Population Dynamics Flashcards
What is a population?
Individuals of a single species living in the same area at the same time
What are the characteristics (definition, types) of a population?
- Size
- Density
- Number/space - Dispersion: pattern of distribution
- Clumped
- Uniform
- Random
What are the factors affecting population growth?
Population Growth:
Birth rate/fecundity (depends of number of individuals in population in reproductive years) + immigration > death rate + emigration
Population Decline:
Death rate/mortality + emigration > birth rate + immigration
What is demography and what does it depend on?
- The study of factors that affect growth/decline of population
- Birth rate and death rate depend on age and sex of individuals in populations
What are the characteristics of demography?
Age structure, generative time, sex ratio
What is age structure and the types?
- Relative number of individuals of each age in a population
- Stable population
- Positive population growth
- Population explosion (many pre-reproductive individuals) - Negative population growth (decline in population)
What is generative time and its effect on population growth?
- Average length of time between birth of individuals and birth of offspring
- If there are 2 populations of same size/fecumity/mortality, the one with short generation time experiences faster growth
What is the sex ratio and what are the cases it will affect population growth?
- Proportion of individuals of each sex in population
- Mate for life: must have equal sex ratio for maximum growth
- Harem: unequal sex ratios doesn’t matter
- Alpha couple: unequal sex ratio doesn’t matter
What are the types of graphs and what does N represent?
Let N = population size
Age pyramid, growth curve, survivorship curve
What is an age pyramid?
Number of individuals of each sex in each age category
What is a growth curve and the types?
-Plots of population size versus time
Exponential
Logistic
Sinusoidal
What is a survivorship curve and the types?
Plots number of individuals in a cohort still alive at each age
Type 1: low mortality until old age
Type 2: equal mortality throughout life
Type 3: very high mortality in youth but survivors live long life
What describes the humans’ population growth and what explains it?
Went from type 1 to type 3 curve
- Medicine
- Agriculture
- Industrial revolution (technology)
Resulted in exponential growth
What is the impact of humans exceeding the carrying capacity?
- Depleting resources
- Habitat destrubtion
- Famine
- Global warming
- Biological magnification (accumulation of heavy metals)
What are the factors influencing the balance of populations?
Fecundity
Interactions
How does fecundity influence the balance of populations? What are the types and when are they advantageous?
Altering fecundity to use energy optimally
- Semiparity
- Organisms invest most energy throughout life
- Used in single large reproductive episode
- Advantageous when living in harsh environment - Iteroparity
- Organisms produce fewer offspring over span of many seasons
- Invest smaller amounts of energy in each reproductive episode
- Advantageous when environment is more stable and favourable (can afford to give energy for reproduction)
What is a community?
many species living in same area
What are mathematical models used for?
Used to predict population growth of species; tells you instantaneous growth of population
What are the types of models?
Exponential
Logistic
What results in the exponential growth model? Is it realistic?
- No limit on population increase
- Unlimited resources (unrealistic as there will be competition for sunlight, food, water, space, etc.)
What does the logistic model focus on?
- Focuses on density/carrying capacity (K) - maximum population environment can support
- If N is close to carrying capacity then population growth is 0
What are the phases for the logistic model?
Early phase: slow growth because number of reproductive individuals is small
Exponential phase: rapid growth because number of reproductive individuals is large and lots of resources
Negative phase: slow growth because of competition for resources
What are the equations for exponential model?
dN/dt=rN, r=b-d
t=0.69/r
What is the equation for logistic model?
dN/dt=rN(K-N/N)
How does a density dependent factor affect population? What are some examples?
- Intensifies as population increases
- Affects fecundity and mortality when population density is high
- Sets limits to population growth (determines carrying capacity)
- Eg. food, sunlight, disease, nesting sites, mates
How does a density independent factor affect population? What are some examples?
- Affects same percentage of individuals regardless of population density
- Prevent population from ever reaching K
- Eg. fire, climate, natural disasters
What is a life history?
events that affects organisms’ schedule of reproduction and death
What are the 2 life history strategies?
- K selected
- R selected
What is a K-selected population?
- Equilibrium
- Living at or near carrying capacity
- Must survive and reproduce with limited resources
What is a R-selected population?
- Opportunistic
- Live in open habitats with little competition
- Variable environment where population fluctuates
- Favour individuals with high growth rate
Answer for K selected populations:
Maturation Time Lifespan Death Rate # of Offspring/Reproductive Episode # of Reproductive Episodes in Lifetime Size of Offspring Generation Time Parental Care of Offspring
Long Long Low Few Many (iteroparity) Large Long Extensive
Answer for R selected populations:
Maturation Time Lifespan Death Rate # of Offspring/Reproductive Episode # of Reproductive Episodes in Lifetime Size of Offspring Generation Time Parental Care of Offspring
Short Short High Many One (semelparity) Small Short None
What is biotic potential?
maximum rate population can increase when no limits on growth rate
What is environmental resistance?
all factors acting to limit growth of population
