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Lecture

# BIO205H5 Lecture Notes - Whooping Crane, Intraspecific Competition, Endangered Species

Department
Biology
Course Code
BIO205H5
Professor
Maria Arts

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Intraspecific Population Regulation
Density independent growth
Density dependent growth
Logistic Model
Intraspecific competition
Types of intraspecific competition
Intraspecific competition affects:
- growth/development
- reproduction
-stress
- social behavior
Outline
A) Discrete(geometric)growth
Populationsthatbreedoverdiscretetime
intervals(eg.oneyearperiod)
Allbirthsoccurinspring;doacensusoneyear
laterafterreproductioniscomplete
N(t)=N(0)t
1.DensityIndependentGrowth
- populations increase and discrete growth has time intervals.
- step graph where breeding occurs in time. if birds breed only in may
then they breed, wait till next year and we see how many are breeding.
look at pops from one year to the next.

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A) Discreteorgeometricpopulationgrowth
N(t)=N(0)t
N(1)=N(0)1
Eg.,ifnumberoffemalesbreedinginspringof2009=41
Andifnumberoffemalesbreedinginspringof2010=49
=49/41
=1.2
1.DensityIndependentGrowth
B)Exponentialorcontinuouspopulationgrowth
Ifreproductioniscontinuous,thenitismore
appropriatetolookattheinstantaneousrateof
increase=r
Independentoftimeperiods:smoothcurve
N(t)/N(0)=
=erorr=ln
Example:graysquirrelpopulation:r=ln(1.2)=0.18
1.DensityIndependentGrowth
Whatisr?
b=instantaneousbirthrateperindividual
d=instantaneousdeathrateperindividual
dN/dt =(bd)N =rN
dN/dt =rN
r=intrinsicrateofincrease
=rateatwhichapopulationgrowsunderidealconditions
1.DensityIndependentGrowth
-
- not all organisms have a discrete breeding period and have a
continuous period - curve. more appropriate to look at
instantaneous rate of growht (r). we know that a change in
pop can give us lambda and can be rearranged to give us e^r
the ln of which will give us the pop at instantaneous slope.
- use this in life table to figure out the exponential pop growth.
- density independent growth - density has no affect on the growht
so the population has no affect on density and vice versa -
r = birth rate - death rate based on pop size that we have.

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“r”
variesamongspecies
variesamongpopulations
dN/dt =(bd)N =rN
Rateofchangeofapopulationovertime,dN/dt,
isafunctionofpopulationsizeN(inrN)
Trend:asyougofromsmalltowardslargeanimals,theintrinsic rateof
increasedeclineswithincreasingsize
PopulationGrowthReflectstheDifferencebetween
RatesofBirthandDeath
WewantanequationtopredictpopulationsizeN(t)under
conditionsofexponentialgrowth
N(t)=N(0)ert
N(t)=numberattimet
N(0)=initialpopulationsizeatt=0
e=baseofnaturallogarithm=2.72
r=intrinsicrateofincreaseinyoung/timeinterval
t=numberoftimeintervals(days,years)
GrowthRatesCanBeUsedtoPredictPopulation
Sizes
Whooping crane
Endangered species: 15 whooping cranes remained in 1941
Calculating Exponential Growth Rate
- Whooping cranes were near extinction due to
overhunting and habitat destruction
Characteristics of population:
-small population size
-protected from hunting
-abundant resources
N = 15 birds in 1941
Q1. If there are 425 birds alive in 2004, what is r?
N(t) =N(0)ert
425 = 15er(63)
425/15 = 28.33 = er(63)
r = ln(28.33)/63
= 3.34/63
= 0.053
- r is not going to be the same among species and among
populations.
- as you go from small to larger animals, the rate of increase
declines with increase in size. a very indicative general trend
that the larger you are for animals, intrinsic rate of ___ declines with
size.
- equation predicts a population size under a certain time under
exponential growth.
- a population is endangered and we can introduce it to an env
that will help it increase in number. take a look at what we can find
out from the data of the population.
- protection laws are put against predators etc and put it in an area
with abundant resources.