Prof. Dr. Asrar M. Khan/Dr. M.Nadeem Hassan

Population Biology

Population biology is a study of populations of organisms, especially the regulation of population size, life history traits such as breeding size, and extinction.

The term population biology is often used interchangeably with population ecology.

A population is a number of organisms of the same species that inhabit a defined geographic area.

The definition of population is particularly important with regard to evolution as populations evolve and not an individual.

study of biological populations: the branch of biology that studies a group of interbreeding animals or plants native to a region.

population is one species, community is more then one , all the populations in one area. Or

population = all the organisms of the same kind living in the same place (for example, all the monkeys in the rainforest in Brazil)community = all the populations living in one place (for example, the jaguar and the monkeys and the birds in the rainforest in Brazil)

Population Biology

Population have many properties like; Number of individuals in the population; Area occupied by the population and Sex ratio of the population. Distribution and abundance of population is

influenced by both biotic and abiotic factors. The size of a population can only change

(increase or decrease) as a consequence of 4 processes: birth, death, immigration and emigration.

Population Biology

Population control; None of the population increase indefinitely in size one

mechanism that can limit the indefinite increase of a population is decrease in birth rate or increase in death rate.

Negative population growth is limited not only by food but it could also be habitat, space, water or sites in which an organism is safe from predators.

Space – limited population; in this case the resource that limits population is not food but space e.g. barnacles and plants.

Age & size limited population; most detailed population studies have shown that age and/or size of an individual has significant effect on population change.

World Population

As of 5 April 2010, the human population of the world is estimated by the United States Census Bureau to be 6,812,800,000.

The United Nations estimated the Earth's human population to be 6,800,000,000 in 2009.

The world population has been growing continuously since the end of the Black Death around 1400 AD.

Bubonic plague that killed 30 – 60% of Europe population. It took roughly 200 years for Europe's population to regain its 1340 level.

The fastest growth rate in human population was seen in 1963 of 2.2%.

In 2008 it has halved to 1.2%.

World population

Annual births have leveled at about 134 million per year.

However, deaths are only around 57 million per year, and are expected to increase to 90 million by 2050. Because births outnumber deaths, the world's population is expected to reach nine billion in 2040, or by 2050.

The rapid increase in human population during the 20th century has raised concerns about whether Earth is experiencing overpopulation. The scientific consensus is that the current population expansion and accompanying increase in usage of resources are linked to threats to the ecosystem, such as rising levels of atmospheric carbon dioxide, global warming, and pollution.

Toba super eruption A dramatic population bottleneck is theorized for the

period around 70,000 BC due to Toba super eruption.

The Toba super eruption (Young Toba Tuff or simply YTT) occurred between 69,000 and 77,000 years ago at Lake Toba (Sumatra, Indonesia), and it is recognized as one of Earth's largest known eruptions.

The related catastrophe theory holds that this super volcanic event plunged the planet into a 6 to 10 year volcanic winter, which resulted in the world's human population being reduced to 10,000 or even a mere 1,000 breeding pairs, creating a bottleneck in human evolution

The Toba eruption produced not only a catastrophic volcanic winter but also an additional 1,000 year cooling episode.

Population

After this time and until the development of agriculture 8,500 BC, it is estimated that the world population stabilized at about one million people whose subsistence entailed hunting and foraging, a lifestyle that by its nature ensured a low population density.

Population Era wise AD 300-400, population in combined Europe

Roman Empire 55 million. World population in 600-700 AD was 200-210

million

World Population

At the founding of the Ming dynasty in 1368, China's population was reported to be close to 60 million, and toward the end of the dynasty in 1644 it might have approached 150 million.

England’s population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500.

The population of the Americas in 1500 may have been between 50 and 100 million. Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Archaeological evidence indicates that the death of 90 to 95% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza.

World Population The population of the Indian subcontinent, which stood at about

125 million in 1750, had reached 389 million by 1941. Today, the region is home to 1.5 billion people. The total number of inhabitants of Java increased from about

five million in 1815 to more than 130 million in the early 21st century.

Mexico's population has grown from 13.6 million in 1900 to about 112 million in 2009.

In eighty years, Kenya's population has grown from 2.9 million to thirty-seven million.

Asia accounts for over 60% of the world population with almost 3.8 billion people.

China and India together have about 40 percent of the world's population.

Africa follows with 840 million people, 12% of the world's population. Europe's 710 million people make up 11% of the world's population. North America is home to 514 million (8%), South America to 371 million (5.3%), and Australia to 21 million (0.3%).

Population

In 1947, at the time of independence, Pakistan's population was 31 million. By 1995 it had escalated to 140 million.

Presently, 41% of the total population in Pakistan is under the age of 15 years. A large number of young people are about to enter their reproductive years, virtually guaranteeing continued rapid population growth for the foreseeable future. By the year 2035, Pakistan's population is projected at 260 million (UNFPA, Pakistan.

The estimated population of Pakistan in 2010 was over 169,155,000 making it the world's sixth most-populous country, behind Brazil and ahead of Russia. The population growth rate now stands at 1.6%.

Note of concern

Food production has kept pace with population growth, but Malthusians point out the green revolution relies heavily on petroleum-based fertilizers, and that many crops have become so genetically uniform that a crop failure would be very widespread.

Food prices in the early 21st century are rising sharply on a global scale, and causing serious malnutrition to spread widely.

From 1950 to 1984, as the Green Revolution transformed agriculture around the world, grain production increased by over 250%. The world population has grown by about four billion since the beginning of the Green Revolution and most believe that, without the Revolution, there would be greater famine and malnutrition than the UN presently documents (approximately 850 million people suffering from chronic malnutrition in 2005).

Note of concern

The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon-fueled irrigation.

As of May 2008, the price of grain has been pushed up by increased farming for use in biofuels, world oil prices at over $140 per barrel, global population growth, climate change, loss of agricultural land to residential and industrial development, and growing consumer demand in China and India.

Food riots have recently occurred in some countries across the world.

Note of concern

The UK government chief scientist has warned that growing populations, falling energy sources and food shortages will create the "perfect storm" by 2030.

He said food reserves are at a fifty-year low but the world will require 50% more energy, food and water by 2030.

The world will have to produce 70% more food by 2050 to feed a projected extra 2.3 billion people.