What is the biotic potential of a species?
The ability of a population to increase in number, assuming ideal environmental conditions.
(# of offsprings per reproductive cycles, lenght of reproductive cycle, …)
unlimited shelter, food and essential ressources and no predators
What is environmental resistance refering to?
The sum of biotic and abiotic factor that limits a population growth.
What are some limiting factors of a population growth?
- Density-dependent factors
(limits pop. growth dependently of the pop. density) (ex: competition, predation, parasitism, disease) - Density-independent factors
(limits pop. growth rate independently of the pop. density) (ex: natural disasters)
What is the formula to calculate the population growth?
The exponential growth model -> for pop. with high biotic potential and low environmental resistance.
G = r x N
G: population’s growth rate
r: per capital growth rate (b (per capita birth rate) - d (per capital death rate)) CONSTANT
N: nb of individuals
How is the graph of a population undergoing exposential growth?
(pop. size vs. time)
J-shaped curve
(characteristic of pop. with high biotic potential & with lots of ressources available)
When does logistic growth occurs?
When density-dependent factors cause population growth to slow as the population increases.
What it the carrying capacity of an environment?
The maximum number of individuals of a species that an environment can sustain without dammage to its ressources production capacity.
(K)
How is the graph of a population undergoing logistic growth?
(pop. size vs. time)
S-shaped curve
- at LOW density, it grows exponentially.
- as density increases, density-dependent limiting factors slow the rate of growth.
- the population size levels off at the carrying capaity for that species.
(characteristic of long-lived, low biotic potential species that puts a lot of care into raising offsprings)
What can happen when a population overshoots the carrying capacity of an environment?
A population crash.
A population grows exponentially and gets so much bigger than the carrying capacity that when food supplies were’t available, they went extinct.
What happens when a population gets larger than the carrying capacity of an environment but not too much?
When the population gets past carrying capacity, it dammage the capacity of the environment to produce ressources, therefore it leads to a new carrying capacity lower thant the initial one.
What is the equation that describes logistic growth?
G = r x N x [(K - N) / K]
G: pop. growth per unit time
r: maximum per capita pop. growth rate
N: nb of individuals
K: carrying capacity
[(K - N) / K]: proportion of ressources not used yet.
When is the logistical growth rate maximal?
When K (tha carrying capacity) is equal to 1/2
