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Hypotheses for Origin of Life on Earth • Divine origin • Extraterrestrial Origin • Abiotic Origin .475 .7 1.7 2 3.5 3.8 4 Oldest fossil is of bacteria 3.5 Billion years old What are stramatolites? Mitochondria and Chloroplasts are thought to have been engulfed by Archaea Bacteria and formed the first eukaryotic cells - 3 bya P 494 Ancient Reducing Atmosphere • Oparin and Haldane proposed that Earth’s ancient atmosphere was reducing rather than oxidizing. • Why was there no free oxygen in Earth’s early atmosphere? • Why would the first life not evolve in an oxidizing atmosphere? Miller and Urey simulated Earth’s early atmosphere electricity simulated lightning Why did they use uV light? An alternate atmosphere contained carbon monoxide, carbon dioxide, nitrogen gas and water vapor Experiments have produce all 20 amino acids, sugars, lipids, purines, pyrimidines What is the importance of amino acids? What is the importance of nucleic acids? Lightning and uV light provided energy for the formation of larger molecules and polymerization Protobionts • Aggregates of molecules that: • can start maintain a different internal environment (homeostasis) • can show rudimentary metabolism (catalytic reactions and modifications) • can show excitability (membrane potential) • can reproduce themselves • maintain genetic material Protobiont Examples • Coacervate (Oparin) made of polypeptides nucleic acids and polysaccharides • Proteinoid Micorspheres (Fox) • Liposomes RNA not only could replicate itself, but it could also act as a catalyst eg. Making proteins RNA with the best autocatlytic activity would to predominate Formerly eubacteria Archaea live in extreme environments and have cell walls with no peptidoglycan Most bacteria range from 15 um while eukaryotes range from 10100 um Coccus shape Bacillus shape Hilical or spiral shape eg. Spirochetes Simple cell wall with relatively large amounts of peptidoglycan Penicillin prevents crosslinking in the peptidoglycan and prevents the formation of a functional cell wall More complex cell wall with less peptidoglycan but with an outer membrane with lipopolysaccharides -carbohydrates bonded to lipids Nucleoid region containing genophore -prokaryotic DNA Prokaryotes have smaller ribosomes that respond to different antibiotics that prevent them from doing protein synthesis Trypanosoma is a kinetoplastid from the Kingdom Euglenozoa it is the cause of African sleeping sickness which is spread by the bite of the Tsetse fly Kinetoplast- an organelle Ceratium is a dinoflagellate from the Kingdom Aveolota Pfiesteria piscicida is another dinoflagellate that can produce toxins that can result in red tides Their characteristic shape is reinforced by internal plates of cellulose they have two flagella set in perpendicular grooves which result in its characteristic spinning motion The apical complex is its characteristic structure Just the micronucleus undergo meiosis and syngamy which increases genetic diversity Rhizopods, Actinopods & Foraminiferans move by pseudopodia or false foot the microtubules and microfilaments of the cytoskeleton help in amoeboid movement Foraminiferans - pore bearing shells many have symbiotic algae in which they derive benefit from photosymthesis Foram fossil are excellent markers for dating marine sediment and sedimentary rock Plasmodial Slime Mold is composed of ONE multinucleated cell or amoeboid mass called a plasmodium most species are diploid Stramenopila • Diatoms • Golden Algae – have yellow and brown caroten and xanthphyll acessory pigments • Water Molds and their relatives (Oomycota) – lack chloroplasts – unicellular or have coenocytic hyphae – cause of the Irish potato famine • Brown Algae Isomorphic alternation of generations in Ulva CHAPTER 29 PLANT DIVERSITY I: HOW PLANTS COLONIZED LAND Section A: An Overview of Land Plant Evolution 1. Evolutionary adaptations to terrestrial living characterize the four main groups of land plants 2. Charophyceans are the green algae most closely related to land plants 3. Several terrestrial adaptations distinguish land plants from charophycean algae Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Introduction • More than 280,000 species of plants inhabit Earth today. • Most plants live in terrestrial environments, including deserts, grasslands, and forests. – Some species, such as sea grasses, have returned to aquatic habitats. • Land plants (including the sea grasses) evolved from a certain green algae, called charophyceans. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Problems Aquatic Plants Face in a Terrestrial Environment • Obtaining enough water • transporting water and dissolved substances from restricted areas of intake to other areas • Preventing dessication • Maintaining enough moist surface area for gas exchange • Supporting a large plant body against gravity • carry out reproduction in an environment where sperm, zygote and embryo will dry out • withstanding extreme fluctuations in environment 1. Evolutionary adaptations to terrestrial living characterize the four main groups of land plants • There are four main groups of land plants: • • • • bryophytes, pteridophytes, gymnosperms, and angiosperms. The most common bryophytes are mosses. The pteridophytes include ferns. The gymnosperms include pines and other conifers. The angiosperms are the flowering plants. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Bryophytes • Mosses • Liverworts • Hornworts • The great majority of modern-day plant species are flowering plants, or angiosperms. – Flowers evolved in the early Cretaceous period, about 130 million years ago. – A flower is a complex reproductive structure that bears seeds within protective chambers called ovaries. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Bryophytes, pteridiophytes, gymnosperms, ands angiosperms demonstrate four great episodes in the evolution of land plants: – the origin of bryophytes from algal ancestors – the origin and diversification of vascular plants – the origin of seeds – the evolution of flowers Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 29.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Homologies between Charophytes and Plants • Homologous chloroplasts – chlorophyll b, betacarotene – thylakoids as grana – DNA • Biochemical similarity – cellulose cell walls – matching enzymes within peroxisomes • Similar mitosis and cytokinesis – dissapearance of nuclear envelope – spindle remains till cytokinesis • similar sperm • similar genes and rRNA • The elongation and branching of the shoots and roots maximize their exposure to environmental resources. • This growth is sustained by apical meristems, localized regions of cell division at the tips of shoots and roots. – Cells produced by meristems differentiate into various tissues, including surface epidermis and internal tissues. Fig. 29.3 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Multicellular plant embryos develop from zygotes that are retained within tissues of the female parent. • This distinction is the basis for a term for all land plants, embryophytes. Fig. 29.4 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • All land plants show alternation of generations in which two multicellular body forms alternate. – This life cycle also occurs in various algae. – However, alternation of generation does not occur in the charophyceans, the algae most closely related to land plants. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • One of the multicellular bodies is called the gametophyte with haploid cells. – Gametophytes produce gametes, egg and sperm. – Fusion of egg and sperm during fertilization form a diploid zygote. Fig. 29.6 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings The cuticle is a secondary product produced on the surface of leaves to prevent dessication The stomata is an adaptation to let in carbon dioxide into the leaf Adaptations to Terrestrial Life • • • • • • Stomata Cuticle lignin sporopollenin gametangia p548 embryophytes • vascular tissue p555 • seeds • flowers • The traditional scheme includes only the bryophytes, pteridophytes, gymnosperms, and angiosperms in the kingdom Plantae. • Others expand the boundaries to include charophyceans and some relatives in the kingdom Streptophyta. • Still others include all chlorophytes in the kingdom Fig. 29.14 Viridiplantae. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Homologies between Charophytes and Plants • Homologous chloroplasts – chlorophyll b, betacarotene – thylakoids as grana – DNA • Biochemical similarity – cellulose cell walls – matching enzymes within peroxisomes • Similar mitosis and cytokinesis – dissapearance of nuclear envelope – spindle remains till cytokinesis • similar sperm • similar genes and rRNA Introduction • The seedless vascular plants, the pteridophytes consists of two modern phyla: – phylum Lycophyta - lycophytes – phylum Pterophyta - ferns, whisk ferns, and horsetails • These phyla probably evolved from different ancestors among the early vascular plants. Fig. 29.21 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Adaptation of Vascular Plants • Root systems – absorbs water and minerals • Aerial shoot systems and leaves – for photosynthesis • Conducting tissue – xylem and phloem • Lignin – to strengthen and support cellulose cell walls • Sporophyte is the dominant stage • Branching in Sporangia – increases the # of spores 1. Pteridophytes provide clues to the evolution of roots and leaves • Most pteridophytes have true roots with lignified vascular tissue. • These roots appear to have evolved from the lowermost, subterranean portions of stems of ancient vascular plants. – It is still uncertain if the roots of seed plants arose independently or are homologous to pteridophyte roots. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 2. A sporophyte-dominant life cycle evolved in seedless vascular plants • From the early vascular plants to the modern vascular plants, the sporophyte generation is the larger and more complex plant. – For example, the leafy fern plants that you are familiar with are sporophytes. – The gametophytes are tiny plants that grow on or just below the soil surface. – This reduction in the size of the gametophytes is even more extreme in seed plants. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Most ferns are homosporous The gametophyte is bisexual producing both sperm and eggs Seedless Vascular Plants • Lycophyte • Horsetails (Sphenophyta) • Ferns (Pterophyta) Introduction • The evolution of plants is highlighted by two important landmarks: (1) the evolution of seeds, which lead to the gymnosperms and angiosperms, the plants that dominate most modern landscapes (2) the emergence of the importance of seed plants to animals, specifically to humans. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Agriculture, the cultivation and harvest of plants (primarily seed plants), began approximately 10,000 years ago in Asia, Europe, and the Americas. – This was the single most important cultural change in the history of humanity, for it made possible the transition from hunter-gather societies to permanent settlements. • The seeds and other adaptations of gymnosperms and angiosperms enhanced the ability of plants to survive and reproduce in diverse terrestrial environments. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 1. Reduction of the gametophyte continued with the evolution of seed plants • An important distinction between mosses and other bryophytes and ferns and other seedless vascular plants is a gametophytedominated life cycle for bryophytes and a sporophyte-dominant life cycle for seedless vascular plants. • Continuing that trend, the gametophytes of seed plants are even more reduced than those of seedless vascular plants such as ferns. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic • For the gametophyte to exist within the sporophyte has required extreme miniaturization of the gametophyte of seed plants. • The gametophytes of seedless vascular plants are small but visible to the unaided eye, while those of seed plants are microscopic. Fig. 30.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • An ovule consists of integuments, megaspore, and megasporangium. – A female gametophyte develops inside a megaspore and produces one or more egg cells. – A fertilized egg develops into a sporophyte embryo. – The whole ovule develops into a seed. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 30.2 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Conifers include pines, firs, spruces, larches, yews, junipers, cedars, cypresses, and redwoods. Fig. 30.8 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Gymnosperm only have tracheids - no vessels Vessels form contiunous tubes and thus are more specialized for transport of water and less for support. The thick lignified xylem cell helps in support 1. Systematists are identifying the angiosperm clades • All angiosperms are placed in a single phylum, the phylum Anthophyta. • As late as the 1990s, most plant taxonomists divided the angiosperms into two main classes, the monocots and the dicots. – Most monocots have leaves with parallel veins, while most dicots have netlike venation. • Recent systematic analyses have upheld the monocots as a monophyletic group. – They include lilies, orchids, yuccas, grasses, and Copyright grains. © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Monocot Dicot one embryonic leaf - cotyledon two embryonic leaves - cotyledons does not have vascular cambium and secondary growth has vascular cambium and secondary growth scattered vascular bundles leaves have parallel venation no petioles flower parts in multiples of three vascular tissue arranged in circular bundles leaves have netted venation has petioles flower parts in multiples of four or five • Refinements in vascular tissue, especially xylem, probably played a role in the enormous success of angiosperms in diverse terrestrial habitats. – Like gymnosperms, angiosperms have long, tapered tracheids that function for support and water transport. – Angiosperms also have fibers cells, specialized for support, and vessel elements (in most angiosperms) that develop into xylem vessels for efficient water transport. Fig. 30.12 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 3. Fruits help disperse the seeds of angiosperms • A fruit is a mature ovary. – As seeds develop from ovules after fertilization, the wall of the ovary thickens to form the fruit. – Fruits protect dormant seeds and/or aid in their dispersal. Fig. 30.15 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • The life cycle of an angiosperm begins with the formation of a mature flower on a sporophyte plant and culminates in a germinating seed. Fig. 30.17 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Ovule turns into embryo sac Female gametophyte 8 nuclei found in embryo sac • When the pollen tube reaches the micropyle, a pore in the integuments of the ovule, it discharges two sperm cells into the female gametophyte. (7) In a process known as double fertilization, one sperm unites with the egg to form a diploid zygote and the other fuses with two nuclei in the large center cell of the female gametophyte. (8) The zygote develops into a sporophyte embryo packaged with food and surrounded by a seed coat. – The embryo has a rudimentary root and one or two seed leaves, the cotyledons. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings CHAPTER 31 FUNGI Section A: Introduction to the Fungi 1. Absorptive nutrition enables fungi to live as decomposers and symbionts 2. Extensive surface area and rapid growth adapt fungi for absorptive nutrition 3. Fungi disperse and reproduce by releasing spores that are produced either sexually or asexually 4. Many fungi have a heterokaryotic stage Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Introduction • Ecosystems would be in trouble without fungi to decompose dead organisms, fallen leaves, feces, and other organic materials. – This decomposition recycles vital chemical elements back to the environment in forms other organisms can assimilate. • Most plants depend on mutualistic fungi that help their roots absorb minerals and water from the soil. • Human have cultivated fungi for centuries for food, to produce antibiotics and other drugs, to make bread rise, and to ferment beer and 1. Absorptive nutrition enables fungi to live as decomposers and symbionts • Fungi are heterotrophs that acquire their nutrients by absorption. – They absorb small organic molecules from the surrounding medium. – Exoenzymes, powerful hydrolytic enzymes secreted by the fungus, digest food outside its body to simpler compounds that the fungus can absorb and use. Extracellular digestion. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • The absorptive mode of nutrition is associated with the ecological roles of fungi as decomposers (saprobes), parasites, or mutualistic symbionts. – Saprobic fungi absorb nutrients from nonliving organisms. – Parasitic fungi absorb nutrients from the cells of living hosts. • Some parasitic fungi, including some that infect humans and plants, are pathogenic. – Mutualistic fungi also absorb nutrients from a host organism, but they reciprocate with functions that benefit their partner in some way. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 2. Extensive surface area and rapid growth adapt fungi for absorptive nutrition • The vegetative bodies of most fungi are constructed of tiny filaments called hyphae that form an interwoven mat called a mycelium. Fig. 31.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Most fungi are multicellular with hyphae divided into cells by cross walls, or septa. – These generally have pores large enough for ribosomes, mitochondria, and even nuclei to flow from cell to cell. • Fungi that lack septa, coenocytic fungi, consist of a continuous cytoplasmic mass with hundreds or thousands of nuclei. • This results from repeated nuclear division without cytoplasmic division. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 30.2a & b • Parasitic fungi usually have some hyphae modified as haustoria, nutrientabsorbing hyphal tips that penetrate the tissues of their host. • Some fungi even have hyphae adapted for preying on animals. Copyright © 2002 Pearson Education, Inc., & publishing as Benjamin Cummings Fig 30.2c d 2. Phylum Zygomycota: Zygote fungi form resistant structures during sexual reproduction • Most of the 600 zygomycete, or zygote fungi, are terrestrial, living in soil or on decaying plant and animal material. • One zygomycete group form mycorrhizae, mutualistic associations with the roots of plants. • Zygomycete hyphae are coenocytic, with septa found only in reproductive structures. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 3. Phylum Ascomycota: Sac fungi produce sexual spores in saclike asci • Mycologists have described over 60,000 species of ascomycetes, or sac fungi. • They range in size and complexity from unicellular yeasts to elaborate cup fungi and morels. Fig. 31.9 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Ascomycetes are characterized by an extensive heterokaryotic stage during the formation of Asexual spores ascocarps. 2 Haploid Fruiting mating types body Sexual spores Fig. 31.10 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 4. Phylum Basidiomycota: Club fungi have long-lived dikaryotic mycelia • Approximately 25,000 fungi, including mushrooms, shelf fungi, puffballs, and rusts, are classified in the phylum Basidiomycota. Fig. 31.11 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • The life cycle of a club fungus usually includes a long-lived dikaryotic mycelium. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 31.12 Chap 32 Animal Evolution (3) The Bilateria can be divided by the presence or absence of a body cavity (a fluid-filled space separating the digestive tract from the outer body wall) and by the structure the body cavity. • Acoelomates (the phylum Platyhelminthes) have a solid body and lack a body cavity. Fig. 32.6a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • In some organisms, there is a body cavity, but it is not completely lined by mesoderm. – This is termed a pseudocoelom. – These pseudocoelomates include the rotifers (phylum Rotifera) and the roundworms (phylum Nematoda). Fig. 32.6b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Coelomates are organisms with a true coelom, a fluid-filled body cavity completely lined by mesoderm. – The inner and outer layers of tissue that surround the cavity connect dorsally and ventrally to form mesenteries, which suspend the internal organs. Fig. 32.6b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Mantle secretes the shell Radula is used for rasping food off of surfaces, but can be modified to bore holes or tear apart tough animal tissue Has trochophore larvae a type of ciliated larvae They lack true segmentation Annelids have a true coelom which allows for easier fluid movement between organs They have body segmentation each segment can become specialized closed circulatory system with hearts- blood with hemoglobin excretory tubes called metanephridia collects wastes from the blood through a funnel called a nephrostome and dumps it outside through nephridia pores. Insecta is the largest class 3 body parts with 3 pairs of legs two pair of wings nitrogenous waste excreted through Malpighian tubules gas exchange through tracheal tubes mandibles (jaws) Echinoderms coelomates Echinoderms have water entering into a madreporite down a water vascular system that operates tube feet deuterostomes They are capable of everting their stomach through their mouth - either dumping the contents or digesting something outside of its body Deuterostomes Mouth forms later (second) Forms ANUS first • Many protostomes undergo spiral cleavage, in which planes of cell division are diagonal to the vertical axis of the embryo. – Some protostomes also show determinate cleavage where the fate of each embryonic cell is determined early in development. • The zygotes of many deuterostomes undergo radial cleavage in which the cleavage planes are parallel or perpendicular to the vertical egg axis. – Most deuterostomes show indeterminate cleavage whereby each cell in the early Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings