Population Ecology: (Ch. 52)
• A population is a
• group of individuals
• single species
• simultaneously occupy the same general area.
• Shaped by interactions between individuals and their environment.
Population Growth
• Change in population size
Change in population = Births during – Deaths during
size during time interval time interval time interval
• How would immigration & emigration affect population growth?
Age Structures showing different growth patterns
2 Types of Population Growth
• Logistic
• slows to match the carrying capacity
• What is the ∆N?
• Exponential
• Doesn’t slow growth rate
• What is the ∆N
• Logistic or exponential growth?
What Causes Changes in Population Growth?
• Ideal Conditions = Unlimited Resources
• Exponential Growth
• Why?
• Typical Conditions
• Limited Resources determines carrying capacity (K)
• maximum stable population size a particular environment can support
Limiting Factors
• Prevent a population from rising above a certain population size.
Density-Dependent Density-Independent
• Food Natural Disasters
• Shelter Storms
• Disease
What is the difference between these two types of Limiting factors?
2 types of limiting factors
• Density-dependent factors
• Effect on population increases as the populationdensity increases.
• closer to K, the smaller ∆N
• Negative feedback.
• Density-independent factors
• Unrelated to populationdensity
• no feedback to slow population growth.
Negative feedback prevents unlimited population growth
• Due to Resource limitations in crowded populations
• Reduction in successful reproduction
Causes of Negative Feedback (limiting factors)
2. Intraspecific competition (2 different species)
• competition for resources
3. Territoriality (Intra or interspecific)
• Competition for space
4. Predation & Food
• Effect on prey population
5. Waste Accumulation
• Yeast fermentation
6. Disease
• Rate of dispersal
What Type of Limiting Factor results in each growth pattern
• K-selection
• Density dependent
• r-selection
• Density independent
K or R strategists?
• Is the carrying capacity consistent?
• Determined by abiotic & biotic factors
Human Population Growth
• K or R strategist?
• 1650 the Plague took an untold number of lives.
• What is allowing the shift from logistic to exponential growth?
• How might this population increase stop?
Survivorship Curve
• Graph of the number of individuals in a group still alive at each age.
• Type I: low death rate early in life (humans).
• Type II : constant mortality rate (squirrels).
• Type III: high death rate early in life (oysters).
• Which are R strategists? Which are K strategists?