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What is true about viruses?

  • Viruses have cellular organization.
  • Viruses can reproduce on their own.
  • Viruses are subcellular particles. (correct)
  • Viruses are living organisms.

    • Viruses can shift between living and nonliving states.

    True

    What did Martinus Beijerinck name the unknown agent smaller than bacteria?

    virus

    Viruses are measured in millimicrons, which is one-millionth of a __________.

    <p>millimeter</p> Signup and view all the answers

    Match the following virus classifications with their respective host organisms:

    <p>Bacterial viruses = Bacteria Plant viruses = Seed plants Human and animal viruses = Human and animal cells</p> Signup and view all the answers

    What are organisms that depend upon other living things for food called?

    <p>Heterotrophs</p> Signup and view all the answers

    Bacteria reproduce by binary fusion.

    <p>False</p> Signup and view all the answers

    What is the term for bacteria that use nonliving or dead organic matter for food?

    <p>Saprophytes</p> Signup and view all the answers

    Match the following phylum of protozoans with their organisms:

    <p>Phylum Sarcodina = Amoeba Phylum Ciliophora = Paramecium Phylum Mastigophora = Euglena Phylum Sporozoa = Plasmodium</p> Signup and view all the answers

    Plasmodium is a protozoan that causes __________ in human beings and other warm-blooded animals.

    <p>malaria</p> Signup and view all the answers

    Which form of life is considered the most common on our planet?

    <p>Bacteria</p> Signup and view all the answers

    Louis Pasteur received the Nobel prize for proving that bacteria could cause diseases.

    <p>False</p> Signup and view all the answers

    What does the slime layer surrounding a bacterium help with?

    <p>Protection</p> Signup and view all the answers

    Bacteria are normally measured in units of ___________.

    <p>millimicrons</p> Signup and view all the answers

    Match the following bacterial shapes with their descriptions:

    <p>Coccus = Sphere-shaped cells Bacillus = Rod-shaped cells Spirillum = Cells shaped like bent rods or corkscrews</p> Signup and view all the answers

    Define microbiology and explain its significance in understanding higher forms of life.

    <p>Microbiology is the study of microorganisms, such as bacteria, viruses, fungi, and parasites. It is significant in understanding higher life forms because these microorganisms play crucial roles in various biological processes, ecosystems, and human health.</p> Signup and view all the answers

    Discuss the reasons for considering viruses living or nonliving.

    <p>Viruses are considered nonliving because they lack the ability to reproduce and carry out metabolic processes on their own. However, they are also considered living because they can replicate inside host cells and evolve over time.</p> Signup and view all the answers

    In what way is a temperate phage a potential 'seed of destruction'? Explain.

    <p>A temperate phage can integrate its DNA into the DNA of its host bacterium and remain dormant for a long time. If conditions change, the phage can become active, replicate, and potentially destroy its host bacterium.</p> Signup and view all the answers

    Explain the structure and composition of bacteriophages. Discuss their significance in virus research.

    <p>Bacteriophages are viruses that infect and replicate within bacteria. They consist of genetic material (DNA or RNA) surrounded by a protein coat. Bacteriophages are significant in virus research as they can be used to study viral infection mechanisms, evolution, and as tools for genetic engineering.</p> Signup and view all the answers

    Describe the structure and size of viruses compared to cells.

    <p>Viruses are much smaller than cells and consist of genetic material (DNA or RNA) enclosed in a protein coat. They lack cellular machinery and organelles present in cells.</p> Signup and view all the answers

    Name five diseases caused by viruses. Explain why many viruses were initially thought to be pathogenic.

    <p>Diseases Caused by Viruses: 1. Influenza 2. HIV/AIDS 3. COVID-19 4. Measles 5. Hepatitis Many viruses were initially thought to be pathogenic because they infect host cells, leading to symptoms of disease. It was believed that all viruses caused harm due to their ability to disrupt cellular functions.</p> Signup and view all the answers

    Explain the discovery of viruses, including the contributions of Dmitri Iwanowski and Wendell Stanley.

    <p>The discovery of viruses involved Dmitri Iwanowski observing that something smaller than bacteria was causing disease, leading to the realization of viruses. Wendell Stanley crystallized the tobacco mosaic virus, proving that viruses are composed of nucleic acids and proteins.</p> Signup and view all the answers

    Name three virus diseases that affect human beings. Explain the impact of viruses on normal cell activity.

    <p>Virus Diseases Affecting Human Beings: 1. COVID-19 2. Influenza 3. HIV/AIDS Viruses can impact normal cell activity by hijacking cellular machinery for replication, causing cell damage, and triggering immune responses that lead to inflammation and tissue damage.</p> Signup and view all the answers

    Biologists frequently say that understanding the life processes of single-celled protozoans helps them to understand the life processes of complicated organisms like a man. Why is this probably true?

    <p>This is likely true because single-celled protozoans share fundamental biological processes with complex organisms, such as metabolism, reproduction, and response to stimuli. Studying these processes in simpler organisms can provide insights into the workings of more complex life forms.</p> Signup and view all the answers

    Compare methods of locomotion, digestion, and sensitive response in the amoeba, paramecium, and euglena.

    <p>Amoeba moves using pseudopods, digests food through phagocytosis, and responds to stimuli by changing direction. Paramecium moves using cilia, digests food in vacuoles, and reacts to stimuli with cilia movement. Euglena moves using a flagellum, performs photosynthesis and phagocytosis for nutrition, and responds to light with its eyespot.</p> Signup and view all the answers

    Study Notes

    Introduction to Microbiology

    • Microbiology is the study of small, living organisms that show the most basic properties of life.
    • These simple organisms can help us understand higher forms of life.

    Viruses

    • Viruses are not considered living organisms, but they show signs of life in the presence of a living cell.
    • Viruses are smaller than cells, and are composed of genetic material (DNA or RNA) surrounded by a protein coat.
    • Viruses can only reproduce inside a host cell, and they do not carry out metabolic processes on their own.
    • There are different types of viruses, including:
      • Bacterial viruses (bacteriophages)
      • Plant viruses
      • Human and animal viruses

    Properties of Viruses

    • Viruses can cause disease, but some are harmless.
    • Viruses can be mutated to produce different strains.
    • Viruses can be affected by the environment in which they grow.
    • Viruses can vary in virulence (ability to cause disease).

    Classification of Viruses

    • Viruses are classified based on the type of host cell they infect.
    • Examples of virus classifications include:
      • Bacterial viruses (bacteriophages)
      • Plant viruses
      • Human and animal viruses

    Bacteriophages

    • Bacteriophages are viruses that infect bacteria.
    • They have a protein coat and a core of genetic material (DNA or RNA).
    • Bacteriophages can be used to combat bacterial diseases.
    • However, using phages to combat disease is still a developing area of research.

    Human and Animal Viruses

    • Many diseases are caused by viruses, including:
      • Chicken pox
      • Measles
      • Warts
      • Virus pneumonia
      • Yellow fever
      • Cold sores
      • Fever blisters
    • Viruses can cause cancer, and researchers are studying the link between viruses and cancer.
    • Bacteria are the most common form of life on Earth.
    • They are found almost everywhere, including:
      • Air
      • Water
      • Soil
      • Food
      • The bodies of plants and animals
    • Bacteria are thought to have been the first form of life on Earth.
    • They are capable of taking energy from various sources, including:
      • Iron
      • Sulfur
      • Nitrogen compounds

    Louis Pasteur and the Birth of Bacteriology

    • Louis Pasteur was a French scientist who made significant contributions to the field of biology.
    • He is credited with:
      • Developing the first vaccine for rabies
      • Defeating the theory of spontaneous generation
      • Studying fermentation and its role in the production of alcohol and lactic acid
      • Developing the germ theory of disease, which states that bacteria can cause disease

    What are Bacteria?

    • Bacteria are small, single-celled organisms that are classified in the kingdom Protista.
    • They are typically measured in millimicrons (mµ).
    • There are different shapes and forms of bacteria, including:
      • Sphere-shaped (coccus)
      • Rod-shaped (bacillus)
      • Spiral-shaped (spirillum)

    Structure of Bacterial Cells

    • Bacterial cells have a cell wall that gives them their shape.
    • They have a thin plasma membrane that surrounds the cytoplasm.
    • They have a nuclear area that contains chromatin bodies made up of DNA.
    • They do not have mitochondria, but have respiratory enzymes on or near the cell membrane.
    • They have a slime layer that surrounds the cell and helps them to stick to a food supply or host cell.### Bacteria
    • The capsule of bacteria is a key factor in their virulence, with forms that produce the capsule causing more serious infections.
    • The capsule may protect the bacteria from the host's natural defenses.
    • Bacteria can move using flagella, which are thread-like structures that extend from the cell membrane.
    • Flagella are made up of protein molecules and can be seen as tiny threads under a light microscope.
    • Bacteria can also move by means of Brownian movement, which is caused by the bumping of molecules and other particles against the bacteria.

    Conditions for Growth of Bacteria

    • Bacteria require certain conditions to grow and reproduce, including temperature, moisture, and darkness.
    • Most bacteria are most active at temperatures between 26°C and 38°C, with some forms growing best at temperatures as low as 0°C or as high as 85°C.
    • Bacteria require moisture to grow, with dry surroundings causing water loss and inactivity.
    • Most bacteria grow best in the dark, with sunlight slowing down growth and ultraviolet rays killing most bacteria.

    Nutrition in Bacteria

    • Bacteria can be autotrophs, making their own food compounds from inorganic substances such as carbon dioxide.
    • Energy is required for this process, which is obtained by breaking down inorganic compounds of iron, sulfur, or nitrogen.
    • Some bacteria can also carry out a form of photosynthesis.
    • Most bacteria are heterotrophs, relying on organic compounds formed by other organisms for food.

    Bacterial Reproduction

    • Bacteria reproduce by binary fission, with a cell dividing into two identical cells.
    • Under good conditions, bacteria can multiply rapidly, with a cell dividing into two cells in as little as 20 minutes.

    Helpful Activities of Bacteria

    • Not all bacteria are disease-causing, with many species being harmless and even helpful.
    • Soil bacteria play a key role in breaking down dead plants and animals, recycling nutrients and allowing plants to grow.
    • Bacteria are used in industry to produce foods such as vinegar and silage, and are important in the dairy industry.

    Preserving Food from Bacterial Action

    • Bacteria are a major competitor for food, causing spoilage and waste.
    • Methods for preserving food include killing all bacteria present, then sealing the food in a container, as well as keeping foods in conditions that slow down bacterial reproduction.
    • Chemical preservatives, cooling, freezing, salt curing, and dehydration can also be used to preserve food.

    Protozoans

    • Protozoans are a group of single-celled organisms that are often classified as animals, but do not fit into the traditional animal kingdom.
    • There are four main phyla of protozoans: Sarcodina, Ciliophora, Mastigophora, and Sporozoa.

    Sarcodina - Amoeba

    • Amoebas are a type of protozoan that move using pseudopodia, which are extensions of the cytoplasm.
    • Amoebas respond to their environment, with no eyes, they are sensitive to light and seek dim or dark areas.
    • Amoebas also respond to food, and can become inactive and withdraw into a round mass called a cyst when conditions are unfavorable.

    Ciliophora - Paramecium

    • Paramecia are a type of protozoan that move using cilia, which are hair-like structures.
    • Paramecia are complex organisms that have a slipper-shaped cell and respond to their environment, including swimming constantly to avoid bumping into objects.

    Mastigophora - Euglena

    • Euglenas are a type of protozoan that move using a flagellum and have a second method of movement called euglenoid movement, which involves a gradual change in the shape of the cell.
    • Euglenas are often classified as plants, but are actually protists, and carry out photosynthesis.
    • Euglenas have a red eyespot, which is highly sensitive to light.

    Sporozoa - Plasmodium

    • Sporozoans are a type of protozoan that are all parasites, and do not have a method of movement on their own.
    • Plasmodium is a type of sporozoan that causes malaria, and is transmitted through the bite of an infected mosquito.

    Fungi

    • Fungi are a group of organisms that are not plants, but are often mistaken for them.
    • Fungi are classified into two phyla: Myxomycophyta, which includes the slime molds, and Eumycophyta, which includes the true fungi.
    • The true fungi are further divided into four classes: Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes.

    Classifying Fungi

    • The classification of fungi is based on the characteristics of their bodies, including the presence or absence of cell walls, the shape of their hyphae, and the formation of spores.
    • Fungi are often classified as either molds or yeasts, depending on their growth habits.

    Phylum Eumycophyta

    • The true fungi are classified into four classes: Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes.
    • Phycomycetes are the alga-like fungi, Ascomycetes are the sac fungi, Basidiomycetes are the club fungi, and Deuteromycetes are the imperfect fungi.

    Phylum Myxomycophyta

    • The slime molds are a type of fungi that are like giant masses of amoebas, and have a plasmodium, which is a mass of protoplasm with many nuclei but no cell walls.
    • Slime molds are often classified as "slime fungi" or "fungus animals" due to their unique characteristics.

    Microbiology

    • Microbiology is the study of microorganisms, including bacteria, viruses, and fungi.
    • Microbiology is significant in understanding higher forms of life, as microorganisms have evolved to live in a wide range of environments and have developed unique characteristics to survive.

    Viruses

    • Viruses are a type of microorganism that are not considered to be living cells, but are capable of reproducing and evolving.
    • Viruses are often considered to be on the border between living and non-living, as they require a host cell to replicate and do not have the characteristics of living cells.
    • Temperate phages are a type of virus that can integrate into the host cell's DNA and remain dormant, but can also cause the host cell to lyse and release new viral particles.
    • The structure and composition of bacteriophages are important in virus research, as they are used to study the genetics of bacteria and the replication of viruses.

    Discovery of Viruses

    • The discovery of viruses is attributed to Dmitri Iwanowski and Wendell Stanley, who discovered that viruses are capable of reproducing and evolving.

    • Viruses were initially thought to be pathogenic, as they were associated with diseases, but it is now known that many viruses are harmless and some are even beneficial.### Discovery of Viruses

    • Dmitri Iwanowski discovered viruses

    • Wendell Stanley made significant contributions to the field of virology

    Virus Diseases Affecting Human Beings

    • Three examples of virus diseases that affect human beings are:
    • These viruses impact normal cell activity by:

    Importance of Understanding Single-Celled Organisms

    • Understanding the life processes of single-celled protozoans helps biologists understand the life processes of complicated organisms like humans because:

    Comparison of Amoeba, Paramecium, and Euglena

    • Locomotion:
      • Amoeba: pseudopodia
      • Paramecium: cilia
      • Euglena: flagella
    • Digestion:
      • Amoeba: phagocytosis
      • Paramecium: oral groove
      • Euglena: chloroplasts and phagocytosis
    • Sensitive Response:
      • Amoeba: sensitive to touch and light
      • Paramecium: sensitive to touch and light
      • Euglena: sensitive to light

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