BIO153 NOTES MIDTERM 2 (Autosaved).docx

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University of Toronto Mississauga
Thottackad Radhakrishnan

BIO153 NOTES- MISTERM CHAPTER 31- FUNGI - Fungi are eukaryotes that grow as single cell or as large, branching networks of multicellular filaments. - Familiar fungi include mushrooms, moulds, mildews, organism that causes athlete’s foot and yeasts found in bread. - Part of 1/3 major lineages of large, multicellular euks that occupy terrestrial environments. - These three species make a living by using different strategies • Land plants make their own by photosynthesis • Animals eat plants, protists, fungi or each other. • Fungi absorb their nutrition from other organisms- dead or alive. That is why they are called heterotrophic absorbers. - Fungi that absorb dead nutrients are of the most important decomposers in the world - When fungi absorb nutrients from live host organisms and DO NOT provide a benefit, they are considered parasites • Most that do benefit their host cells provide a benefit, in this case they are called mutualists. - Fungi are the master traders and recyclers in terrestrial ecosystems. Some fungi release nutrients from dead plants and animals; others transfer nutrients they obtain to living plants. - Because they recycle key elements such as carbon, nitrogen and phosphorus and because they transfer key nutrients to plants. In terms of nutrient cycling on the continents, fungi make the world go round. 31.1- Why Do Biologists Study Fungi? - FUNGI PROVIDE NUTRIENTS FOR LAND PLANTS • Fungi that live in close association with plant roots are said to be mycorrhizal. • The seedlings of plants without this type of fungi still grow but not as much. With the fungal roots, they grow 3-4 times as fast. - FUNGI SPEED THE CARBON CYCLE ON LAND • Fungi that make their living by digesting dead plant material are called saprophytes. • When trees die, fungi are the organisms that break down wood into sugars and other small organic compounds. They use this as food. • When fungi die, the molecules are passed along to other organisms who feed off of the dead fungi. - Two basic components of the carbon cycle: 1) The fixation of carbon by land plants- meaning that carbon in atmospheric CO is 2educed to cellulose, lignin and other complex organic compounds in the bodies of plants and… 2) The release of CO 2rom plants, animals and fungi as the result of respiration- meaning the oxidation of glucose and production ofATP that sustains life - If fungi had not evolved the ability to digest lignin and cellulose soon after land plants evolved the ability to make these compounds, carbon atoms would have been sequestered in wood for millennia instead of being rapidly recycled into glucose molecules and CO . Terrestrial environments would be 2 radically different than they are today and probably much less productive. - FUNGI HAVE IMPORTANT ECONOMIC IMPACTS • Only about 31 species of fungi out of hundreds of thousands regularly cause disease in humans. • Penicillin was the first antibiotic that was used and was isolated through fungus. 31.2- HOW DO BIOLOGISTS STUDY FUNGI -ANALYZING MORPHOLOGICALTRAITS • Simple bodies, grow in two forms, either singe celled forms called yeasts and multicellular, filamentous structures called mycelia. • Many species of fungus grow either as a yeast or a as a mycelium, but some regularly adopt both growth forms. Most grow as mycelia. - THE NATURE OF THE FUNGAL MYCELIUM • Mycelia constantly grow in the direction of food sources and die back in areas where food is running out. The body shape of a fungus can change almost continuously throughout its life. - THE NATURE OF HYPHAE • The filaments within a mycelium are called hyphae – long, narrow filaments that branch frequently. • Hyphae may be haploid or dikaryotic (two-kernel), meaning that each cell contains two haploid nuclei, one from each parent. • In most fungi, each filament is broken into cell-like compartments by cross-walls called septa. • Septa do not close off segments of hyphae completely. Instead, gaps called pores enable a wide variety of materials, even organelles and nuclei, to flow from one compartment to the next. • These gaps may be large or small and in large numbers – this is where nutrients, mitochondria and even genes can flow through the entire mycelium, the fungal mycelium is intermediate between multicellular land plant or animal and an enormous single-celled organism. • Some fungal species are even coenocytic – meaning that they lack septa entirely. Coenocytic fungi have many nuclei scattered throughout the mycelium. They are single, gigantic cell. th • Fungal hyphae are 1/100 of the size of a root tip. Fungal mycelia can penetrate tiny fissures in soil and absorb nutrients that are inaccessible to plant roots. - MYCELIAHAVEALARGE SURFACEAREA • Because mycelia are composed of complex, branching networks of extremely thin hyphae, fungi have the highest surface-area-to-volume ratios observed in multicellular organisms. • Alarge surface area is beneficial because it allows for efficient absorbing of food, which is how fungi feed. • The downside is that due to the large surface area, they lose a lot of water and are prone to drying out that is why fungi are mostly found in moist environments. • Spores are resistant to drying so they can endure long periods dry periods, then germinate and resume growth when conditions improve. - REPRODUCTIVE STRUCTURES • Mushrooms, puffballs and other dense multicellular structures that arise from mycelia do not absorb food. Instead they function in reproduction. Typically they are a part of a fungus that is exposed to the atmosphere, where drying is a problem. • Few species of fungi make the reproductive organs called mushrooms, others make 1 of 4 types of distinctive reproductive structures: 1) Swimming gametes and spores - Species that live primarily in water and wet soils, the spores that are produced during asexualAND sexual reproduction have flagella. - Known as CHYTRIDS 2) Zygosporangia - In some species, haploid hyphae from two individuals meet and become yoked together. - Cells from yoked hyphae fuse to form a distinctive spore-producing structure called a zygosporangium. - Known as ZYGOMYCETES 3) Basidia - Inside a mushroom, bracket, or puffball, specialized cells called Basidia form at the ends of hyphae and produce spores. - Species with Basidia are called BASIDIOMYCETES. 4) Asci - Inside cups, morels, and some other types of aboveground reproductive structure, specialized cells asci form at the ends of hyphae and produce spores. - These species are known as ASCOMYCETES. - FUNGIARE CLOSELY RELATED TO ANIMALS • Three key morphological traits link animals and fungi. 1) Most animals and fungi synthesize the tough structural material called chitin. - Chitin is a prominent component of the exoskeleton of arthropods and the cell walls of fungi. 2) The flagella that develop in chytrid spores and in chytrid gametes are similar to those observed: as in animals, the flagella in chytrids are single, are located at the back end of reproductive cells, and move in a whiplash manner. 3) Both animals and fungi store food by synthesizing the polysaccharide glycogen. 3 forms of symbiotic relationships Mutualism- benefits both species Parasitic- benefits one species, but not the other Commensal- benefits one species, other is unaffected EMF- Ectomycorrhizal fungi "ecto" = outer Usually species from Basidiomycota and some ascomycetes participate in this. The hyphae extend out from the sheath-like portion of the mycelium into the soil. EMF form sheaths around roots and penetrate between root cells. deliver and release enzymes (peptidase) between a.a. bonds in dead tissues. The a.a.'s released are transported to spaces between roots of cells and absorbed by plants. AMF-Arbuscular mycorrhizal fungi "arbu"= into Usually species from glomeromycota participate in this They are also called endomycorrhizal fungi because they penetrate the interior of root cells. The hyphae of AMF penetrate the cell wall and contact the plasma membrane of the root cells directly. The highly branched hyphae are thought to be an adaptation that increases the surface area available for molecule exchange between fungus and its host. most important function is to transfer P atoms from soil to host plant as they form a pipeline from inside plant cells in the root to the soil beyond the root Endophytic: fungi that live in the above ground parts of plants. Some endophytes are mutualists. Adaptations that help fungi decompose plant tissue • large SAfor exceptionally efficient nutrient absorption • saprophytic fungi grow towards dead tissue that supply their food • extracellular digestion-lignin & cellulose Lignin degradation-basidiomycetes degrade lignin by breaking apart the lignin to expose cellulose used for growth and reproduction Cellulose degradation- cellulases that are secreted are further broken down into glucose for a food source and can catalyze hydrolysis reactions Reproduction of fungi The spore is the most fundamental reproductive cell in fungi. They are the dispersal stage in the fungi life cycle and are produced during asexual and sexual reproduction. Fertilization Only chyrtridiomycota produce gametes. Fertilization occurs in 2 steps. 1.) fusion of cells 2.) fusion of nuclei from the fused cells plasmogamy: cytoplasm from 2 hyphae fuse into a single hypha karogamy: dikaryotic mycelium fuse to form a diploid zygote. The nuclei produced divide by meiosis to form haploid spores During asexual reproduction spores are generated by mitosis and produced by a haploid mycelium. The offspring are generally identical to their parents. 4 major types of life cycles 1.)Chytrids- alternation of generation occurs →swimming gametes are produced in haploid adults by mitosis →gametes from the same individual or different individuals fuse to form a diploid zygote →zygote grows into sporophyte 2.)Zygomycetes- form yoked hyphae that produce zygosporangium (produces spores) →sexual reproduction occurs when hyphae from different individuals fuse →plasmogamy forms the zygosporangium. Inside it, the nuclei from the mating partners fuse so karogamy occurs 3.)Basidiomycota- have reproductive structures (basidia) that produce spores →karogamy occurs within the basidia →Diploid nucleus that results undergoes meiosis, and 4 haploid spores mature 4.)Ascomycota- have reproductuve structures (asci) that produce spores →produced by a dikaryotic hypha →a short dikaryotic hypha (one nuclei from each parent) emerges and grows into asci. →Karogamy occurs inside each ascus, and meiosis occurs after haploid spores are produced. CHAPTER 32-AN INTRODUCTION TOANIMALS - Animals are a monophyletic group of eukaryotes • They are multicellular, will cells that lack cell walls but have extensive extracellular matrix (ECM). The ECM includes proteins specialized for cell-wall adhesion and communication. - Animals are the only multicellular heterotrophs on the tree of life that ingest their food. - Animals are the largest predators, herbivores and detritivores on earth. - All animals except sponges 1. Specialized cells called neurons that transmit electrical signals to other cells 2. Muscle cells that can change the shape of the body by contracting. - Muscles and neurons are adaptations that allow a large, multicellular body to move efficiently. BIOLOGICAL IMPORTANCE - Animals are key consumers in virtually every ecosystems that range in climate and environment. - 10 million to 50 million species living today. ROLE IN HUMAN HEALTH AND WELFARE - Humans largely depend on wild and domestic animals as food, primarily as sources of protein and fat. Most commercial fruit growers rely on bees and other animals to pollinate their crops. - Animals also have a role in providing material like fibres, blankets, and leather to name a few. - In some places, animals are used as a primary source of transportation. - Animals also transmit diseases like west nile (mosquitos) ANIMALSAS MODEL ORGANISMS - Humans share a large portion of their genome with other animals. So research on animals have revealed fundamental aspects of cellular and developmental biology that are shared by humans. - Because genetic homologies between humans and other animals are so extensive, most drug testing is done on animals like rats and mice or primates. 32.2 – How Do Biologists StudyAnimals - The origin and early evolution of animals was based on four aspects of the fundamental architecture, or body plan of animals: 1. The origin and elaboration of tissues – especially the tissues found in embryos 2. The origin and elaboration of the nervous system and the subsequent evolution of a cephalized body – one with a distinctive head region 3. The evolution of a fluid – filled body cavity 4. The variation in the events of early embryonic development THE ORIGINAND DIVERSIFICATION OF TISSUES - All animals have groups of similar cells that are organized into the tightly integrated structural and functional units called tissues. Embryotic tissues are organized in layers, called germ layers. - Animals whose embryos have two types of tissue are called diploblasts • Ectoderm and endoderm. Ecto meaning outer and endo meaning inner • The outer and inner skins of diploblast embryos are connected by a gelatinous material that may contain some cells. - Animals whose embryos have three types of tissue are called triploblasts • In triploblasts, there exists a layer of skin called mesoderm which is located between the ectoderm and endoderm. - The embryotic tissues found in animals develop into distinct adult tissues, organs, and organ system. • Ectoderm gives rise to skin and the nervous system • Endoderm gives rise to the lining of the digestice tract • Mesoderm gives rise to the circulatory system, muscle and internal structures such as bond and most organs. - In general, then, ectoderm produces the covering of the animal and endoderm generates the digestive tract. Mesoderm gives rise to the tissues in between. - The same pattern holds in diploblasts, except that (1) muscle is simpler in organization and is derived from ectoderm and (2) reproductive tissues are derived from endoderm. - Traditionally, two groups are animals are known as diploblasts, Cnidaria and anemones NERVOUS SYSTEM, BODY STRUCTURE SYMMETRYAND CEPHALIZATION - Besides cnidarians and ctenophores, all other animals have a central nervous system (CNS). • Neurons are clustered into one or more large tracts or cords and project throughout the body • Others are clustered into masses called ganglia - Nerve nets and CNS are associated with two contrasting types of body symmetry: radial symmetry (meaning anyway you cut, you will get two equal halves) and bilateral (meaning you cut from top to bottom) symmetry - Cnidarians and ctenophores, along with many sponges, have radial symmetry – meaning they have at least two planes of symmetry. • Radially symmetric organisms are equally likely to encounter prey and other aspects of the environment in any direction. As a result, a diffuse nerve net can receive and send signals efficiently - Organisms with bilateral symmetry tend to have long, narrow bodies. • Bilaterally symmetric organisms tend to encounter prey and other aspects of the environment at one end. As a result, it is advantageous to have many neurons concentrated at the end, with nerve tracts that carry information from there down the length of the body. - The evolution of bilateral symmetry occurred along cephalization: the evolution of a head, or anterior region, where structures for feeding, sensing the environment and processing information are meshed. - The large mass of neurons that is located in the head, and that is responsible for processing information from throughout the body is called the cerebral ganglion, or the brain - ALLTRIPLOBLASTIC ANIMALS HAVE BILATERALSYMMETRY, except for species in the phylum Echinodermata. - To explain the pervasiveness of bilateral symmetry, biologists point out that locating and capturing food is particularly efficient when movement is directed by a distinctive head region and powered by the rest of the body. In combination with the origin of mesoderm, a bilaterally symmetric body plan enabled rapid, directed movement. WHY IS THE EVOLUTION OF ABODY CAVITY IMPORTANT? - The third element that distinguishes animal phyla is the presence of an enclosed, fluid-filled cavity called a coelom. • The coelom creates a container for the circulation of oxygen and nutrients, along with space where internal organs can move independently of each other. - The handful of triploblasts that do not have a coelom are called acoelomates. - Those that possess a coelom are known as coelomates. - In a few coelomate groups, the enclosed cavity forms between the endoderm and mesoderm layers in the embryo. - The cavity is called a pseudocoelom and has mesoderm only on the outer side of the fluid-filled cavity, while a coelom has mesoderm on both the inner and the outer sides. - The coelom – pseudocoelom – was a critically important innovation during animal evolution because an enclosed, fluid-filled chamber can act as an efficient hydrostatic skeleton. Soft bodied animals with hydrostatic skeletons can move efficiently even if they do not have fins or limbs. - Movement is possible because the fluid inside the coelom stretches the body wall meaning that it is under tension. This force exerts pressure on the fluid inside the coelom. When muscles in the body wall contract against the pressurized fluid, the force is transmitted through the fluid, changing the body’s shape. WHATARE THE PROTOSOMEAND DEUTEROSTOME PATTERNS OF DEVELOPMENT? - Except for adult echinoderms, all of the coelomates – including juvenile forms of echinoderms – are bilaterally symmetric. This large group is called the Bilateria that are divided into 2 subgroups: 1) Protosomes – in which the mouth develops before the anus, a
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