Population dynamics addresses change in population size, composition, and distribution.

Population Dynamics

 

Population dynamics addresses change in population size, composition, and distribution.

 

One of the basic units of study in ecology is the population, a group of individuals of the same species occupying the same area at the same time. Population dynamics refers to the changes that occur in the number of individuals in a population. Understanding population growth requires understanding the factors affecting that growth. These factors include reproductive rate, resource availability, and competition. Population growth is regulated by four factors: (1) birthrate, (2) death rate, (3) immigration, and (4) emigration. The balance between the number of individuals being added to the population and the number of individuals being removed from it determines whether the population grows or declines. In a closed population (no immigration and emigration, only births and deaths) with unlimited resources, populations could grow without any limits. If you were to graph population growth under these conditions, it would resemble a J-shaped graph. This type of growth is called exponential growth.

 

In reality, however, biotic and abiotic factors (food, space, competition, etc.) limit population growth. The maximum number of individuals an area can support is the environment’s carrying capacity. When a population exceeds the carrying capacity, the environment cannot support all the individuals. In response to the unsustainable population size, the death rate increases, birthrate decreases, and/or individuals leave the population (emigrate). Once the population falls below the carrying capacity, growth resumes. This type of population growth is called logistic growth, and results in an S-shaped, or sigmoid, graph.

 

There are two categories of factors that limit population growth: densitydependent and densityindependent. Density-dependent factors are those that affect populations in direct proportion to population size, becoming more seen as the population grows. For example, as populations grow, food supplies and space decrease, while predation, competition, and disease increase. Density-independent factors affect populations regardless of population size. For example, a hurricane that strikes a population is going to kill individuals, whether the population size is 10 or 10,000. Often in the real world, density-dependent and independent factors interact on populations.

 

How Many People Can the Earth Support?

 

There is probably no other subject that has a greater bearing upon the future for a sustainable environment and quality of life on earth than human population. Prior to the 1800s, some environmental degradation was occurring. However, with some exceptions, the impacts of wood burning, deforestation, mining, and raw sewage disposal, etc. were localized because human populations were still relatively low. Following the industrial revolution, advances in agricultural technology, medical science, and public health awareness, the human population (and impacts from their activities) grew exponentially.

 

Today, more than 7 billion people exist on earth. If it took you one minute to read the discussion populations to this point, about 180 more people were added to the world’s population as you read.

 

By the year 2020,  8 billion humans are expected to inhabit the planet…..and 9-10 billion by 2050.  Do you think the world is overpopulated? How about the United States (more than 300 million)? What environmental effects result from overpopulation in Third World countries, and the United States? How does consumption tie in with population in developed countries, such as the United States? Does overpopulation in other countries encourage migration (both legal and illegal) into the United States? Are there any problems (social, political, environmental) associated with migration? What are some social costs (and benefits) to having a large population?

 

It is important to note that in fact there is a limit to the number of people the Earth’s resources will support on a sustainable basis, despite advances in technology. There may be room on earth for 10, 20, 30, or 50 billion people. However, the impact of feeding, clothing, providing transportation for sanitation, medical needs, cemetery space, power and utility demands, etc. would render the quality of life unacceptable in today’s terms.

 

This information was in an edition of  THE OKLAHOMAN…….from an article written by AP National Writer David Crary

 

According to the UN Population Fund, as of 10-31-11 7 billion people will be sharing the Earth’s land and resources!!!!!!!

Here are some other interesting tidbits:

According to demographers, the world’s population didn’t  reach 1 billion until 1804, and it took 123 years to hit the 2 billion mark in 1927.  Then the pace accelerated – 3 billion in 1959,  4 billion in 1974, 5 billion in 1987, 6 billion in 1998.  Looking ahead, the UN projects the world population will reach 8 billion by 2025, 10 billion by 2083.  But the numbers could be much higher or lower, depending on such factors as access to birth control, infant mortality rates and average life expectancy – which has risen from 48 years in 1950 to 69 years today.

Food and water shortages could fan the fire of political destabilization in developing countries……family planning goals will need to be established (especially in the realm of encouraging young adolescent girls to stay in school and empowering women with knowledge to control the number of offspring they produce)

Food for thought………

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