Topic 11 Population growth lecture notes Flashcards
change in total numbers of individuals in a population formula (2)
Delta N/Deta T
birth rate-death rate
Per capita birth rate (b)
b=B/N
B=number of births
N=population number
Per capita birth rate (b)
b=B/N
B=number of births
N=population number
Per capital death rate (d)
d=D/N
# of death/Population Number
per capital growth rate (r)
b-d
birth rate-death rate
What does it mean when r is +,0 and -?
r=0
population is no change
r=+ growing population
r=- declining population
rmax
intrinsic rate of increase
idealized value when there is no external pressure operating on it
rmax is related to
generation time, time to sexual maturity
not really to size because cicadas, are small buy they have a 17 year generation time.
rmax and gen time
longer generation time= lower rmax
formula for determining the size of a population growing exponentially
Nt=N0(1+rmax)^t
N and R relationship
as population size (N) gets bigger, growth rate is decreasing.
What limits population growth? (6)
- predators
- limited food
- limited shelter
- temperature
- precipitation
- disease
How close the population size is to the carrying capacity changes____
r
the three scenarios with N, K and r
- when N=K r=0
- when N<K.>0</K.>
- when N>K, r<0
growth rate (rt) formula (Logistic model) + verbal explanations
rt=rmax ((K-Nt)/K)
innate capacity for increase X Unutilized opportunity for growth
population size growing logistically formula
Nt+1=N(1+rt)
you have to calculate growth rate every year
bc the difference between the population size and carrying capacity
density dependent factors (6)
biotic
food avaliability
shelter
mates
predation
disease
Density Independent factors (6)
abiotic
temp
precipitation
disturbance (fires, floods)
Exponential model
When populations experience unlimited growth
Logistic Models
populations growth is limited bc resources are finite
Tracking changes in number of individuals in a population involve monitoring 4 types of demographic change
- number of births
- number of deaths
- number of immigrants
- Number of emigrants
the intrinsic rate of increase is high for_____ and low for those
protists and animals with short generation time and low for those with long generation rime
generation time
the average interval between the birth of an individual and the birth of its offspring.
K according to textbook is
a property of the environment that can vary from one habitat to another
Logistic model (3)
- r decrease as the population gets larger
- r decrease linearly as population size increase
-population growth slows as population size approaches K
K-N/K
What proportion of the carrying capacity still available
What does Crowding do?
- Decrease individual growth rate,
- decrease adult size
- decrease survival of plants and animals
Individuals living in very dense populations are (4)
unable to harvest enough resources, grow slowly and tend to be small weak and less likely to survive.
females in crowded populations (2)
produce either fewer offsprings or smaller offsprings that are less likely to survive.
**less energy for reproduction after meeting its basic needs for maintenance
population density and population size relationship
increase in population density causes population size to decrease. Decrease in density cause it to increase
How does predation cause density dependent population regulation
as a particular prey species becomes more numerous, predators may consume more of it because it is easier to find and catch. Once a prey species exceeds some threshold density, predators may consume a larger percent of its population amounting to a density dependent effect
Density-dependent factors with K relationship
are limiting factors that contribute to determining carrying capacity while depending on the density of the population. That is, density-dependent factors tend to be more strongly effective at regulating population growth once a population reaches a certain range or level.
Density-independent factors and K relationship
are limiting factors that do not regulate population growth for populations reaching certain levels. These factors tend to be abiotic (nonliving) such as unusual weather, cataclysms, natural disasters, and pollution; all of which can affect birth and death rates but without being determined by a population’s current range.
The success of r selected depends on
flooding the the environment with a large quantity of young because only some may be successful.
r selected can be reduced by___ so they may never
changes in abiotic environmental factors so that they may never grow large enough to reach K and face a shortage of limiting resources
Most K selected species have
low rmax meaning their population often grow slowly
the success of K selected species depends on
the production of a relatively small number of high quality offspring that join an already well established population
