Climate Change

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Climate Change

• The Study of Populations

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Population

• In ecology, a population includes all living
  species
• group of individuals of a single species
  inhabiting a specific area
• share the same environment, they benefit from the
  same resources, like water, food and sunlight
• probabilities that they interact together are
  very high (ex. at time of the reproduction)

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Size of Population

• the number of individuals in the group
• Over time, size of a population can increase,
  remain stable, or decrease.
• Four factors explain variations in the size of a
  population birth rate, death rate, immigration,
  and emigration.

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Factors affecting size of population
Factor Birth rate Death rate Immigration Emigration Description Birth of individuals within a population Death of individuals within a population Arrival of individuals from other regions Departure of individuals to other regions
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Methods of Measuring the Size of Populations

• Counting Individuals
• Use of quadrants
• Capture-recapture

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Counting Individuals

• When possible, the number of individuals within a
  region are counted
• May use aerial photographs to count large mammals
  in open areas

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Quadrats

• Rectangular piece of land separated by rope or
  tape which divides the piece of land
• Count all individuals in the quadrant

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Average Number of individuals per quadrat Size
of Population Area of quadrat
Total Area
Size of Population Average number of individuals
per quadrat Total Area
Area of quadrat
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Capture-Recapture

• Used to estimate size of upwardly mobile animals
  such as birds, fish, seals, whales
• Install cages or nets in the region that the
  population occupies
• Counting captured animals and mark with tags,
  bands, or paint
• Release animals to mix with other unmarked
  animals
• Replace cages or nets
• Count captured animals and recaptured animals

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Estimated Population Size

• Number of animals marked and recaptured number
  of animals marked
• Number of animals captured second time
  size of population
• Size of population number of animals marked
  number of animals captured second time
• 
  number of animals marked and recaptured

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Example

• 100 geese are captured, marked, and released
• 200 geese are captured the second time and 50 are
  already marked
• Size of population 100 200
• 50
• 400 individuals

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Density of a Population

• Number of individuals per unit of area or unit of
  volume
• Density of a population
• individuals / space(area or volume) occupied
• For the same species, the density of the
  population may vary depending upon the habitat

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Density of a Population

• Density of population number of individuals
  
  
  space occupied (area or volume)
• Example A 100 L aquarium has 5 goldfish in it.
• Density of population 5 individuals
• 100 L of water
• 0.05 individuals per liter of
  water

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Distribution of a Population

• Way in which the individuals are spread out
  within the space that the population occupies
• Clumped distribution, regular distribution,
  random distribution

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Clumped Distribution

• Most frequent type of distribution in which
  individuals form groups
• Attraction between individuals or attraction to a
  common resource
• Ex. fish living in schools

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Uniform Distribution

• Individuals are uniformly spaced throughout the
  environment
• Antagonistic interactions between individuals or
  local depletion of resources

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Random Distribution

• An individual has an equal probability of
  occurring anywhere in an area
• Neutral interactions between individuals, and
  between individuals and local environment

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Ecological Factor

• An element in an environment which can have an
  effect on the other living species which live
  there
• Abiotic- (nonliving) physical or chemical
  elements ex. pH
• Biotic- (living) linked to actions of living
  organisms ex. predation

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Abiotic and Biotic Factors
Abiotic Factors Biotic Factors
Quantity of light Birth
pH of soil or water Sickness
Terrain Amount of food
Thickness of snow Predation
Temperature competition
Humidity of the air Human activities
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Limiting Factors

• Ecological factor which reduces the density of a
  population
• An ecological factor can be limiting if it is
  absent in an environment, if there is an
  insufficient amount, or if it is in excess
• Ex. light, water, prey

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Biological Cycles

• Includes periods during which the population
  increases in size and decreases in size. These
  periods are of fixed duration and repeat
  continuously.

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Notes

• See word document