lecture 9: Logistic Growth and Population Regulation Flashcards
(16 cards)
Yield
= number of individuals of a species harvested per unit time
Sustainability
matching quantities of harvest rate to the rate of population growth (supply rate =
demand rate
What is the definition of Maximum Sustainable Yield (MSY)?
MSY is the largest average harvest that can be continuously taken from a population without causing it to decline (supply ≥ harvest).
What is the main goal of MSY?
To maximize economic gains while ensuring long-term sustainability.
What is the harvest rate in MSY supposed to equal?
The replacement rate (population growth rate)
At what population size is MSY achieved according to the logistic growth model?
When the population is at K/2 (half the carrying Cap)
Why is K/2 the ideal population size for MSY?
Because the population growth rate (dN/dt) is highest at K/2, maximizing the number of individuals that can be harvested sustainably.
How do you maintain MSY in practice?
By harvesting enough individuals to keep the population size close to K/2.
Q3: What are density-dependent factors?
Biotic factors that become stronger as population density increases (e.g. competition, disease, predation).
What are density-independent factors?
Abiotic factors that affect populations regardless of density (e.g. storms, temperature).
What does the logistic model assume?
A: Population growth is density-dependent; as population size (N) increases, growth rate (r) Decreases
What is the carrying capacity (K)?
The maximum population size the environment can support long-term.
What happens when N < K, N= K, and N> K
N< K → Population increases (r > 0)
* N= K → No growth (r = 0)
* N> K → Population decreases (r < 0)
What determines the effect of D-D and D-I factors?
The life history traits of the species
* The frequency and intensity of environmental changes
What is sustainable yield?
Harvesting a renewable resource at the same rate it regenerates.
Why is estimating MSY difficult? (5 key problems)
- Hard to accurately measure population size (N)
- K constantly changes with the environment
- Unpredictable density-independent factors
- Changing age structure affects growth rate
- Economic and political pressure to maintain high harvests
