Life 103, exam 1 study guide
Life 103, exam 1 study guide Life 103
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This 17 page Study Guide was uploaded by Addy Carroll on Friday February 5, 2016. The Study Guide belongs to Life 103 at Colorado State University taught by Dr. Dale Lockwood and Dr. Tanya Dewey in Winter 2016. Since its upload, it has received 183 views. For similar materials see Biology of organisms-animals and plants in Biology at Colorado State University.
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Life 103 Study Guide Exam 1 Phylogeny • Terminology -Evolution: “The change in allele frequencies in a population over time.” As an allele is a specific version of a gene, this definition means that certain gene versions become more/less prominent in a population as time progresses. -Four ways evolution can occur 1. Selection: “Changes in allele frequencies due to organisms with advantageous alleles reproducing more successfully than organisms with other alleles.” This simply means that certain organisms with one version of the gene reproduce more frequently/with more success than other organisms. 2. Genetic Drift: “Random changes in allele frequencies in a population.” In addition to just knowing this simple definition, it might be helpful to note that these changes are completely based on chance; for example, if a natural disaster happened to take out more organisms with one allele than the organisms with a different allele. 3. Mutation: “The source of all new allelic diversity.” This is an evolutionary change that occurs on a more molecular level. The actual gene sequence of an organism has to change. 4. Migration: “Movement of alleles between populations.” This could happen, for example, if an organism having a certain allele reproduces with an organism from another population where the allele is never found to be present. Thus, this would introduce the allele to the population. -Adaptation: “A trait that evolves by selection for a particular function (because it increases fitness) from an ancestor that did not have that trait.” ~ Adaptations can be morphological, behavioral, or molecular ~Adaptations solve problems faced by populations and different populations may have different solutions to similar problems -Phylogeny: “The evolutionary relationships of a group of organisms (species level and higher)” -Phylogenetic tree: “Diagram of the ancestral relationships among species” (see “Phylogenetic trees” section below for more details” ~Describe patterns ~Provide information about when certain large events may have occurred • Phylogenies show evolutionary relationships -Taxonomy is the ordered division and naming of organisms -In the 18 century, Carl Linnaeus published a system of taxonomy based on resemblances -Two key features of his system remain useful today: two-part names for species (see “binomial nomenclature” section below) and hierarchical classification (see “Hierarchical Classification” section below) • Binomial Nomenclature -The two-part scientific name of a species is called a binomial -The first part of the name is the genus -The second part, called the specific epithet, is unique for each species within the genus -The first letter of the genus is capitalized, and the entire species name is italicized Ex. Homo sapiens (human) -Both parts together name the species (not the specific epithet alone) • Hierarchical Classification (see textbook figure 26.3) -Linnaeus introduced a system for grouping species in increasingly broad categories -The taxonomic groups from broad (most inclusive) to narrow (least inclusive) are domain, kingdom, phylum, class, order, family, genus, and species -A taxonomic unit at any level of hierarchy is called a taxon • Phylogenetic trees -Darwin used the metaphor of a tree to explain the relationship between similar species -How do we build these trees? ~What type of evidence/data can we use to reconstruct a tree? (see textbook figure 26.12) 1. Morphological traits 2. Behavior 3. Chemical composition 4. Chromosome number 5. DNA ~These types of data are called characters. It may be important to note, characters are not the same as characteristics. A characteristic is a specific character. For example, “In observing the character of hair color in the classroom, we saw that 69% of the students had the characteristic of blonde hair color.” ~Character state: variation among characters • Phylogenetic Tree Terminology (see textbook figures 26.5, 26.10) -Each branch point represents the divergence (split) of two species -Sister taxa are groups that share an immediate common ancestor -A rooted tree includes a branch to represent the last common ancestor of all the taxa in the tree -A polytomy is a branch from which more than two groups emerge • A simplified tree of life -The tree of life suggests that animals and fungi are more closely related to each other than plants -The tree of life is based largely on rRNA (ribosomal RNA) genes, as these have evolved slowly Ecology • Ecology (eco-=house, -ology=study of) -The study of the distribution and interaction of organisms with other organisms and the environment -Word coined by Ernst Haeckel -Most interdisciplinary (involving two or more areas of knowledge) discipline in biology • Organismal Ecology -The study of the interaction of an organism and its environment -Behavioral Ecology ~Response to stimulus ~Foraging ~Group interaction -Evolutionary Ecology ~Adaptations to the environment (see phylogeny notes for adaptations) -Events in ecological time (the length of time an organism experiences) influence evolutionary time processes • Population Ecology -A population is a group of individuals of the same species living in the same area -Population Ecology focuses on factors affecting how many individuals of a species live in an area ~Most mathematically based subdivision of ecology • Community Ecology -A community is a group of interacting populations of different species in an area -Community ecology deals with the whole array of interacting species in a community • Ecosystem Ecology -An ecosystem is the community of organisms in an area and the physical factors with which they interact -Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components ~Movement of carbon, nitrogen, and other chemicals through the ecosystem ~Climate change • Ecological interactions -Organisms and Environment -Species Distributions ~Range limitations -Environment is composed of: 1. Biotic factors (living; see “Biotic Factors” section below) 2. Abiotic factors (nonliving; see “Abiotic Factors” section below) • Biotic Factors -Organisms interacting with other species ~Interactions can be positive, negative, or neutral Ex.) plant/pollinator predator/prey herbivore/plant competition • Abiotic Factors -Nonliving parts of the environment ~Chemical Ex.) pH, salinity ~Physical Ex.) weather (temperature, moisture, soil), light, nutrients (O 2 N 2 • Dispersal -The movement of individuals ~One way trip, while migration is a round trip -Dispersal is natural Bacteria and Archaea -Prokaryotes are made up of two domains 1. Bacteria 2. Archaea • The problem with prokaryotes -Biologically, prokaryotes are a non-monophyletic group (see textbook figure 26.10a and/or phylogeny notes) -Thus, the term prokaryote is not a biologically sensible term • Bacteria and Archaea -Life is mostly single-celled -Highly adaptable (see adaptation in phylogeny notes) ~live just about everywhere ~hot, cold, acid, sulphurous, salty conditions -Vast numbers ~More bacteria in a cup of soil than the number of humans that have ever existed -Very high genetic diversity -Bacteria are unicellular, although some species form colonies -Most bacteria are 0.5-5 micrometers, much smaller than the 10-100 micrometers of many eukaryotic cells -Bacterial cells have a variety of shapes (see textbook figure 27.2) ~The three most common shapes are spheres (cocci), rods (bacilli), and spirals • Cell Walls -Most bacteria have them -Maintains shape -Physical protection -Prevents bursting in hypotonic environment -Bacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides • Both eukaryotes and archaea contain polysaccharides and proteins, but lack peptidoglycan • Gram Stain (see textbook figure 27.3) -Used to make bacteria visible -Classifies many bacterial species ~Gram-positive ~Gram-negative • Gram-negative bacteria -Have less peptidoglycan -Have outer membrane ~Can be toxic -More likely to be antibiotic resistant • Some prokaryotes have fimbriae (also called attachment pili; see textbook figure 27.6), which allow them to stick to their substrate or other individuals in a colony • Most motile bacteria propel themselves by flagella (see textbook figure 27.7) -Structurally and functionally different from eukaryotic flagella -Allows for taxis, the ability to move in response to stimuli • Both bacteria and archaea cells usually lack complex compartmentalization -No organelles • Some bacteria and archaea have specialized membranes that perform metabolic functions -Respiratory membranes in aerobic bacteria -Thylakoid membranes in photosynthetic bacteria • Bacteria DNA -The genome of bacteria is smaller than eukaryotic genomes -Most of the genome consists of a circular chromosome -Some species of bacteria also have smaller rings of DNA called plasmids -The typical bacterial genome is a ring of DNA that is not surrounded by a membrane and that is located in a nucleoid region • Bacteria can form exospores or endospores • Endospores -Internal to the bacterium -Resistant to UV radiation, desiccation, alcohol, and chemicals -Can survive for extended periods of time • Exospores -Formed differently -Less robust • Reproduction -Bacteria reproduce quickly by binary fission and can divide every 1-3 hours -Generally, each offspring is identical genetically -Mutations can cause variation in offspring ~Mutations are rare, but reproduction is very fast • Genetic variation -Bacteria and archaea have considerable genetic variation -Three factors contribute to this genetic diversity 1. Rapid reproduction 2. Mutation 3. Genetic recombination • Genetic recombination -Bacterial DNA from different individuals can be brought together by transformation, transduction, and conjugation -A bacterial cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformation -Transduction (see textbook figure 27.11) is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria) • Transformation -First shown in 1928 -Bacteria that can transform are competent ~about 1% of bacteria species are naturally competent under laboratory conditions -Techniques can make bacteria artificially competent • Conjugation (see textbook figures 27.12, 27.13) -The process where genetic material is transferred between bacterial cells -Sex pili allow cells to connect and pull together for DNA transfer -A piece of DNA called the F factor is required for the production of sex pili -The F factor can exist as a separate plasmid or as DNA within the bacterial chromosome • R plasmids carry genes for antibiotic resistance • Antibiotics select for bacteria with genes that are resistant to the antibiotics • Antibiotic resistant strains of bacteria are becoming more common • Antibiotic Resistance -Misuse and overuse of antibiotics ~Agricultural uses ~Patients demanding antibiotics for nonbacterial infections -Majority of ear and sinus infections are viral -Patients not using antibiotics properly ~Antibiotic products -soaps, toys treated with antibiotics, etc. ~Lateral gene transfer allows multiple resistance Ex.) MRSA- Methicillin resistant Staphylococcus aureus ~First appeared in 1961, 2 years after methicillin was first used ~Now resistant to penicillin, oxacillin, and amoxicillin, tetracycline, erythromycin, and clindamycin ~85% of infections occur in hospitals ~Over 18,000 deaths in 2005 ~Most are skin infections -Can spread to other organs • Bacterial nutritional adaptations -Phototrophs obtain energy from light -Chemotrophs obtain energy from chemicals -Autotrophs require CO as2a carbon source -Heterotrophs require an organic nutrient to make organic compounds • Chemoautotrophs -Black smoker deep sea vents -Major primary producers • The role of oxygen in metabolism -Bacteria metabolism varies with respect to O 2 ~Obligate aerobes require O fo2 cellular respiration ~Obligate anaerobes are poisoned by O and 2se fermentation or anaerobic respiration ~Facultative anaerobes can survive with or without O 2 • Nitrogen metabolism -Bacteria can metabolize nitrogen in a variety of ways -In nitrogen fixation, some bacteria convert atmospheric nitrogen (N ) to 2 ammonia (NH ) 3 • Metabolic cooperation -Cooperation between bacteria allows them to use environmental resources they could not use as individual cells -In the cynobacterium Anabaena, photosynthetic cells and nitrogen-fixing cells called heterocytes exchange metabolic products (see textbook figure 27.14) • Proteobacteria -These gram-negative bacteria include photoautotrophs, chemoautotrophs, and heterotrophs -Some are anaerobic, and others aerobic • Subgroup: Alpha Proteobacteria -Many species are closely associated with eukaryotic hosts -Scientists hypothesize that mitochondria evolved from aerobic alpha proteobacteria through endosymbiosis -Example: Rhizobium, which forms root nodules in legumes and fixes atmospheric N 2 -Example: Agrobacterium, which produces tumors in plants and is used in genetic engineering • Subgroup: Gamma Proteobacteria -Examples include sulfur bacteria such as chromatium and pathogens such as legionella, salmonella, and vibrio cholera -Escherichia coli resides in the intestines of many mammals and is not normally pathogenic • Subgroup: Epsilon Proteobacteria -This group contains many pathogens including campylobacter, which causes stomach ulcers -Ulcers and their history -Drs. Marshall and Warren -Nobel Prize in 2005 -Helped define the concept of “don’t try this at home” • Gram-positive bacteria -Gram-positive bacteria include: ~Actinobacteria, which decompose soil ~Bacillus anthracis, the cause of anthrax ~Clostridium botulinum, the cause of botulism ~Some staphylococcus and streptococcus, which can be pathogenic ~Mycoplasms, the smallest known cells ~Steptomyces, the source of many antibiotics • Ecological relationships and bacteria -Symbiosis is an ecological relationship in which two species live in close contact: a larger host and smaller symbiont -Prokaryotes often form symbiotic relationships with larger organisms -Parasites that cause disease are called pathogens • Benefits of Bacteria -Fermentation -Waste management -Toxic spill cleanup -Genetic engineering -Antibiotics • Archaea -Archaea share certain traits with bacteria and other traits with eukaryotes (see textbook table 27.2) -Some archaea live in extreme environments ad are called extremophiles -Extreme halophiles live in highly saline environments -Extreme thermophiles thrive in very hot environments -Methanogens live in swamps and marshes and produce methane as a waste product ~Methanogens are strict anaerobes and are poisoned by O 2 Protists and Algae • Protists -Protista is the informal name of the “kingdom” of mostly unicellular eukaryotes ~Advances in eukaryotic systematics have caused the classification of protists to change significantly ~Protists constitute a paraphyletic group (see phylogeny notes and/or textbook figure 26.10), and protista is no longer valid as a kingdom -Protists are eukaryotes and thus have organelles and are more complex than prokaryotes -Most protists are unicellular, but there are some colonial and multicellular species • Basic Protist Biology -Protists exhibit more structural and functional diversity than any other group of eukaryotes -Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell -Protists, the most nutritionally diverse of all eukaryotes, include: ~Photoautotrophs, which contain chloroplasts ~Heterotrophs, which absorb organic molecules or ingest larger food particles ~Mixotrophs, which combine photosynthesis and heterotrophic nutrition • Protists can reproduce asexually or sexually • Mutualisms in Protists -There is now considerable evidence that much protist diversity has its origins in endosymbiosis (a type of symbiosis in which a symbiont dwells within the body of its symbiotic partner) -Mitochondria evolve by endosymbiosis of an aerobic prokaryote -Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium -The plastid-bearing lineage of protists evolved into red algae and green algae -On several occasions during eukaryotic evolution, red and green algae underwent secondary endosymbiosis (see textbook figure 28.3), in which they were ingested by a heterotrophic eukaryote • Five Supergroups of Eukaryotes (see textbook figure 28.2) -It is no longer thought that amitochondriates (lacking mitochondria) are the oldest lineage of eukaryotes -Our understanding of the relationships among protist groups continues to change rapidly -One hypothesis divides all eukaryotes (including protists) into five supergroups • Excavata -The clade excavata is characterized by its cytoskeleton -Some members have a feeding groove -This controversial group includes diplomonads, parabasalids, and euglenozoans ~Diplomonads -Have modified mitochondria called mitosomes -Are often parasites, for example Giardia intestinalis ~Parabasalids -Have reduced mitochondria called hydrogenosomes Include Trichomonas vaginalis, the pathogen that causes yeast infections in human females ~Euglenozoa -Diverse clade that all have a spiral or crystalline rod of unknown function inside their flagella -Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast -Euglenids have one or two flagella that emerge from a pocket at one end of the cell • Chromalveolata -Clade is monophyletic and originated by a secondary endosymbiosis event (with red algae) -This clade is controversial and includes the alveolates and the stramenopiles ~Superphylum Alveolata protists have membrane bounded sacs (alveoli) just under the plasma membrane ~Alveolata includes the dinoflagellates, apicomplexans, and ciliates -Phylum Dinoflagellates are a diverse group of aquatic mixotrophs and heterotrophs -They are abundant components of both marine and freshwater phytoplankton -Each has a characteristic shape that in many species is reinforced by internal plates of cellulose -Dinoflagellate blooms are the cause of toxic “red tide” ~Not all red tides are red ~Not all red tides are harmful ~Phylum Apicomplexa are parasites of animals, and some cause serious human diseases -One end, the apex contains a complex of organelles specialized for penetrating a host -Most have sexual and asexual stages that require two or more different host species for completion -The apicomplexan Plasmodium is the parasite that causes malaria (see textbook figure 28.16 for life cycle) ~Plasmodium requires both mosquitoes and humans to complete its life cycle ~Approximately 2 million people die each year from malaria ~Sickle-cell anemia confers some protection • Phylum Stramenopila (or Heterokonts) -Diatoms are unicellular algae with a unique two-part, glass-like wall of hydrated silica -Golden algae are unicellular (some colonial) named for their color, which results form their yellow and brown carotenoids -Brown algae are the largest and most complex algae ~All are multicellular, and most are marine ~Brown algae include many species commonly called “seaweed” • Brown algae (see textbook figure 28.13 for life cycle) -The algal body is plantlike but lacks true roots, stems, and leaves and is called a thallus -The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades • Alternation of Generations -A variety of life cycles have evolved among the multicellular algae -The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms -Heteromorphic generations are structurally different, while isomorphic generations look similar • Rhizaria -DNA evidence supports Rhizaria as a monophyletic clade -Amoebas move and feed by pseudopodia; some but not all belong to the clade Rhizaria -Rhizarians include forams and radiolarians ~Both groups have hard shells called tests ~Pseudopodia extend through holes in the test • On the way to Plants -Archaeplastida is a supergroup used by some scientists and includes red algae, green algae, and land plants -Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont -The photosynthetic descendants of this ancient protist evolved into red algae and green algae -Land plants are descended from the green algae • Red Algae -Red algae are reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll -Red algae are usually multicellular, the largest are seaweeds • Green Algae -Named for their grass-green chloroplasts -Plants are descended from the green algae -The two main groups are chlorphytes and charophyceans (see textbook figure 28.23 for life cycle of chlorphyte) -Most chlorophytes live in fresh water, although many are marine -Other chlorophytes live in damp soil, as symbionts in lichens, or in snow • Watermelon Snow -Chlamydomonas nivalis -Pink comes from carotenoid astaxanthin ~Extracted from krill ~Used as a dye in farmed salmon • Unikonts -Proposed supergroup of eukaryotes ~Includes animals, fungi, and closely related protists -Amoehozoans ~Well supported clade ~Amoebas ~Slime molds (see textbook figures 28.25, 28.26) Fungi • Fungi -Fungi are diverse and widespread -They are essential for the well being of most terrestrial ecosystems (see ecology notes for more on ecosystems) because they break down organic material and recycle vital nutrients -In spite of their diversity, fungi share key traits, most importantly the way in which they derive nutrition • Fungal Nutrition -Fungi are heterotrophs (see protist and algae notes for more on heterotrophs) and absorb nutrients from outside of their body -Fungi use enzymes to break down a large variety of complex molecules into smaller organic compounds -Enzymes excreted break down ~Lignin (oxidases) ~Carbohydrates (cellulases) ~Phosphates (phosphatases) ~Proteins (proteases) *Note, all the above names in parentheses are types of enzymes, hence the suffix –ase -Human uses of fungal enzymes ~Effects of climate change ~Beer production ~Wastewater treatments ~Paper production • Body Form -The most common body structures are multicellular filaments and single cells (yeasts) -Some species grow as either filaments or yeasts; others grow as both • Fungal Morphology -The morphology of multicellular fungi enhances their ability to absorb nutrients -Fungi consist of mycelia, networks of branched hyphae adapted for absorption -Most fungi have cell walls made of chitin -Some fungi have hyphae divided into cells by septa with pores allowing cell-to-cell movement of organelles -Coenocytic fungi lack septa (see textbook figure 31.3) • Some fungi are carnivores -Hyphae can act as nooses, nets, or sticky traps -Hyphae penetrate victims • Mycorrhizae are mutually beneficial relationships between fungi and plant roots -Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex -Arbuscular mycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane • Specialized Hyphae in Mycorrhizal Fungi -Some unique fungi have specialized hyphae called haustoria that allow them to penetrate the tissues of their host (see textbook figure 31.4) • Mutualist dynamics -The fungus gains access to carbohydrates -The plant gains an increased ability to uptake water and minerals • Fungus Reproduction (see textbook figure 31.5 for life cycles) -Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually -Fungi can produce spores from different types of life cycles -Fungal nuclei are normally haploid, with the exception of transient diploid stages formed during the sexual life cycles -Sexual reproduction requires the fusion of hyphae from different mating types -Fungi use sexual signaling molecules called pheromones to communicate their mating type -Plasmogamy is the union of two parent mycelia -In most fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon -In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic -Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion -During karyogamy, the haploid nuclei fuse, producing diploid cells -The diploid phase is short-lived and undergoes meiosis, producing haploid spores -Reproducing without a partner ~Molds produce haploid spores by mitosis and form visible mycelia ~Yeasts reproduce asexually by simple cell division and the pinching of “bud cells” from a parent cell • Five Major Groups of Fungi -Chytrids ~Chytrids (phylum chytridiomycota) are formed in freshwater and terrestrial habitats ~They can be decomposers, parasites, or mutaulists ~Chytrids are unique among fungi in having flagellated spores, called zoospores ~Chytrids are a paraphyletic group ~Chytrids and Amphibians -Batrachochytrium dendrobatidis infects thousands of species of amphibians ~Drives populations to extinction -Frog mutations are caused by a flat worm (more on this later in the course) -Zygomycetes (see textbook figure 31.12 for life cycle) ~The zygomycetes (phylum zygomycota) exhibit great diversity of life histories ~They include fast-growing molds, parasites, and commensal symbionts ~The zygomycetes are named for their sexually produced zygosporangia ~Cool poo-based Shooting Fungus -Pilobolus grows on the excrement of herbivores -A Sporangium forms on the top of the stalk of a fruiting body -The stalk builds up fluid pressure and then explodes, shooting the spores toward the light (up to 2 meters) -Spores land on plants that are then eaten by herbivores -Glomeromycetes ~The glomeromycetes (phylum glomeromycota) were once considered zygomycetes ~They are now classified in a separate clade ~Glomeromycetes form arbuscular mycorrhizae (see mycorrhizae section above) -Ascomycetes (see textbook figure 31.16 for life cycle) ~Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats ~The phylum is defined by production of sexual spores in saclike asci, usually contained in fruiting bodies called ascocarps ~Ascomycetes are commonly called sac fungi ~Ascomycetes vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels ~Ascomycetes reproduction -Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia -Conidia are not formed inside sporangia; they are produced asexually at the tips of specialized hyphae called conidiophores -Ascomycetes also reproduce sexually (see fungus reproduction notes above) ~Ascomycetes and history -Claviceps purpurea -Known as Ergot -Infects grasses in 60 genera -Rye is very susceptible and it can be difficult to see an Ergot infection in rye flour -When eaten, it causes ergotism ~Symptoms include diarrhea, nausea, hallucinations, convulsions, tremor, burning sensations in the fingers and toes, gangrene, and the loss of extremities ~Often fatal -Ergotism ~The burning sensation lead to the name, Saint Anthony’s fire -Records of outbreaks go from 857 to 2004 -Religious order formed to take care of the afflicted -Founded more than 370 hospitals in Europe ~Outbreaks often in rural communities -Urban populations tend to eat white bread while rural would eat more rye ~Other hypothesized ergot effects include -Bewitching including the Salem Witch Trials -The Pied Piper of Hamlin ~Ergotism in history -1722 is when Peter the Great attempted to take the Dardanelles from the Ottoman Empire -The army would live off the land and farmers supplied the army with a large amount of rye -Horses and soldiers quickly showed signs of illness -20,000 soldiers died -Campaign failed and the modern state of Turkey owes much of its size to fungus -Basidomycetes (see textbook figure 31.18 for life cycle) ~Basidomycetes (phylum Basidiomycota) include mushrooms, puffballs, and shelf fungi, mutualists, and plant parasites ~The phylum is defined by a clublike structure called a basidium, a transient diploid stage in the life cycle ~The basidiomycetes are also called club fungi ~The life cycle of a basidiomycete usually includes a long-lived dikaryotic mycelium ~In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies called basidiocarps ~Mushrooms are examples of basidiocarps ~The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores • Fungus-Plant Mutualisms -Mycorrhizae are enormously important in natural ecosystems and agriculture -Plants harbor harmless symbiotic endophytes that live inside leaves or other plant parts -Endophytes make toxins that deter herbivores and defend against pathogens • Fungus-Animal Symbioses -Some fungi share their digestive services with animals -These fungi help break down plant material in the guts of cows and other grazing mammals -Many species of ants and termites use the digestive power of fungi by raising them in “farms” • Lichens (see textbook figure 31.23) -A lichen is a symbiotic association between a photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae -The fungal component of a lichen is most often an ascomycete (but can be a basidomycete) -Algae or cyanobacteria occupy an inner layer below the lichen surface -The algae provide carbon compounds, cyanobacteria provide organic nitrogen, and fungi provide the environment for growth -Morphological types of lichens ~Fruticose are shrublike ~Crustose are encrusting -Grow flat and spread across the surface (often rock) ~Foliose are leaflike -Humans and Lichens ~Used as dyes -Harris Tweeds from Scotland ~Used in perfumes and incense ~Susceptible to air pollution -Different species react to different amounts -Can be an indicator species like freshwater invertebrates can be used for water pollution • Fungi as Pathogens -About 30% of known fungal species are parasites or pathogens, mostly on or in plants -Some fungi that attack food crops are toxic to humans -Animals are much less susceptible to parasitic fungi than are plants -The general term for a fungal infection in animals is mycosis • Human Pathogens -Candida ~Common name is thrush ~Affects immunocompromised ~30% or more of systemic infections are fatal -Aspergillus ~Found on cereals and nuts ~Produces aflatoxins -Toxin and carcinogen -Cryptococcus ~Cause of meningitis in immunocompromised -Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread -Some fungi are used to produce antibiotics for the treatment of bacterial infections, for example, the ascomycete Penicillium -Genetic research on fungi is leading to applications in biotechnology ~For example, insulin-like growth factor can be produced in the fungus Saccharomyces cerevisiae • Quiz 1 Answers -Science is the study of the natural world and scientists look for patterns and work to understand the mechanisms that give rise to them. -An adaptation has evolved by selection -Chromosome number, behavior, and DNA are used to determine a phylogenetic tree -Bacteria cells are smaller than eukaryotic cells -Bacterial motility is aided by flagella -The process by which bacteria incorporate foreign DNA from the environment is transformation • Quiz 2 Answers -Which of the following taxa have chemoheterotrophs? Fungi -Which of the following is true of Archaea? Archaea is a sister taxon of Eukaryotes -The roots of the word, thermophile mean Heat Loving -Protists are non-monophyletic -The scientific discipline that is most interested in studying the movement of carbon and nitrogen through various biotic and abiotic sources is ecosystem ecology -The pellicle is found on euglena -Which of the following are the cause of “red tides?” Dinoflagellates -The plasmodium the merozoite is found on liver cells -The body of a brown algae is called thallus -Alternation of generations occurs in some multicellular organisms
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