Population Growth

Correct answer: A. Time required for population to double from its current size

Doubling time is the period required for a population to become twice its present size. It is linked to the rate of population growth, although the question asks for the meaning of the term rather than a numerical calculation. If growth is faster, the population generally reaches twice its size sooner; if growth is slower, doubling takes longer.

For example, a population of 10 million would become 20 million after one doubling time under the relevant growth conditions. The term does not describe doubling land area, eliminating births, or ending migration. Therefore option A, the time required for population to double from its current size, is correct.

Correct answer: B. Shorter

Doubling time is the period required for a population to become twice its present size. When the growth rate is higher, the population adds people more quickly in each period, so it reaches twice its starting size sooner. When the growth rate is lower, the same doubling requires more time. Thus doubling time and growth rate generally move in opposite directions.

For a positive growth rate, a commonly used approximation is doubling time ≈ \(70\div r\), where \(r\) is the percentage growth rate. The exact value is not required here; the relationship is enough. Therefore, a high growth rate means a shorter doubling time, so option B is correct. “Unrelated to growth rate” is incorrect because the rate directly affects how quickly the population doubles.

Correct answer: C. Doubling time increases

Doubling time is the period required for a population to become twice its present size. When the growth rate is low, population adds new members more slowly. Consequently, reaching an amount equal to the starting population takes longer than it would at a higher growth rate.

Thus, a low growth rate produces a longer doubling time, so option C is correct. In a simple approximation, doubling time is inversely related to the annual growth rate, often expressed through the Rule of 70. The statement that doubling time always remains the same is wrong because it changes when the growth rate changes.

Correct answer: A. Water and food

Rapid population growth means that more people need essential goods and services. Demand can rise for food, drinking water, housing, energy, schools, medical care, and employment. If supply does not grow at a similar pace, these resources may come under pressure.

Water and food are basic resources required by every population, so they are directly affected by population increase. Latitude, longitude, and time zones are geographical reference concepts, not consumable resources whose supply is reduced by having more people. Therefore option A is correct. The question asks which resource may face greater pressure, not which one is the only affected resource.

Correct answer: B. Housing demand may increase

Housing is a basic need, so a growing population usually creates demand for more homes. More people and households require additional rooms, houses, or apartments. If construction, land supply, and public services do not expand quickly enough, the result may include higher rents or prices, overcrowding, and growth of informal settlements.

Therefore, option B is correct: housing demand may increase. The word “may” is important because the actual outcome also depends on migration, household size, incomes, and construction policies. Rapid population growth does not make all houses vacant, automatically enlarge land, or reduce housing demand. It generally puts additional pressure on available housing.

Correct answer: C. Demand and pressure on them may increase

Rapid population growth can increase the number of children needing education and the number of people needing medical care. It can also increase demand for classrooms, teachers, hospital beds, doctors, nurses, medicines, and related facilities. If these services do not expand as quickly as the population, existing institutions may become crowded and their workload may rise.

Therefore, option C is correct: demand and pressure on schools and hospitals may increase. The effect is not automatic closure or automatic reduction in their number. Authorities may respond by building new facilities and hiring staff, but until capacity catches up, congestion and pressure can remain. The word “may” allows for differences in planning, resources, and local conditions.

Correct answer: D. Unemployment or underemployment

Employment must grow sufficiently to provide work for new members of the labour force. If population and the number of job seekers rise faster than available jobs, some people may remain without work. Others may work fewer hours than desired or in jobs that do not fully use their skills; this is underemployment.

Thus, option D is correct: unemployment or underemployment may increase. The statement does not claim that every person will lose a job, because outcomes depend on education, migration, investment, and the type of economic growth. The other choices are not logical consequences: population growth cannot automatically enlarge land, equalize incomes, or make death rates zero.

Correct answer: A. Increase in resource use and waste

Population growth can increase the total demand for food, water, energy, land, housing, transport, and manufactured goods. If production and consumption are not managed sustainably, this greater demand can lead to more extraction of natural resources and more solid waste, sewage, air pollution, or greenhouse-gas emissions. The exact environmental effect depends on technology, consumption patterns, planning, and resource management, so the question appropriately asks for one possible effect rather than an unavoidable result.

Option A is correct because increased resource use and waste are plausible consequences of a larger population. Option B is impossible: population growth does not enlarge Earth's physical size. Option C does not follow because the length of a day is not determined by ordinary population change. Option D is also impossible; the number of continents does not increase simply because more people live on Earth.

Correct answer: B. Negative population growth

Population growth describes the change in the number of people over a specified period. When the final population is smaller than the initial population, the change is negative. This situation is called negative population growth or population decline.

Such a decline may occur when deaths exceed births, when more people leave than enter, or when both conditions occur together. Therefore option B is correct. A population explosion means very rapid increase, and positive growth means the population rises. The phrase “decreasing” directly rules out those choices.

Correct answer: D. If out-migration exceeds natural increase

Population change has two components: natural increase and migration. Natural increase is births minus deaths. If births exceed deaths, this component is positive. However, people may also leave the region. When net out-migration is greater than the natural increase, the total number of people falls despite more births than deaths.

For example, if natural increase adds 10,000 people but 15,000 more people leave than enter, the total population changes by \(10000-15000=-5000\). Thus, population declines. Therefore, option D is correct. High in-migration would instead tend to increase population, and zero deaths would not create a decline by itself.

Correct answer: A. Because growth is measured between points in a specified period

Answer: A. Population growth means the change in population over time, so a time period is essential. We compare population at a starting point with population at a later point, such as 2010 and 2020. Without these two time references, we cannot know whether the population increased, decreased, or remained unchanged, nor can we calculate a growth rate. B is wrong because time is central to measuring change. C is wrong because population studies may cover years or decades, not only one day. D is wrong because land area does not necessarily always change and is not the definition of population growth. Memory cue: growth always needs a ‘from when to when’ comparison.

Correct answer: C. To compare growth of populations of different sizes

Percentage population growth measures the change in relation to the starting population. It is calculated as change divided by initial population, multiplied by 100. This gives a relative measure rather than merely an absolute number. Relative measurement is useful because countries and regions may begin with very different population sizes.

Thus option C is correct: percentage growth helps compare populations of different sizes. An increase of 10,000 people may be very large for a small town but quite small for a huge country. Percentage growth shows the scale of change fairly in relation to the original population. It is not a tool only for measuring land, births, or longitude, so options A, B, and D are unrelated.

Correct answer: A. Because their initial populations may differ

Absolute growth is the actual number added to a population, whereas percentage growth compares that addition with the starting population. Therefore, the same numerical increase can represent a large change for a small country and a small change for a large country. The denominator in the percentage calculation is the initial population, so different starting sizes produce different percentages.

For example, an increase of 100,000 is 10% of an initial population of 1,000,000 but only 1% of an initial population of 10,000,000. Thus option A is correct. Land area, equal births and deaths, or excluding population are not explanations for this difference.

Correct answer: B. 25000

Absolute increase means the actual number of people added, not the percentage increase and not the final population. It is found by subtracting the initial population from the final population. Here the initial population is 500,000 and the final population is 525,000.

The calculation is \(525,000-500,000=25,000\). Therefore the population increased by 25,000 people, making option B correct. The number 525,000 is the final total, while 50,000 would be an incorrect subtraction. No percentage calculation is needed because the question asks for an absolute, or actual-number, increase.

Correct answer: C. 5 percent

Percentage growth compares the increase with the starting population, not with the final population. First find the absolute increase by subtracting the initial value from the final value. Then divide that increase by the initial value and multiply by 100. This method works for population, money, production, or any other quantity.

The increase is \(420000-400000=20000\). Hence percentage growth is \(\frac{20000}{400000}\times100=5\) percent. Therefore, option C is correct. Using 420000 as the denominator would calculate a different proportion and would not represent the standard growth relative to the original population.

Correct answer: D. Decrease of 5000

An absolute change is the numerical difference between the final and initial values. It is calculated as final value minus initial value. A negative result indicates a decrease, while a positive result indicates an increase. The question asks for the size and direction of the population change, so both the difference and its meaning matter.

Calculate \(95000-100000=-5000\). The minus sign shows that the population fell, and the amount of the fall is 5000 people. Therefore, the correct choice is option D, decrease of 5000. The value 95000 is only the final population, and 100000 is only the initial population; neither is itself the absolute change.

Correct answer: A. In-migration and out-migration are equal

Net migration is the number entering a region minus the number leaving it. Migration has no net effect when these two numbers are equal, because the gain is exactly cancelled by the loss. Therefore, the correct choice is A: in-migration and out-migration are equal.

For example, if 1,000 people enter and 1,000 people leave, net migration is \(1000-1000=0\). The region may still experience movement and its residents may change, but migration has not changed the total population overall. If only people leave, the population falls through migration; if only people enter, it rises. Other population processes, such as births and deaths, may still change the total separately.

Correct answer: B. Natural increase is based on births and deaths while total growth can also include migration

Natural increase is the change produced by births and deaths within a population. It is calculated as births minus deaths, without including migration. Total population growth is broader: it combines natural increase with net migration, which is immigration minus emigration. Therefore, a place may grow even with low natural increase if it receives many migrants, or it may grow slowly if people move away.

Option B is correct because it identifies this difference. Option A is not always true, since migration can change total growth. Option C wrongly defines natural increase through migration, and option D incorrectly excludes births and deaths from total growth. In rate form, the relationship is total growth = natural increase + net migration. This distinction is essential when explaining population change.

Correct answer: C. It will increase

Population change has two main components: natural increase and net migration. Natural increase is births minus deaths. If natural increase is zero, births and deaths balance each other, so they produce no net change in population. Net migration is the difference between people entering and people leaving. A positive net migration value means more people enter than leave.

Therefore, even though births and deaths cancel out, the incoming migrants add people to the country. The total population will increase, so option C is correct. It cannot be described as immediately doubling, because no size or time information supports that claim. It would remain unchanged only if net migration were also zero, and it would decline if net migration were negative. The supplied answer is accurate.

Correct answer: D. It may decline

Total population change can be represented as natural increase plus net migration: \(\Delta P=\text{natural increase}+\text{net migration}\). Natural increase is positive when births exceed deaths, but net migration is negative when more people leave than enter. If the negative migration value is larger in magnitude than the positive natural increase, the sum becomes negative.

For example, a natural increase of 200 combined with net migration of \(-300\) gives a total change of \(-100\). The population would therefore decline, so option D is correct. It need not decline in every situation unless “even more negative” is interpreted by magnitude, as the question intends. The other options ignore the offsetting effect of out-migration.

Correct answer: A. To understand future needs for services and resources

Studying population growth helps people and governments understand how the number and composition of residents may change in the future. This information supports planning for schools, hospitals, housing, food, drinking water, transport, employment, energy, and other infrastructure. It also helps identify areas where services may become insufficient or where resources need to be distributed more carefully.

Therefore, option A is the major purpose among the choices: understanding future needs for services and resources. Counting continents, measuring mountain heights, and determining time zones are useful geographical tasks, but they do not explain why population growth is studied. Population analysis connects demographic change with practical planning and public policy.

Correct answer: D. Births, deaths, migration, and the time period should be considered together

Population growth is the change in population over a stated period. It cannot be understood reliably from births alone, deaths alone, or migration alone. Births add people, deaths remove people, and migration transfers people into or out of the area. The length of the time period is also essential because the same numerical change can occur quickly or slowly.

Therefore, option D is the most complete statement. In a simple balance, population change is related to births minus deaths plus net migration, considered over time. A region can have many births but little growth if deaths are also high, or it can grow despite more deaths than births if net migration is strongly positive. The other options leave out important components.

Correct answer: C. 40000

Absolute population growth means the actual numerical increase in people, not the percentage increase. It is calculated by subtracting the initial population from the final population. Here, \(840000-800000=40000\). Therefore, the region gained 40,000 people. This measure simply tells how many additional persons were added during the period; it does not describe the rate of growth or compare the increase with the original population.

Option C is correct because it gives the result of the subtraction. Option A, 20,000, and option B, 30,000, are smaller than the actual difference. Option D, 80,000, is the initial population rather than the increase. The wording asks for absolute growth, so no division by the initial population and no percentage calculation is required.

Correct answer: C. 500

Total population change has two parts: natural change and net migration. Natural change is births minus deaths, while net migration is in-migrants minus out-migrants. Both parts must be included because people can be added through birth or arrival and removed through death or departure.

Here, natural increase is \(1200-900=300\). Net migration is \(500-300=200\). Adding them gives total change \(300+200=500\). The region therefore gains 500 people during the period, so option C is correct. Counting only births minus deaths would give 300 and ignore migration; counting all movements without subtracting departures would also overstate the increase.

Correct answer: A. When the gap between births and deaths becomes smaller but remains positive

Population growth is determined by the balance between births and deaths, ignoring migration in this question. A country can have a smaller growth rate when the difference between births and deaths becomes smaller, yet the total population will still rise if births remain more numerous than deaths.

For example, if births previously exceeded deaths by a large amount and later exceed them by a smaller positive amount, each year still adds people, but at a slower pace. Therefore option A is correct. If births stop completely, or deaths remain higher than births, natural increase would not produce the stated result. A population also does not immediately become half merely because its growth rate declines.