1. Ecology of a Population
By:Tara Hill

2. Population Defined
A population is:
A group of organisms of the same species
occupying a particular space at a particular
time

3. Population Characteristics:
Distribution:where organisms are found on
earth, determined by biotic/abiotic factors
Dispersion: spatial distribution of individuals of
a population -- three general kinds of
patterns:

4. clumped (aggregated) dispersion -- individuals
clumped together -- resources in a habitat
may be patchy in distribution which causes
organisms to form "clumps"

5. Uniform-individuals are about equal distance
from one another
-caused by competition among individuals in the
same population

6. Random-habitat is relatively uniform so
individuals are neither repelled or attracted to
one another.

7. Population Size
A balance between:
• Natality=birth rate (b)
• Mortality=death rate (d)
(b)>(d)=population size increases
(b)<(d)=population size decrease
(b)=(d)=population size is constant

8. Factors affecting population size besides
natality/mortality
• Immigration rate (i) (increases pop. size)
• Emigration rate (e) (decreases pop. size)
Growth rate equation:
r=(b-d) + (i-e)

9. Population Growth
Biotic Potential=
-promotes positive growth
-intrinsic factors(litter size, gestation)
Environmental Resistance=
-limits growth
-extrinsic factor(weather, food supply)

10. Patterns of growth
Exponential growth (J shaped curve)
• biotic potential(rm)=maximum value

11. Logistic growth (S shaped)
K=carrying capacity=population size that is
based on number of resources available

12. Limiting factors:
Density dependent:
-competition
-disease
-predation
-food
Density independent:
-weather
-catastrophes

13. Natural Selection:
• limiting factors place
stresses on a population
• the best adapted organisms
will survive and get to
reproduce and pass on their
genes with the adaptation
to their offspring
• over long periods of time
this can lead to a change in
species

14. Population Growth
Biotic Potential=
-promotes positive growth
-intrinsic factors(litter size, gestation)
Environmental Resistance=
-limits growth
-extrinsic factor(weather, food supply)

15. Patterns of growth
Exponential growth (J shaped curve)
• biotic potential(rm)=maximum value

16. Logistic growth (S shaped)
K=carrying capacity=population size that is
based on number of resources available

17. Limiting factors:
Density dependent:
-competition
-disease
-predation
-food
Density independent:
-weather
-catastrophes

18. Natural Selection:
• limiting factors place
stresses on a population
• the best adapted organisms
will survive and get to
reproduce and pass on their
genes with the adaptation
to their offspring
• over long periods of time
this can lead to a change in
species

19. • proportionally massive eyes
making vision acute for locating
prey
• movable ears for better hearing
making them good nocturnal
hunters
• can rotate their heads a full 180
degrees to help them avoid
predators such as wild cats
• Long back legs to help them
jump twenty feet, an important
survival skill in the jungle
• Long tail providing power for
jumping and holding onto tree
Ex:Phillipine Tarsier

20. Survivorship curves:
-based on a cohort of individuals from birth until
death
-cohort=a group of individuals of the same age
-survivorship curves are meant to show the
number of individuals surviving at each age
for a particular species
-three types of curves

21. Type 1=good early survival, die of old age, low
birth rates, provide lots of parental care
(humans)
Type 2=die at constant rate regardless of age
(birds, lizards)
Type3 =poor early survival,
survival thatimproves with
age, lots of offspring, low
parental care
(fish,plants)

22. Life History Patterns:
r selected species: species inhabiting fluctuating
or unpredictable environments-environments
keep populations below carrying capacity (lots
of predation, competition over resources)
k selected species-species inhabiting stable,
predictable environments-keep population
size near carrying capacity and resources are
scarce