1. CHAPTER 35 Population Dynamics
Modules 35.1 – 35.5

2. Keep track of all graphing exericises
Keep track of all graphing exericises!!! If you are not sure how to get data, ask!!!!

3. The Spread of Shakespeare's Starlings
In the 1800s and early 1900s, introducing foreign species of animals and plants to North America was a popular, unregulated activity
In 1890, a group of Shakespeare enthusiasts released about 120 starlings in New York's Central Park
It was part of a project to bring to America every bird species mentioned in Shakespeare’s works

4. Today, the starling range extends from Mexico to Alaska
Their population is estimated at well over 100 million
Current
1955
Current
1955
1945
1935
1925
1945
1905
1915
1925
1935
1925
1935

5. Over 5 million starlings have been counted in a single roost
Starlings are omnivorous, aggressive, and tenacious
They cause destruction and often replace native bird species
Attempts to eradicate starlings have been unsuccessful

6. The starling population in North America has some features in common with the global human population
Both are expanding and are virtually uncontrolled
Both are harming other species
Population ecology is concerned with changes in population size and the factors that regulate populations over time

7. 35.1 Populations are defined in several ways
Ecologists define a population as a single-species group of individuals that use common resources and are regulated by the same environmental factors
Individuals in a population have a high likelihood of interacting and breeding with one another
Researchers must define a population by geographic boundaries appropriate to the questions being asked
Small contained area, i.e. sea anemones in a tide pool
Expanded view, i.e. humans exposed to HIV includes all humans on planet.
Two important characteristics of population included density and dispersion.

9. POPULATION STRUCTURE AND DYNAMICS
35.2 Density and dispersion patterns are important population variables
Population density is the number of individuals in a given area or volume
It is sometimes possible to count all the individuals in a population
More often, density is estimated by sampling
Divide area in plots, count numbers in a few of those plots, and get an average density, then multiply average times total number of plots.

10. One useful sampling technique for estimating population density is the mark-recapture method – see Eco packet exercise
Figure 35.2A

11. The dispersion pattern of a population refers to the way individuals are spaced within their area
Clumped
Uniform
Random

12. Clumped dispersion is a pattern in which individuals are aggregated in patches
This is the most common dispersion pattern in nature
It often results from an unequal distribution of resources in the environment
Figure 35.2B

13. A uniform pattern of dispersion often results from interactions among individuals of a population
Territorial behavior and competition for water are examples of such interactions
Figure 35.2C

14. Random dispersion is characterized by individuals in a population spaced in a patternless, unpredictable way
Example: clams living in a mudflat
Environmental conditions and social interactions make random dispersion rare

15. 35.3 Idealized models help us understand population growth
Idealized models describe two kinds of population growth
exponential growth
logistic growth

16. Exponential growth is the accelerating increase that occurs during a time when growth is unregulated
A J-shaped growth curve, described by the equation G = rN, is typical of exponential growth
G = the population growth rate
r = the intrinsic rate of increase, or an organism's maximum capacity to reproduce (birth rate – death rate)
N = the population size

17. Exponential growth model
Exponential growth model. This models the growth of a population under ideal conditions with unlimited resources. The rate of growth is exponential and depends on the number of individuals in the population:
The graph shows a J-shaped curve, representing population size increasing without limit. As N increases, so does G. This type of growth, if exhibited by a bacterium growing in an unlimited environment, would result in an inconceivably large number of bacteria in less than two days
No population can grow exponentially indefinitley
Starlings 100 -> 1 million in 100 years
2 elephants -> 19 million in 750 years

18. Slope = Growth rate
Figure 35.3A

19. Logistic growth is slowed by population-limiting factors
It tends to level off at carrying capacity
Carrying capacity is the maximum population size that an environment can support at a particular time with no degradation to the habitat
Figure 35.3B

20. The equation G = rN(K - N)/K describes a logistic growth curve
K = carrying capacity
The term (K - N)/K accounts for the leveling off of the curve
K varies based on species and resources available
Figure 35.3C

21. The logistic growth model predicts that
a population's growth rate will be low when the population size is either small or large (death rate rises/birth rate falls)
a population’s growth rate will be highest when the population is at an intermediate level relative to the carrying capacity (birth rate rises/ death rate falls)
Neither model perfect, represents a starting point.

22. Cougar Lab -> to be continued at later date

23. 35.4 Multiple factors may limit population growth
Increasing population density directly influences density-dependent rates
such as declining birth rate or increasing death rate
The regulation of growth in a natural population is determined by several factors
limited food supply
the buildup of toxic wastes
increased disease
predation

24. Field studies of the song sparrow have demonstrated that birth rates may decline as a limited food supply is divided among more and more individuals
Figure 35.4A

25. Density-independent factors limit population no matter the size and are often abiotic factors, i.e. fires, flood, storms, seasonal temperature change or moisture, and human activity
Aphids show exponential growth in the spring and then rapidly die off when the climate becomes hot and dry in the summer
Figure 35.4B

26. Most populations are probably regulated by a mixture of factors
Density-dependent birth and death rates
Abiotic factors such as climate and disturbances
Populations often fluctuate in number
A natural population of song sparrows often grows rapidly and is then drastically reduced by severe winter weather
Figure 35.4C

27. 35.5 Some populations have "boom-and-bust" cycles
Some populations go through boom-and-bust cycles of growth and decline
Example: the population cycles of the lynx and the snowshoe hare
The lynx is one of the main predators of the snowshoe hare in the far northern forests of Canada and Alaska

28. Lynx and hare

29. About every 10 years, both hare and lynx populations have a rapid increase (a "boom") followed by a sharp decline (a "bust")
Figure 35.5

30. For the lynx, prey availability often determines population changes.
Recent studies suggest that the 10-year cycles of the snowshoe hare are largely driven by
Excessive predation. . .
But they are also influenced by fluctuations in the hare's food supply
Population cycles may also result from a time lag in the response of predators to rising prey numbers

31. 35.6 Life tables track mortality and survivorship in populations
LIFE HISTORIES AND THEIR EVOLUTION
35.6 Life tables track mortality and survivorship in populations
Life tables and survivorship curves predict an individual's statistical chance of dying or surviving during each interval in its life
Life tables predict how long, on average, an individual of a given age can expect to live

32. This table was compiled using 1995 data from the U. S
This table was compiled using 1995 data from the U.S. Centers for Disease Control
Table 35.6

33. Population ecologists have adopted this technique, constructing life tables for various plant and animal species

34. Survivorship curves plot the proportion of individuals alive at each age
Three types of survivorship curves reflect important species differences in life history
Figure 35.6

35. Survivorship curves
Type 1 (whales, elephants, humans) = low birth rates, low infant mortality, and life histories that fit the K-selection model
Type 2 (squirrels, Hydra) = intermediate
Type 3 (oysters, sea lettuce) = high birth rates, high infant mortality and life histories fitting the r-selection model

36. 35.7 Evolution shapes life histories
An organism's life history is the series of events from birth through reproduction to death
Life history traits include
the age at which reproduction first occurs
the frequency of reproduction
the number of offspring
the amount of parental care given
the energy cost of reproduction

37. The effects of predation on life history traits of guppies has been tested by field experiments for several years.
Heritability demonstrated by retention of characteristics over generations in predator-free environments.
Guppies from pike-cichlid population moved to where small offspring were preyed on. Soon fewer, larger offspring produced
Experimental transplant of guppies
Predator: Killifish; preys mainly on small guppies
Guppies: Larger at sexual maturity than those in “pike-cichlid” pools
Predator: Pike-cichlid; preys mainly on large guppies
Guppies: Smaller at sexual maturity than those in “killifish” pools
Figure 35.7A

38. In nature, every population has a particular life history adapted to its environment
The agave illustrates what ecologists call "big-bang reproduction"
It is able to store nutrients until environmental conditions favor reproductive success
Might not bloom for years, until large enough rainfall acts as trigger.
Figure 35.7B

39. Natural selection favors a combination of life history traits that maximizes an individual's output of viable, fertile offspring

41. Selection for life history traits that maximize reproductive success in uncrowded, unpredictable environments is called r-selection
Such populations maximize r, the intrinsic rate of increase
Individuals of these populations mature early and produce a large number of offspring at a time
Many insect and weed species exhibit r-selection

42. Selection for life history traits that maximize reproductive success in populations that live at densities close to the carrying capacity (K) of their environment is called K-selection
Individuals mature and reproduce at a later age and produce a few, well-cared-for offspring
Mammals exhibit K-selection

44. Most of the increase is due to improved health and technology
THE HUMAN POPULATION
35.8 Connection: The human population has been growing exponentially for centuries
The human population as a whole has doubled three times in the last three centuries
The human population now stands at about 6.1 billion and may reach 9.3 billion by the year 2050
Most of the increase is due to improved health and technology
These have affected death rates

45. The history of human population growth
Figure 35.8A

46. The ecological footprint represents the amount of productive land needed to support a nation’s resource needs
The ecological capacity of the world may already be smaller than its ecological footprint

47. Ecological footprint in relation to ecological capacity
Figure 35.8B

48. The exponential growth of the human population is probably the greatest crisis ever faced by life on Earth
Figure 35.8C

49. The case for curing cancer
Is finding a cure for cancer a good thing as related to the overall population problems facing the world today?
Think about it for a few moments and then discuss with your partner pros and cons for curing cancer.

50. Red Alert!!!! Extra Credit!!!!! 25 pts. !!!!!!!
What’s your ecological footprint?
New website  see home page for link and assignment information.
DUE WED May 7th!!!

51. 35.9 Birth and death rates and age structure affect population growth
Population stability is achieved when there is zero population growth
Zero population growth is when birth rates equal death rates
There are two possible ways to reach zero population growth (ZPG)
ZPG = High birth rates - high death rates
ZPG = Low birth rates - low death rates

52. The demographic transition is the shift from high birth and death rates to low birth and death rates
During this transition, populations may grow rapidly until birth rates decline
Figure 35.9A

53. The age structure of a population is the proportion of individuals in different age-groups
Age structure affects population growth
Hand out paper – Do “World” as a class
Europe and USA done in computer lab next week

54. RAPID GROWTH
SLOW GROWTH
ZERO GROWTH/DECREASE
Kenya
United States
Italy
Male
Female
Male
Female
Male
Female
Ages 45+
Ages 45+
Ages 15–44
Ages 15–44
Under 15
Under 15
Percent of population
Percent of population
Percent of population
Figure 35.9B

55. Age-structure diagrams not only reveal a population's growth trends
They also indicate social conditions
Increasing the status and education of women may help to reduce family size

56. Principles of population ecology may be used to
Connection: Principles of population ecology have practical applications
Principles of population ecology may be used to
manage wildlife, fisheries, and forests for sustainable yield
reverse the decline of threatened or endangered species
reduce pest populations

57. Renewable resource management is the harvesting of crops without damaging the resource
However, human economic and political pressures often outweigh ecological concerns
There is frequently insufficient scientific information

58. The collapse of the northern cod fishery
Estimates of cod stocks were too high
The practice of discarding young cod (not of legal size) at sea caused a higher mortality rate than was predicted

59. Collapse of northern cod fishery
Figure 35.10A

60. For species that are in decline or facing extinction, resource managers try to increase population size
Carrying capacity is usually increased by providing additional habitat or improving the quality of existing habitat

61. Endangered species

62. Endangered species often have subtle habitat requirements
The red-cockaded woodpecker was recently recovered from near-extinction by protecting its pine habitat and using controlled fires to reduce undergrowth
Figure 35.10B

63. IPM relies on knowledge of
Integrated pest management (IPM) uses a combination of biological, chemical, and cultural methods to control agricultural pests
IPM relies on knowledge of
the population ecology of the pest
its associated predators and parasites
crop growth dynamics
One objective of IPM is to minimize environmental and health risks by relying on natural biological control when possible

64. Interpreting data