Ecology of Populations
(1) Limiting factors that affect
populations in an ecosystem
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Ecology of Populations
(2)__________- Study of the interactions of organisms
with other organisms and the physical environment
(3)__________ - Place where an organism lives.
(4) _______________ All the organisms within an area
belonging to the same species.
(5) ______________ All various populations interacting at
same locale.
(6) ______________Community of populations including
biotic and abiotic factors.
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Ecological Levels
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Locust plagues
Factors that affect
population growth
and depend on
(9)_________
Human (10)____________ such
as tuberculosis often become
epidemics in crowded cities.
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Weather Events
Temperature
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Regulation of Population Size
• Density - Dependent Factors
– Number of organisms present (13)influences the
effect of the factor.
(14) Competition
(15) Predation (predators)
(16) Disease
• Density - Independent Factors
– Number of organisms present does (17) not
influence the effect of the factor.
(18) Natural Disasters
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Question 1:
Which situation is caused by a density-independent limiting factor?
A. The influenza outbreak of 1918-1919 killed over 20 million people.
(number of organisms was influenced by factor)
B. The cones of the jack pine need heat from a fire to help release seeds.
(number of organisms was not influenced by factor)
C. A parasite alters reproduction in a woodpecker population causing fewer
births.(number of organisms was influenced by factor)
D. A queen bee regulates the number of eggs she lays according to the
amount of food available. . (number of organisms was influenced by
factor)
Density - Independent Factors
•Number of organisms present does not influence
the effect of the factor.
• Natural Disasters and Temperature
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Question 2
Which limiting factor is density-Independent for rainbow trout?
A. Size of the stream (number of organisms was not influenced by
factor)
B. Spread of parasites (number of organisms was influenced by
factor)
C. Competition for food (number of organisms was influenced by
factor)
D. Supply of dissolved oxygen (number of organisms was influenced
by factor)
Density - Independent Factors
•Number of organisms present does not influence
the effect of the factor.
• Natural Disasters and Temperature
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Question 3:
Which statement BEST describes the relationship between natural disasters
or human-caused disasters and population size?
A. Natural and human-causing disasters are density-dependent factors.
(Not Natural Disaster)
B. Natural and human-causing disasters are density-independent factors.
(Natural Disasters are density-independent)
C. Human-causing disasters are density-independent whereas natural
disasters are density-dependent. (Not Natural Disaster)
D. Human-causing disasters are density-dependent whereas natural
disasters are density-independent. (Not Natural Disaster)
Density - Independent Factors
•Number of organisms present does not influence the effect of the
factor.
• Natural Disasters
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Question 4:
Which relationship BEST identifies a density-dependent limiting
factor?
A. A bobcat population declines due to disease. (number of organisms
influence the effect of the factor; competition, predation, disease)
B. A fish population declines due to a severe drought.(not
competition or predation but natural disaster)
C. A bird population declines due to pollution. (not competition or
predation but disaster)
D. A wolf population declines due to a cold winter. (Number of
organisms present does not influence the effect of the factor.- Independent)
• Density - Dependent Factors
– Number of organisms present influences the effect of the factor.
• Competition
• Predation
• Disease
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Question 5:
Study the table below. Caterpillars can destroy trees by eating too
many leaves and making them susceptible to disease or drought.
Which student has correctly identified the density-dependent and
density-independent limiting factors associated with an invasion of
Gypsy Moth Caterpillars?
Student
Populations of Caterpillars
Disease
Drought
1
Density-independent
Density-dependent
Density-dependent
2
Density-dependent
Density-independent
Density-independent
3
Density-independent
Density-independent
Density-independent
4
Density-dependent
Density-dependent
Density-independent
Density - Independent Factors
•Number of organisms present does not influence the effect of the factor.
• Natural Disasters
•
Density - Dependent Factors
– Number of organisms present influences the effect of the factor.
• Competition and Predation and Disease
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Question 6:
Study the table below. Which student identified only density-independent limiting
factors?
Student’s Identification of Density-Independent Limiting Factors
Student
Disease
Clear-cutting
1
X
X
2
3
4
X
X
Predation
Natural
Disaster
X
X
X
X
Filling
Wetlands
X
X
X
X
Density - Independent Factors
•Number of organisms present does not influence the effect of the factor.
• Natural Disasters
•
Density - Dependent Factors
–
Number of organisms present influences the effect of the factor.
 Competition and Predation and Disease
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Question 7: Which statement BEST explains why a disease
my affect one population more than another population?
A.
Because disease is a density-dependent limiting factor, a larger population
makes it easier for the virus to spread from person to person
B. Because disease is a density-independent limiting factor, a large
population makes it easier for the virus to spread from person to person
C. Because disease is a density-dependent limiting factor, climate can
influence the disease, making it more or less affective.
D. Because disease is a density-independent limiting factor, climate can
influence the disease, making it more or less affective.
Density - Independent Factors
•Number of organisms present does not influence the effect of the factor.
• Natural Disasters
•
Density - Dependent Factors
–
Number of organisms present influences the effect of the factor.
 Competition and Predation and Disease
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Uniform Distribution
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Random Distribution
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Clumped Distribution
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