Nonvascular plants Seedless vascular plants Vascular plants with seeds “Vascular” refers to the tissues and structures that transport water and minerals from the roots to all the tissues (namely, the Phloem and Xylem). Nonvascular plants (phylum: Bryophyta) Seedless vascular plants (phylum: Trachophyta) Vascular plants with seeds (phylum: Trachophyta) Nonvascular Plants • PHYLUM: Bryophyta • Nonvascular plants include the liverworts, hornworts, and the mosses. • Nonvascular plants lack vascular tissues throughout their life cycle; they lack true roots, stems, and leaves. • Sperm require water to swim to the egg. Liverworts (a bryophte) • The liverwort has a flattened, lobed body known as thallus. • Rhizoids (rootlike hairs) project from the lower surface into the soil. • Can reproduce asexually by forming gemmae, groups of cells in gemmae cups on the upper surface of thallus. • In sexual reproduction, umbrella-like gametophores produce gametes (star-shaped for female, disc-like for males). Mosses (a bryophyte) • • Following fertilization, the dependent moss sporophyte consists of a foot, stalk, and a capsule or sporangium within which spores are produced by meiosis. They are dispersed by the wind. In the moss life cycle, antheridia produce swimming sperm that use external water to reach the eggs in the archegonia. Life-Style of Nonvascular Plants • Mosses are usually found in moist habitats because the sperm are flagellated. • However, mosses can live in shady cracks of hot, exposed rocks. • Liverworts can only live in a moist environment. Adaptations and Uses of Nonvascular Plants • Sphagnum is bog or peat moss that is used to hold water in garden soil. • Dried peat is sometimes used as fuel. “Vascular” refers to the tissues and structures that transport water and minerals from the roots to all the tissues. Nonvascular plants (phylum: Bryophyta) Seedless vascular plants (phylum: Trachophyta) Vascular plants with seeds (phylum: Trachophyta) Seedless Vascular Plants (phylum: Trachophyta) • Vascular plants have vascular tissue: xylem (conducts water and minerals from the soil) and phloem (transports organic nutrients within the plant). • Vascular plants have true roots, leaves, and stems. • Waxy cuticles prevent leaves from drying out. Seedless Vascular Plants (phylum: Trachophyta) Ferns • Whisk ferns, club mosses, horsetails, and ferns are the seedless vascular plants that were prominent in swamp forests during the Carboniferous period. • Their incomplete decomposition formed much of the coal we burn today. Whisk fern, Psilotum Club moss, Lycopodium Horsetail, Equisetum • Ferns • Ferns have very large fronds (leaves) that grow from a rhizome; ferns have vascular tissue and have true roots, stems and leaves (leaflets). • Sporangia are within sori on the underside of the leaflets of a frond; meiosis occurs within a sporangium, producing spores. • A windblown spore develops into a separate gametophyte, a heart-shaped prothallus, that bears both egg-producing archegonia and sperm-producing antheridia. Fern Life-Cycle Fern diversity “Vascular” refers to the tissues and structures that transport water and minerals from the roots to all the tissues. Nonvascular plants (phylum: Bryophyta) Seedless vascular plants (phylum: Trachophyta) Vascular plants with seeds (phylum: Trachophyta) Vascular Seed Plants • Phyllum: Tracheophyta (Contain Xylem and Phloem) • Both gymnosperms and angiosperms disperse by seeds. • A seed has a seed coat and contains an embryonic sporophyte and stored food that supports growth when the seed germinates. • Gymnosperms have exposed or “naked” seeds. • In angiosperms (flowering plants), seeds are enclosed by a fruit. Gymnosperm diversity (naked-seed plants) Gymnosperms • This group includes cycads, the ginkgo, and conifers. • Cycads are palm-like, tropical and subtropical plants that flourished during the era of dinosaurs. • Ginkgo is planted in parks because it does well in polluted areas. Also used in Japanese art. • Conifers are the largest group of gymnosperms and include cone-bearing pine, spruce, fir, and redwood trees. Pine life cycle fertilized “pinecones” scales fly on the wind with wings! “pinecones” are female! • Life Cycle of a Conifer • The gymnosperm microspore develops into a pollen grain which develops in a pollen cone. • The megagametophyte develops within an ovule located on the scale of a seed cone. • Following wind pollination and fertilization that do not require external water, the ovule becomes a winged seed that is dispersed by wind. • Adaptation and Uses of Conifers • Conifers supply much of the wood used for construction of buildings and production of paper. • Many valuable chemicals are extracted from resin, a substance that protects conifers from fungi and insects. • The oldest trees in the world, at 4,500 years old, are bristlecone pines in Nevada. Impressive!!!! Trees can live longer than any other organism! They were around 2500BC, during the time of TROY…..Pharoh’s age! Some trees today were around to see King Tut, Jesus, Mohammed Angiosperms (enclosed-seeds) • Angiosperms are flowering plants and include tropical and subtropical trees. • All hardwood trees are angiosperms. • Angiosperms are divided into moncots (such as the grass family) and dicots (such as the maple and rose families). Flowering plant life cycle The fruit you eat, is a plants ovary. The seeds inside are fertilized! • Life Cycle of Angiosperms • Like conifers, angiosperms produce sperm and eggs, except angiosperms do so within their flowers (instead of a pinecone). • The ovules (eggs – usually a lot!) develops into seeds, each one consisting of a seed coat, stored food, and an embryo. The ovary and adjacent parts of the flower develop into a fruit. • Fruits aid in seed dispersal. • The Flower • The flower accounts for the success of angiosperms. • The flower both attracts animals that aid in pollination and produces seeds enclosed by fruits that aid dispersal. Summary • Plants resemble algae in using chlorophylls a and b and carotenoid pigments for photosynthesis, BUT unlike algae, plants protect the embryo (seed) to keep it moist so that it can live on land existence. Summary • Nonvascular plants are low-growing and lack a means of water transport and internal support, whereas vascular plants have a system that transports water and also provides internal support. • In nonseed plants, spores disperse the species; in seed plants, seeds disperse the species. • In seed plants, a pollen grain transports sperm to the egg.