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Characteristics of Population

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Micayla Minicucci

on 8 January 2016

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Transcript of Characteristics of Population

Exponential Growth
A pattern of population growth where organisms reproduce continuously at a constant rate (yeast cells)
Geometric Growth
A pattern of population growth where organisms reproduce at fixed intervals at a constant rate (white tailed deer)
A population of 2500 yeast cells in a culture tube is growing exponentially. If the intrinsic growth rate
r
is 0.030 per hour, calculate the initial instantaneous growth rate of the population
Characteristics of Population
Growth
Example
dN/dt = rmaxN x [(k-N)]/k
dN/dt=rN
td=0.69/r
r = 0.030 per hour
n = 2500
dN/dt=rN
= 0.030 x 2500
= 75 per hour
Calculate the time it will take for the population to
double in size
r = 0.030
td = 0.69/r

= 0.69/0.030
= 23 hours
Example
=(N(t+1))/(N(t))
N(t) = n(0)
Example
Logistic Growth
A model of population growth describing growth that levels off as the size of the population approaches its carrying capacity (fur seals)
dN/dt = rmaxN x [(k-N)]/k
Sinusoidal Growth
A pattern of population growth where an increase of reproduction is symmetrical to the decrease of reproduction - common in predator vs prey (foxes and rabbits)
Density
Population Density:
the number of individuals of the same species that occur per unit area or volume
Crude Density:
measured in terms of number of organisms of the same species within the total area of the entire habitat
D = N/S
Ecological Density
Measured in terms of the number of individuals of the same species per unit area or volume actually used by the individuals
D=N/(space total-space unused)
Distribution
Population Distribution:
the arrangement of individuals in a given area
Individuals are usually drawn to favourable living conditions such as adequate precipitation, food supply and healthier atmospheres
Uneven population distribution worldwide
3 types of distribution: clumped, uniform and random
Population Density
vs
Population Distribution
Distribution
Density
how the population is spread across one area
determined by economic, political and social factors
number of people in a certain area
determined by resources, climate and quality of land
Populated Areas
Sparsely Populated:
harsh areas, few people
Example: Antarctica
Carrying Capacity
The maximum number of organisms that can be sustained by available resources over a limited period of time
Factors: food supply, birth/death rates, biotic potential and environmental resistance
Biotic Potential:
the maximum reproductive capacity of a population under optimum environmental conditions
Environmental Resistance:
the resistance presented by the environmental conditions to limit a species from growing out of control or to stop them from reproducing at maximum rate
Humans have not reached carrying capacity because of:
advances in technology
recycling programs
biomeditation
power generating systems (solar cells)

Carrying Capacity of The Earth
The earth can hold up to an estimated 10-15 billion people
Depending on various conditions the maximum and minimum carrying capacity determines the growth of a population
Earth's carrying capacity is predicted by using equations (e.g. logistic equations)
Advanced technology allows the human population to grow to a wide availability of natural resources
rmax
[(k-N)]/k
population size N
population growth rate
0.50 20 980/1000 9.8
0.50 200 800/1000 80
0.50 500 500/1000 125
t
Densely Populated:
many benefits, many people
Example: Europe
Example
Calculate the crude density of a population of painted turtles if 34 turtles were counted in a 200 hectare park
D = N/S
= 34/200
=0.17
Each May, harp seals give birth on pack ice off the coast of Newfoundland. In a hypothetical scenario, an initial population of 2000 seals gives birth to 950 pups, and during the next 12 months, 150 seals die
Year 1, population change = 950 seals - 150 seals

= 800 seals
Initial population N(0) = 2000 seals
Population at end of year 1, N(1) = 2000 + 950 - 150
=(N(t+1))/(N(t)) = 2800/2000 = 1.4

N(t+1) = N(t)
N(2) = 2800 x 1.4
= 3920
Assuming the population is growing geometrically, what will the harp seal population be in two years?
k = 1000 rmax = 0.5
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