2. What is population ecology?
-Science that deals with measuring
changes in population size and
composition
-Identify the factors that cause the
changes
3. Studying Populations
• A population consists of all the
individuals of a species in a given
area.
• Population structure describes the
age distribution of individuals, and
how those individuals are spread
over the environment.
4. Why is it important for scientist to describe
natural populations?
5. • To assess the health of
population
• To determine the endangered
or threatened status
•To predict the population
dynamics
6. What is population ?
A group of individual of the same species of
organisms that occupy the same area, using
the same resources and acted upon by the
same environmental factors
7. Population dynamics
• Study how and why population size
changes over time
• Study the factors affecting growth,
stability and decline of populations
(birth rate, mortality, survivorship, migration)
• All populations undergo 3 phases in life
cycle :
- growth, stability, decline
9. • Populations have size and geographical
boundaries.
– The density of a population is measured as the
number of individuals per unit area.
– The dispersion of a population is the pattern of
spacing among individuals within the geographic
boundaries
– The size of a population
The characteristics of populations are
shaped by the interactions between
individuals and their environment
11. MEASURING DENSITY
Density
Number of individuals per unit
of area at a given time
• Expressed in terms of items or organisms
per unit area
• For example: the number of paddy plants
per square meter of a paddy field
• Population density varies due to limiting
factors
12. • Measuring density of populations is a
difficult task.
– We can count individuals; we can estimate
population numbers.
13. Mark and recapture method
One way to estimate the size of a
population is to capture and mark
individuals from the population,
release them, and then resample to
see what fraction of individuals carry
marks.
15. Three general patterns:Three general patterns: clumping, uniformclumping, uniform
distribution, and random dispersiondistribution, and random dispersion
Most species live in clumps or groupsMost species live in clumps or groups..
Population DistributionPopulation Distribution
17. Clumped dispersion
• Also known as aggregated distribution
• Individuals aggregate in patches
• Caused by : environment where the resources
concentrated in patches
• Other factors : mating, limited seed dispersal
• Importance : for protection, reducing
competition, increasing feeding efficiencies
19. Uniform dispersion
• Pattern of equally spaced individuals
• Caused by the ability to survive anywhere in
the habitat
• Used the resources found immediately around
them
• Importance : able to set up the zone of
territories for feeding, nesting, breeding
21. Random dispersion
• Spacing pattern based on total
unpredictability
• Individual in a population are spaced all over
an area in a way that in unrelated to the
presence of others
• Caused by the ability to live anywhere in a
given area except, they are limited to grow
wherever they are first set root (for plants)
24. Changes in a Population
• 3 factors determine population
changes
–births
–deaths
–migration
• immigration
• emigration
25. Continues…
Population of organism able to change
over time
Increase in population size usually due
to natality (birth rate)
Decrease in population size as a result
of mortality
26. Determining the rate of changes in
population.
• Changes in time must taken into thought
ΔN / Δt = N (b-d)
Δ = change in equations
N = number of individuals
t = time
b =natality
d = mortality
29. • Logistic growth: Exponential growth when
resources are unlimited and slowed growth as
species approach carrying capacity of environment.
– Growth curve called an S-curve because of its shape.
• Environmental resistance: factors that tend to
reduce population growth rates.
31. Exponential growth curve
• Mode of population that assume birth rate and
death rate remain constant over time
• Describing an idealized population in an unlimited
population
• Ignoring immigration and emigration
• The result in exponential growth is that
if
b > d, r > 0
32. • Typically, unlimited resources are
rare.
–Population growth is therefore
regulated by carrying capacity (K),
which is the maximum stable
population size a particular
environment can support.
The logistic model of
population growth incorporates
the concept of carrying capacity
33. LOGISTIC GROWTH RATE
Assumes that the rate of population
growth slows as the population size
approaches carrying capacity, leveling
to a constant level. S-shaped curve
CARRYING CAPACITY
The maximum sustainable population
a particular environment can support
over a long period of time.
POPULATION GROWTH RATE
36. Density-Independent Factors
• Severe storms and flooding
• Sudden unpredictable severe cold
spells
• Earthquakes and volcanoes
• Catastrophic meteorite impacts
37. List of reference
Choudyhury. S. (2009). Population Ecology. Available from:
http://www.slideshare.net/Shohail/population-ecology-1968004?v=default&b=&from_search=1
Pointer. K. (2011). Community Ecology: Populations. Available from: http
://www.slideshare.net/coachpointer/population-ecology-9976847?
v=default&b=&from_search=2
Tnewberry. (2008). Ecology 1: Population Ecology. Available from:
http://www.slideshare.net/tnewberry/population-ecology-514438?
v=default&b=&from_search=3
Sojhk. (2010). Population Ecology. Available from:
http://www.slideshare.net/sojhk/chapter-54-4835841
Faranany. (2013). Population Ecology. Available from:
http://www.slideshare.net/faranany/population-ecology-16591693
Editor's Notes
Unfortunately, it is usually impractical to attempt to count individuals in a population.
One sampling technique that researchers use is known as the mark-recapture method.
Individuals are trapped, captured, tagged, recorded, and then released.
