If we multiply this, as shown above, by the current population, we get the increase in humans per year: 0. That is the equivalent of 2. It is 1. An astounding growth rate, even though the net reproductive rate is actually quite small. But growth is not evenly distributed around the world. Certain countries are growing faster than others, while some are actually losing growth deaths and emigration exceed births plus immigration - Albania is an example. Remember, only two things affect population growth: births and deaths.
So, have these changed? Liberia 3. Canada 0. Mexico 1. England 0. For example, if the world growth rate is 1. When I was born, the population was about 2 Billion in It is now 50 years later, and the population is 6.
That is nearly a tripling!! The world population growth rate was much higher in the past 50 years than it currently is. If you have more young people, then you have more opportunity to make babies!! Developing countries have more young people than developed ones. In developed countries, couples wait longer to have babies, and, they tend to have fewer per couple.
In undeveloped countries, children are produced sooner, and couples have larger families than in developed countries. There are two simple ways to lower population growth: increase the number of deaths, or, decrease the number of births.
The table below shows how your interest accumulates. The formula to calculate future population given current population and a growth rate is:.
To calculate your future balance in the above example the formula would be:. The formula to calculate a growth rate given a beginning and ending population is:.
You have to do a little algebraic manipulation to solve for i. Understanding how to calculate growth rate can help you measure change over time and represent that change as a percentage. In this article, we teach you several methods for calculating growth rate with examples.
Growth rate is the amount in which the value of an investment, asset, portfolio or business increases over a specific period. The growth rate provides you with important information about the value of an asset or investment as it helps you understand how that asset or investment grows, changes and performs over time. This information can help you predict the future revenue of a specific asset or investment. Growth rate is important because it tells you how much an asset, investment, portfolio or business grows over a specific period and helps you make predictions about future growth.
Growth rate can be used to represent:. The expected future growth of other assets and investments. There are three types of formulas you can use to calculate growth rate depending on your situation:. The straight-line percent change method is the most common formula used to calculate basic, simple growth rates. This growth rate calculation method works best when calculating simple growth rates that you don't need to compare to other results. However, it is important to know that this formula may not produce uniform results for negative changes in growth.
This limitation of the straight-line percent change method is known as the end-point problem. The midpoint-method is a formula used to calculate growth rate when you need to use the information to make comparisons. The benefit of using the midpoint method is that it provides uniform results regardless of the direction of change and avoids the end-point problem that exists when using the straight-line percent change method.
The midpoint method overcomes this challenge by using the average of the original and ending values as the denominator. The straight-line percent change calculation method and the midpoint calculation method work well when you are comparing the change in growth between two years.
However, when you are comparing the change in growth for several years, it is best to use this calculation method to find the average growth rate per year.
Follow these steps to calculate growth rate using the straight-line percent change method:. The first step is to write out the straight-line percent change formula. The formula will act as the foundation for your calculation.
For this formula, you will need to know the original value and the new value. The formula used for the straight-line percent change method is to divide the absolute change by the original value. The first calculation you need to find when using the straight-line percent change method is the absolute change between the new value and the original value. You can calculate absolute change simply by subtracting the original value from the new value.
The resulting difference is the absolute change. Compound Interest 6. Replacement Reproduction vs. Zero Pop. Growth 9. Thinking Questions About Population Growth 1.
Final population size with given annual growth rate and time. Phillips ] number in initial population N o growth rate r decimal value length of time t same units as r number in final population N 1. Population sizes with different growth rates and time periods. T he above Table 1 will calculate the population size N after a certain length of time t. All you need to do is plug in the initial population number N o , the growth rate r and the length of time t. The constant e is already entered into the equation.
It stands for the base of the natural logarithms approximately 2. Growth rate r and time t must be expressed in the same unit of time, such as years, days, hours or minutes.
For humans, population growth rate is based on one year. Another way to show this natural growth rate is to subtract the death rate from the birth rate during one year and convert this into a percentage. It is called natural growth rate because it is based on birth rate and death rate only, not on immigration or emigration. The growth rate for bacterial colonies is expressed in minutes, because bacteria can divide asexually and double their total number every 20 minutes.
In the case of wolffia the world's smallest flowering plant and Mr. Wolffia's favorite organism , population growth is expressed in days or hours. E ach wolffia plant is shaped like a microscopic green football with a flat top. An average individual plant of the Asian species W. But the undisputed world's smallest flowering plants belong to the genus Wolffia , minute rootless plants that float at the surface of quiet streams and ponds.
Two of the smallest species are the Asian W. An average individual plant is 0. One plant is , times shorter than the tallest Australian eucalyptus Eucalyptus regnans and seven trillion times lighter than the most massive giant sequoia Sequoiadendron giganteum. The growth rate r can be determined by simply dividing.
Since the doubling time t for Wolffia microscopica is 1. Note: When using a calculator, the value for r should always be expressed as a decimal rather than a percent.
The total number of wolffia plants after 16 days is 7, This exponential growth is shown in the following graph where population size Y-axis is compared with time in days X-axis.
Exponential growth produces a characteristic J-shaped curve because the population keeps on doubling until it gradually curves upward into a very steep incline. If the graph were plotted logarithmically rather than exponentially, it would assume a straight line extending upward from left to right. Sixteen days of exponential growth in Wolffia microscopica. W olffia plants have the fastest population growth rate of any member of the kingdom Plantae.
Under optimal conditions, a single plant of the Indian species Wolffia microscopica may reproduce vegetatively by budding every 30 hours. One minute plant could mathematically give rise to one nonillion plants or 1 x 10 30 one followed by 30 zeros in about four months, with a spherical volume roughly equivalent to the size of the planet earth!
Note: This is purely a mathematical projection and in reality could never happen! The following illustration shows a comparison of the size of one minute wolffia plant, roughly intermediate between a water molecule and the planet earth! I f a water molecule is represented by 10 0 , then a wolffia plant is about 10 20 power larger than the water molecule. The earth is about 10 20 power larger than a wolffia plant, or 10 40 power larger than the water molecule.
Starting with one couple, assume that every female has 4 children 2 boys and 2 girls. The following table compares the population growth in 7 generations. The original couple has 4 children, two of which are girls which give rise to 8 children 2 x 4. Four of the 8 children are girls which give rise to 16 children 4 x 4 , etc.
This is an exponential increase in which the population doubles each generation.
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