Symbiotic Relationships in Biology
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Questions and Answers

What is a defining characteristic of the association between Yeti crabs and Riftia pachyptila?

  • Both are gutless organisms
  • Both require sunlight for survival
  • Both are found in association with deep-sea hydrothermal vents (correct)
  • Both live in shallow waters

Which of the following is NOT one of the major types of symbiotic associations mentioned?

  • Mutualism
  • Parasitism
  • Predation (correct)
  • Commensalism

What is the primary benefit to herbivores from their bacterial symbionts?

  • Enhanced ability to photosynthesize
  • Reduction in body mass
  • Improved breathing efficiency
  • Supplementation of nutritional needs (correct)

Which example illustrates a vertically inherited intracellular endosymbiont lifestyle?

<p>Buchnera and aphids (A)</p> Signup and view all the answers

What is a major advantage of developing symbiotic relationships for multicellular life forms?

<p>Increased metabolic diversity (B)</p> Signup and view all the answers

What type of association is represented by the relationship between Rhizobium and legumes?

<p>Mutualism (C)</p> Signup and view all the answers

In what way can symbiotic microorganisms contribute to an animal host's survival?

<p>Detoxifies harmful substances (B)</p> Signup and view all the answers

Which of these relationships would be classified as mutualism?

<p>A cow and its gut bacteria (C)</p> Signup and view all the answers

What type of symbiotic relationship allows both organisms to benefit?

<p>Mutualism (C)</p> Signup and view all the answers

In which scenario does one organism benefit while the other remains unharmed?

<p>Commensalism (C)</p> Signup and view all the answers

Which term describes a symbiotic relationship where one organism cannot survive without its partner?

<p>Obligate (C)</p> Signup and view all the answers

What characterizes facultative symbiosis?

<p>Survival is not dependent on the symbiosis (C)</p> Signup and view all the answers

What is a key characteristic of Buchnera aphidicola in relation to aphids?

<p>It is an obligate endosymbiont (C)</p> Signup and view all the answers

What role typically defines the host in a symbiotic association?

<p>The larger member of the association (B)</p> Signup and view all the answers

Which of the following is an example of ectosymbiosis?

<p>A lichen growing on a rock surface (D)</p> Signup and view all the answers

What is one main benefit of the symbiotic relationship between fungi and algae in lichens?

<p>Algae provide nutrients in inhospitable environments (A)</p> Signup and view all the answers

Which statement accurately describes the nutritional benefits of symbiotic relationships?

<p>Symbionts can supply vitamins and essential amino acids to the host. (C)</p> Signup and view all the answers

In what form can defense and protection benefits be provided in symbiotic associations?

<p>Producing enzymes for detoxification (C)</p> Signup and view all the answers

What is a characteristic of endosymbiosis?

<p>The symbiont is often intracellular. (A)</p> Signup and view all the answers

What is a primary factor that can affect symbiotic relationships over time?

<p>Availability of resources (D)</p> Signup and view all the answers

Which of the following types of associations involves clear cost/benefit analysis?

<p>Mutualism (B)</p> Signup and view all the answers

What is the primary nutrient that aphids obtain from the plant phloem?

<p>Non-essential amino acids (D)</p> Signup and view all the answers

What advantage does Buchnera provide to the aphid host?

<p>Essential amino acids (B)</p> Signup and view all the answers

What factor has limited genetic exchange for Buchnera?

<p>Being sequestered inside the host (A)</p> Signup and view all the answers

How do Rhizobium and Agrobacterium primarily differ?

<p>In the types of plasmids they possess (B)</p> Signup and view all the answers

What type of relationship does Agrobacterium have with plants?

<p>Parasitism (D)</p> Signup and view all the answers

What is the estimated size of Buchnera's genome?

<p>Approximately 0.5 Mb (B)</p> Signup and view all the answers

What ecological role do Rhizobium and Agrobacterium share?

<p>Both can exist as free-living organisms (C)</p> Signup and view all the answers

Which of the following statements is true about the nutritional mutualism between aphids and Buchnera?

<p>Aphids rely on Buchnera for essential amino acids. (B)</p> Signup and view all the answers

Which type of symbiotic relationship involves both partners benefiting but not being entirely dependent on each other?

<p>Facultative mutualism (C)</p> Signup and view all the answers

In the relationship between Euprymna scolopes and Aliivibrio fischeri, what advantage does the light produced by the bacteria provide to the squid?

<p>Counter illumination for predator avoidance (B)</p> Signup and view all the answers

What is the primary function of the VirA/VirG two-component system in Agrobacterium?

<p>To initiate T-DNA transfer into plant cells (C)</p> Signup and view all the answers

What is one role of leghemoglobin in the symbiotic relationship between rhizobia and legumes?

<p>It regulates oxygen levels for nitrogen fixation. (B)</p> Signup and view all the answers

Which compound do legumes secrete to attract rhizobia?

<p>Flavonoids (C)</p> Signup and view all the answers

Which term best describes symbiotic relationships where one partner benefits at the expense of another?

<p>Parasitism (D)</p> Signup and view all the answers

How do rhizobia identify compatible legume partners?

<p>By swimming toward root exudates via chemotaxis. (C)</p> Signup and view all the answers

During symbiont acquisition, what anatomical adaptation helps the squid capture Aliivibrio fischeri?

<p>Specialized mantle and gill structures (D)</p> Signup and view all the answers

What role do chemical signals play in symbiotic relationships within soil environments?

<p>They help symbionts locate their host (D)</p> Signup and view all the answers

What do rhizobia specifically provide to legumes in the symbiotic relationship?

<p>Ammonium ions for amino acid biosynthesis. (A)</p> Signup and view all the answers

What triggers transcriptional changes in the plant during the nodulation process?

<p>The recognition of nod factors by cell surface receptors. (C)</p> Signup and view all the answers

What happens to obligate endosymbionts over time regarding their genetic makeup?

<p>They become metabolic specialists and lose many genes (A)</p> Signup and view all the answers

What could happen if plant mechanisms to regulate carbon flow to nodules are suppressed?

<p>The plant may potentially die due to overgrowth of rhizobia. (C)</p> Signup and view all the answers

What type of symbiotic relationship allows some partners to benefit without the other being affected?

<p>Facultative commensalism (A)</p> Signup and view all the answers

How do rhizobia induce root hair curling in legumes?

<p>By activating gene expression with nod factors. (D)</p> Signup and view all the answers

What type of interaction exists between rhizobia and legumes?

<p>Mutualism. (D)</p> Signup and view all the answers

Flashcards

Symbiosis

A close and often long-term interaction between two different species where at least one species benefits.

Mutualism

A type of symbiosis where both species benefit from the interaction.

Commensalism

A type of symbiosis where one species benefits while the other is neither harmed nor helped.

Parasitism

A type of symbiosis where one species benefits at the expense of the other.

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Endosymbiont

An organism that lives within the body of another organism.

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Ectosymbiont

An organism that lives on the surface of another organism.

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Horizontal Gene Transfer

The transfer of genetic material between organisms that are not parent and offspring, often through viruses or plasmids.

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Evolution

The process of gaining new functions through mutations or gene transfer.

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Host

The larger member of a symbiotic association, not necessarily the one providing benefits.

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Lichen

A symbiotic relationship between a fungus and an alga or cyanobacterium that creates a unique and resilient organism.

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Obligate mutualism

A type of mutualism where both partners cannot survive without each other.

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Facultative mutualism

A type of mutualism where both partners can survive independently of each other, but benefit from the interaction.

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Direct transmission of symbionts

The transfer of symbionts from one host to another through direct contact, such as from parent to offspring.

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Buchnera

A tiny bacterium that lives inside aphids and helps them obtain essential amino acids.

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Plasmid

A small, circular piece of DNA that can replicate independently of the main chromosome and can be transferred between bacteria.

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Rhizobia

Bacteria that can fix atmospheric nitrogen (N2) into usable ammonia (NH3) for plants.

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Legumes

Plants that host Rhizobia in their roots and form symbiotic relationships with them.

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Leghemoglobin

A protein that binds oxygen in legume root nodules, regulating oxygen levels for nitrogen fixation.

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Rhizobia chemotaxis

A bacterial chemotaxis response towards plant root secretions.

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Flavonoids

Plant-produced compounds that activate nodulation genes in Rhizobia.

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Nod factors

Molecules produced by Rhizobia that trigger root hair curling and nodule formation in legumes.

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C-flow regulation

The process where the plant controls and regulates the flow of carbon (sugars) to the nodule.

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Agrobacterium tumefaciens

A bacterium that can cause crown gall disease in plants by transferring its DNA into the plant genome.

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Facultative Commensalism

A relationship in which both species benefit, but the interaction is not essential for either to survive. One species can live without the other.

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Study Notes

Symbiosis I: Definitions and Diversity

  • Yeti Crab ( Kiwa hirsuta) is found associated with deep-sea hydrothermal vents.

Additional Symbiotic Species

  • Kiwa puravida is another species found in the same environments as the Yeti Crab.

  • Giant, gutless worms ( Riftia pachyptila), 1-2 meters in length, are found in deep-sea hydrothermal vents.

Types of Symbiosis and Associations

  • Defining an Association: Describing the cost/benefit analysis of symbiotic relationships.

  • Lichens: A partnership between fungi and algae or cyanobacteria. The partnership allows these microbes to live in more inhospitable environments.

  • Aphids & Buchnera: Buchnera aphidicola (a proteobacterium) is an obligate and intracellular endosymbiont inside pea aphids. It's been around for over 150 million years.

  • Rhizobium & Agrobacterium: Both are gram-negative proteobacteria found in soil, either free-living or closely associated with plants. They differ in the genes on giant plasmids.

    • Rhizobium: Has a Sym (symbiosis) plasmid that allows it to invade plant roots, form root nodules, and fix nitrogen. This is a mutualistic relationship.
    • Agrobacterium tumefaciens: Has a Ti (tumor inducing) plasmid that infects plant cells, sometimes resulting in a parasitism relationship.
  • Euprymna scolopes and Aliivibrio fischeri: Euprymna scolopes (squid) uses light from Aliivibrio fischeri (bacteria) for predator avoidance. The squid is born without these bacteria.

Symbiosis Characteristics & Types

  • Host: The larger organism in a symbiotic association.
  • Symbiont: The smaller organism in a symbiotic association.
  • Ectosymbiosis: Symbiont lives on or outside the host.
  • Endosymbiosis: Symbiont lives inside the host's cells (usually intracellular).

Types of Associations Defined by Cost/Benefit

  • Mutualism: All members benefit from the association.
  • Commensalism: One member benefits, and the other is unaffected.
  • Parasitism: One member benefits at the expense of the other.

Terminology and Considerations

  • Obligate: The organism cannot survive without its partner.
  • Facultative: The organism can survive with or without its partner.
  • Direct Transmission: Symbionts transferred from one host to another or from parent to offspring.
  • Acquisition from environment: The organism acquires symbionts from the environment every generation.

Additional Information

  • Syntrophy: A type of mutualistic relationship where one member provides nutrition to the other or to one organism that lives off of metabolic products of the other.

  • Impact of Association on Buchnera Evolution: Buchnera has a tiny genome (~0.5 Mb) and massive gene loss. It's an obligate endosymbiont and lacks genetic exchange.

  • Mutualism or Controlled Parasitism: Once established, the bacteria fix nitrogen, and the plant maintains bacteria in its roots while the bacteria suppress natural defenses of the plant.

  • Agrobaterium tumefaciens: Causes crown gall disease in plants. It attaches to wounded plants, takes plant DNA from its Ti plasmid, and integrates it into the plant cell's nucleus.

  • Ti Plasmid ("Tumor inducing"): A plasmid in Agrobacterium tumefaciens that transfers DNA into plant cells, causing uncontrolled growth and the production of opines.

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Description

Test your knowledge on the various types of symbiotic associations and their characteristics in biological contexts. This quiz covers examples, benefits, and the roles of symbiotic microorganisms in ecosystems, focusing on mutualism and other relationships. Perfect for students studying biology and ecology.

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