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Q5:
What is the ecological principle behind the biological control method of managing with pest insects?
Solution :
Theoretical Foundation: The Concept of Predation and Parasitism
The biological control of pest insects is fundamentally governed by the ecological principle of Interspecific Interaction, specifically focusing on the dynamics of Predation and Parasitism as outlined in the Lotka-Volterra model of population ecology. [Per the ecological interaction classification].
Step 1: Analysis of Trophic Interactions
In a balanced ecosystem, natural regulation of population density occurs through predator-prey or parasite-host relationships. The principle posits that a biological control agent (a predator or parasitoid) will feed upon or infect a target pest species, thereby keeping the pest population density below the Economic Injury Level (EIL). [By the law of Top-Down Regulation].
Step 2: Mathematical Basis of Population Control
The interaction can be modeled using the Lotka-Volterra equations, where the population growth of the prey (pest) is constrained by the presence of the predator (control agent):
$\frac{dN}{dt} = rN - aNP$
$\frac{dP}{dt} = faNP - qP$
- $N$: Density of pest population.
- $P$: Density of predator/parasitoid population.
- $r$: Intrinsic rate of increase of the pest.
- $a$: Searching efficiency of the predator.
- $f$: Conversion efficiency.
- $q$: Mortality rate of the predator.
[By Lotka-Volterra Predatory Equation Logic].
Step 3: Ecological Mechanisms
Biological control relies on the following specific ecological traits to maintain stability:
| Mechanism | Description |
|---|---|
| Specificity | The predator must be host-specific to avoid non-target mortality. |
| Density Dependence | The control agent's impact increases as the pest density increases, preventing runaway growth. |
| Numerical Response | The ability of the predator to increase its population size in response to increased prey availability. |
Visualization of Predator-Prey Oscillations
Conclusion on Ecological Stability
Unlike chemical pesticides which often disrupt the food web or lead to biomagnification, biological control utilizes the principle of Niche Specialization. By introducing a natural enemy that occupies the same niche or trophic level as a competitor/predator of the pest, the system returns to an equilibrium state where the pest population is naturally suppressed. [Per the Competitive Exclusion Principle and Community Ecology Theory].
Final Solution: The ecological principle is based on the biotic interaction of predation and parasitism, where the population of a pest is regulated by the introduction of its natural enemy, which suppresses the pest density through density-dependent interactions, effectively maintaining ecosystem equilibrium without the use of synthetic chemicals.
More Questions from Class 12 Biology Organisms and Populations EXERCISES
- Q1: List the attributes that populations possess but not individuals.
- Q1: List the attributes that populations possess but not individuals.
- Q2: If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase (\(r\)) of the population?
- Q2: If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase ((r)) of the population?
- Q3: Name important defence mechanisms in plants against herbivory.
- Q3: Name important defence mechanisms in plants against herbivory.
- Q4: An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?
- Q4: An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?
- Q5: What is the ecological principle behind the biological control method of managing with pest insects?
- Q6: Define population and community.
- Q6: Define population and community.
- Q7(a): Define the following terms and give one example for each: (a) Commensalism
- Q7(a): Define the following term and give one example for it: Commensalism
- Q7(b): Define the following terms and give one example for each: (b) Parasitism
- Q7(b): Define the following term and give one example for it: Parasitism
- Q7(c): Define the following terms and give one example for each: (c) Camouflage
- Q7(c): Define the following term and give one example for it: Camouflage
- Q7(d): Define the following terms and give one example for each: (d) Mutualism
- Q7(d): Define the following term and give one example for it: Mutualism
- Q7(e): Define the following terms and give one example for each: (e) Interspecific competition
- Q7(e): Define the following term and give one example for it: Interspecific competition
- Q8: With the help of suitable diagram describe the logistic population growth curve.
- Q8: With the help of suitable diagram describe the logistic population growth curve.
- Q9: Select the statement which explains best parasitism.
- Q9: Select the statement which explains best parasitism.
- Q10: List any three important characteristics of a population and explain.
- Q10: List any three important characteristics of a population and explain.
CBSE Solutions for Class 12 Biology Organisms and Populations
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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