Population Growth Flashcards
Reindeer on St. Paul Island
- Important food source
- population increased exponentially
- eventually population plummeted
What do you need to understand to predict a collapse?
- population growth
- density dependence
- resource exploitation
- stochastic events
birth rate
number of young born per female
fecundity
table of birthrates for females of different ages
Annual plants: what are they, which one did we study, and what type of population growth do they have?
- Annual plants live for one year
- we studied phlox drummondii
- They demonstrate geometric growth
Geometric rate of increase equation
future population / current population
R0 (net production rate)
- growth rate per generation
- in annual plants its the same as the rate of increase
- normally it is Ixmx
Exponential population growth
- overlapping generations
- unlimited environment
- constant rate
- usually when a population is coming to a new area for the first time
Exponential growth formula for current population
N0e^rt
r
intrinsic rate of increase
Net population growth (R)
r(change in t)N
change in population right now
rN
Scott’s pine
- growth seen in pollen accumulation in lakes
- after colonization, experienced exponential growth for 500 years
Whooping crane
-after federal protection, they experienced exponential growth
Elephants in Kruger park, south africa
- grew at exponential rate after hunting was banned
- not necessarily a good thing. Large mammals tend to reach a peak and then plummet when they grow like this
Collared dove
- had new habitat
- grew exponentially at first
- rate of growth started decreasing
- most likely bc of density dependence
Density independant growth
growth set by fixed parameters (R, r, or gamma)
density independent factors
fires, floods, tornados, etc…
Density dependent growth
assumes limiting factor in the environment
density dependent factors
food, water, nest sites, disease
logistic population growth
for populations that are density dependent
-S curve
K (carrying capacity)
the limit to the population that an environment can sustain
-birth and death rates at this number will even each other out
equation for current logistic growth
rN(K-N)/K
Demography
The study of all these statistics and how they change in a population over time
Survivorship curve
Shows log of survival rate at different ages
Types of survivorship curves
- Tend to die when they’re old
- Constant rate of death throughout life
- Tend to die when they’re young
Age structure diagrams
show history of survival, reproduction, and growth
- blue on bottom, tan in middle, red on top
- steeper pyramid means faster growth
White oaks
biased towards young trees
-must be sufficient reproduction for replacement
Rio Grande Cottonwood
- old trees weren’t being replaced
- no floods = fewer germination areas
life table
age specific summary of survival and reproduction rate within a population
-usually follows a cohort
3 types of life tables
1: cohort = identifies individuals born at the same time and keeps records from birth
2: static = records age of death for individuals
3: age distribution = calculates difference in proportion of individuals at different ages
