In a country, at any time, the population has the same number of young and mature ones. What type of growth does it reflect?
Stable
Understanding Population Growth Types
The question asks about the type of population growth in a country where, at any given time, the number of young individuals is equal to the number of mature individuals. This characteristic relates directly to the age structure of the population, which is a key indicator of its growth pattern.
Analyzing Population Age Structure
The distribution of individuals among different age groups (young, mature, old) significantly influences population growth. Let's consider what the condition "same number of young and mature ones" implies:
- Young individuals: These are pre-reproductive or early reproductive individuals who will contribute to future births. A large proportion of young individuals suggests high birth rates and potential for rapid growth.
- Mature individuals: These are typically in the reproductive age group. The number of mature individuals indicates the current reproductive potential of the population.
- Equal numbers: Having the same number of young and mature individuals suggests a relatively balanced age distribution, where there isn't a significantly larger cohort entering the reproductive phase compared to those currently in it. This balance is often associated with stable birth rates and stable death rates.
Exploring the Population Growth Options
Let's look at the given options and how they relate to age structure:
- Expanding population: Typically characterized by a high proportion of young individuals and high birth rates. The age structure would show a broad base of young people tapering off towards older ages (a pyramid shape). This reflects rapid growth.
- Declining population: Often has a low proportion of young individuals and low birth rates, possibly coupled with higher death rates or emigration. The age structure might show a narrower base than the older age groups, indicating fewer births than deaths or aging individuals (an inverted pyramid or urn shape). This reflects population decrease.
- Stable population: Characterized by relatively balanced birth and death rates. The number of births roughly equals the number of deaths. The age structure tends to have a more uniform distribution across young and mature age groups, often resembling a column or rectangle shape before tapering off at older ages. Having an equal number of young and mature individuals points towards this balanced age structure, where the replacement rate is near one. This reflects little to no overall population change over time.
- S-shaped growth: This refers to logistic growth, where a population initially grows exponentially but then slows down as it approaches the environmental carrying capacity, eventually stabilizing at that capacity. While the final phase of S-shaped growth involves a stable population size, the term 'S-shaped' describes the overall trajectory of growth over time, not necessarily the immediate age structure at a specific point. However, a population that has reached the stable phase of logistic growth would indeed exhibit a stable age structure. Given the direct description of age structure ("same number of young and mature ones"), "Stable" is the most direct and accurate description of the growth type reflected by that structure.
Conclusion
A population with the same number of young and mature individuals indicates a balanced age structure. This type of age structure is characteristic of a stable population, where birth rates and death rates are roughly equal, leading to minimal overall population change. Therefore, this scenario reflects stable growth.
Based on the analysis of the age structure and the characteristics of different growth types, the scenario described best fits a stable population.
Revision Table: Population Growth Types & Age Structure
| Growth Type | Age Structure Description | Growth Rate |
|---|---|---|
| Expanding | Large proportion of young; pyramid shape | High; Population increases rapidly |
| Declining | Small proportion of young; inverted pyramid/urn shape | Low or Negative; Population decreases |
| Stable | Relatively equal young/mature; column/rectangle shape | Near Zero; Little to no population change |
| S-shaped (Logistic) | Describes growth trajectory; final phase is stable population with stable age structure | Varies over time; eventually approaches zero at carrying capacity |
Additional Information on Population Dynamics
Population dynamics is the study of how populations change in size and structure over time. Key factors influencing population dynamics include:
- Birth Rate: The number of live births per 1,000 people per year.
- Death Rate: The number of deaths per 1,000 people per year.
- Migration: The movement of people into (immigration) or out of (emigration) a country or region.
- Age Structure: The distribution of individuals across different age groups. This is often visualized using population pyramids.
A stable population achieves equilibrium when the birth rate plus immigration equals the death rate plus emigration. In the absence of significant migration, this means birth rate approximately equals death rate. The age structure stabilizes when the proportion of individuals in each age group remains relatively constant over time.
The concept of "young" and "mature" can vary, but generally, "young" refers to pre-reproductive and early reproductive ages, while "mature" refers to the main reproductive ages. Having roughly equal numbers in these broad categories suggests that the number of individuals entering the reproductive phase is balancing the number of individuals in that phase, which is characteristic of a population that is not undergoing rapid expansion or contraction.
Stable
✅ Correct Answer: Stable
Explanation:
When a population has an equal number of young and mature individuals, it indicates a Stable growth pattern.
This means the birth rate and death rate are nearly equal, leading to a balanced population over time.
Stable
The correct answer is:
✅ Stable
Explanation:
A stable population occurs when the number of young individuals (pre-reproductive) is roughly equal to the number of mature individuals (reproductive/post-reproductive).
This balance indicates:
Constant birth and death rates (zero population growth in the long term).
Stationary age pyramid (equal width across age groups).
Why Not Other Options?
Expanding: More young than mature (pyramid-shaped, high birth rates).
Declining: Fewer young than mature (inverted pyramid, low birth rates).
S-shaped: Logistic growth (ecological term, not demographic).
Key Insight:
Stable populations are typical in developed countries with replacement-level fertility (~2.1 children per woman).
Answer: Stable (Option 3) ✅
Similar Questions
Which of the following equation is correct about Verhulst-Pearl Logistic Growth?
Name the population interaction which takes place when one species is benefitted and another species has no effect (no benefit, no harm).
Identify the incorrect matching from the following population interactions:
Species A Species B Interaction + + Mutualism + – Parasitism – – Predation – 0 Amensalism (1) +, + → Mutualism
(2) +, – → Parasitism
(3) –, – → Predation
(4) –, 0 → Amensalism
Given below are two statements:
Statement I: An orchid grows as an epiphyte on a mango branch where the mango tree does not derive any apparent benefit from it.
Statement II: An orchid growing on a mango tree is an example of commensalism.
In the light of the above statements, choose the correct answer from the options given below:
Match List-I with List-II:
List-I (Examples) List-II (Interactions) (A) Extinction of Abingdon tortoise after introduction of goats on Galapagos Islands (I) Parasitism (B) Infestations of marine fish by copepods (II) Commensalism (C) Cattle egret and grazing cattle (III) Mutualism (D) Fig tree and wasp (IV) Competition Choose the correct answer from the options given below:
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(2) Every winter Keoladeo National Park hosts the birds coming from Siberia – Migration
(3) Under unfavourable conditions, many zooplankton species in ponds enter the stage of suspended development – Diapause
(4) If a predator is too efficient, it overexploits its prey – Extinction
Match List-I with List-II:
List-I (Interspecies Relationships)
List-II (Features)
List-I List-II (A) Commensalism (I) One species is benefitted at the expense of the other (B) Mutualism (II) One species is harmed and the other is unaffected (C) Amensalism (III) Both the species are benefitted (D) Parasitism (IV) One species benefits, and the other remains unaffected Choose the correct answer from the options given below:
Two closely related species can co-exist indefinitely and violate the Gause’s ‘Competitive Exclusion Principle’ by:
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Some of the fresh water fishes commonly found in India are: (A) Hilsa (B) Pomfrets (C) Catla (D) Rohu (E) Common carp
Which of the following does not show parthenogenesis?
'Barnacles' growing on the back of a whale is a classical example of:
The interaction between two species where one species benefits and the other is neither benefitted nor harmed is known as:
In a laboratory population of 80 fruit flies, 8 died in a week. What is the death rate of fruit flies?
