NAME
Marine Biology--Mr. Nelson
POPULATIONS AND EXPONENTIAL GROWTH
INTRODUCTION:
In Ecology, a population is a group of organisims of the same species, that live in a particular area (ex. A
pod of bottlenose dolphins) If you were to grow five centimeters a year you would have a linear growth rate;
that is growth that is constant over a period of time. Imagine how tall you would be if, instead of linear
growth, you grew faster and faster as you grew taller and taller! This is an example of exponential growth.
Most populations reproduce in this way; the more "critters" there are, the faster the total population grows.
Any kind of growth where the rate of growth depends on the number or size of things, is called exponential
growth. In this activity, you will compare the doubling time (the time for a thing such as size or population to
double) in linear and exponential growth. Also, you will examine the question of the impact of each type of
growth on the environment.
PURPOSE:
* How does exponential growth differ from linear growth?
* How populations grow and the effects they have on the environment.
* Rules for graphing.
PROCEDURE:
1. LINEAR GROWTH: A person has five dollars. They go to work and earn $5 an hour. Fill in the chart
below to indicate the total money they have for each of the first 15 hours they work. Now, use the data chart to
make a graph of the total money they have for each of the first 15 hours. You will make an "XY (Scatter)"
single line graph. On your spreadsheet: column A (x-axis) is Hour and column B (y-axis) is Dollars.
2. LINEAR GROWTH: A baby is 50 centimeters tall at birth and grows 10 centimeters a year until the child is
15 years old. Fill in the Data Chart below, then make a graph of the child's total height for each of these 15
years. You will make an "XY (Scatter)" single line graph On your spreadsheet: column A (X-axis) is Age In
Years and column B (y-axis) is Height (cm).
3. EXPONENTIAL GROWTH: There is a one-celled marine plankton organism that splits every hour. After
one hour there are two, after two hours there are four and so on. Fill in the data chart below, then make a
graph of the total number of organisms for the first eight hours. You will make an "XY (Scatter)" single line
graph. On your spreadsheet: column A (X-axis) is Hours and column B (y-axis) is Population Number.
4. When you are done with all three graphs, answer the questions in the observations section and insert your
graphs onto individual pages at the end of this document..
0
5
DATA CHARTS
Hour
Money ($)
Population #
Age (years)
Height (cm)
Hours
15
80
0
50
0
1
8
15
200
OBSERVATIONS for procedure #1: Look at your first graph:
1. Is this growth linear or exponential?
256
The Doubling Time is the number of hours it takes to double your money
2. How long, in hours, is the first doubling time ($5 to $10 )?
3. How long, in hours, is the second doubling time ($10 to $20 )?
4. How long, in hours, is the third doubling time?
5. How long, in hours, is the fourth doubling time?
6. What happens to the doubling time in this kind of growth; does it increase, decrease, or stay constant?
OBSERVATIONS for procedure #2: Look at your second graph:
7. Is this growth linear or exponential?
The Doubling Time is the number of years it takes the baby to double in height.
8. How long is the first doubling time (50 to 100 cm )?
9. How long is the second doubling time?
10. What happens to the doubling time in this kind of growth does it increase, decrease, or stay constant?
OBSERVATIONS for procedure #3: Look at your third graph:
11. Is this growth linear or exponential?
The Doubling Time is the number of hours it takes the population # to double.
12. how long is the first doubling time (total of 2)?
13. how long is the second doubling time?
14. how long is the third doubling time?
15. What happens to the doubling time in this kind of growth does it increase, decrease, or stay constant?
CONCLUSIONS:
1. What happens to the amount of doubling time in linear growth over time?
2. Describe the shape of the line on your linear growth graphs.
3. What happens to the amount of doubling time in exponential growth over time?
4. Describe the shape of the line on your exponential growth graph.
5. Which of the doubling time applies to most populations of organisms. Linear growth doubling time or exponential growth
doubling time?
6. In real life, organisms are attacked by disease, face competition for resources and must contend with natural enemies
(predators). This controls the growth rate, often holding populations in a steady state after a growth period. This steady state is
called the Carrying Capacity. Using the tools in Word and the axes below, draw a graph that shows exponential population
growth that reaches a Carrying Capacity.
P
O
P
U
L
A
T
I
O
N
#
TIME (YEARS)
7. What would happen to populations in ocean ecosystems if they never reached a carrying capacity?
8. Believe it or not, Homo sapiens still show continuous exponential growth. In 1991, the world population of human beings was
at about 5.2 billion with an expected doubling time of about 40 years.
On February 3, 2012, World population was 6,942,338,690.
On February 12, 2013, World population was 7,014,329,919.
On February 12, 2014, World population was 7,083,574,380.
As of Tuesday, March 10, 2015, World population was 7,229,565,520
What impact might this contiuous exponential growth have on Earth’s abiotic environment?
INSERT GRAPHY #1 HERE
INSERT GRAPHY #2 HERE
INSERT GRAPHY #3 HERE