Key Points

Growth of population: Population growth is the increase in the number of individuals in a population. India’s annual increase in population is large enough to neutralize efforts to conserve the resource endowment and environment. It depends on the following factors.

Changes in Population:

• There are three main processes of change of population: birth rates, death rates, and migration.
• The natural increase of population is the difference between birth rates and death rates.

Birth rate:

• The birth rate is the number of live births per thousand persons in a year.
• It is a major component of growth because, in India, birth rates have always been higher than death rates.

Death rate:

• The death rate is the number of deaths per thousand persons in a year.
• The main cause of the rate of growth of the Indian population has been the rapid decline in death rates.
• Till 1980, high birth rates and declining death rates led to a large difference between birth rates and death rates resulting in higher rates of population growth.
• Since 1981, birth rates have also started declining gradually, resulting in a gradual decline in the rate of population growth.
• The rapid decline in population due to the high mortality rate is the Population crash.

Migration:

• The third component of population growth is migration.
• Migration is the movement of people across regions and territories.
• Migration can be internal (within the country) or international (between the countries)

Important Points

Literacy rate:

• The literacy rate of the population is defined as the percentage of literates to the total population aged 7 years and above who can read, write and understand any one language.
• The results of the 2011 census revealed that there has been an increase in literacy in the country. 
• The literacy rate in the country is 74.04 percent, 82.14 for males and 65.46 for females.
• Kerala retained its position by being on top with a 93.91 percent literacy rate, closely followed by Lakshadweep (92.28 percent) and Mizoram (91.58 percent).
• Bihar with a literacy rate of 63.82 percent ranks last in the country preceded by Arunachal Pradesh (66.95 percent) and Rajasthan (67.06 percent).

Hence, the literacy rate is not an indicator of change in the population of a place.

Explanation:

• Natural family planning method: It is a method of contraception used by the females in which she monitors and records all the changes in their menstrual cycle that are indications of their being pregnant
• Measuring BBT and changes in cervical mucous are effective ways of natural family planning

The rhythm method also called the calendar method or the calendar rhythm method is a form of natural family planning.

• To use the rhythm method, women track their menstrual history to predict when they'll ovulate.
• This helps you determine when women are most likely to conceive.

Basal Body Temperature:

• The temperature of the body when it is at complete rest is called the Basal Body temperature
• The BBT varies in response to the ovulation in females, it falls down just before the release of the egg and ranges between 97°F (36.1°C) and 97.5°F (36.4°C)
• It starts to rise again after 24 hours of the ovulation and ranges between 97.6°F (36.4°C) to 98.6°F (37°C).
• In this method, the females measure her BBT every morning before leaving the bed 
• Measure the temperature 3 days in a row when your temperature is higher than all of the previous 6 days. It is likely that the female is not fertile in this period 

Additional InformationCervical Mucous: 

• It is a vaginal discharge secreted by cervical and endocervical glands.
• The texture of cervical mucous changes throughout the menstrual cycle. 
• It can be checked by placing the finger gently into the vagina for the initial days the vagina feels dry but as your hormone levels rise to prepare your body for ovulation the vagina becomes sticky due to mucus.
• This is the start of the fertile period 

Three primary factors account for population change, or how much a population is increasing or decreasing. These factors are birth rate, death rate, and migration.

• Births and deaths are natural causes of population change. The difference between the birth rate and the death rate of a country or place is called the natural increase. The natural increase is calculated by subtracting the death rate from the birth rate.

Key Points

• Human migration involves the movement of people from one place to another with intention of settling, permanently or temporarily, at a new location.

Additional Information

• Zero population growth refers to a population that is unchanging – it is neither growing nor declining; the growth rate is zero.
• Immigration is the international movement of people to a destination country of which they are not natives or where they do not possess citizenship in order to settle as permanent residents or naturalized citizens.

Natural change and Migration are the two factors that affect population change for a particular area. Therefore Option 4 is the correct answer.

Concept:

• In exponential growth, a population's per capita (per individual) growth rate stays the same regardless of population size, making the population grow faster and faster as it gets larger.
• In nature, populations may grow exponentially for some period, but they will ultimately be limited by resource availability.
• In logistic growth, a population's per capita growth rate gets smaller and smaller as population size approaches a maximum imposed by limited resources in the environment, known as the carrying capacity (KKK).
• Exponential growth produces a J-shaped curve, while logistic growth produces an S-shaped curve.

Explanation:

Here, a = J-shaped curve and b = S-shaped curve.

• Red line = J-shaped curve,
• Blueline = S-shaped curve.

Additional Information The J-shaped and the S-shaped curves are different in the following ways:

The correct answer is to Express the age-sex distribution of a population.

Key Points

• Population pyramids are important graphs for visualizing how populations are composed when looking at groups divided by age and sex.

• The population pyramid is a graphical representation of the age and sex composition of a specific population.
• Age structure represents the number of people of different age groups and is an important indicator of population composition.
• Demographers express the share of the dependent age groups using a metric called the 'age dependency ratio'. This measures the ratio between 'dependents' (the sum of young and old) to the working-age population that is aged between 15 to 64 years old.
• The large size of the population in the age group of 15- 59 indicates a large working population.
• A greater proportion of the population above 60 years represents an ‘ageing population’ or ‘the elderly population’ which requires more expenditure on health care facilities.
• A high proportion of the young population would mean that the region has a high birth rate and the population is youthful. This population is known as children and young adolescents who are under 15 years old.

Concept:

• In order to define K selected species, one has to know that K selected species are the ones that are identified based on the r and K selection theory.
• The r/K selection theory states that the selection of the different combinations of traits in the organism is a trade-off between the quantity and quality of the offspring. 
• The focus is to choose whether an increased number of offspring at the expense of individual parental investment as in the case of r-strategists or on a reduced number of offspring but with significant increased parental investment as in the case of K-strategists, varies widely.
• It is based on the conditions required for success in particular environments.
• These concepts of quantity or quality of the offspring are sometimes said to be either cheap or expensive which is a comment on the expendable nature of the offspring and the parental commitment made to them.

Explanation:

There are numerous K-selected traits, including:

• Slow development
• Low reproductive rate
• Late reproductive age
• Large body size
• Multiple reproductive cycles
• Long lifespan
• Strong competitive ability
• Low offspring mortality
• Relatively steady population size near the carrying capacity
• Limited offspring dispersal
• Presence in mature, undisturbed habitats
• Good parental care

Hence the correct option is Multiple reproductive cycles.

The correct answer is Thomas Malthus.

Key Points

• Thomas Robert Malthus was a famous British economist known for the population growth philosophies in the 18th-century. He outlined in his book "An Essay on the Principle of Population" in the year 1798.
• In it, Malthus theorized that populations would continue expanding until growth is stopped or reversed by  famine, war,  disease, or calamity.
• He is also known for developing an exponential formula used to forecast population growth, which is currently known as the Malthusian growth model.
• The theory states that food production will not be able to keep up with growth in the human population, resulting in disease, famine, war, and calamity.

Key Points

• Epidemic
• • An epidemic is an occurrence of a disease that is temporary of high prevalence.
  • An epidemic occurring over a wide geographical area (e.g., worldwide) is called a pandemic.
  • The rise and decline in the epidemic prevalence of an infectious disease are a probability phenomenon dependent upon the transfer of an effective dose of the infectious agent from an infected individual to a susceptible one.
  • After an epidemic has subsided, the affected host population contains a sufficiently small proportion of susceptible individuals that reintroduction of the infection will not result in a new epidemic.
  • Since the parasite population cannot reproduce itself in such a host population, the host population as a whole is immune to the epidemic disease, a phenomenon termed herd immunity.
• Pandemic
  • A pandemic is an outbreak of infectious disease that occurs over a wide geographical area and that is of high prevalence, generally affecting a significant proportion of the world’s population, usually over the course of several months.
  • Pandemics arise from epidemics, which are outbreaks of disease confined to one part of the world, such as a single country.
  • Pandemics, especially those involving influenza, sometimes occur in waves, so that a post-pandemic phase, marked by decreased disease activity, may be followed by another period of high disease prevalence.
  • In March 2020 an ongoing outbreak of a novel coronavirus known as severe acute respiratory syndrome coronavirus-2 (SARS-CoV2) was declared a pandemic by WHO officials.
  • Infection with SARS-CoV2 produced an illness known as coronavirus disease 2019 (COVID-19).
  • The illness was characterized primarily by fever, cough, and shortness of breath.
• Endemic
  • An epidemic is a sudden severe outbreak within a region or a group, as with AIDS in Africa or AIDS in intravenous drug users.
  • A pandemic occurs when an epidemic becomes very widespread and affects a whole region, a continent, or the entire world.
  • An endemic disease is a disease that is always present in a certain population or region.
  • One of the most talked-about endemic diseases is malaria.
  • The CDC estimates that around half the world's population live in areas where they are at risk of Malaria infection.
  • It is endemic in large parts of Africa as well as some areas of South America.
• Epizootic
  • Epizootic disease is a disease event in an animal population akin to an epidemic in humans.
  • It generally refers to outbreaks of disease which cause serious economic or public health issues and are of major importance in the international trade of animals and animal products.
  • Examples of epizootic diseases include avian influenza, swine fever, and foot and mouth disease.
  • An example of an epizootic would be the 1990 outbreak of the Newcastle disease virus in double-crested cormorant colonies on the Great Lakes that resulted in the death of some 10,000 birds.

The correct answer is High birth rate and high death rate.

Key Points

• The demographic condition on the eve of independence there was a High Birth Rate and Death Rate. Hence, Option 4 is correct.
  • High birth rates and high death rates are treated as indices of backwardness of a country.
  • Both birth rate and death rate were very high at 48 and 40 per thousand persons respectively.
  • High Infant Mortality Rate.
  • It refers to the death rate of children below the age of one year. It was about 18 per thousand live births.
  • Low Life Expectancy. Life expectancy means the number of years that a newborn child on average is expected to live. It was as low as 32 years.
  • Mass Illiteracy. Mass illiteracy among the people of a country is taken as an indicator of its poverty and backwardness. The population census of 1941 (which was the last census under British rule) estimated the literacy rate at 17%.
  • This means that 83 percent of the total population was illiterate.

Environmental degradation is the deterioration of the environment through depletion of resources such as air, water, and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; and pollution.

Man-made or Human activity is causing environmental degradation in many ways: overpopulation (Population explosion), pollution, burning fossil fuels, urbanization, poverty, and deforestation. Changes like these have triggered climate change, soil erosion, poor air quality, and undrinkable water.

1) Population

• It impacts on the environment primarily through the use of natural resources and production of wastes and are associated with environmental stresses like loss of biodiversity, air, and water pollution, and increased pressure on arable land.
• The population explosion is one of the major threats to the environment through expansion and intensification of agriculture, uncontrolled growth of urbanization and industrialization, and destruction of natural habitats. 

2) Poverty

• It is amongst the consequences of population growth and its lifestyle play a major role in depleting the environment either its fuel demands for cooking or for earning livelihood for their survival.
• The unequal distribution of resources and limited opportunities cause push and pull factors for people living below the poverty line that in turn overburdened the population density and environment get manipulated by manifolds. 

3) Deforestation

• It is the cutting down of trees to make way for more homes and industries.
• Rapid growth in population and urban sprawl are two of the major causes of deforestation. 
• The uses of forest land for agriculture, animal grazing, harvest for fuelwood, and logging are some of the other causes of deforestation.
• Deforestation contributes to global warming as decreased forest size puts carbon back into the environment.

Hence, we can conclude from the above points that population explosion, urbanization, poverty and deforestation are the interlinked human activity that causes environmental degradation.