Ecology of Populations
(1)____________ ____________ that affect populations in an ecosystem.
Ecology of Populations
(2)__________ - Study of 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 a same locale.
(6)__________-community of populations including biotic and abiotic factors.
Density-Dependent Factors
Include (7) ___________ and (8)_____________. Factors that affect population growth and
depend on (9)___________.
Number of organism present (13)c____________ the effect of the factor.
(14) _____________ (15) ______________ (16) ________________
Density-Independent Factors
Major Events and Temperatures: for example: (10) ______________, (11)_____________ or
(12) __________.
Number of organism present does (17)______ influence the effect of the factor as in
(18)______________
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)
Remember: Density – Independent Factors:
 Number of organism present does not influence the effect of the factor
 Natural Disasters
 Temperature
Question 2:
Which limiting factor is density-Independent for rainbow trout?
A. Size of the stream
B. Spread of parasites
C. Competition for food
D. Supply of dissolved oxygen
Remember: Density – Independent Factors:
 Number of organism present does not influence the effect of the factor
 Natural Disasters
 Temperature
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.
B. Natural and human-causing disasters are density-independent factors.
C. Human-causing disasters are density-dependent whereas natural disasters are densityindependent.
D. Human-causing disasters are density-dependent whereas natural disasters are densityindependent.
Remember: Density – Independent Factors:
 Number of organisms present does not influence the effect of the factor.
 Natural disasters
 Temperature
Question 4:
Which relationship BEST identifies a density-dependent limiting factor?
A. A bobcat population declines due to disease.
B. A fish population declines due to a severe drought
C. A bird population declines due to pollution
D. A wolf population declines due to a cold winter
Remember: Density – Dependent Factors
Number of organism present influences the effect of the factor. Competition, Predation, or
Disease
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
1
2
3
4
Population of
Caterpillars
Densityindependent
Density-dependent
Densityindependent
Density-dependent
Disease
Drought
Density-dependent
Density-dependent
Densityindependent
Densityindependent
Density-dependent
Densityindependent
Densityindependent
Densityindependent
Remember: Density – Independent Factor
 Number of organisms present does not influence the effect of the factor. Natural Disasters
Remember: Dependent Factors
 Number of organisms present influences the effect of the factor. Competition and
Predation and Disease
Question 6:
Study the table below. Which student identified only density-independent limiting factors?
Student
Disease
Clear-cutting
1
2
3
4
X
X
X
X
X
Predation
X
X
Filling
Wetlands
X
X
Remember: Density – Independent Factors
 Number of organism 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
Natural
Disaster
X
X
X
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.
Question 8: Which situation is cause by a density-independent limiting factor?
A. The influenza is caused by a density-independent limiting factor?
B. The cones of the jack pin need heat from a fire to help release seeds.
C. A parasite alters reproduction in a woodpecker population causing fewer births
D. A queen bee regulates the number of eggs she lays according to the amount of food
available