Maharashtra Board Class 12 Environmental Education Chapter 1 Humans and Environment PDF Download

1. Humans And Environment

1.1 Population Growth

The human species dates back to 3 million years ago. Until about 12,000 years ago, humans were mostly hunters and gatherers who typically moved as they needed to find enough food for survival. Since then, there have been three major cultural changes.

1. Agricultural revolution (which began 10,000-12,000 years ago)

2. Industrial revolution (which began about 275 years ago)

3. Information and globalization revolution (which began about 50 years ago)

These major cultural changes have:

1. Provided much more energy and new technologies with which to alter and control more of the planet to meet our basic needs and increasing demands.

2. Allowed expansion of the human population, mostly because of increased food supplies and longer life spans.

3. Increased human environmental impact because of increased resource use, pollution and environmental degradation.

By 1st Christian Era (C.E.) there were more than 170 million human beings on earth. They had acquired enough skills and tools to manipulate the natural world and to some extent had begun to carve niches, which were entirely man-made. This led to a faster growth of population, which is indicated by an addition of more than one hundred million members to the human race, by 1000 C.E. By then various civilizations of human beings were prospering in different parts of the world, and man was ready to take a giant leap.

The next one thousand years saw unprecedented growth in human population, from around 300 million to 6000 million. The industrial revolution boosted the growth of human population tremendously. The human population increased by 2000 million in a span of just 25 years between the years 1975 and 2000.

Terms frequently used with population growth are described below:

Birth rate (Natality): The number of live births per 1000 population in a given year.

Death rate (Mortality): The number of deaths per 1000 population in a given year.

Growth rate: The number of persons added or subtracted from a population in a year due to natural increase and net migration.

Doubling time: The number of years required for the population of an area to double its present size given the current rate of population growth.

Carrying capacity: The maximum number of individuals of a species that an area can support. Many environmentalists, however believe that there are definite limits to growth and the earth's carrying capacity. The growing population has affected the carrying capacity of the planet eventually resulting in a number of problems like inadequate resources, standard of living, unhygienic and improper sanitation facilities etc. Today, due to population pressures and human impact, the natural elements like air, water and soil have been polluted to a great extent.

Ecological balance: The fine balance that exists between living and non-living things, food webs and environmental conditions of an ecosystem.

Population growth rate: The net annual percentage increase in population.

Exponential growth: The growth of a quantity with time in such a way that the curve is relatively flat in the beginning, but becomes steeper and steeper with time.

Teacher's Note

Population growth happens when more babies are born than people die. In India, our population grows very fast, which is why we need more schools, hospitals and food for everyone.

Exam Trick

Remember: Birth rate minus death rate equals growth rate. Like adding and removing students from your class - more joining means the class grows bigger.

Points to Remember

Three big changes happened in human history: farming, factories, and computers and the internet.
Humans learned to change nature to get what they need.
Population grew very fast after factories started.
Birth rate is babies born. Death rate is people dying.
Carrying capacity means how many people Earth can support.

Increase In World Human Population Over Time

The figure shows the growth of population over time. It can be seen that curve was flat for a long time and from about 1650 C.E. it started spiking and became parallel to y axis.

Mathematically, this is called an exponential curve. The world population started increasing rapidly with the onset of the scientific and industrial revolution in Europe. Between 1850 and 1950 the population doubled to 2 billion. The 5 billion mark was reached in 1987 and 6 billion mark in 1999. Right now the world's population is 7.7 billion and India's population is approximately more than 1.25 billion.

Demographic Transition

There is a close relationship between population growth rate and economic development. Due to improvement in economic conditions, natality as well as mortality declined resulting in low population growth rate in developed countries. This process is known as demographic transition.

Demographic transition occurs in four stages due to development in industrialization and consequent urbanization.

1. Pre-industrial Phase: Harsh living conditions lead to a high birth rate (to compensate for high infant mortality) and a high death rate. Thus, there is little population growth.

2. Transitional Phase: As Industrialization began, food production increased and health care improved. At the same time death rates dropped and birth rates remained high, so the population growth was rapid. Many countries such as India, Bolivia and Saudi Arabia were in this category.

3. Industrial Phase: Industrialization is widespread. The birth rate drops and the death rate also decreases. Reasons for this convergence of rates include better access to birth control, decline in the infant mortality rate, increased job opportunities for women and increased investment in basic education for children and other social changes. Most developed countries are now in this third stage. This stage is characterized by sudden decline in birth rate and death rate. For example, China and Indonesia.

Teacher's Note

Demographic transition means how a country changes as it becomes richer and more developed. In rich countries like America, fewer babies are born because families choose to have small families.

Exam Trick

Remember the 4 phases like stages of growing up: childhood (pre-industrial) has many kids, youth (transitional) has rapid growth, adulthood (industrial) slows down, old age (post-industrial) stays stable.

Points to Remember

In poor countries, many babies are born but many people die too.
When countries become richer, fewer babies are born and fewer people die.
Rich countries have older populations with fewer children.
Poor countries have younger populations with many children.
This change happens as countries develop and get better medicines and education.

Age And Sex Structure Of A Population

Age and sex structure of a population in a country may be represented by age and sex pyramids through the proportion of males and females in a specific age groups.

Population Pyramid: The population pyramid is a plot of the number of people belonging to various age groups. Population pyramid is an important feature to understand a country's demographic situation. This information is very useful for the government to plan for improvement.

i) Pyramid for Developing Countries: In this type of population pyramid, there is large number of young population and the proportion of old people is less.

ii) Pyramid for Developed Countries: In this type of pyramid, the birth rates and death rates are low.

iii) Urn shaped Population Pyramid: In this type of pyramid, the proportion of pre-reproductive age group population is very small in comparison to people belonging to reproductive age group. This represents countries in the post industrial phase.

Do you know? There is a big difference in the population growth pattern between the developing and the industrialized (developed) nations. Nearly 99 per cent of population increase takes place in developing countries. The population remains the same or even declines in the industrialized nations. By 2050, the population of developing countries is likely to go up by 55 per cent. However, the total population of industrialized countries is expected to increase only by about 4 per cent.

Teacher's Note

A population pyramid looks like a pyramid or a triangle for young countries, but like an urn for old countries. India's pyramid is wide at the bottom because we have many young people.

Exam Trick

Remember: Wide bottom = young population = poor country. Narrow bottom = old population = rich country. Like a triangle shape means lots of kids are born.

Points to Remember

Developing countries have pyramid shape with lots of young people.
Developed countries have narrow bottom because fewer babies are born.
The urn shape means very few young people and many old people.
Population pyramids help governments plan for schools and hospitals.
A country with pyramid shape will grow faster than one with urn shape.

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