Population Ecology
UEQ: Why populations change?
Name: _________________________________Date: ___________________Period: ____
LEQ:
What are the important characteristics of populations?
What are the factors that can limit population growth?
PA Standard: 4.6.10 A. Explain the biotic & abiotic components of an ecosystem & their interactions.
4.6.12 A. Analyze the interdependence of an ecosystem.
The ____________ health of a population can often be ______________ by tracking how its
size changes.
Population _____ describes the number of individual ___________ present in a given population at
a given ___________.
POPULATION ECOLOGY
•
Deals with the # of individuals of a particular ________ that are found in an area and how and
why those _________________ change or remain fixed over time.
Population ecologists study…
•
•
How populations respond to its _______________
Competition for resources, predations, _________ and other environmental pressures
•Determine population size by _______________.
Instead of counting every individual, ecologists
count every _________________ in a small area than _____________ the number of
individuals in the larger ___________.
POPULATION DENSITY
Population density describes the _____________of individuals within a population per unit area.
For example: 1500 golden toads per 4 sq. kilometers
In general, _________animals have lower population _______ because they need more
_______. High population __________ can make it easier to find __________ and group
together. However, it also leads to more competition for __________. Overcrowded organisms
can also lead to _______________of disease and vulnerable to predators.
1
AGE STRUCTURE
Age structure diagrams show the number of _______& _______in different age groups within a
population. ____ ___ ____________ describes the relative number of organisms of each age
with in a population. Age structure diagrams are a visual _______to show the age structure of
populations.
1. Stable – approximately the _______ number of individuals at each age grouping, mix of young
and old
2. Growing – mostly ___________
3. Declining – the largest portion of population is ___________
Generalized age structure diagrams
Stable
Growth
Declining
2
POPULATION GROWTH
A population’s growth rate is determined by births, deaths, immigration & emigration.
All things being ________, when a population __________ is greater than its death rate,
population size will __________. When death rate is ___________ than its birth rate, population
size will ______________.
1. Birthrate – number of _________births per 1000 in a given year
2. Death rate – number of ________ per 1000 in a given year
In addition to births & deaths, population size can also change by ______________ moving in & out.
3. Immigration – movement of individuals into a ___________________
4. Emigration – movement of individuals ____________ of a population
CALCULATING GROWTH RATE
Growth rate (r) = birth rate (b)+ I – death rate (d) + E
Populations can grow exponentially or logistically.
Exponential growth is when a population ___________________by a fixed percentage each year.
Exponential growth occurs in nature only when the starting population is __________& the
environmental conditions are ____________. This type of growth usually does not last _______.
Most populations are constrained by __________ ____________.
Limiting factors are characteristics of the environment that limit ______________ _________.
Limiting factors determine a population’s carrying capacity.
Carrying capacity is the largest population ________a given environment can sustainably _____.
Example: New population is introduced…mold growing on bread.
3
Logistic Growth describes how a population’s initial exponential_________ is slowed & finally
stopped by limiting factors.
•Carrying capacities are not __________.
•Examples of limiting factors:
1)
2)
3)
4)
5)
Food
_______________
Predators
Space
______________
LIMITING FACTORS & BIOTIC POTENTIAL
Limiting factors have more of an effect in ___________populations & other limiting factors affect
all populations in the ______________ way.
1. Density–DEPENDENT factor: factors that ____________ the population size or density
A. Disease (example: HIV)
B. Competition
C. Predators
D. Parasites
E. Food
2. Density INDEPENDENT factor: affect ALL populations, regardless of size
A. Temperature
B. Storms
C. Floods
D. Drought
E. Volcanic eruption
Biotic potential is the maximum ability to produce offspring in ideal conditions.
A. Rapid life history (example: mosquitoes)
a. Rapid reproduction
b. High number of offspring
c. Small __________ size
d. Organisms mature ____________
e. Reproduce ____________
f. Organisms have a short life ______
4
B. Slow life history (example: elephant)
a. Slow reproduction
b. _________ number of offspring
c. Large body size
d. Organisms mature ____________
e. Reproduce late
f. Organisms have a long __________span
g. Organisms tend to have _____________care
LIMITING FACTORS
1. Fill in the 8 ovals with different limiting factors.
2. Then, go back and color the limiting factor.
a. Density dependent - red
b. Density independent – blue
Population size
5
Turkey Vultures
The graph at the right shows the
average number of turkey vultures
that were counted on protected
lands at the Hawk Mountain
Sanctuary in Pennsylvania. In
this activity, you will interpret the
graph by describing the trends that
it shows and drawing conclusions
about the annual migration cycle of
turkey vultures.
Interpreting the Graph
To understand the information in a graph, the first step is to figure out the information that
it shows. Study the axes and note the trend shown by the graph.
1. What do the x and y-axes show?
2. What do the two bars for each month represent?
3. To describe the annual trend in the graph, look at the overall changes in the bar height
over the entire year. Describe what you see.
Inferring From the Graph
Turkey vultures migrate from the north onto the sanctuary lands and reside there for a while
before migrating south. You know that when the vultures migrate through the sanctuary, they
will increase the population size. Answer the questions below to help you identify when the
vultures migrated through the sanctuary.
4. In which two months is the turkey vulture population significantly greater than in the
other months?
5. When would you conclude that the vultures migrating from the north arrive at the
sanctuary?
6. When would you conclude that the vultures leave the sanctuary and begin to migrate
south?
6
The Disappearance of the Golden Toad
What can cause a thriving population of
animals to disappear in the span of one or
two years? In the case of the golden toad
of Monteverde in Costa Rica, thousands
of toads were initially observed during the
mating season each year. Then one year,
there were only a few toads. Two years later,
only a single toad was observed, and then
the toads disappeared completely.
7
Use the information in The Disappearance of the Golden Toad to answer the questions below.
1. How many golden toads could be observed during mating season when the toad’s
population was thriving?
2. Based on the golden toad population’s habitat, why was extinction of the golden toad
puzzling?
3. Explain why it was significant that large numbers of other frogs and toads became extinct
at the same time the golden toads disappeared.
4. Explain what happens to cloud mist as the number of “dry days” increases.
5. Assuming the Lifting Cloud Base Hypothesis to be correct, which part of the Monteverde
cloud forest would likely be the least affected by the decrease in moisture? Explain.
6.
Relate this case to the Big Question: “How do changes in population size
relate to environmental conditions?” Describe the sequence of events that could have led
to the extinction of the golden toad, according to the Lifting Cloud Base Hypothesis.
8
Populations (8 days)
SLM
Ecology – Mrs. Sim
PA Standards
4.1.10.A – Examine the effects of limiting factors on population dynamics.
Optional
Instructional Tools:
Unit Essential Question(s):
Why populations change?
M&M population lab
Age structure
diagrams
How many fish in Bud
Lake?
Population dynamics
4.1.10.A
What are the important characteristics of
populations?
What are the factors that can limit population
growth?
Vocabulary:
Density dependent
Density independent
Limiting factor
Carrying capacity
Exponential growth
Logistic growth
Population sampling
Population density
Population size
Biotic potential
Birth rate
Death rate
Emigration
Immigration
Age structure
Age structure diagram
Growth rate
9
Vocabulary:
1) Density dependent: a limiting factor whose influence changes with population density;
includes competition, predation, and disease
2) Density independent: a limiting factor whose influence is not affected by population density;
includes catastrophic events
3) Limiting factor: a characteristic of the environment that restricts population growth
4) Carrying capacity: the largest population a given environment can support
5) Exponential growth: the pattern of population growth in which a population increases by a
fixed percentage each year
6) Logistic growth: the pattern of population growth in which exponential growth is slowed &
finally stopped by limiting factors
7) Population sampling: estimating the number of organisms in a large area
8) Population density: the number of individuals in a population per unit of area
9) Population size: the number of individual organism present in a population at a given time
10)
Biotic potential: the growth rate of a population under ideal conditions
11)
Birth rate: # of live births per 1000
12)
Death rate: # of deaths per 1000
13)
Emigration: the movement of individuals away from a given area
14)
Immigration: the movement of individuals to a given area
15)
Age structure: the relative number of organisms of each age within a population
16) Age structure diagram: a chart that shows the age distribution of a population; also called
age pyramid
17)
Growth rate: the change in a size of a population over a specific period
10