Applications Of Population Growth Models Flashcards
What’s exponential growth
Unlimited growth of population
Observed during colonisation of unoccupied habitats
Density independent model - rate of population growth does not change as population gets bigger
What’s logistic growth
Density dependent model - rate of population growth slows down as population size increases.
What drives the time lag in density dependent response.
Animals may survive on stored reserves and continue to grow/reproduce after limiting resources deplete.
Reproductive period may be completed before reduced resources affect population.
The rate of population growth is influenced by:
The population size ara a precious time, by it’s overall rate of increase (birth rate - death rate), and the available resources (carrying capacity)
Time lag in density dependence Daphnia
They store food in form of oil droplets, can survive and reproduce with absence of food.
Once food resource is exhausted death rate increases due to starvation and density decreases.
Due to this time lag, population continuously overshoots and undershoots the carrying capacity.
What happens during convergent oscillations
At medium rates of increase (r) and medium time lag population size oscillates above and below carrying capacity score settling at equilibrium density (convergent oscillations)
What happens during stable limit cycle
If rate of increase (r) is high and time - lag is long population enters a stable limit cycle, periodically rising and falling above K but never reach equilibrium population size.
What happens during chaotic irregular fluctuations
If rate of increase is very high and time lag is very long the population shows irregular chaotic fluctuations around the equilibrium density.
When do El Niño events occur
Every 3-7 years
Manifests in pacific water la off west coast of South America.
What happens during El Niño
Between December and January water temperatures increase 2 - 10°C above average.
What affect does El Niño have of marine life.
Fish abundance plummet.
In the Galápagos penguin, mortality increases and reproduction decreases.
When is the fishery sustainable
Of removals can be replaced by stock production each year then the fishery is sustainable.
When is sustainable yield greatest.
I’d stick size is maintained at half it’s carrying capacity the population growth rate is faster and sustainable yield is greatest.
