Bell Work
• Main word/ idea: Population(s)
1. Write as much information as you can
about:_________________________________
2. A ______________________________is like a
_____________________________ because:
3. Describe why it is important to study
________________________________?
4. What are some important characteristics of
_______________________________________?
Population Ecology
Chapter 19 pg 236-237
Characteristics of populations
Objectives
• TLW: review definition of population.
• TLW: List the characteristics used to
describe a population.
Objectives
• TLW: review definition of population.
• TLW: List the characteristics used to
describe a population.
• TLW: create science vocabulary cards for
this chapter.
What is population biology?
It is the study of how and why
populations change
Define population
A Population
• Group of
•
organisms of the
same species living
in the same place
at the same time
Individuals may
come and go, but
the population can
remain the same
Characteristics of Populations
Important characteristics of a populations
ability to survive is based upon:
– Food supply
– Predation and disease
– Birth rate
– Death rate
– Immagration
– Emmagration
Today’s Assignment
• Period 1:
– Reading assignment
– Define and draw a picture to show
• Population
• Lag
• Exponential (log)
• Death phase
• Sigmoidal population growth curve (S curve)
• Immagration
• Emigration
Today’s Assignment
• Science vocabulary card group project
• Words for project:
–
–
–
–
–
–
–
–
Population
Immigration
Emigration
Exponential growth
Limiting Factor
Carrying capacity
Density-dependent factor
Density –independent factor
Bell Work
How can you determine the size of a
population of organisms when the
organisms move around and are hard to
locate?
Population Density &
Sampling Techniques
Objectives
• TLW: simulate the Mark-Recapture
technique to determine population size.
Vocabulary
• Quadrants
• Indirect counting
• Mark-recapture
Review: Population Density
• The number of individuals of a species per unit
or area or volume.
• How do we measure the number of individuals in
a given area?
• In most cases it is impractical or impossible to
count all the individuals in a population.
• As a result, scientists use a number of sampling
methods: Quadrants, indirect counting, and
Mark- Recapture.
Sampling Techniques
• Quadrants
– Count # of
species in a
particular area.
– Move Quadrant
& repeat
process
– Next, average
results to get a
population
estimate
Sampling Techniques
• Indirect counting
– Used when organisms
move around a lot and
are too difficult to see.
– Involves counting
nests, burrows, tracks,
etc.
Ex. African Termite population:
Size and # of mounds are counted
instead of individuals
Sampling Techniques
• Mark – Recapture
–
–
–
–
Trap animals for study
Tag them
Release individuals
Trap animals again,
counts # of marked
and unmarked to get
an estimate of
population size.
Today’s Activity
• Simulate the Mark-recapture sampling
method.
– Packums: determining population size
Bell Work
• Take a couple of minutes and update your
I-notebook:
– Table of contents
– Loose papers
– Number pages, etc.
Ecology
Population Growth
Objectives
• TLW: Identify factors that affect
population size.
• TLW: Differentiate between exponential
growth and logistic growth.
Vocabulary
• Immigration
• Emigration
• Exponential Growth
• Logistic Growth
Population Growth
• Populations can increase in number or
decrease in number.
– Factors that affect population size:
• Number of births
• Number of deaths
• And number of individual entering or leaving the
population.
Population Growth
• More births than deaths = population
growth
• More deaths than birth = population
decline
• Birth rates = death rates = population
stays the same
Population growth
• Immigration: the movement of individuals
into an area, can cause a population to
grow.
• Emigration: the movement of individuals
out of an area, can cause a population to
shrink.
Population Growth Models
Population Growth Models
• There are two models that are used to
explain population growth:
– Exponential growth model
– Logistic growth model
Population Growth Models
• If resources are unlimited, population will
grow exponentially.
• Exponential growth: when the individuals
in a population reproduce at a constant
rate.
– Growth rate at first is slow, then as the
population gets larger it grows more quickly.
– A J-shaped curve indicates that the population
is in exponential growth.
Exponential Growth
• Exponential growth: resources are unrestricted so
the given population quickly grows.
Generation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
# of bacteria
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16,384
32,768
65,536
131,072
262,144
524,288
1,048,576
2,097,152
4,194,304
8,388,608
time
0
15min
30min
45min
1hr
75min
90min
105min
2hrs
3hrs
4hrs
5hrs
Turn to your neighbor:
What is exponential growth?
Can a population continue to
grow and grow?
Why not?
Population Growth Models
• A population cannot continue to grow at
an exponential rate due to limited
resources such as:
– Food shortages
– Lack of space
– Accumulation of own waste products
– Lack of other resources like oxygen, living
space etc.
Population Growth
• As resources become less available, the
growth rate of a population slows or stops,
called logistic growth.
– The growth pattern curve is S-shaped
Logistic Growth
• Logistic growth: resources are limited so the growth
of the population slows or stops.
A comparison of the logistic growth model
and the exponential growth model
Exponential growth
Carrying
capacity
Logistic growth
Show me what you know
1. The number of individuals of a single
species per unit is known as:
A. Carrying capacity
B. Logistic growth
C. Population density
D. Population growth rate
Show me what you know
2. The movement of individuals into an area
is called
A. Demography
B. Carrying capacity
C. Immigration
D. Emigration
Show me what you know
3. The range or area occupied by a
population is its
A. Growth rate
B. Geographic distribution
C. Age structure
D. Population denisty
Show me what you know
4. This graph
represents
A. Carrying
capacity
B. Exponential
growth
C. Logistic growth
D. Limiting factor
Today’s assignment
• Problem-solving lab 4.1 (left-hand side)
• Exponential Growth Worksheet
• Due tomorrow: Mark-recapture lab writeup
Bell Work
• Some bacteria can reproduce every twenty
minutes. Calculate the growth of a
population of 10 bacteria for 24 hours.
(Don’t forget – 10 bacteria are at time 0)
Ecology
Limits to Population Growth
Objectives
• TLW: Identify factors that limit population
growth.
• TLW: Relate limiting factors and carrying
capacity
Vocabulary
• Limiting factors
• Carrying capacity
Limits to population Growth
• Limiting Factors:
– A factor that causes a
population growth to
decrease.
• Competition
• Predation
• Parasitism & disease
• Drought (climate
extremes)
• Human disturbances
Limits to Population Growth
• When environmental factors limit a
population’s growth rate the population is
said to have reached its carrying capacity.
• Carrying Capacity:
– The number of organisms in a population that
the environment can maintain or “carry” with
no increase or decrease in the population.
– Birth rate = death rate
Today’s Assignment
• Grade I-notebooks
• Lesson of the Kaibab activity
Bell Work (period 1)
• What is carrying capacity? Give an
example.
Bell Work (periods 3-5)
• Describe the most likely population growth
curve you would expect to see in a small
town made up mainly of senior citizens.
Compare this growth curve to that of a
small town made up of newly married
couples in their twenties.
Week at a glance
• Tuesday:
– Finish section 4.1
– Study Guide 4.1 due
• Wednesday:
– Vocabulary quiz
– Human population growth section 4.2
• Thursday: Concept map/ review
• Friday:
– Chapter 4 test
– Parent Signatures in I-book due
Density factors and Population
Growth
Today’s Objective
• Differentiate between density-dependent and
•
density-independent limiting factors.
Describe how other organisms limit population
growth.
Key Vocabulary
• Density-Independent Factor
• Density-Dependent Factor
• Predation
• Competition
Density factors and population growth
• How organisms are dispersed can be
important.
• Three patterns of dispersal are random,
clumped, and uniform.
Random
Clumped
Uniform
Density factors and population growth
• There are two types of limiting factors that are
related to dispersal:
– density-dependent
– density-independent factors.
• Reminder: population density describes the
number of individuals in a given area.
Density factors and population growth
• Density-dependent factors include disease,
competition, predators, parasites, and food.
• Disease, for example, can spread more quickly
in a population with members that live close
together.
Density factors and population growth
• Density-independent factors can affect all
populations, regardless of their density.
• Most density-
independent factors
are abiotic factors,
such as temperature,
storms, floods,
drought, and major
habitat disruption.
Organism Interactions Limit
Population Size
Organism Interactions Limit
Population Size
• Population sizes are limited not only by abiotic
factors, but also are controlled by various
interactions among organisms that share a
community.
• Organism interactions that can limit population
size include: Predation, Competition, Crowding,
and stress
Predation affects population size
• Predation increases
the chance that
resources will be
available for the
remaining individuals
in a prey population.
• However, when a
predator consumes
prey on a large
enough scale, it can
have a drastic effect
on the size of the
prey population.
Competition within a population
• Competition is a density-dependent factor.
• When only a few individuals compete for
resources, no problem arises.
• When a population increases to the point at
which demand for resources exceeds the
supply, the population size decreases.
The effects of crowding and stress
• When populations of certain organisms
become crowded, individuals may exhibit
symptoms of stress.
• These symptoms include aggression, decrease
in parental care, decreased fertility, and
decreased resistance to disease.
• They symptoms then become limiting factors
for growth and keep populations below
carrying capacity.
Today’s assignment
• Period 1: Section 4.1 worksheet
• Periods 3, 4, & 5:
– $2.00 summary
– Radio commercial activity due Thursday
Bell Work
• List three density-dependent factors and
three density-independent factors that can
limit the growth of a population.
Bell work (periods 3-5)
• Why might a contagious virus that causes
a fatal disease be considered a densitydependent limiting factor
Population Ecology
Chapter 4.2 pages 100-103
Human Population
Objectives
• TLW: describe what could happen if the
human population reaches it carrying
capacity.
• TLW: examine how populations of
different regions of the world compare
with regards to numbers and food
availability.
Key Vocabulary
• Demography
World Population
• In the United States, a census is taken every ten
years.
• One of the most useful pieces of data is the rate at
which each country’s population is growing or
declining.
• These figures are the basis for demography,
the study of human population size, density
and distribution, movement, and its birth and
death rates.
Human population growth
• Human population growth is different than other
organisms because humans have the ability to
change their environment.
• For example, man has learned to expand the
•
carrying capacity of his environment by increasing
food supply, combating pests and curing diseases.
Today’s world population statistics:
http://www.census.gov/main/www/popclock
.html
Question: Can the Earth support
this ever increasing population?
Human population Growth
• Damage to the planet will eventually
reduce the carrying capacity for humanity
and slow the growth of the human
population.
• What are some limiting factors for the
human population?
Ecology and growth
• Resources that are needed for life, such as food
and water, could become scarce or contaminated.
Ecology and growth
• Also, the amount of waste produced by a
•
population may become too difficult to dispose of
properly.
These conditions can lead to stress on current
resources and contribute to the spread of
diseases that affect the stability of human
populations both now and to come.
Today’s Assignment
• Take a stand
• Food for thought
• Human population graph