104
Population Ecology Cover Page
105
Population Ecology
At the end of this unit, I will
o
o
o
o
o
o
o
o
o
o
o
o
o
calculate the size of various populations using sampling as well as the mark and capture method.
graph and interpret human population graphs
explain the various dispersion patterns of a population and determine the reasons or for these patterns.
identify factors that limit population growth, which includes differentiating between density dependent vs.
density independent population growth factors.
distinguish the difference between exponential and logistical growth models.
identify factors that influence the population growth rate. Infer how these factors influence population
growth models.
explain what determines the carrying capacity of ecosystems.
use mathematical and/or computational representations to support explanations of factors that affect
carrying capacity of ecosystems at different scales.
evaluate the evidence for the role of group behavior on individual and population’s chances to survive and
reproduce.
design and engineer a worm box with the ideal conditions to increase the population worms and
document engineering project via blog
use the process of natural selection to explain the evolution of behavior
create an infographic on Google Presentation that reveal how group behavior increases survival and
reproduction of a population.
explain the role of genes in behavior
Roots, Prefixes and Suffixes I will be able to understand when I see them in words are:
o
im-, em-, natal-, mortal-, gene-, different-, logis-, exponent-,
The terms I can clearly define are:
o
o
o
o
o
population, immigration, emigration, natality, mortality
logistical growth, exponential growth, carrying capacity (K)
density-dependent factors, density-independent factors, limiting factors, predator, prey
dispersion, clumped, uniform, random
innate behavior, evolution, natural selection, genetic variation, selective pressure, differential reproduction,
heredity
The assignments I will have completed by the end of this unit are:
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Parts of an Ecosystem Review
Population Ecology Notes
Estimating Population Size: Mark and Recapture
Population Ecology Reading
Oh Moose!
Examining Population Density and Dispersion
Human Population Pyramids
Understanding Exponentials
The History of Human Population Growth
Exploring Growth Models – Viva Amoeba
Population Trends
Population Trends Storyboard
Population Trends Predator-Prey Model
Predator-Prey Relationships
Group Behavior Google Presentation
Common Core: Genes and Social Behavior
Population Ecology Study Guide
106
Review: Use the following info-graphic to define organism, population, and community.
107
Population Dispersion Patterns
Concept Cards: Density Independent Factors vs. Density Dependent Factors
108
Population Ecology Notes
(Use your textbook, pages 92-104 to fill out your
notes)
What is population density?
Population density is ______________________________________
_______________________________________________________
Dispersion is the ______________ of spacing of a _______________
in an area.
What is dispersion? List the
three types.

_______________________

_______________________

_______________________
_______________ _______________ determines dispersion patterns.
Density independent factors do not depend on
________________________________________________
What are density independent
factors?

Usually __________________

Include ________________________ (ex. flood, drought,
extreme heat or cold, tornadoes, hurricanes)
What are density dependent
factors?
Density dependent factors depend on
________________________________________________

Often __________ (ex. predation, disease, parasites,
competition)
109
110
Define population growth rate
and its characteristics.
Population growth rate explains ______________________
________________________________________________

Natality: __________ rate

Mortality: __________ rate

Emigration: number of individuals moving
___________________ a population

Immigration: number of individuals moving
___________________ a population
Describe exponential growth.
Exponential growth starts slow (called the _____ phase)
Exponential growth is illustrated by a ____________ curve.
It is also called __________________ growth.
All populations grow exponentially until _________________
________________________________________________
__________________ become limited and population growth slows.
Describe logistic growth.
Logistic growth is illustrated by a _____________ curve.
Logistic growth occurs when ________________________
__________________________________________at the carrying
capacity. (K)
A population stops increasing when:
What is carrying capacity?

births __________ deaths

emigration _________ immigration
The ___________________________________________ that an
environment can support for the long term is the carrying capacity,
represented by the letter “K.”
111
Estimating Population Size: Mark and Recapture
Introduction
One of the goals of population ecologists is to explain patterns of species distribution
and abundance. In today’s lab we will learn some methods for estimating population
size and for determining the distribution of organisms.
Measuring Abundance: Mark-Recapture
Mobile animals are usually simpler to define as individuals, but harder to count,
because they tend to move around, mix together, and hide from ecologists. Quadrats
are not a good approach with mobile animals because immigration and emigration in
and out of the study site make it hard to know what area the entire population
occupies. For largemouth bass in a farm pond, you could easily draw a line around a
map of the population, but how would you define the edges of a population of house
sparrows in your community? Although house sparrows tend to be more
concentrated in towns and urban areas, they do not stop and turn back at the city limit
sign. For zoologists, a fuzzy definition of the space occupied by the population often
forces an arbitrary designation of the survey group, such as the "population" of robins
nesting on your campus in the spring. Knowing the number of animals in a designated
study area is interesting, but we must bear in mind that the ecological population is
defined in terms of interactions among organisms of the same species, and not by the
ecologist's convenience.
After defining the individual and establishing the limits of the population you wish to
count, your next task is to choose a counting method. Arctic and prairie habitats lend
themselves to accurate survey by aerial reconnaissance. This approach works poorly in
forests, at night, underwater, or in soil habitats. If animals can be collected or
observed in a standard time or collecting effort, you can get an idea of relative
abundance, but not absolute numbers. For example, the number of grasshoppers
collected in 50 swings with an insect net through an old field community produces
data that could be used to compare relative abundance in different fields, but would
not tell you how many grasshoppers were in the population.
For estimates of absolute numbers, mark-recapture methods can be very effective.
The first step is to capture and mark a sample of individuals. Marking methods
depend on the species: birds can be banded with a small aluminum ankle bracelet,
snails can be marked with waterproof paint on their shells, butterflies can have labels
112
taped to their wings, large mammals can be fitted with collars, fish fins can be
notched, and amphibians can have nontoxic dyes injected under the skin.
Marked animals are immediately released as close as possible to the collection site.
After giving the animals time to recover and to mix randomly with the whole
population, the ecologist goes out on a second collecting trip and gathers a second
sample of the organisms. The size of the population can then be estimated from the
number of marked individuals recaptured on the second day.
The assumption behind mark-recapture methods is that the proportion of marked
individuals recaptured in the second sample represents the proportion of marked
individuals in the population as a whole. In algebraic terms,
M = Animals Marked and Released
R = M
S
N
N = Population Size
R = Animals Recaptured on the Second Day
S = Size of the Sample on the Second Day
Let’s consider an example. Let’s say you want to know how many box turtles are in a
wooded park. On the first day, you hunt through the woods and capture 24 turtles.
You put a spot of paint on the shell of the turtles found, and release them all the
turtles back where you found them. A week later, you return to the same area and
capture 60 turtles. Of these 15 are marked, and 45 are unmarked. Since you know
how many were marked (M), sampled (S), and re-captured (R), you can figure out the
size of the whole population (N).
15 = 24
60 N
This can be rearranged algebraically to N= (24) (60)
15
N = 96 turtles
This method is called the Lincoln-Peterson Index of population size. In the
rearranged version of the general formula, notice that the smaller the number of
recaptures, the larger the estimate of population size. This makes good biological
sense, because if the population is very large, the marked animals you release into the
wild will be mixing with a greater number of unmarked animals, so you will recapture
a lower percentage of them in your second sample.
113
Estimating Population Size: Mark and Recapture Lab
Objective: You will be expected to estimate the size of a sample population using the
mark-recapture technique. Be able to apply the technique to new population
problems and compare the mark and recapture technique to other methods of
population estimating.
Opening Discussion: If you were in charge of a team given the responsibility to
determine the number of sunfish in Horseshoe Lake, discuss with your partner how
would you accomplish this task and describe in detail below.
Technique 1: Sampling
A technique called sampling is sometimes used to estimate population size. In this
procedure, the organisms in a few small areas are counted and projected to the entire
area. For instance, if a biologist counts 10 squirrels living in a 200 square foot area,
she could predict that there are 100 squirrels living in a 2000 square foot area.
2. A biologist collected 1 gallon of pond water and counted 50 paramecium. Based
on the sampling technique, how many paramecium could be found in the pond if the
pond were 20,000 gallons.
3. What are some problems with this technique? What could affect its accuracy?
114
Technique 2 - Mark and Recapture
In this procedure, biologists use traps to capture the animals alive and mark them in
some way. The animals are returned unharmed to their environment. Over a long
time period, the animals from the population are continued to be trapped and data is
taken on how many are captured with tags. A mathematical formula is then used to
estimate population size.
Procedure:
1. You will receive a bag that represents your population (beans, pennies, chips,
beads)
2. Capture “animals” by removing them randomly from the bag. Record the
number that was originally captured.
3. Place a mark on them using tape.
4. Return the “animals” to the container.
5. With your eyes closed, select a handful of “animals” from the container. This
is the recapture step. Record the number of “animals” captured the 2nd time
and the number of animals that have a mark on the data table.
6. Return the “animals” to the bag and repeat. Do 10 recaptures.
7. When the ten recaptures are completed, enter the total number captured on the
data table.
8. Also enter the total number of recaptured that have a mark
115
Data Table
Original Number Marked _________
Trial
Number
Number
Captured
Number
Recaptured
with mark
1
2
3
4
5
6
7
8
9
10
Average
Calculations
In order to estimate your population size, follow this formula
Estimate of Total Population = (total number captured) x (number marked)
(total number recaptured with mark)
1. What is the mean estimation of your population? Show your calculations
below:
Estimated Population Size ___________
116
2. Count how many “animals” are really in your population.
Actual Population Size: ____________
3. Compare the actual size to the estimated size. Did you overestimate or
underestimate?
4. Repeat the experiment, this time add another 10 data fields to the ten trials you
already have.
Trial
Number Number
Number Captured Recaptured
with mark
11
12
13
14
15
16
17
18
19
20
Average
(over 20
trials)
117
5. Recalculate your estimated population size, using the formula. (Show
calculations below)
Estimated Population Size _____________
6. What does this say about the number of trials that should be conducted in a
real mark and capture?
Going Further: Given the following data, estimate the size of a butterfly population
in Wilson Park.
1. A biologist originally marked 40 butterflies in Wilson Park. Over a month long
period butterfly traps caught 200 butterflies. Of those 200, 80 were found to
have tags. Based on this information, what is the estimated population size of
the butterflies in Wilson Park? (Show calculations)
2. In what situations would sampling work best for estimating population size, in
what situations would mark & recapture work best? You’ll probably have to
think about this one. Justify your claims.
118
Population Ecology Reading
Directions: Read and mark the following text about population ecology. Number
your paragraphs. Circle “essential terms,” and highlight definitions, explanations,
phenomena, or processes.
A population is a group of organisms of the same species that live in a certain
area. Ecologists regularly monitor the number of organisms in many populations, but
why do they do this? Why do we care if the number of organisms in an area is
growing or shrinking?
Well, populations that are growing and shrinking can be indicators of potential
problems occurring in the organisms’ environment, and gives ecologists a “heads up”
if something is going wrong. But it is not enough to simply know if the number of
organisms in an area is going up or going down; ecologists need to know why the
number of organisms is fluctuating. So, one of the main questions ecologists ask
themselves is this: Why is a population’s size going up or going down?
There are many factors that can cause a population’s size to change. But first,
you must understand the basic reasons behind why a population grows or shrinks.
Any population, whether it be humans, chipmunks, the mold growing on bread, or
the bacteria living in your intestines, will grow if more organisms are being created, or
born, than are dying. If a population has more organisms dying than are being born,
then the population will shrink. The number of births in a population is called the
birth rate (also referred to as natality). The number of organisms that are dying in a
population is called the death rate (also referred to as mortality). Thus, if the birth
rate is greater than the death rate, a population will grow. If the death rate is greater
than the birth rate, then the population will decrease in size.
While populations would probably like to continue to grow in size, a
population of organisms cannot grow forever—its growth will be limited, or stopped,
at some point, and the death rate will be greater than the birth rate. A population’s
growth is limited by two general factors: density-independent factors and densitydependent factors. Why are these factors named in such a complicated way? Well,
actually, these names aren’t as complicated as they seem; in fact, they can even help
you remember what each of the terms means.
To understand why scientists named these factors in the way they did, you
must first understand the concept of population density. A population’s density is
NOT whether or not the population will float or sink. Population density refers to
how many organisms there are in one particular spot. If a population’s density is very
high, that means there are a lot of organisms crowded into a certain area. If a
population’s density is low, that means there are very few organisms in an area.
119
Now that you know about population density, we can talk about the difference
between the two types of limiting factors. If a factor that stops a population’s growth
is influenced by the population’s density, then it is called a density-dependent
limiting factor. If the population’s density does not influence whether or not the
factor stops the population’s growth, then it is called a density-independent
limiting factor.
Density-independent limiting factors that can stop a population from growing
can be such things as natural disasters, temperature, sunlight, and the activities of
humans in the environment. Natural disasters such as tornadoes, floods, and fires will
stop a population from growing no matter how many organisms are living in a certain
area. The same goes for the temperature of an area and the amount of sunlight an area
receives—if the temperature increases due to global warming, or if the ash kicked up
into the atmosphere from an asteroid smashing into the earth blocks out a lot of
sunlight for a few decades, these will both cause a decrease in a population’s numbers,
no matter how large or small the population was to begin with. Human activities that
alter the environment will also decrease the amount of organisms in a population, no
matter the size of the population.
Density-dependent limiting factors come into play when a population reaches a
certain number of organisms. Thus the number of organisms in the population
matters when talking about density-dependent limiting factors. For example, when a
population reaches a certain size, there won’t be enough resources (food, shelter,
water) for all of the organisms. This could cause the population to stop growing when
it reaches the maximum number of organisms that can be supported, or “carried,” by
the environment. This number is known as the population’s carrying capacity. Each
population of organisms has a different carrying capacity, depending on the area in
which it lives and the amount of resources available in that area. Below is a graph of a
bacteria population that has reached its carrying capacity:
This type of population growth
is called logistic population growth;
it represents what actually occurs as a
population’s numbers get too large for
the environment to support it. First
there is a lag phase, where population
growth is slow. Then the population
will increased rapidly (exponential
phase) due to the abundance of
resources. In other words, there are
no limiting factors. The bacterial
growth began to slow down towards
the end after 3 hours. Once the
120
population numbers leveled off, roughly equal numbers of bacteria were dying as
being born.
Before a population reaches its carry
capacity, it experiences a period of rapid growth.
This period of growth is called exponential
population growth, because, mathematically,
the population is adding organisms at an
exponential rate. During this time period, there
are plenty of resources available for all
organisms, so more organisms are being born
than are dying. The graph for exponential
population growth looks sort of like the graph
for logistic population growth, only without the
flat “leveling off” line at the end of it.
Create an essential terms list
of your reading here.
Write a summary of your reading.
121
Intentionally Left Blank
for notes, diagrams, brainstorming
122
Oh Moose!
Objectives: In this activity, you will identify three limiting factors that animals need to
survive. Limiting factors are factors that limit the growth of a population.
Examples of limiting factors are elements of habitat, such as food, water, and shelter.
If animals do not have these necessities, their chances for survival and reproduction
are greatly reduced, and they may die.
Activity Overview:
In this simulation, ¼ of the class will act as “moose” while ¾ of the class will become
the components of habitat. Each moose must find three habitat essentials: food,
water, and shelter. When a moose is looking for food, it holds his hands (hooves)
over its stomach. When a moose is looking for water, it holds its hands over its
mouth. When a moose is looking for shelter, it holds its hands over its head.
At the beginning of each round, a moose can decide what to look for. Once a moose
has chosen what to look for, it cannot change until the beginning of the next round.
Each player in the habitat group randomly chooses to be one of the essentials – food,
water, or shelter – at the beginning of each round. These students will use the same
hand gestures to indicate their identity.
The moose group and the habitat group will be standing apart across a field with your
backs facing each other. Your teacher will ask all the players to make hand gestures
for food, shelter, or water. On the count of three, all students will turn around to see
the other group.
Moose continues to hold their hand gestures and run or walk to a player at the other
line displaying the same habitat gesture. They escort the habitat person back to the
moose line, because “successful” moose are able to survive and reproduce. If a moose
does not obtain its needed essential, it “dies” and turn into a habitat component in the
next round.
Your teacher will keep track of the number of moose at the beginning of each round
of play. The game will be played for 8 – 15 rounds.
123
Oh Moose!
Data table:
Time in
0
Years
Number
of Moose
Population
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15
Graph:
Title:
124
Oh Moose!
Analysis:
1. Examine your graph and analyze it. Determine if there are any parts of the
graph that demonstrates fast growth phase of your population, a leveling off of
the population, or a decline in your population. Mark your graph.
2. Analyze the data on the graph. Explain areas in the graph where the birth rate
exceeded the death rate. Use the graph to defend your answer.
3. Are there any periods on the graph where the death rate and the birth rate were
equal? If so, explain where. Use the graph to defend your answer.
4. Are there any periods on the graph where the death rate exceeded the birth
rates? Use the graph to defend your answer.
5. Define “limiting factor”, then explain which limiting factors caused a decline in
the population of moose.
125
6. Explain the difference between density dependent and density independent
factors, then determine if the limiting factors in this simulation were density
dependent or density independent.
7. Define carrying capacity, and then defend if your moose population ever
reached its carrying capacity.
126
Intentionally Left Blank
for notes, diagrams, brainstorming
127
Examining Population Density and Dispersion
Examine the map of the human population and discuss/brainstorm the following
ideas with your table group:
- Where on the map do you see the greatest population? The least population?
- What “pattern of spacing,” or dispersion do you notice?
- Why do you see this type of population distribution and density amongst
humans?
Now examine the next image presented by your teacher. What density, dispersion,
and reproductive strategies do you notice?
128
Essential Concept:
Each population has a
a) ______________,
b) __________________, and a
c) __________________/________________ strategy.
Human Population Pyramids: Watch the history of the world population growth
video in less than 7 minutes. Then complete the following activity.
What are at least four factors that influenced human population growth?
1.
3.
2.
4.
The graph to the left is used by
demographers to study the
distribution of people across age
categories.
Why do you think it is called a
“population pyramid?
What is the largest age cohort?
129
130
Matching Population Pyramids to Data
The figures on the worksheet represent the population (in thousands) of each age group within each
gender for each particular country. In order to construct the country’s pyramid, students must first
calculate the percentage of the population of each gender in each age group.
Complete these calculations for each cohort (age group).
a. Example: According to the worksheet, the total population of the United States in 2004
was 293,028,000. (The table shows Population in Thousands). The population of males
aged 0-4 was 10,334,000 in the United States.
b. Example problem:
10,334,000 = 0.035 or 3.5 %
293,028,000
Once you have calculated the percent of the population that each cohort represents, label the
population pyramid with the name of the country.
131
132
Creating Population Pyramids
1. Calculate the percentage of the population of each gender in each age group from the opposite
page.
2. Use the graph paper below to construct population pyramids for the designated countries.
a. The percentages of the population will be plotted along the x-axis – females to the right,
males to the left of the center-line.
b. The age groups will be running up the y-axis with the youngest at the bottom, oldest at the
top.
c. Use colored pencils to shade in the bars that represent the cohort.
France
Age
Male
Female
2.
133
Analyzing Population Pyramids
1. Can you tell from the data if there are more boy babies or girl babies in each country?
How?
2. Are there more elderly women or men? Why might that be the case?
3. Which country has the most people?
How can you tell?
4. Of the six graphs, which look most like pyramids?
What does that indicate about their population growth rates?
5. What factors would change the shape of the pyramids in the future?
6. Looking at the pyramids, which country appears to have the slowest rates of population
growth?
How can you tell?
7. Which are the two biggest age groups in the United States in 2004?
8. In which countries do children make up the biggest percentage of the population?
134
Understanding Exponentials
Consider this:
An employer offers you two equal jobs for one hour each day for fourteen days. The first pays $10
an hour. The second pays only 1 cent per hour, but the rate doubles each hour. In the graph below,
graph a model of which job you think will pay the best rate over the course of 14 days. You will
need to graph two lines, one that represents the rate of pay for job 1, and the second line that
represents the rate of pay for job 2.
Rate of Pay for Job 1 vs. Job 2
135
Understanding Exponentials
After creating your initial model, complete the following calculations:
Job 1: Paid $10/hour for 14 days. Calculate the RATE of pay for 14 days in the 2nd row. In the 3rd
row, calculate the total amount of pay over the 14 days
Day
1
2
3
$10
$10
$10
Total $10
Pay
$20
Rate
4
5
6
7
8
9
10
11
12
13
14
Job 2: Pays only 1 cent per hour, but the rate doubles each hour. Calculate the RATE of pay for 14
days in the 2nd row. In the 3rd row, calculate the total amount of pay over the 14 days
Day
1
2
3
$.01
$.02
$.04
Total $.01
Pay
$.03
Rate
4
5
6
7
8
9
10
11
12
13
136
14
Understanding Exponentials
After completing the calculations from the previous page, revise your original model. Label
your new graphical model with the lag phase and exponential phase.
Rate of Pay for Job 1 vs. Job 2
Now, how much would your employer owe you if you stayed at this job for another 2 weeks?
What would happen if this type of growth took place within a population?
137
The History of Human Population Growth
138
The History of Human Population Growth
On the grid provided on the opposite page, graph the data below. Once the data is graphed, use the graph to answer
the questions.
Questions (after the graph is completed):
1. If you had to compare the shape of the graph to a letter in the alphabet, what does it look like?
2. If growth slowed down considerably, what letter of the alphabet would the shape of the curve begin to
look like?
3. At the current rate of growth, the population is projected to reach approximately 10 Billion by 2050.
What do you think this growth rate will mean in terms of resources and quality of life?
4. Can this rate of growth go on forever? Why or why not?
5. How is this graph different from a population pyramid? What does this graph reveal?
139
Exponential Growth
140
Logistic Growth: Staying at Carrying Capacity (K)
141
Population Trends
Do Fruit flies and rabbits show similar trends in population growth?
Fruit Fly Population Growth
Days
Number of Fruit flies
5
100
10
105
15
1000
20
1600
25
2400
30
3350
35
8000
40
13,150
142
Rabbit Population Growth
Generations
1
Number of Rabbits
10
2
50
25
100
37
200
55
300
72
310
86
320
100
320
143
Population Trends Analysis: Use the tables and graphs to answer the following questions:
1. What type of growth pattern does the fruit fly population exhibit?
2. Does the rabbit population experience the same type of growth as the fruit flies? Explain.
3. Does either graph indicate there is a carrying capacity for the population? If so, when does
the population reach its carrying capacity?
4. What is the maximum number of individuals that can be supported at that time?
5. Using the storyboard template provided, tell a story about the population that reached its
carrying capacity. Be sure to include the following: logistical growth, exponential growth,
carrying capacity, and the three factors that affect population growth (birth, death, and the
movement into/out of the population, which are immigration and emigration).
144
145
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
Freeology.com – Free Teaching Resources
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
Name(s): ______________________________________________________________Date: ___________ Period: _______
Storyboard
Population Trends Predator-Prey Model
Animals such as foxes and cats often prey on rabbits. Based on the growth curve of the rabbit
population, what might happen if a group of predators move into the rabbits’ habitat during the
tenth generation and begin eating rabbits? Draw a model of what you think would happen to your
population graph that you drew on page 143. In this model, you should have two lines: one line to
represent your rabbit population and another line to represent your predator population. Make sure
to include a legend in your model. Do your best in drawing your model. You will get the chance to
revise your model, as you learn more about predator-prey relationships.
146
Population Trends Predator-Prey Model Revision
Examine your initial predator-prey model that you created on page 146. Your teacher may choose a
few student models to display on the projector and analyze. Go over the various student models and
analyze the flaws in each model. After you analyze various flaws, re-vise your predator-prey graph
model here on this graph. Use the space below the graph to explain your revised predator-prey
graph. If you do not have enough space to write, continue on the back of the page.
147
Intentionally Left Blank
148
Predator-Prey Relationships
Ecologists gather data about population densities of different organisms in order to understand how
these organisms interact with their environments. The graph in Figure 1 represents a growth curve
for the population of a single species. This type of curve is called a logistic growth curve. From
this curve, you can read the carrying capacity of the population. Carrying capacity is the number
of individuals that can be supported in an environment with the resources available. When the
population has reached carrying capacity, the curve will level off.
1. Time is represented on the
-axis.
2. The number of individuals is represented on the
-axis.
3. At which point on the curve (I, II, III) is the population increasing at the fastest rate?
4. At which point on the curve (I, II, III) is the population leveling off?
5. At which point on the curve (A or B) has the population reached the carrying capacity or the
maximum population density for its environment?
6. What would happen to the growth curve if the temperature suddenly dropped, a pollutant
or a new predator were introduced, thus making the environment less than ideal for this
organism?
149
Examine the following graphs of populations that have reached their carrying capacity. Remember
that the carrying capacity (K) of any population can be found on the graph of population growth.
Carrying capacity has been reached when the logistic population curve levels off.
7. Populations tend to fluctuate over time.
This population growth curve for sheep has
been normalized, which means that a smooth
curve has been drawn to show approximate
carrying capacity. What is the carrying capacity
of the sheep in this environment?
8. A population of daphnia in a pond has
been shown to have a growth curve like the one to
the right. How long does it take this population
to reach carrying capacity?
9. What is the carrying capacity of this population?
10. The graph to the right shows the population growth
curve for a population of bacteria in two different
media. Since this is their environment, what is the
difference between the carrying capacity of this population
in Medium 154 and the EpiLife medium?
11. It takes large mammals a greater amount of time to
reach carrying capacity than it does for a population
of small animals or bacteria. What is the carrying
capacity of this deer population in its present
environment?
How can a population of deer be kept at or near
in their environment? (Hint: Think of something that
will limit the growth of the deer population.)
150
In the tundra, where both reindeer and wolves live, the number of reindeer in a herd does not
exceed the carrying capacity of the environment. In 1944, the United States Coast Guard
transported 29 reindeer to St. Matthew Island in the Bering Strait. St. Matthew Island has the typical
climate for tundra, but no wolves live there. The graph shown in Figure 2 represents the growth
curve for the reindeer population there.
12. What is the increase in the reindeer population increase between 1945 and 1963?
13. What is the decrease in the reindeer population decrease between 1963 and 1966?
14. Did the reindeer exceed the carrying capacity of their environment?
Explain your answer
15. Why do you think the population increased so rapidly in less than 20 years?
16. Why do you think that the population declined so rapidly, from 6000 to 42, in 3 years?
17. What do you think would have happened if wolves had been brought to the island with the
reindeer
151
Opening Discussion and Brainstorm: Is there a genetic basis for behavior? Discuss this
idea with your table? Consider your claim, and be prepared to defend your claim with evidence. Jot
down your claim and evidence discussed by your table group on this paper.
What is your group’s Claim?
Evidence to support your claim?
Now watch the video presented by your teacher. Decide, after watching the video, whether you need
to re-think your claim.
Define innate behavior:
What is the revised claim?
What evidence do you have to support your claim?
Your class will now read the cartoon “Survival of the Sneakiest” on the following pages. As you
read, consider how cricket behavior evolved.
152
153
154
155
156
157
Evolution of Behavior by way of Natural Selection
Behaviors evolve much the same way that physical features evolve. In the cartoon, there were
specific genetically based behaviors that either increased or decreased the cricket’s ability to survive,
reproduce, and thus determined which genes were passed on to the next generation. Evolution is
defined as change over time. The change can be a behavioral change or a physical feature. Natural
Selection, however, is the process of how evolution occurs. Outline the steps for natural selection of
cricket behavior with your teacher here.
Step 1: Genetic Variation
Step 2: Struggle for Survival/Selective Pressures That Lead to Differential
Reproduction.
Step 3: Heredity
158
Group Behavior
Within populations, animals can exhibit group behaviors. Examples of behaviors include herding,
flocking, colonies, hunting, migrating, kin altruism, reciprocity, swarming, territoriality, migrating,
schooling, shoaling, and swarming. All of these behaviors benefit the group in survival and
reproduction.
You will work with your classmates to analyze a particular behavior and put together one or two
Google Presentation slides to teach the rest of the class about your behavior. You will need to
conduct independent research to determine how the behavior increases the chances of the
population’s survival and reproductive capacity.
Your Google Presentation slide will need to include the following:





Title of your group behavior
Definition of your behavior
At least two examples of the behavior in different species
Choose images that represent these examples
Explanations of how the behavior benefits the population in survival and reproduction.
As a class, you will all be working off of the same Google Presentation. So, it is extremely
important that you do not interfere with another group’s slide during this process.
159
Type of behavior
Claim: Why do
individuals take part in
these behaviors?
Evidence/ Examples:
To support your claim
160
Type of behavior
Claim: Why do
individuals take part in
these behaviors?
Evidence/ Examples:
To support your claim
161
Central Dogma of Molecular Biology
Genes and Social Behavior in a Population
How Do Genes Work?
Genes are often called the blueprint for life, because they tell each of your cells what to do and when
to do it: be a muscle, make bone, carry nerve signals, and so on. And how do genes orchestrate all
this? They make proteins. In fact, each gene is really just a recipe for a making a certain protein.
And why are proteins important? Well, for starters, you are made of proteins. 50% of the dry weight
of a cell is protein of one form or another. Meanwhile, proteins also do all of the heavy lifting in
your body: digestion, circulation, immunity, communication between cells, motion-all are made
possible by one or more of the estimated 100,000 different proteins that your body makes.
But the genes in your DNA don't make protein directly. Instead, special proteins called enzymes
uses the DNA as a template to build a single-stranded molecule of RNA. This RNA leaves the
nucleus and travels out into the cytoplasm of the cell. There, protein factories called ribosomes read
the mRNA code and use it to make the protein specified in the DNA recipe.
If all this sounds confusing, just remember: DNA is used to make RNA, then RNA is used to make
proteins-and proteins run the show.
162
Common Core Practice: Use the information from the reading and the diagram on the
opposite page to explain the genetic basis for behavior. In other words, how do genes influence
social behavior in a population?
163
164
r and K reproductive strategies
Organisms that live in stable environments tend to make few, "expensive" offspring. Organisms
that live in unstable environments tend to make many, "cheap" offspring.
Imagine that you are one of the many invertebrate organisms which existed during the Cambrian or one of
their descendents living today. Maybe you live in a tide pool which is washed by waves. A storm appears
on the horizon. The waves increase in height. You feel yourself being dashed upon the rocks or into the
mouth of a much larger and predatory animal. Finally, you begin to see your brothers and sisters die, one
by one, as the forces of nature change your unpredictable environment.
If you could design a "strategy" to overcome the problems created by an unpredictable environment, you
would have two choices - go with the flow or cut and run to a more stable environment.
Suppose you stayed. Then, one thing you could do would be to increase the number of offspring. Make
lots of cheap (requiring little energy investment) offspring instead of a few expensive, complicated ones
(requiring a lot of energy investment). If you lose a lot of offspring to the unpredictable forces of nature,
you still have some left to live to reproductive age and pass on your genes to future generations. Many
invertebrates follow this strategy - lots of eggs are produced and larvae are formed but only a few survive
to produce mature, reproductive adults. Many insects and spiders also follow this strategy.
Alternatively, you could adapt to a more stable environment. If you could do that, you would find that it
would be worthwhile to make fewer, more expensive offspring. These offspring would have all the bells
and whistles necessary to ensure a comfortable, maximally productive life. Since the environment is
relatively stable, your risk of losing offspring to random environmental factors is small. Large animals,
such as ourselves, follow this strategy.
Plants are also subject to the same sorts of forces as animals. Some live in unstable environments such as
a floodplain near a river or a gap in the forest caused by falling trees. Others live in a quite stable
environment, such as a climax forest.
165
The two evolutionary "strategies" are termed r-selection, for those species that produce many
"cheap" offspring and live in unstable environments and K-selection for those species that produce
few "expensive" offspring and live in stable environments.
Of course, the animal or plant is not thinking: "How do I change my characteristics?" Natural selection is
the force for change, not the individual's conscious decision. But, natural selection has produced a
gradation of strategies, with extreme r-selection at one end of the spectrum and extreme K-selection at the
other end.
The following table compares some characteristics of organisms which are extreme r or K strategists:
r
K
Unstable environment, density independent
Stable environment, density dependent
interactions
small size of organism
large size of organism
energy used to make each individual is low
energy used to make each individual is high
many offspring are produced
few offspring are produced
early maturity
late maturity, often after a prolonged period of
parental care
short life expectancy
long life expectancy
each individual reproduces only once
individuals can reproduce more than once in their
lifetime
type III survivorship pattern
in which most of the individuals die within a
short time
but a few live much longer
type I or II survivorship pattern
in which most individuals live to near the maximum
life span
166
The terms "r-selected" and "K-selected" come from a description of the population growth regimes
of the two types of organisms.
If you are in an unstable environment, you are unlikely to ever have population growth to the point where
density dependent factors come into play. The population is still at low values relative to the carrying
capacity of the environment and thus is growing exponentially with intrinsic reproductive rate r (when it
is not subject to environmental perturbations.), hence the name r-strategist.
An extreme K-strategist lives in a stable environment which is not seriously affected by sudden,
unpredictable effects. Thus the population of a K-strategist is near the carrying capacity K.
167
Surviorship curves give us additional insight into r and K-selected strategies. Notice that the
vertical axis of the survivorship plots is on a log scale and that horizontal axis is scaled to the
maximum lifetime for each species.
One of the interesting differences between r and K strategists is in the shape of the survivorship curve.
We can generate a survivorship curve by ploting the log of the fraction of organisms surviving vs. the age
of the organism. To compare different species, we normalize the age axis by stretching or shrinking the
curve in the horizontal direction so that all curves end at the same point, the maximum life span for
individuals of that species. Notice that the vertical axis is on a log scale, dropping from 1.0 (100%) to 0.1
(10%) to 0.01 (1%) to 0.001 (0.1%) in equally spaced intervals.
Extreme r-strategists, such as the oyster, lose most of the individuals very quickly, relative to the
maximum life span for the species. But, a very few individuals do survive much longer than the rest. But,
for extreme K-strategists, such as man, most individuals live to old age (again relative to the maximum
life span for the species).
These survivorship data are very valuable when studying the ecology of various organisms. Two
components are involved in reproduction: 1) How many females survive to each age and 2) the average
number of female offspring produced by females at each age. By using these data, we can compute the
intrinsic rate of reproduction, r, a key parameter in models of population growth.
168
Population Study Guide
1. According to the predator-prey graph
to the left, which line represents the
predator? Which line represents the
prey? How do you know?
Predator-Prey Relationship Cottontale vs. Red Fox
1600
1400
1200
Population
1000
Series1
800
Series2
600
400
200
0
5/7/1990
9/19/1991
1/31/1993
6/15/1994
10/28/1995
3/11/1997
7/24/1998
12/6/1999
Dates
2. According to the graph, the prey population decreases when the predator population does
what?
3. What is a habitat?
4. In the following blank squares, draw what a clumped, uniform, random dispersion pattern
looks like.
Clumped
Random
Dispersed
5. What determines dispersion patterns?
6. Wildflowers tend to have a random dispersion pattern. Infer why this may be the case.
169
7. In the blank graphs below, sketch what an exponential growth model and a logistical
growth model look like. For the logistical growth model, label carrying capacity (k). To
the right of the graphs in the box, jot down some notes or information about the
characteristics of each of the growth models.
Exponential Growth Model
Logistical Growth Model
8. Define carrying capacity. Then, give examples of how carrying capacity can be lowered
or increased.
9. Contrast the reproductive strategy of an r-strategist with a k-strategist.
170
10. Analyze the population pyramids below. Label them and predict how their populations will grow
(or shrink) in the future.
11. What is the difference between immigration and emigration?
12. Define the terms below in your own words:
a. Population –
b. Community –
c. Ecosystem –
171
13. Suppose that you capture 10 individuals of a rare subspecies of brook trout from an
impounded watershed. You place a pit tag (a very small radio activated tag) in the body
cavity of each individual and then release these fish. You come back a month later and
capture 20 fish and find that four of these are individuals that you had previously
captured and released. Calculate the population size, N. Show all of your work!
14. Suppose that a naturalist determines that there are 500 deer in a rectangular forest that is
5 miles wide and 10 miles long. What will the density of the deer be per square mile?
15. Suppose that the high school in a town has 500 students. A random survey of 200 people
in the town finds 40 high school students. What is the estimate for the number of people
in the town?
172
Common Core Practice: Analyzing a text
ESLAF DAM BREAKS
Heavy rains over the western portion of the
state caused the Eslaf Dam to burst last
night. The dam ruptured at 6 p.m. Pacific
Time. As a result, water from the Eslaf
River overflowed its banks and flooded a
huge area of the state. Farmers reported
many of their crops were ruined because of
water standing in the fields. Others reported
large amounts of topsoil being carried away
by the rushing waters. Some forest areas
were also flooded, causing some animals to
seek safer, high ground. People in the flood
area are warned not to drink the water
without first boiling it. Boiling will kill the
microbes and remove unsafe pollutants.
Flood damage is estimated in the millions of
dollars. Luckily, no loss of human life has
been
reported.
Answer the following questions about the article:
16. According to the newspaper article, is soil being lost or gained?
________________________
What statement of evidence from the article do you have to support this claim? (Use a
direct quote from the article.)
17. According to the newspaper article, is food supply being reduced or is it increasing?
____________________
What statement of evidence do you have to support this claim?
18. Is the drinking water safe? ____________________
What statement of evidence from the article do you have to support this claim?
19. Are habitats increasing or decreasing? _____________________
What statement of evidence from the article do you have to support your claim?
20. Define “limiting factors”.
173
21. What factors could limit the size of populations of animals and plants in this area and
why?
174
Use the graph below to answer the following questions:
22. Which curve(s) show the effect of a density dependent factor?
23. Which curve(s) show the effect of a density independent factor?
24. Which curve(s) show a likely r-strategist’s growth curve?
25. Which curve(s) show a likely k-strategist’s growth curve?
26. What is the carrying capacity of organism B?
27. What is the carrying capacity of organism C? (draw a trend line for the data on the graph)
175
28. Draw two trend lines (one for each type of paramecia. Use two different colored lines.)
29. Calculate the highest growth rate for each paramecium based on your trend line.
30. Label the “lag phase” and “exponential phase”. Explain these phases and use evidence
from the graph to support your explanation.
31. Predict why these two organisms have different carrying capacities.
176
32. Bluestripe snapper often swim together in large groups going in the same direction. This
is called “schooling”. Write a paragraph below that answers the following questions:
a. How does the population benefit from schooling?
b. How does the individual benefit from schooling?
c. Explain how the behavior (schooling) is connected to the genetics of bluestripe
snapper. Include the terms protein, DNA, RNA, and gene in your explanation.
177
Population Unit Concept Map
178
Parent/Significant Adult Review Page
Student Portion
Unit Summary (write a summary of the past unit using 5-7 sentences. Use your concept map to guide your
writing):
Explain your favorite activity and why:
Adult Portion
Dear Parent/ Significant Adult:
This Interactive Notebook represents your student’s learning to date and should contain the work your
student has completed. Please take some time to look at the unit your student just completed, read his/ her
reflection and respond to the following
Ask your child to explain to you the difference between exponential growth and logistical growth. Write what
they explained here.
Parent/Significant Adult Signature
179
180