Human population is growing rapidly and steadily. Ultimately, there can be no long-term solutions to environmental problems unless the human population stops increasing. Countries with a high standard of living (developed countries) have moved more quickly to a lower birth rate than have countries with a low standard of living.(developing countries). Human Population and the Environment

1.) In the earliest part of human history-probably less that a few million hunters and gatherers 2.) The rise of agriculture allowed for a much greater density of people and the first major increase in human population. 3.) The industrial revolution, with improvements in healthcare and food supply led to the most rapid increase in population. 4.) Today, the rate of population growth has slowed in industrialized nations but continues to increase in poorer, less developed nations. A brief history of human population growth

Carrying capacity-the maximum population of a particular species that a given area of habitat can support over a given period of time. A sustainable supply of resources defines the carrying capacity for a particular population in a particular environmental system. Carrying Capacity

Basic definitions: Population-a group of individuals of the same species living in the same area or interbreeding and sharing genetic information. Species-made up of populations Human Population and the Environment

Five Key Properties of any Population are: 1.) Abundance-the size of any population now, in the past and in the future 2.) Birth rates 3.) Death rates 4.) Growth rates 5.) Age structure Demography-is the statistical study of human populations. Population Dynamics-the general study of population changes over time. Human Population and the Environment

Linear vs. Exponential growth rates Growth rates of populations can be characterized by two different growth rates: linear and exponential.

Linear Growth Linear growth occurs at a contant rate. An example would be if your employer increases your salary by exactly $ every year. This would result in a gradual increase in your salary. We call it linear because the resulting graph would be a straight line.a

Exponential growth Most species are capable of increasing their population at an exponential rate. An example of exponential growth would be if a population of mice increased their number by 10% each month. In this case the resulting graph would be a sharp upward curve illustrating the population explosion of mice.

PICK AN OPTION FOR YOUR SUMMER JOB(50 days): Option 1: Day 1: $0.01 Day 2: $0.02 Day 3: $0.04 Day 4: $0.08 Option 2: Day 1: $ Day 2: $ Day 3: $ Day 4: $100.00

Outcome (summer job) $ job: Day 20: $ total Day 50: $ total for the summer $.01 job: Day 20: $10,486 total Day 50: $ trillion dollars total for the summer

Exponential growth (j-curve)

Human Population Growth

Can a population continue to experience exponential growth indefinitely?

Logistic Growth (s-curve) K=carrying capacity

As a population increases in size, the same resources must be shared by a greater and greater number of individuals. The decreasing supply of resources may lower the population’s birth rate, increase its death rate, or both-until births and deaths are in balance. At that point of balance, and as long as the resource supply remains constant, the population should stabilize at some equilibrium size. This is the carrying capacity Carrying capacity

Population age structure graphs show the proportion of the population of each age. The age structure of a population affects current and future birth rates, death rates, and growth rates, has an impact on the environment, and has implications for current and future social and economic conditions. Population Age Structure

Age Structure

Limiting factor-anything preventing the growth of a population Examples of things that may be limiting factors: Space Food Climate and weather Cover Disease Human activity shade Limiting Factors

Density-dependent limiting factors Limiting factors that are dependent on the size and density of a population Examples include disease, competition, and predation

Density-independent limiting factors Limiting factors that effect all members of a group equally regardless of the population density Examples-limited food supply, natural disasters, environmental stress

How many people can live on the Earth at the same time? The answer depends on what quality of life people desire and are willing to accept. Estimates of how many people the planet will support range from 2.5 billion to 40 billion. (currently 6.6 billion) What is the human carrying capacity of the Earth?