Factors affecting population growth The two types of limiting factor: Density Independent and Density Dependent

2. ECHON, JOHN FLORENTINO E.
Environmental Science

3. ECHON, JOHN FLORENTINO E.
Environmental Science

4. Limiting Factor
In the context of
populations,
a limiting factor is a
factor that causes
population growth to
decrease.
ECHON, JOHN FLORENTINO E.
Environmental Science

5. Density-dependent
and
Density-independent
Population density describes the
number of individuals in a given
Two types of limiting
factors
ECHON, JOHN FLORENTINO E.
Environmental Science

6. A limiting factor that
depends on population
size is called a density-
dependent limiting
factor.
Density-Dependent
Factors
ECHON, JOHN FLORENTINO E.
Environmental Science

7. Density-dependent limiting
factors include:
• competition
• predation
• parasitism
• disease
ECHON, JOHN FLORENTINO E.
Environmental Science

8. When populations become
crowded, organisms
compete for food, water
space, sunlight and other
essentials.
Competition among
members of the same
Competition
ECHON, JOHN FLORENTINO E.
Environmental Science

9. Populations in nature are
often controlled by
predation.
The regulation of a
population by predation
takes place within a
predator-prey
relationship, one of the
best-known mechanisms
Predation
ECHON, JOHN FLORENTINO E.
Environmental Science

10. Parasites can limit the
growth of a population.
A parasite lives in or on
another organism (the
host) and consequently
harms it.
Parasitism and
Disease
ECHON, JOHN FLORENTINO E.
Environmental Science

11. Density-dependent
factors operate only when
the population density
reaches a certain level.
These factors operate
most strongly when a
population is large and
dense.
They do not affect small,
Remember
ECHON, JOHN FLORENTINO E.
Environmental Science

12. Density-independent
limiting factors affect all
populations in similar
ways, regardless of the
population size.
Density
Independent Factor
ECHON, JOHN FLORENTINO E.
Environmental Science

13. Examples of density-
independent limiting factors
include:
• unusual weather
• natural disasters
• seasonal cycles
• certain human
activities—such as
damming rivers and clear-
cutting forests ECHON, JOHN FLORENTINO E.
Environmental Science

14. Density-dependent limiting factors Density-independent limiting
factors
Are usually biological in nature
(competition, disease, predation).
Are usually physical in nature
(hard winters, failure of rainy
season).
Are more important for large
organisms (which are buffered
from physical environment).
2. Are more important for small
organisms, because small
organisms are not as well buffered
against physical environment.
Are more important in physically
benign and constant
environments.
Are more important in extreme or
highly seasonal environments than
in mild, stable environments.
Can interrupt exponential growth Can interrupt exponential growth
Let’s Compare
ECHON, JOHN FLORENTINO E.
Environmental Science

15. Thank You for Listening

16. References:
• highered.mheducation.com/sites/dl/free/.../ch17_Conce
pt_Review.doc
• http://study.com/academy/lesson/the-limiting-factors-
of-population-growth.html
http://www.nhptv.org/natureworks/nwep12a.htm