Biology - Monera - Quick Guides | Biology

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Study GuideBiology–Monera1. Introduction to Prokaryotes and VirusesWhat Are Prokaryotes?Prokaryotes aremicroscopic organismsfound in two major domains:BacteriaandArchaea. Thesecells are very simple in structure compared to plant oranimal cells.•Prokaryotic cellsdo not have a nucleus.•They alsolack membrane-bound organellessuch as mitochondria or chloroplasts.•The only structures they have for making proteins areribosomes.Instead of a nucleus, their genetic material is located in a region called thenucleoid. This DNA is:•Asingle loop•Double-stranded•Free within the cell (not enclosed by a membrane)1.1How Prokaryotes ReproduceProkaryotes reproduce through a simple, asexual process known asbinary fission.Here’s what happens:1.The DNA is copied.2.The cell grows longer.3.The cell splits into two identical cells.Unlike human cells, this process doesnot involve mitosis. Even without mitosis, binary fission is fastand very effective.

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Study Guide1.2Where Prokaryotes LiveProkaryotes are incredibly adaptable. You can find themalmost everywhere on Earth, including:•Soil•Water•Air•On and inside living organismsThey have been around for about3.5 billion years, making them some of theoldest life formsonthe planet. Over time, they have evolved to survive in nearly every environment—on the surface,underground, and even in extreme conditions.1.3Shapes of Prokaryotic CellsScientists often classify prokaryotes based on theirshape, which helps with identification.•Cocci(singular:coccus) arespherical•Bacilli(singular:bacillus) arerod-shaped•Spiral-shaped bacteriacome in two forms:○Spirochetesif they are rigid○Spirilla(singular:spirillum) if they are flexible1.4Prokaryotes and the Human BodyRecent research has highlighted how important prokaryotes are to human health, especially throughthemicrobiome.Themicrobiomerefers to the many bacterial communities that liveon and inside the human body.These microorganisms play key roles in digestion, immunity, and overall health.•Your intestines alone contain about700 different speciesof prokaryotes.•Amazingly, prokaryotic cells in your bodyoutnumber your own human cells by about tento one.

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Study GuideThis means that prokaryotes are not just tiny organisms around us—they are essential partners inkeeping us healthy.1.5Why Prokaryotes MatterAlthough prokaryotes are small and simple, they are powerful, ancient, and essential to life on Earth.Understanding them helps us better understand biology, health, and the world around us.2. Quiz Prokaryotes and Viruses1. QuestionWhich of the following doesNOTdescribe prokaryotic cells?Answer Choices•Their hereditary material is a single loop of double-stranded DNA•They contain no organelles, only ribosomes•They divide by mitosisCorrect AnswerThey divide by mitosisWhy This Is CorrectProkaryotic cellsdo not divide by mitosis. Instead, they reproduce through a simpler process calledbinary fission, which does not involve the stages of mitosis seen in eukaryotic cells.The other statements correctly describe prokaryotic cells:•Their DNA exists as asingle loop of double-stranded DNAin a region called the nucleoid.•Theylack membrane-bound organellesand contain only ribosomes for protein synthesis.2. QuestionHow long haveprokaryotes been on Earth?

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Study GuideAnswer Choices•1.5 billion years•2.5 billion years•3.5 billion yearsCorrect Answer3.5 billion yearsWhy This Is CorrectProkaryotes are theoldest known forms of life on Earth. Scientific evidence shows they haveexisted for about3.5 billion years, surviving and evolving in nearly every environment on the planet.This long history explains their incredible diversity and ability to live in extreme conditions.3. QuestionWhich of the following descriptions isCORRECT?Answer Choices•bacilli = spiral•cocci = spherical•spirochete = rod shapedCorrect Answercocci = sphericalWhy This Is CorrectBacteria are commonly classified by theirshape:•Cocciarespherical(round) in shape.•Bacilliarerod-shaped, not spiral.•Spirochetesarespiral-shaped, not rods.

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Study GuideTherefore, the only correct description iscocci = spherical.4. QuestionWhat isthe microbiome?Answer Choices•all the species of bacteria living in a community•all the species of bacteria living in an ecosystem•all the species of bacteria living in or on the human bodyCorrect Answerall the species of bacteria living in or on the human bodyWhy This Is CorrectThemicrobiomerefers to the collection of microorganisms—especially bacteria—that livein and onthe human body, such as on the skin, in the mouth, and in the digestive tract. These microorganismsplay important roles in digestion, immunity, and overall health.5. QuestionHuman intestines are home to how many species of prokaryotes?Answer Choices•100•1,000•200Correct Answer1,000

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Study GuideWhy This Is CorrectThe human intestines contain avery diverse microbiome, withabout 1,000 different species ofprokaryotes. These microorganisms help with digestion, vitamin production, and protection againstharmful pathogens.3. Domain BacteriaWhat Is DomainBacteria?Domain Bacteriaincludes the prokaryotic organisms that people come into contact with every day.These bacteria are found almost everywhere—on surfaces, in food, in soil, and even inside ourbodies. Although they are tiny, they are incredibly diverse and play many important roles in natureand industry.3.1Characteristics of BacteriaHow Bacteria Get Their FoodMost bacteria areheterotrophic, which means they cannot make their own food. Instead, they getenergy fromorganic matter.•The largest group of bacteria aresaprobic.These bacteria feed ondead or decaying plants and animals.•A smaller number of bacteria areparasitic.These bacteria live inside ahost organismand can cause disease.Not all bacteria rely on other organisms for food. Some areautotrophic, meaning theymake theirown food.3.2Autotrophic BacteriaSome autotrophic bacteria carry outphotosynthesis, similar to plants.

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Study Guide•They usepigmentsdissolved in their cytoplasm to capture energy from light.•Two major groups of photosynthetic bacteria are:○Green sulfur bacteria○Purple bacteria•The pigments in these bacteria are similar to plant pigments, even though they are not plants.Other autotrophic bacteria arechemosynthetic.•These bacteria usechemical reactionsinstead of sunlight as their energy source.•They use this energy to produce their own food.3.3Where Bacteria Can LiveBacteria are extremely adaptable and can survive in many different environments.3.3.1 Temperature Preferences•Psychrophilic bacterialive invery coldtemperatures.•Mesophilic bacterialive atmoderate temperatures, such as human body temperature.•Thermophilic bacteriathrive invery hotenvironments.3.3.2 Oxygen Requirements•Aerobic bacteriarequireoxygento survive.•Anaerobic bacterialive in environmentswithout oxygen.•Facultative bacteriacan survivewith or without oxygen, depending on what is available.3.3.3 pHLevels•Most bacteria prefer aneutral pHof about7.•Some bacteria live inacidic environments, such as yogurt or sour cream.

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Study Guide•Others live inalkaline environments.•Certain bacteria can even survive at apH of 2, like that found in the humanstomach.3.4Activities of BacteriaBacteria in the EnvironmentBacteria are essential to life on Earth.•Some bacteria live on the roots oflegume plants(such as beans and peas).•These bacteriafix nitrogenfrom the air and convert it into forms plants can use.•Plants use nitrogen to makeamino acids and proteins, which then pass to animals throughfood chains.Other bacteria act asdecomposers.•They break down dead organisms and waste in landfills and natural environments.•This processrecycles essential elements, returning them to the ecosystem.3.5Bacteria in Industry and MedicineBacteria are also extremely useful to humans.In thefood industry, bacteria are used to make:•Cheese•Yogurt and other fermented dairy products•Sauerkraut•PicklesInindustry and medicine, bacteria are used to produce:•Antibiotics•Chemicals and dyes•Vitamins and enzymes

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