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Q7(d):
Define the following terms and give one example for each:
(d) Mutualism
Solution :
Definition & Ecological Framework of Mutualism
In population ecology, Mutualism is defined as a specialized interspecific interaction in which both interacting species derive a net biological, reproductive, or physiological benefit. Within the standard ecological interaction matrix, mutualism is denoted by the mathematical notation $(+, +)$, indicating a positive impact on the evolutionary fitness of both populations involved.
[Per the principles of evolutionary biology, mutualistic relationships often drive co-evolution, where the two species tightly evolve in response to each other's physiological or structural changes over time.]
Step 1: Structural Dynamics of Mutualism
Mutualistic interactions can be broadly categorized based on the degree of biological dependence:
- Obligate Mutualism: A strict interdependence where neither species can survive, grow, or reproduce without the other (e.g., the relationship between a specific fig tree species and its specific pollinator wasp).
- Facultative Mutualism (Protocooperation): An interaction where both species benefit but can survive independently if separated (e.g., oxpeckers feeding on the ticks of a rhinoceros).
Step 2: Visual Representation of Mutualistic Interaction Dynamics
The following vector diagram illustrates the bidirectional flow of energy, resources, or services that characterizes a $(+, +)$ mutualistic interaction.
Step 3: Detailed Example & Biological Evidence
Example: Lichens (Fungi and Algae/Cyanobacteria)
A classic and highly rigorous example of obligate mutualism is the formation of Lichens. Lichens are composite organisms arising from algae or cyanobacteria (the photobiont) living among filaments of multiple fungi species (the mycobiont) in a mutualistic relationship.
- Role of the Fungi (Mycobiont): The fungal partner provides a structural anchor, retains high amounts of moisture, and absorbs essential inorganic minerals (like nitrogen and phosphorus) from the substratum. It essentially creates a protected micro-environment that shields the delicate algae from physical stress and desiccation.
- Role of the Algae (Photobiont): In return, the photosynthetic algae utilize the water and minerals provided by the fungus to synthesize organic carbohydrates (sugars) via photosynthesis. These organic nutrients are then translocated to the fungal partner, supplying its entire energy requirement.
[By the Principle of Resource Partitioning and Ecological Niche theory, neither the fungi nor the algae could independently colonize the extreme environments (such as bare rock or arctic tundras) that lichens readily inhabit as a mutualistic unit.]
Additional Classic Examples (For Context)
| Mutualistic System | Species 1 Contribution $(+)$ | Species 2 Contribution $(+)$ |
|---|---|---|
| Mycorrhizae | Fungi: Absorbs water and phosphorus from soil for the plant. | Higher Plants: Provide energy-yielding carbohydrates to the fungi. |
| Fig & Fig Wasp | Fig Tree: Offers safe oviposition (egg-laying) sites and developing seeds as food for wasp larvae. | Fig Wasp: Acts as the sole, highly specific pollinator for the fig inflorescence. |
Final Solution: Mutualism is an obligate or facultative interspecific biological interaction characterized by a $(+, +)$ dynamic, wherein both interacting species experience increased evolutionary fitness or survival benefits. A prominent example is the Lichen, a symbiotic unit where a fungus provides shelter, water, and minerals, while an alga (or cyanobacterium) provides organic nutrients synthesized via photosynthesis.
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?
- 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 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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