populations ecology unit newark academy summer session 2014
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PopulationsPopulationsEcology Unit
Newark Academy Summer Session 2014
PopulationPopulation
A group of organisms all of the same species living within a particular place at the same time
Population SizePopulation Size
Population size is the number of individuals it contains.
Size is a fundamental and important property of a population but it can be difficult to measure directly.
Population DensityPopulation Density
Population density is the number of individuals per unit area or volume.
Population density helps to measure how crowded a population is.
Population Dispersion – describes Population Dispersion – describes the spatial distribution of the spatial distribution of individuals within a population.individuals within a population.
Population DynamicsPopulation Dynamics
All populations are dynamic – they change in size and composition over time.
Birth rate: number of births occurring in a period of time.
Death Rate: (mortality rate) number of deaths in a period of time.
How do these terms relate to population growth?
Age Structure : The distribution of Age Structure : The distribution of individuals among different ages individuals among different ages in a population.in a population.
Patterns of Mortality – Patterns of Mortality – Survivorship CurvesSurvivorship Curves
Survivorship CurvesSurvivorship Curves
Population Growth RatePopulation Growth Rate
The amount by which a population’s size changes in a given time.
Influenced by four factors:◦Birth rate◦Death rate (mortality rate)◦Immigration◦Emigration
Calculating ChangeCalculating Change
Per capita = Per individualBirth rate / 1,000 individualsDeath rate / 1, 000 individuals
Birth rate – death rate = growth rate / capita
What if it is a negative number?What if it is a positive number?
Calculating ChangeCalculating Change
Suppose there are 38 births / 1,000 people (birth rate = 0.38)
There are 89 deaths / 1,000 people (death rate = 0.89)
Calculating change (growth rate or N):
0.38 – 0.89 = -0.51 What is happening to the population?Assuming the current population is 200,000
people, what will be expected population the following year?
Population Growth - Population Growth - ExponentialExponential
Limiting FactorLimiting Factor
A factor that restrains the growth of a population is known as a limiting factor.
Examples of limiting factors include (but not limited to) ◦Food◦Space◦Ability to eliminate waste◦Dissolved oxygen
Logistic Model of Population Logistic Model of Population GrowthGrowth
The Logistic Model of population growth builds on the exponential model but takes into consideration limiting factors.
The logistic model takes into consideration the carrying capacity of the environment.
Carrying capacity (K) = the number of individuals an environment cam support over a long period of time.
Logistic ModelLogistic Model
Exponential vs. LogisticExponential vs. Logistic