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Q7(a):
Define the following term and give one example for it: Commensalism
Solution :
Definition: Commensalism
Commensalism is a type of biological interaction between two distinct species in which one organism (the commensal) derives a benefit—such as nutrients, shelter, support, or locomotion—while the other organism (the host) remains neither significantly harmed nor helped by the association [Per the ecological theory of biotic interactions, this is denoted as a ($+, 0$) relationship].
Theoretical Basis
In a commensal relationship, the fitness of the commensal is positively influenced by the presence of the host, while the host’s fitness remains neutral. Unlike mutualism ($+, +$), there is no reciprocal exchange of benefits, and unlike parasitism ($+, -$), there is no metabolic or physical detriment inflicted upon the host.
Illustrative Example: Epiphytic Orchids
Orchids growing as epiphytes on the branches of mango trees represent a classic instance of commensalism. In this scenario:
- The Commensal (Orchid): The orchid benefits by gaining access to better sunlight and pollination opportunities, which are restricted on the dense forest floor [Based on the principle of resource partitioning in canopy layers].
- The Host (Mango Tree): The mango tree is unaffected by the presence of the orchid, as the orchid does not derive water or mineral nutrients from the tree’s tissues (unlike a parasite), nor does it compete for soil resources.
Summary Table of Interaction Dynamics
| Interaction Type | Species A Effect | Species B Effect |
|---|---|---|
| Commensalism | $+$ (Benefited) | $0$ (Neutral) |
Final Solution: Commensalism is a ($+, 0$) population interaction where one species benefits and the other remains unaffected; a primary example is an orchid growing on a mango tree branch.
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(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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