AP Biology
Population Ecology
population
ecosystem
community
biosphere
organism
AP Biology
Why Population Ecology?
 Scientific goal
 understanding the factors that influence the
size of populations
 ...
AP Biology
Life takes place in populations
 Population
 group of individuals of same species in
same area at same time
...
AP Biology
 Abiotic factors
 sunlight & temperature
 precipitation / water
 soil / nutrients
 Biotic factors
 other ...
AP Biology
Characterizing a Population
 Describing a population
 population range
 pattern of Dispersion
 Density of p...
AP Biology
Population Range
 Geographical limitations
 abiotic & biotic factors
 temperature, rainfall, food, predators...
AP Biology
Population Dispersion
 Spacing patterns within a population
uniform
random
clumped
Provides insight into the
e...
AP Biology
Population Size
 Changes to
population size
can occur by:
AP Biology
Population Growth Rates
 Factors affecting population growth rate
 sex ratio
 how many females vs. males?
 ...
AP Biology
Life tableLife table
Demography
 Study of a populations vital statistics and
how they change over time
 Life ...
AP Biology
Age structure
 Relative number of individuals of each age
What do these data imply about population growth
in ...
AP Biology
Survivorship curves
 Graphic representation of life table
Belding ground squirrel
The relatively straight line...
AP Biology
Survivorship curves
 Generalized strategies
What do these graphs
tell about survival &
strategy of a species?
...
AP Biology
Trade-offs: survival vs. reproduction
 The cost of reproduction
 To increase reproduction may decrease
surviv...
AP Biology
Reproductive strategies
 K-selected
 late reproduction
 few offspring
 invest a lot in raising offspring
 ...
AP Biology
Trade offs
Number & size of offspring
vs.
Survival of offspring or parent
Number & size of offspring
vs.
Surviv...
AP Biology
Survivorship Curves with Reproductive Strategy
0 25
1000
100
Human
(type I)
Hydra
(type II)
Oyster
(type III)
1...
AP Biology
Population Growth Rate Models
 Exponential growth
 Rapid growth
 No constraints
 Logistic growth
 Environm...
AP Biology
Population Growth Math
 Change in population = Births – Deaths
 Per capita birth rate = b
 Per capita death ...
AP Biology
Exponential Growth (ideal conditions)
 No environmental barriers
 Growth is at maximum rate
dN/dt = rmaxN
N =...
AP Biology
African elephant
protected from hunting
Whooping crane
coming back from near extinction
Exponential Growth
 Ch...
AP Biology
K =
carrying
capacity
K =
carrying
capacity
Logistic rate of growth
 Can populations continue to grow
exponent...
AP Biology
Logistic Growth Equation
dN/dt = rmaxN(K-N)/K
K = carrying capacity of population
Ex: If a population has a car...
AP Biology
500
400
300
200
100
0
200 10 30 5040 60
Time (days)
Numberofcladocerans
(per200ml)
 Maximum
population size
th...
AP Biology
Changes in Carrying Capacity
 Population cycles
 predator – prey
interactions
KK
KK
AP Biology
Regulation of population size
 Limiting factors
 density dependent
 competition: food, mates,
nesting sites
...
AP Biology
Introduced species
 Non-native species (INVASIVE)
 transplanted populations grow
exponentially in new area
 ...
AP Biology
Zebra musselssel
ecological & economic damage
~2 months
 reduces diversity
 loss of food & nesting sites
for ...
AP Biology
Purple loosestrife
19681968 19781978
 reduces diversity
 loss of food & nesting sites
for animals
 reduces d...
AP Biology 2007-2008
Any
Questions?
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Population ecology 2014

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Population ecology 2014

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  • Within a population’s geographic range, local densities may vary substantially. Variations in local density are among the most important characteristics that a population ecologist might study, since they provide insight into the environmental associations and social interactions of individuals in the population. Environmental differences—even at a local level—contribute to variation in population density; some habitat patches are simply more suitable for a species than are others. Social interactions between members of the population, which may maintain patterns of spacing between individuals, can also contribute to variation in population density.
  • A Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants.
  • A Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants.
  • The J–shaped curve of exponential growth is characteristic of some populations that are introduced into a new or unfilled environment or whose numbers have been drastically reduced by a catastrophic event and are rebounding. The graph illustrates the exponential population growth that occurred in the population of elephants in Kruger National Park, South Africa, after they were protected from hunting. After approximately 60 years of exponential growth, the large number of elephants had caused enough damage to the park vegetation that a collapse in the elephant food supply was likely, leading to an end to population growth through starvation. To protect other species and the park ecosystem before that happened, park managers began limiting the elephant population by using birth control and exporting elephants to other countries.
  • Decrease rate of growth as N reaches K
  • Population ecology 2014

    1. 1. AP Biology Population Ecology population ecosystem community biosphere organism
    2. 2. AP Biology Why Population Ecology?  Scientific goal  understanding the factors that influence the size of populations  general principles  specific cases  Practical goal  management of populations  increase population size  endangered species  decrease population size  pests  maintain population size  fisheries management  maintain & maximize sustained yield
    3. 3. AP Biology Life takes place in populations  Population  group of individuals of same species in same area at same time  rely on same resources  interact  interbreed  rely on same resources  interact  interbreed Population Ecology: What factors affect a population?Population Ecology: What factors affect a population?
    4. 4. AP Biology  Abiotic factors  sunlight & temperature  precipitation / water  soil / nutrients  Biotic factors  other living organisms  prey (food)  competitors  predators, parasites, disease  Intrinsic factors  adaptations Factors that affect Population Size
    5. 5. AP Biology Characterizing a Population  Describing a population  population range  pattern of Dispersion  Density of population #individuals per unit area 1937 1943 1951 1958 1961 1960 19651964 1966 1970 1970 1956 Immigration from Africa ~1900 Equator range
    6. 6. AP Biology Population Range  Geographical limitations  abiotic & biotic factors  temperature, rainfall, food, predators, etc.  habitat adaptations to polar biome adaptations to polar biome adaptations to rainforest biome adaptations to rainforest biome
    7. 7. AP Biology Population Dispersion  Spacing patterns within a population uniform random clumped Provides insight into the environmental associations & social interactions of individuals in population Provides insight into the environmental associations & social interactions of individuals in population Why uniform? Why clump? Why random?
    8. 8. AP Biology Population Size  Changes to population size can occur by:
    9. 9. AP Biology Population Growth Rates  Factors affecting population growth rate  sex ratio  how many females vs. males?  generation time  at what age do females reproduce?  age structure  #females at reproductive age in cohort?
    10. 10. AP Biology Life tableLife table Demography  Study of a populations vital statistics and how they change over time  Life tables, Age Structure Diagrams and Survivorship Graphs Why do teenage boys pay high car insurance rates?Why do teenage boys pay high car insurance rates? females males What adaptations have led to this difference in male vs. female mortality?
    11. 11. AP Biology Age structure  Relative number of individuals of each age What do these data imply about population growth in these countries?
    12. 12. AP Biology Survivorship curves  Graphic representation of life table Belding ground squirrel The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females. The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females.
    13. 13. AP Biology Survivorship curves  Generalized strategies What do these graphs tell about survival & strategy of a species? What do these graphs tell about survival & strategy of a species? 0 25 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 10075 Survivalperthousand I. High death rate in post-reproductive years I. High death rate in post-reproductive years II. Constant mortality rate throughout life span II. Constant mortality rate throughout life span III. Very high early mortality but the few survivors then live long (stay reproductive) III. Very high early mortality but the few survivors then live long (stay reproductive)
    14. 14. AP Biology Trade-offs: survival vs. reproduction  The cost of reproduction  To increase reproduction may decrease survival: (think about…)  age at first reproduction  investment per offspring  number of reproductive cycles per lifetime  parents not equally invested  offspring mutations  Life History determined by costs and benefits of all adaptations. Natural selection favors a life history that maximizes lifetime reproductive success Natural selection favors a life history that maximizes lifetime reproductive success
    15. 15. AP Biology Reproductive strategies  K-selected  late reproduction  few offspring  invest a lot in raising offspring  primates  coconut  r-selected  early reproduction  many offspring  little parental care  insects  many plants K-selected r-selected
    16. 16. AP Biology Trade offs Number & size of offspring vs. Survival of offspring or parent Number & size of offspring vs. Survival of offspring or parent r-selected K-selected “Of course, long before you mature, most of you will be eaten.”
    17. 17. AP Biology Survivorship Curves with Reproductive Strategy 0 25 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 10075 Survivalperthousand K-selection r-selection
    18. 18. AP Biology Population Growth Rate Models  Exponential growth  Rapid growth  No constraints  Logistic growth  Environmental constraints  Limited growth
    19. 19. AP Biology Population Growth Math  Change in population = Births – Deaths  Per capita birth rate = b  Per capita death rate = d  # of individuals = N  Rate of population growth (r) = b – d  Survivorship = % surviving Ex: If there are 50 deer in a population, 13 die and 27 are born the next month. What is the population size the following month?  (Answer: 27-13 = 14, so new population is 64) Ex: What is the birth rate for the deer? #Births/N = b  Answer: 27/50 = .54  Death rate (d) = 13/50 = .26 Ex: What is the rate of growth for the deer? r = .54 -.26 = .28
    20. 20. AP Biology Exponential Growth (ideal conditions)  No environmental barriers  Growth is at maximum rate dN/dt = rmaxN N = # individuals Rmax = growth rate
    21. 21. AP Biology African elephant protected from hunting Whooping crane coming back from near extinction Exponential Growth  Characteristic of populations without limiting factors  introduced to a new environment or rebounding from a catastrophe
    22. 22. AP Biology K = carrying capacity K = carrying capacity Logistic rate of growth  Can populations continue to grow exponentially? Of course not!Of course not! effect of natural controls effect of natural controls no natural controlsno natural controls What happens as N approaches K?
    23. 23. AP Biology Logistic Growth Equation dN/dt = rmaxN(K-N)/K K = carrying capacity of population Ex: If a population has a carrying capacity of 900 and the rmax is 1, what is the population growth when the population is 435? 1 x 435 (900-435)/900 = 224 What if the population is at 850? What if it is at 1010? Explain the results of each problem.
    24. 24. AP Biology 500 400 300 200 100 0 200 10 30 5040 60 Time (days) Numberofcladocerans (per200ml)  Maximum population size that environment can support with no degradation of habitat  varies with changes in resources Time (years) 1915 1925 1935 1945 10 8 6 4 2 0 Numberofbreedingmale furseals(thousands) Carrying capacity What’s going on with the plankton?
    25. 25. AP Biology Changes in Carrying Capacity  Population cycles  predator – prey interactions KK KK
    26. 26. AP Biology Regulation of population size  Limiting factors  density dependent  competition: food, mates, nesting sites  predators, parasites, pathogens  density independent  abiotic factors  sunlight (energy)  temperature  rainfall swarming locusts marking territory = competition competition for nesting sites
    27. 27. AP Biology Introduced species  Non-native species (INVASIVE)  transplanted populations grow exponentially in new area  out-compete native species  reduce diversity  examples  African honeybee  gypsy moth kudzu gypsy moth
    28. 28. AP Biology Zebra musselssel ecological & economic damage ~2 months  reduces diversity  loss of food & nesting sites for animals  economic damage  reduces diversity  loss of food & nesting sites for animals  economic damage
    29. 29. AP Biology Purple loosestrife 19681968 19781978  reduces diversity  loss of food & nesting sites for animals  reduces diversity  loss of food & nesting sites for animals
    30. 30. AP Biology 2007-2008 Any Questions?
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