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Q1:
List the attributes that populations possess but not individuals.
Solution :
Definition of Population Attributes
In biological ecology, an individual organism possesses characteristics such as birth, death, and sex. However, a population—defined as a group of individuals of the same species living in a specific geographical area at a specific time—possesses unique emergent properties that cannot be attributed to a single organism. These attributes are statistical properties derived from the collective behavior of the group.
Key Attributes of Populations
The following table delineates the distinction between individual attributes and their corresponding population-level expressions:
| Attribute | Description for Individuals | Description for Populations |
|---|---|---|
| Birth Rate (Natality) | An individual is either born or not. | Expressed as the number of births per capita per unit time [per capita birth rate]. |
| Death Rate (Mortality) | An individual either dies or is alive. | Expressed as the number of deaths per capita per unit time [per capita death rate]. |
| Sex Ratio | An individual is either male or female. | The ratio of males to females in the population (e.g., 40% males to 60% females). |
| Age Distribution | An individual has a specific chronological age. | The percentage of individuals of different ages (Pre-reproductive, Reproductive, and Post-reproductive). |
| Population Density | N/A | The total number of individuals of a species per unit area or volume at a given time. |
Visual Representation of Population Age Pyramids
Analytical Justification of Population Properties
- Per Capita Metrics: Birth and death rates are calculated using the formula $\frac{\Delta N}{N \cdot \Delta t}$, where $\Delta N$ is the change in population size, $N$ is the initial population size, and $\Delta t$ is the time interval [Per Ecological Population Dynamics].
- Age Pyramids: The shape of the age pyramid reflects the growth status of the population. A triangular pyramid indicates a growing population, while an urn-shaped pyramid indicates a declining population [Per Demographic Transition Theory].
- Population Density ($N$): This is the most vital metric for assessing the success of a species in an ecosystem, influenced by immigration ($I$), emigration ($E$), natality ($B$), and mortality ($D$), expressed as $N_{t+1} = N_t + [(B + I) - (D + E)]$.
Final Solution: The attributes that populations possess but individuals do not include: Population Density (number of individuals per unit area), Birth Rate (per capita natality), Death Rate (per capita mortality), Sex Ratio (ratio of males to females), and Age Distribution (proportion of individuals at different life stages).
More Questions from Class 12 Biology Organisms and Populations EXERCISES
- 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 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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