lec 17
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what is predicted by the population model
If we have data on how the population has been growing, with the right model we can predict the number of individuals in the future
Differential equations/ continuous time
• Time steps are small • Growth is smooth • Good for species that reproduce continuously (humans, bacterias, etc )
Difference equations/discrete time
• Time steps are discrete units (days, weeks, months) -Growth is bumpy • Good for species with breeding season • birds: their population is not always changing, they have breeding seasons
logistic model
• The logistic model will only produce an S shaped curve when we start from a small population size (far from K) • when the population is small, theres lot of food so the population will grow initally • as it grows, theres less resource so the population growth slows down
Density dependent regulation
Growth of population depends on the population
Density independent reduction
Severe weather or natural disaster that reduces population size
sign of lamda/r
• If lambda/r is bigger than 1, there’s more individuals in the future than now so the population grows • If lambda/r is less than 1, there’s less individuals in the future than now so the population decreases
equation of logistic model
dn/dt = rN(1-N/K)