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 2.71828). 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. If a population of people grew from 1000 to 1040 in one year, then the percent increase or annual growth rate is x 100 = 4 percent. 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. If the birth rate during one year is 52 per 1000 and the death rate is 12 per 1000, then the annual growth of this population is 52 – 12 = 40 per 1000. The natural growth rate for this population is x 100 = 4%. 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.
It weighs in at 150 micrograms (1/190,000 out of an ounce), or perhaps the estimate pounds from 23 grains off dining table sodium
Elizabeth ach wolffia bush was designed like a tiny green sporting events having a condo most useful. An average private plant of one’s Asian types W. globosa, or the equally time Australian types W. angusta, was short enough to pass through the interest regarding a standard stitching needle, and you may 5,000 plant life could easily squeeze into thimble. 
T listed here are more than 230,100000 species of discussed flowering plants in the world, and additionally they assortment in proportions outof diminutive alpine daisies merely a couples in significant so you can enormous eucalyptus woods in australia more three hundred foot (a hundred yards) high. Nevertheless the undeniable planet’s littlest blooming flowers fall into the brand new genus Wolffia, time rootless plant life you to definitely float at facial skin off silent streams and you will lakes. Two of the minuscule kinds would be the Far eastern W. globosa and Australian W. angusta . An average individual bush was 0.6 mm much time (1/42 off an inches) and you will 0.3 mm wide (1/85th from an inch). One to bush is 165,100 moments shorter than the highest Australian eucalyptus ( Eucalyptus regnans ) and seven trillion minutes mild as compared to very enormous monster sequoia ( Sequoiadendron giganteum ).
T he growth rate for Wolffia microscopica may be calculated from its doubling time of 30 hours = 1.25 days. In the above population growth equation (N = N _{o} e rt ), when rt = .695 the original starting population (N _{o} ) will double. Therefore a simple equation (rt = .695) can be used to solve for r and t. The growth rate (r) can be determined by simply dividing .695 by t (r = .695 /t). Since the doubling time (t) for Wolffia microscopica is 1.25 days, the growth rate (r) is .695/1.25 x 100 = 56 percent. Try plugging in the following numbers into the above table: N _{o} = 1, r = 56 and t = 16. 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 7,785. This exponential growth is shown in the following graph where population size (Yaxis) is compared with time in days (Xaxis). Exponential growth produces a characteristic Jshaped 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.
