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Questions and Answers
What is the most direct form of antagonism in biological control?
Which type of pathogens does Pasteuria penetrans target?
Root-knot nematodes
Which of the following is a type of mixed-path antagonism?
Hypoviruses infect the _____ fungus.
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2,4-diacetylphloroglucinol is produced by Agrobacterium radiobacter.
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Name one antibiotic produced by Bacillus subtilis.
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Match the antibiotic with its target pathogen:
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Direct antagonism does not involve killing the pathogen.
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What is the primary function of homeostasis in an ecosystem?
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What occurs if homeostasis is unsuccessful in an organism?
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Which behavior is described as a mechanism for maintaining homeostasis in mammals and birds?
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What is a consequence of overcrowding in small consumer species?
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How can prey abundance impact predator populations?
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Which factor does NOT contribute to the homeostasis mechanisms in ecosystems?
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What does a stable ecosystem primarily rely on for successful homeostasis?
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What is the result of multiple stress factors acting on a population in an ecosystem?
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What is one of the main benefits of biodiversity in an ecosystem?
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How does biodiversity contribute to the adaptability of a community?
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Which of the following is a consequence of monoculture that biodiversity helps to mitigate?
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What is a characteristic of ecosystems with high biodiversity?
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In terms of biodiversity, what risk is associated with monoculture systems?
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What does a diverse ecosystem provide that enhances agricultural resilience?
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Which factor is NOT a benefit of biodiversity in ecosystems?
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Why is biodiversity important for the adaptation of species within an ecosystem?
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What has contributed significantly to improvements in crop productivity and quality over the past 100 years?
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What is one harmful effect of using broad spectrum pesticides in agriculture?
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What is a potential consequence of pest resistance development due to pesticide use?
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What percentage of sprayed insecticides typically reaches non-target species or environments?
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What is a major concern regarding the environmental impact of excessive pesticide use?
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Which statement best reflects the balance in natural ecosystems regarding pests?
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What political action is being taken regarding chemical pesticides?
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How do agrochemicals affect pest populations when a specific crop is grown?
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Study Notes
Biological Control of Plant Pathogens
- Utilizes natural antagonistic organisms to suppress plant pathogens.
Mechanisms of Biological Control
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Direct Antagonism: Involves hyperparasitism and predation, where a biological control agent (BCA) directly attacks the pathogen.
- Examples include:
- Ampelomyces quisqualis: hyperparasitic fungus.
- Lysobacter enzymogenes: suppresses various plant pathogens.
- Trichoderma virens: effective against several soil-borne fungi.
- Examples include:
-
Mixed-path Antagonism: Combines multiple mechanisms, such as:
- Antibiotics: compounds like 2,4-diacetylphloroglucinol and phenazines produced by bacteria.
- Lytic Enzymes: enzymes like chitinases and glucanases that degrade pathogen cell walls.
- Unregulated Waste Products: toxic compounds such as ammonia and hydrogen cyanide affecting pathogens.
- Physical/Chemical Interference: Involves blockage of soil pores or consumption of germination signals.
-
Indirect Antagonism:
- Competition for resources, including nutritional compounds and physical space.
- Induction of host resistance via interactions with pathogen-associated molecular patterns.
Hyperparasitism and Predation
- Considered the most direct form of antagonism.
-
Classes of Hyperparasites:
- Obligates, such as Pasteuria penetrans, which targets root-knot nematodes.
- Hypoviruses which can reduce the virulence of pathogens like Cryphonectria parasitica.
Antibiotic-Mediated Suppression
- Involves the secretion of microbial toxins that inhibit other microorganisms, functioning at low concentrations.
- Important antibiotics include:
- 2,4-diacetylphloroglucinol: Effective against Pythium spp., causes damping-off.
- Agrocin 84: Targets Agrobacterium tumefaciens, responsible for crown gall disease.
- Bacillomycin D: Aflatoxin contamination control against Aspergillus flavus.
- Xanthobaccin A: Suppresses Aphanomyces cochlioides, also linked to damping-off.
- Gliotoxin: Targets Rhizoctonia solani, responsible for root rots.
Additional Antibiotics Produced by BCAs
- Iturin A: Effective against Botrytis cinerea and Rhizoctonia solani, responsible for damping-off.
- Phenazines: Combat Gaeumannomyces graminis var.tritici, causing take-all disease.
- Mycosubtilin: Targets Pythium aphanidermatum, associated with damping-off.
- Pyoluteorin: Addresses Pythium ultimum, involved in damping-off.
The Biological World: Balance in Natural Communities
- Homeostasis is the property of living organisms that maintains stable internal conditions.
- Disruption of homeostasis can lead to diseases and cellular malfunction.
- Ecosystem homeostasis reflects a dynamic equilibrium that adapts to changing environmental conditions.
Homeostatic Mechanisms
- Ecosystems utilize self-regulating processes for stability while adapting to survival conditions.
- Key homeostatic mechanisms include:
- Matter cycling and energy flow
- Protection of production levels
- System structure
Attack-Avoidance Behavior
- In mammals and birds, members of the same species engage in harassing behavior, expending energy in interactions that prevent serious harm but regulate population dynamics.
Overcrowding and Its Effects
- Overcrowding in small animals like mice can cause stress that damages the thyroid gland, resulting in severe population declines due to endocrine issues.
Prey-Predator Dynamics
- Abundant prey populations lead to increased predator births, creating cycles of abundance and eventual crashes when resources decline.
- Predators may migrate or risk starvation when prey becomes scarce.
Reproductive Homeostasis
- Reproductive strategies like multiple births are influenced by population density, with crowded conditions favoring single births.
Biodiversity vs Monoculture
- Biodiversity: Greater variety of organisms strengthens community resilience, adaptability, and stability.
- Monoculture: Involves cultivating a single crop species repeatedly, leading to decreased diversity.
Consequences of Monoculture
- Heavy reliance on chemical fertilizers and pesticides increases disease susceptibility and environmental degradation.
- Results include crop failures, reduced soil fertility, increased erosion, loss of genetic diversity, and diminishing habitats for beneficial species.
Biological Control of Plant Pathogens
- Controlling plant diseases is critical for maintaining food production quality and quantity.
- Traditional reliance on chemical pesticides is being challenged due to environmental pollution concerns.
Natural Ecosystem Balance
- Pests exist in a complex equilibrium with plant communities, where both beneficial and harmful interactions occur.
- Disturbance through intensive crop production disrupts this balance, leading to pest population shifts.
Harmful Effects of Pesticides
- Chemical pesticides can lead to:
- Pest resistance and resurgence
- Harm to non-target organisms
- Increased pesticide residues in crops and animals
- Environmental pollution
Pesticide Usage Statistics
- Global pesticide usage is approximately 3 million tons annually, significantly boosting agricultural productivity.
- Over 98% of insecticides and 95% of herbicides end up beyond their target, affecting non-target species and environmental elements.
Health and Environmental Concerns
- Synthetic pesticides pose risks to humans and the environment, prompting calls for reduced chemical usage and alternative agricultural methods.
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Description
Explore the mechanisms and types of interspecies antagonism that lead to effective biological control of plant pathogens. This quiz delves into concepts like hyperparasitism, predation, and examples such as Ampelomyces quisqualis. Ideal for students studying plant pathology and biological control methods.
