Viruses: Discovery and Infection Methods

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Questions and Answers

What term did Beijerinck coin after isolating the virus from diseased plant liquid?

Lytic

Prophage

Virus (correct)

Retrovirus

What is a key characteristic that differentiates lytic infection from lysogenic infection?

Lysogenic infection uses RNA exclusively

Lytic infection destroys the host cell while lysogenic does not (correct)

Lysogenic infection creates mRNA for rapid reproduction

Lytic infection occurs slowly while lysogenic occurs rapidly

Which of the following viruses is classified as an RNA virus?

Tuberculosis

Ebola

Influenza

Common Cold (correct)

What does the term 'prophage' refer to?

The viral DNA integrated into the host's DNA Signup and view all the answers

How do viruses typically replicate within a host cell?

By using the host's cellular machinery to produce copies Signup and view all the answers

Why are viruses not considered alive?

All of the above Signup and view all the answers

What makes retroviruses unique compared to other viruses?

They convert RNA into DNA during replication Signup and view all the answers

What is a significant difference between cells and viruses?

Cells contain organelles, whereas viruses do not Signup and view all the answers

What is the main structural component of bacterial cell walls?

Peptidoglycan Signup and view all the answers

Which method do bacteria primarily use for reproduction?

Binary Fission Signup and view all the answers

What distinguishes Archaea from bacteria at a cellular level?

Absence of Peptidoglycan in cell walls Signup and view all the answers

What is a role of prokaryotes in the ecosystem?

Photosynthesis and oxygen production Signup and view all the answers

Which type of organism primarily uses light energy for its metabolic processes?

Photoautotroph Signup and view all the answers

How do fungi primarily reproduce under favorable conditions?

Sexually Signup and view all the answers

Which of the following is not a classification of fungi?

Ciliatae Signup and view all the answers

What is a characteristic of facultative anaerobes?

Can utilize oxygen or ferment for energy Signup and view all the answers

What is the primary benefit of the mycorrhizae relationship between fungi and plants?

Increases nutrient absorption for plants Signup and view all the answers

What causes superbugs to develop?

Overuse of antibiotics leading to resistance Signup and view all the answers

What is an example of an obligate anaerobe's reaction to oxygen?

Experiences toxicity and dies Signup and view all the answers

What distinguishes protists from fungi and plants?

Their classification as unicellular or multicellular organisms Signup and view all the answers

What do pseudopods enable some protists to do?

Change shape and move Signup and view all the answers

Which of the following conditions can lead to the formation of endospores in bacteria?

Unfavorable growth conditions Signup and view all the answers

What is the primary reason that bryophytes, such as mosses, are limited in height?

They have no water-conducting tissues. Signup and view all the answers

Which plant group includes conifers that produce seeds in cones?

Gymnosperms Signup and view all the answers

In the plant life cycle, what is the term for the diploid phase?

Sporophyte Signup and view all the answers

What adaptation allows gymnosperms to not require water for fertilization?

The production of pollen Signup and view all the answers

Which type of plant has vascular tissues that enable transport of nutrients and water?

Tracheophytes Signup and view all the answers

What phase do gametophytes represent in the alternation of generations?

Haploid Signup and view all the answers

What is the primary function of rhizoids in mosses?

Anchoring the plant Signup and view all the answers

Which of the following groups of plants can conduct water through tissues?

Gymnosperms Signup and view all the answers

In angiosperms, what structure protects the seeds?

Ovary Signup and view all the answers

Which group of plants is primarily characterized by having flowers?

Angiosperms Signup and view all the answers

What occurs during asexual reproduction in first plants?

Cells burst out to form zoospores Signup and view all the answers

How long can a zygote remain dormant in the lifecycle of certain plants?

Several years Signup and view all the answers

Which form of algae is recognized as part of the plant kingdom?

Green algae Signup and view all the answers

What is the function of fronds in ferns?

Photosynthesis Signup and view all the answers

What is the main role of the Casparian Strip in a plant?

It prevents nutrient ions from exiting back into the soil. Signup and view all the answers

Which type of roots are typically associated with monocot plants?

Fibrous Roots Signup and view all the answers

What primarily causes water to enter the leaf through the stoma?

Transpiration Signup and view all the answers

What is primarily produced by the vascular cambium in woody plants?

Wood Signup and view all the answers

How do guard cells respond to low water pressure?

They close the stoma. Signup and view all the answers

Which hormone is primarily responsible for promoting growth in plant roots?

Auxins Signup and view all the answers

What is the role of the palisade mesophyll in a leaf?

Absorbing light for photosynthesis Signup and view all the answers

What type of flowers bloom in response to long periods of darkness?

Short-Day Flowers Signup and view all the answers

What is phototropism?

Growth towards a light source Signup and view all the answers

What factors influence the seasonal movement of nutrients within a plant?

Pressure flow and chemical signals Signup and view all the answers

What occurs as water evaporates from the leaf during transpiration?

Water from the roots rushes in. Signup and view all the answers

What is the primary function of the cork cambium in a plant?

To generate bark Signup and view all the answers

What role does ethylene play in plant development?

Induces fruit ripening Signup and view all the answers

Which structure in leaves prevents tearing during harsh weather?

Dermal Tissue Signup and view all the answers

What characteristic differentiates dicots from monocots?

Dicots have flower petals in multiples of 4 or 5. Signup and view all the answers

Which part of a flower is responsible for protecting the developing bud?

Sepals Signup and view all the answers

What is a defining feature of woody plants compared to herbaceous plants?

Woody plants have thick cells known as wood. Signup and view all the answers

During the angiosperm life cycle, what is formed after the pollen tube grows into the embryo sac?

A zygote Signup and view all the answers

Which of the following statements about vascular tissue is true?

Xylem transports water using tracheids and vessel elements. Signup and view all the answers

What are the three types of ground tissue primarily known for?

Support, storage of carbohydrates, and protection Signup and view all the answers

What process allows for the creation of new buds or roots by utilizing unspecialized cells?

Vegetative reproduction in meristems Signup and view all the answers

Which of the following describes a characteristic of annual plants?

They live for only one growing season. Signup and view all the answers

What role do companion cells play in the phloem?

Keeping the nuclei of sieve tubes alive Signup and view all the answers

What is the function of the polar nuclei in the angiosperm life cycle?

They will fertilize another sperm cell to create an endosperm. Signup and view all the answers

Which tissue is primarily responsible for protecting the plant's epidermis?

Dermal tissue Signup and view all the answers

What distinguishes collenchyma from sclerenchyma in ground tissue?

Collenchyma provides flexible support. Signup and view all the answers

What happens to the ovary walls after fertilization in an angiosperm?

They thicken to form a fruit surrounding the seed. Signup and view all the answers

Which type of roots are associated with monocots?

Fibrous roots Signup and view all the answers

Study Notes

Viruses and Their Discovery

Ivanoski extracted diseased plant liquid, leading to Beijerinck's discovery and the term "virus".
Stanley isolated virus crystals, proving viruses are not living (living things don't crystallize).
Viruses consist of lipids, proteins, and nucleic acid (DNA or RNA).
Nucleic acid is contained within a capsid, varying between viral types.

Methods of Infection

Viruses require a host cell for survival.
Viruses have specific proteins binding to host cell receptors.
Infection often kills the host cell, with the cell bursting (lysing) and releasing the virus's genetic material.
Lytic Infection: Fast, active reproduction. Replicates viral genetic material and disrupts cell function, leading to cell lysis within 2 days.
Lysogenic Infection: Slow, steady passive reproduction. Inserts viral DNA into host DNA (prophage) without immediate cell destruction, replicating with the host's DNA. The prophage becomes lytic under certain conditions.

RNA Viruses

Also known as retroviruses, many viruses contain RNA.
RNA is directly used for replication, bypassing DNA transcription.
Examples include the Common Cold and HIV.
Common Cold replicates in the nose.
HIV is dormant until conditions allow it to destroy the immune system.

Diseases and Treatments

Viruses cause disease by disrupting cellular processes.
Viruses can be treated via vaccination and hygiene.

Virus vs. Cell

Viruses rely on host cells for reproduction, likely evolved after cells.
Viruses store genetic material in a capsid; cells store it in a nucleus.
Cells have organelles; viruses do not.
Viruses reproduce using a host; cells reproduce via mitosis.
Viruses use DNA or RNA; cells only use DNA.
Viruses do not grow, develop, obtain energy, or respond to stimuli; they are therefore not alive.

Prokaryotes

Unicellular organisms lacking a nucleus, including bacteria and archaea.
Bacteria cell walls are made of peptidoglycan, have outer membranes, flagella for movement, and pili for attachment.
Archaea are similar to bacteria but lack peptidoglycan, and their DNA structure is more like eukaryotic cells.

Prokaryote Structure and Function

Prokaryotes come in bacilli (rod-shaped), cocci (circular), and spirilla (spiral) forms.
Some are non-motile; others use flagella (flagellates) or cilia (ciliates) for movement.
Flagella can rotate or swing; cilia can pedal or row.
Reproduction involves binary fission (dividing into two).
Under unfavorable conditions, prokaryotes form endospores (protective walls).
Prokaryotes can evolve through mutations or conjugation (information exchange).

Prokaryote Energy Gain and Loss

Heterotrophs: Obtain energy from organic materials.
Photoheterotrophs: Use light energy in addition to organic materials.
Photoautotrophs: Use light to convert CO2 into organic compounds.
Chemoautotrophs: Obtain energy from chemical reactions.
Obligate aerobes: Require oxygen for cellular respiration.
Obligate anaerobes: Cannot tolerate oxygen, use fermentation.
Facultative anaerobes: Can use either cellular respiration or fermentation.

Prokaryote Roles

Decompose dead organisms.
Produce oxygen via photosynthesis.
Fix nitrogen.
Produce drugs and food products (e.g., yogurt).
Digest waste.
Form microbiomes in humans.

Pathogenic Strains

Bacteria cause disease by disrupting cellular processes and disrupting homeostasis.
Controlling bacteria involves methods like sanitation, proper food storage, disinfection, heat sterilization, and antibiotics.
Superbugs are resistant to many antibiotics.

Emerging Diseases

Previously unknown or harder-to-control diseases.

Prions

Prions are misfolded proteins (PrP) that cause brain diseases like scrapie and mad cow disease.

Protists

Eukaryotic organisms not fitting other kingdom classifications.
Mainly unicellular, with some multicellular examples (e.g., brown algae).
Protists predate other eukaryotic kingdoms.
No single evolutionary lineage (not a true clade).
Once grouped as plant-like and animal-like; now grouped into 8 categories.

Protist Movement and Reproduction

Some protists use pseudopods (cytoplasmic extensions) for movement.
Others use flagella or cilia.
Some are non-motile, relying on wind, water, or other organisms.
Reproduction is mostly mitotic (asexual) under favorable conditions.
Sexual reproduction forms zygotes through alternation of generations under unfavorable conditions.

Protist Roles

Autotrophs (photosynthesis) in aquatic ecosystems.
Mutualistic or parasitic relationships.
Examples include zooxanthellae, trichonympha, cryptosporidium, giardia, entamoeba, trypanosoma, and plasmodium.

Fungi

Heterotrophic eukaryotes with chitin cell walls.
Chitin is also found in arthropod exoskeletons.

Fungi Structure and Function

Some fungi are unicellular (yeasts).
Others are multicellular, consisting of branching filaments (hyphae).
Hyphae may have cross-walls (septa).
The visible mushroom part is the fruiting body; the underground network is the mycelium.

Fungi Reproduction

Primarily reproduce sexually (via gametes).
Some produce spores of similar sizes; others produce a smaller and larger gamete.
Mushrooms are usually haploid.

Diversity of Fungi

Basidiomycota: Sexual spores form in club-shaped structures (basidia).
Ascomycota: Sexual spores form in sac-like structures (asci).
Zygomycota: Produces zygospores that can remain dormant.
Chytridiomycota: Spores are flagellated with cellulose-digesting abilities.

Roles of Fungi

Decomposition of organic matter through enzyme use.
Parasites harming crops or other organisms.
Symbiotic relationships (e.g., lichens, mycorrhizae).
Production of food (bread, alcohol), and some medicines.

Plants

Eukaryotic, non-motile organisms, autotrophic via photosynthesis.
Cellulose in cell walls. Few are parasitic or saprobic.
Need sunlight, CO2, water, and minerals.

Plant Origins

Earliest plants were aquatic and unicellular.
Oldest land plant fossils date back 472 million years.
Plants adapted to land by developing water conservation and reproduction methods.

Plant Classifications

Algae (first plants): Initial aquatic plants.
Bryophytes (mosses): Develop embryos.
Tracheophytes (ferns): Transport water using specialized tissues.
Gymnosperms (conifers): Produce seeds (naked).
Angiosperms (flowers): Produce seeds within a fruit.

General Plant Life Cycle

Follows alternation of generations (sporophyte/gametophyte).
Sporophyte (diploid) produces haploid spores via meiosis.
Spores develop into gametophytes.
Gametophytes produce gametes which fuse to form a diploid zygote.
Zygote develops into a new sporophyte.
Gametophyte is smaller than sporophyte, and sporophyte is often the dominant phase in later plant evolution.

First Plants

Early plants were aquatic and small, lacking seeds.
Green algae are the only algae belonging to the plant kingdom (e.g. Spirogyra, Volvox).

First Plant Life Cycle

Asexual reproduction forms identical cells (zoospores).
Sexual reproduction forms zygotes that may remain dormant until conditions are suitable.

Bryophytes

Mosses, hornworts, liverworts.
First plants to colonize land but with no vascular tissue.
Limited height due to water dependence.
Sporophyte is dependent on gametophyte for nutrients.
Need water for sperm to reach egg (fertilization).

Bryophyte Life Cycle

Spores germinate to form gametophytes.
Gametophytes produce gametes (antheridia/archegonia).
Sperm swim to egg; zygote forms.
Zygote grows into sporophyte.
Sporophyte produces spores.

Tracheophytes

Ferns, and others.
Have vascular tissues (xylem/phloem).
Lignin strengthens vascular tissues.
Allow for taller growth (up to 130 meters).
Contain root systems (rhizomes, fronds).

Tracheophyte Life Cycle

Sporophyte (fern) produces spores via meiosis.
Spores germinate to form gametophytes.
Gametes (sperm/egg) need water for fertilization; zygote forms.
Zygote develops into sporophyte.

Gymnosperms

Conifers and others.
Produce seeds in cones, making fertilization less dependent on water.

Gymnosperm Life Cycle

Meiosis produces pollen.
Ovules are found on cone scales.
Pollen lands on ovule, growing a pollen tube.
Sperm fertilizes egg, forming a zygote.
Zygote develops into embryo.
Embryo develops into mature sporophyte within seeds.

Angiosperms

Flowering plants.
Seeds enclosed within a fruit for protection and dispersal.
Monocots (one cotyledon) vs. dicots (two cotyledons).

Angiosperm Diversity

Monocots vs. Dicots: Differ in seed leaf (cotyledon) number, vein pattern, flower petal number, vascular bundle arrangement, and root systems.
Woody vs. Herbaceous: Woody plants have lignin-reinforced tissues; herbaceous plants do not.
Annuals, Biennials, Perennials: Differ in lifespan.

Parts of a Flower

Sepals: Enclose and protect the developing flower.
Petals: Attract pollinators.
Stamens (male): Produce pollen.
Carpels/Pistils (female): Receive pollen.

Angiosperm Life Cycle

Meiosis produces male gametes (pollen).
Meiosis produces female gametes (embryo sac).
Pollen lands on stigma, growing a pollen tube to ovule.
Double fertilization (two sperm fuse with female cells).
Zygote forms embryo; endosperm nourishes embryo.
Ovary wall develops into a fruit; protects seeds.
Seed can be dispersed by wind, water, or animals.
Some reproduce asexually through vegetative reproduction.

Plant Structure and Function

Dermal Tissue

Protects the plant (epidermis, cuticle).
Trichomes are leaf projections.

Vascular Tissue

Transports water and nutrients (xylem/phloem).
- Xylem components: Tracheids, vessel elements.
- Phloem components: Sieve tubes, companion cells.

Ground Tissue

Provides support and stores food (parenchyma, collenchyma, sclerenchyma).

Meristems

Unspecialized cells for growth (apical, floral).

Roots, Stems, and Leaves

Roots: Anchor plant, absorb water & nutrients.
Stems: Support, transport materials.
Leaves: Photosynthesis, transpiration, gas exchange

Plant Growth and Development

Primary Growth: Apical meristems increase stem length.
Secondary Growth: Vascular cambium and cork cambium increase stem girth.

Other relevant concepts

Transpiration: Water loss through stomata.
Transpirational Pull: Water movement through the plant.
Pressure Flow Hypothesis: Nutrient transport in phloem.
Hormones: Regulate plant growth and development through Target Cells and receptors.
- Auxins: Growth, phototropism, apical dominance.
- Cytokinins: Cell division, delay aging.
- Ethylene: Fruit ripening, abscission.
- Gibberellins: Growth, seed germination.
- Abscisic Acid: Growth inhibition, dormancy.
Tropisms: Growth responses to stimuli.
Photoperiodism: Flowering response to light/dark cycles (long-day, short-day).
Winter Dormancy: Seasonal adaptations in response to long nights and cold temperatures.
Human Uses of Plants: Agriculture, food production, building materials, GMOs, heirloom plants.

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Description

Explore the fascinating world of viruses, from their discovery by Ivanoski and Beijerinck to the methods of infection they employ. This quiz covers the structure of viruses, their requirements for host cells, and the differences between lytic and lysogenic infections.