Introduction phenomenon: How do scientists determine the size of a population?
Why do we need to know a population's size?
Geographic distribution – the area a pop lives(range)
Population Density – the number of individuals in an area
Number of births
Number of deaths
Emigration (out) & Immigration (in)
For example, In Springfield, 45 babies are born in the year 2008. 15 people died that same year. What is the growth rate for the city?
Positive Growth rate = population increase
Negative Growth rate = decrease
Exponential Growth –reproduce at a constant rate. Occurs under ideal conditions (no limits)
Logistic Growth – resources become less available, growth slows or stops
Carrying Capacity – the number an environment can support
Limiting Factor – causes population growth to decrease
Density-Dependent Factors –depends on population size
parasitism and disease
Density-Independent Factors – does not depend on population size
Some human activities
Predator Prey Relationships
As prey population goes up, so does predator population. What happens when the prey population goes down?
Demographic Transition – a dramatic change in birth and death rates
Age Structure Diagrams can be used to evaluate populations