Populations

1
Populations

• Population- a group of organisms that belong to
  the same species and live in a particular place
  at the same time.
• Properties of Populations
• Population size-the number of individuals that
  the population contains.
• Population density-measures how crowd a
  population is.
• Dispersion- spatial distribution of individuals
  within the population
• Clumped distribution
• Uniform distribution
• Random distribution

2
Population Dynamics

• All populations are dynamic
• they change over time
• Important measurements
• Birth rate
• Death rate (mortality rate)
• Life expectancy

3
Population Dynamics

• Age Structure- the distribution of individuals
  among different ages in a population.
• Presented as Graphs

4
Measuring PopulationsHow population grow and
what factors limit their growth

• Four processes that affect growth rate
• 1) birth rate
• 2) death rate
• 3) emigration
• 4) immigration
• Calculation of growth rate
• Birth rate death rate growth rate

5
The Exponential Model

• Exponential model
• A pattern of increase in number due to a steady
  growth rate.
• Graph
• J-shaped curve
• Population size grows slowly when its small, but
  growth speeds up as individuals join the
  population.
• Useful to predict or explain patterns that can be
  observed in reality
• Does not apply to most populations, because
  populations cannot growth indefinitely.
• All populations are limited by the environment

6
Limiting Factors

• Resources become scarce
• Food
• Water
• Space
• Shelter
• Harmful waste accumulate
• Competition among individuals for resources
  intensifies.

7
Logistic Model

• This model accounts for the influence of limiting
  factors
• Carrying capacity (K)
• Graph
• S-shaped

8
Small Populations

• Vulnerable to extinction
• Environmental disturbances
• Storms
• Floods
• Disease outbreaks
• Reduction of limiting factors
• Likelihood of inbreeding
• reduces genetic variability
• Less likely to adapt to environmental changes