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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?
Solution :
Step 1: Identification of the Ecological Interaction
The interaction between an orchid plant and a mango tree is ecologically classified as commensalism. Furthermore, the specific physical relationship in which one plant grows on the surface of another without deriving nourishment from the host is termed epiphytism.
Step 2: Analysis of the Benefiting Species (The Orchid)
In this interaction, the orchid acts as an epiphyte [from Greek epi- meaning 'upon' and phyton meaning 'plant'].
- Advantage Gained ($+$): Orchids naturally grow in dense forest environments where competition for light is intense. By anchoring themselves onto the elevated branches of a mango tree, they gain superior access to sunlight for photosynthesis.
- Nutrient and Water Acquisition: The orchid does not possess haustoria (parasitic roots). Instead, it possesses specialized aerial roots covered in a spongy, water-absorbing tissue called velamen. This allows the orchid to absorb atmospheric moisture and dissolved nutrients directly from rain and humid air.
Step 3: Analysis of the Host Species (The Mango Tree)
The mango tree serves purely as a physical substrate for the orchid.
- Lack of Harm: The orchid does not penetrate the host's vascular system (xylem or phloem). Consequently, it does not siphon water, minerals, or photosynthates from the mango tree.
- Lack of Benefit: The presence of the orchid provides no selective advantage, nutritional supplement, or physical benefit to the mango tree.
Step 4: Theoretical Justification via Population Interaction Matrix
According to population ecology, interspecific interactions are categorized based on the effect each species has on the other.
Let Species A be the Orchid and Species B be the Mango tree:
| Interaction Type | Species A (Orchid) | Species B (Mango Tree) | Resulting Notation |
|---|---|---|---|
| Commensalism | Benefited ($+$) | Unaffected ($0$) | $+/0$ |
[Per the principles of population dynamics, a $+/0$ interaction unequivocally defines commensalism, distinguishing it from mutualism ($+/+$) and parasitism ($+/-$).]
Step 5: Visual Representation of the Epiphytic Relationship
The diagram below illustrates the spatial relationship and ecological dynamics between the epiphyte and the host tree.
Final Solution: The interaction between an orchid and a mango tree is described as Commensalism ($+/0$). The orchid (an epiphyte) is benefited ($+$) by gaining structural support and improved access to light without tapping into the host's nutrients, while the mango tree remains completely unaffected ($0$), neither suffering harm nor gaining any ecological advantage.
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?
- 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 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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