1. POPULATION DYNAMICS,
CARRYING CAPACITY, AND
CONSERVATION BIOLOGY
The Walker School
Environmental Science

2. Population Ecology
 The study of individual
species in relation to the
environment.
 The field is concerned
with conservation and
focuses on Population and
Population Viability
Analysis (PVA)

3. Population Viability Analysis
 A species-specific method of
risk assessment.
 Brings together species
characteristics and
environmental variability to
forecast population health and
extinction risk.
 Begins with the question: “Is this
species at risk of becoming
endangered? If so, why?”.
 A research example may
include: “What are the effects
of industrial forestry on
biodiversity.”

4. WHAT ARE THE MAJOR
CHARACTERISTICS OF A
POPULATION?

5. Populations
 A group of individuals of a single species that
simultaneously occupy the same general area.

6. Populations Under Study
 Diseases (prions, viruses, bacteria)
 Vegetation (crops, orchards, forests)
 Terrestrial Animals (cattle, sheep, pigs, chickens)
 Aquatic Organisms (fish, shrimp)
 Humans

7. HIV Population in South Africa
Arcview GIS

8. Characteristics of Populations
 Distribution
 Numbers (size)
 Age Structure
 Density (#/area)
Celestichthys

9. WHAT IS BIOGEOGRAPHY?

10. Biogeography
 The study of the size and
distribution of biodiversity
over space and time. It
aims to reveal where
organisms live, and at
what abundance.
Giant Pandas

11. Factors Explaining Species Distributions
 Speciation
 Extinction
 Continental drift
 Glaciations
(associated variations
in sea level, river
routes)
 River capture

12. Speciation & Population Types
 Ranges
 Physical Structures
 Food Resources

13. Paleobiogeography
 goes one step further
to include
paleogeographic data
and considerations of
plate tectonics.
 Uses molecular
analyses and fossils to
determine the change
in a species over
millions of years.
Hominid Evolution

14. HOW ARE POPULATIONS
TRACKED?

15. Mark-Recapture Method
 A method commonly used in ecology to estimate population
size and population vital rates (i.e., survival, movement, and
growth)

16. Lotek Wildlife GPS Monitors
http://www.lotek.com/

17. The Process
1. Researcher visits a study area and uses traps to
capture a group of individuals alive.
2. Captured animals are marked with tags, collars,
bands, or spots of dye and then is released
unharmed back into the environment.
3. Sufficient time is allowed to pass for the marked
individuals to redistribute themselves among the
unmarked population.
4. Next, the researcher returns and captures another
sample of individuals.

18. Analysis

19. WHAT FACTORS GOVERN
CHANGES IN POPULATION
SIZE?

20. Demography
 The study of the vital statistics that affect population
size.
•Size
•Density
•Age Distribution
•Dispersion

21. Clumped
(elephants)
Uniform
(creosote bush)
Random
(dandelions)
Population Dispersion Patterns

22. Factors Affecting Distribution
 Competition for
Resources
 Predation
 Parasitism
 Infectious Disease
 Floods
 Hurricanes
 Unseasonable
Weather
 Fire
 Clear Cutting
 Pesticide Spraying
Density Dependant Density Independent

23. Changing and Clumping
 Availability and variation
of resources
 Provide protection in
numbers
 Packs have a better
chance of obtaining food
 Temporary groups for
mating

24. Factors that Govern Population Size
 Crude Birth Rate (CBR)
 Crude Death Rate (CDR)
 Immigration
 Emigration
Population Change = (births + immigration) – (deaths + emigration)

25. Population Age Structures

26. WHAT LIMITS POPULATION
GROWTH?

27. Resources and Competitors
 Biotic Potential (r)
 Ecosystem Carrying
Capacity (K)
 Rate of Increase
 Environmental
Resistance
Carrying Capacity

28. © 2004 Brooks/Cole – Thomson Learning
Time (t) Time (t)
Populationsize(N)
Populationsize(N)
K
Exponential Growth Logistic Growth
Population Growth Curves:
J-Curve & S-Curve

29. 2.0
1.5
1.0
.5
Numberofsheep(millions)
1800 1825 1850 1875 1900 1925
Year
Population growth strives for dynamic equilibrium:
Logistic Growth of a Sheep

30. 2,000
1,500
Numberofreindeer
1910 1920 1930 1940 1950
Year
1,000
500
Organisms can exceed their carrying capacity:
Exponential Growth and Crash of Reindeer

31. Reasons for Diebacks
 Catastrophic Loss of Resources
 Introduction of New Predator
 Disease

32. WHAT KINDS OF POPULATION
CHANGE CURVES DO WE FIND
IN NATURE?

33. © 2004 Brooks/Cole – Thomson Learning
Numberofindividuals
Time
Irruptive
Stable
Cyclic
Irregular
General Types of Population Curves in Nature

34. Populationsize(thousands)
160
140
120
100
80
60
40
20
0
1845 1855 1865 1875 1885 1895 1905 1915 1925 1935
Year
Hare
Lynx
Cycles in Hare and Lynx
Populations

35. Community Organization –
Trophic Cascade Model
 Postulates that it is mainly predation that controls
community organization
 Predators control herbivores

36. Community Organization –
Bottom-Up Model
 Mineral nutrients control community organization
 Nutrients control plant types and numbers
 Plants control predators
 Changes in this community are done by adding or
removing minerals

37. Activity: Radio Expeditions
Species Extinctions
 Audio Evidence of Ivory-Billed Woodpecker
 http://www.npr.org/templates/story/story.php?storyId=4814860
 Audubon Bird Count, Lost Woodpecker Rediscovered
 http://www.npr.org/templates/story/story.php?storyId=5067655
 Slate's Explainer: Determining Species Extinction
 http://www.npr.org/templates/story/story.php?storyId=5015201

38. Activity: Radio Expeditions
Species Extinctions Questions
 Populations are classified by size, density, age distribution, and dispersion
type. Briefly explain each of these concepts and describe one
environmental factor that would limit the population growth of a bird
species.
 Discuss the difference between an endangered and a threatened species.
 Design a population count experiment to determine if a bird population is
threatened or endangered. Make sure to discuss how the study area was
selected and what method will be used to estimate population.
 Discuss one biological intervention, economic incentive and one legislative
policy to restore an endangered bird population.
 Discuss what technology could be used to periodically monitor the program.

39. WHAT TYPE OF
REPRODUCTIVE PATTERNS DO
SPECIES HAVE?

40. Sexual Partners Are Not Always Needed
 Asexual Reproduction
 Sexual Reproduction

41. Sexual Reproduction Methods
 Semelparity
 Onetime reproductive event
 Iteroparity
 Repeated reproduction

42. Many small offspring
Little or no parental care and protection of offspring
Early reproductive age
Most offspring die before reaching reproductive age
Small adults
Adapted to unstable climate and environmental
conditions
High population growth rate (r)
Population size fluctuates wildly above and below
carrying capacity (K)
Generalist niche
Low ability to compete
Early successional species
r-Selected Species
cockroach dandelion
General Characteristics of r-Selected Species

43. Fewer, larger offspring
High parental care and protection of offspring
Later reproductive age
Most offspring survive to reproductive age
Larger adults
Adapted to stable climate and environmental
conditions
Lower population growth rate (r)
Population size fairly stable and usually close
to carrying capacity (K)
Specialist niche
High ability to compete
Late successional species
elephant saguaro
K-Selected Species
General Characteristics of k-Selected Species

44. Carrying Capacity of Species
Numberofindividuals
Time
Carrying capacity
K species;
experience
K selection
r species;
experience
r selection
K

45. WHAT ROLE DOES GENETICS
PLAY IN THE SIZE OF
POPULATIONS?

46. Vulnerability of Populations
 Founders Effect
 Results from the migration of a population to a geographically
isolated area.
 Demographic Bottleneck
 Results from a natural catastrophe such as fire or a hurricane.
 Genetic Drift
 Results from random changes in the gene frequencies in a population.
 Interbreeding
 Results when individuals from a small population breed with each
other.

47. HOW DO ECOLOGISTS USE
LIFE TABLES AND
SURVIVORSHIP CURVES TO
MONITOR POPULATIONS?

48. Death Will Come:
Survivorship Curves
 Late Loss
 Early Loss
 Constant Loss
Percentagesurviving(logscale)
100
10
1
0
Age

49. Life Table
Life Expectancy at Birth of Epidemic Malaria Area in Papua New Guinea
 An age-specific summary of the
survival pattern of a population.
 Life tables are constructed by
following a cohort from birth to
death.
 A cohort is a group of individuals
of the same age.
 The table is constructed from the
number of individuals that die in
each age-group during a
defined time period.
 Life tables are graphically
displayed in survivorship curves.

50. Geographical Information Systems
Used to Map Population Data
 Captures, stores, analyzes,
manages, and presents data
that refers to or is linked to
location.
 Geographic information system
technology can be used for
scientific investigations for the
environmental science,
environmental impact
assessment, urban planning and
other purposes.
 Can be used for spacial
analysis and data modeling.