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lecture note

Course Code
Ingrid L.Stefanovic

of 2
L04- BIO 120
New Section: Population Ecology
now, we will discuss populations: collection of individuals of the same
species in the same are (N)
what influences N?
unlike humans, some plants have unusual reproduction ( see larkspur
and aspen on slides)
larkspur- normal, one seed produces many identical plants
aspen- many unique seeds that produce many unique plants
dandelions- no sex, identical seeds as mother, produces many identical
Strangler fig- starts as an epiphyte[canopy], bring down roots to the
ground, and once they are big enough and many, the roots start to
come together, and look more like a tree.
Slide 6:
Continuous growth such as humans, babies are born throughout the
Discrete growth- birds for instance have babies at specific times in a year
two models: density-dependant:
density-independent: those that are growing unrestrained
S7- structure of typical population growth model
most important: N and t ( changes with time)
Nt : N at a specific time t
Nt+1: N in the future
Nt+1=f(Nt) [f-function]
S8- for modeling continuous pop. Growth, use calculus.
S10- pop. change from Nt to Nt+1 Nt+1=Nt-D(died)+b(born)-E(emigrate)
S11- assume no immigration + emmigrtion
birth and deaths are per-capita rates, fixed constants
lambda, factor by which population changes over time, called net
reproductive rate
S12- exponential growth
S13- dN/dt is the instantaneous growth tangent to growth curve
S16- lmaba and r have different impacts, lamba is 1 when a population
neither grows or decline. R is 0 when the population isnt growing( births
S17- Darwin used elephants to show populations gowrth? Why? Elephants
have the longest life span, an a reproductive cycle
S20- what prevents lambda from getting bigger than 1 or less than 1 for long
If lamba is greater than 1, populations will grow increasing, and when
lambda is less than 1, population will go instinct
Therefore, this model is not GODD for longer period of time
S22- added some math to slow down population growth
K- carrying capacity of a population, how many individuals can the
environemt support.
As N gets closer to K, it gets closer to 0, growth decreases. When N and K are
the same, growth is 0.
This is LOGISTIC growth
S27- all the logistic graphs end at carrying capacity
S31- add a time-delay, we can get elaborate functions