Population Density kendricknovak

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					What kind of plants do we see in a
       climax community?
Agenda for Thursday May 26th
1. Communities and populations notes
2. Random sampling lab
• Def. – a group of interacting populations that
  occupy the same area at the same time

• Different organisms occupy different biomes
  – Different adaptations
• Limiting factors – any biotic or abiotic factor
  that limits the number, reproduction, or
  distribution of an organism
  – Sunlight, food, temperature

• Tolerance – ability of an organism to survive
  when subjected to abiotic or biotic factors
  – Upper and lower limit = range
• Populations – members of a single species that
  live in once place at a single time
       Population Characteristics
• Population Density – # of organisms per area

• Dispersion – pattern of spacing of a population
  within an area
  – Based on available resources (food)
  – 3 types
     • Uniform
     • Clumped
     • Random
Dispersion Pattern: Uniform
Dispersion Pattern: Clumped
Dispersion Pattern: Random
• Smaller animals usually clump
  – Larger animals usually independent
  – Fish

Q: What advantage do smaller fish (animals)
  gain by forming schools (clumped groups)?
  Safety, confuses predators
Q: Which type of population distribution allows
  you to predict more accurately how many
  individuals reside in a given area?
Determine how many oak trees are
in the forest using the random
sampling technique. Use the grid.
Agenda for Friday May 27th                   3
1. Quiz                                  5
                             8       7
2. Population sampling
  1. Mark and recapture
If you were in charge of a team given the
   responsibility to determine the number of
   sunfish in Horseshoe Lake, discuss with a
   partner how would you accomplish this task.
• A technique called sampling is sometimes used to
  estimate population size.

• Organisms in a few small areas are counted and
  projected to the entire area.

• Example: A biologist counts 10 squirrels living in a
  200 square foot area, she could predict that there
  are 100 squirrels living in a 2000 square foot area.
1. A biologist collected 1 gallon of pond water
   and counted 50 paramecium. Based on the
   sampling technique, how many paramecium
   could be found in the pond if the pond were
   1,000 gallons?

2. What are some problems with this
   technique? What could affect its accuracy?
            Mark and Recapture
• Biologists use traps to capture the animals alive
  and mark them in some way
  – Animals are returned unharmed to environment
• Animals trapped and data is taken on how many
  are captured with tags
• A mathematical formula is then used to estimate
  population size
  Formula for Mark and Recapture

• Ecologists marked 20 bears in an area. Over 5
  years they captured 100 bears. Of those 100
  captured 50 had a tag. What is the population
  of the bears?

Population estimate = (total number captured) x (original # with mark)

                         (Total number captured with mark)
    What is mark and recapture?
Agenda for Tuesday May 31st
1. Mark and recapture notes and lab
2. Finish population notes
      Mark and Recapture Concerns
• Capturing the animal could injure the animal or scientist
• Disturb animal's normal behavior pattern
• The marks used to track the animals, such as ear punches, may
  cause injury to the animals or get lost between captures
• Marked animals may be more or less attractive to predators
  because of markings
• Assumes all animals require the same effort to get caught,
   – might catch the weaker or younger animals more
• Some animals learn to fear the traps and avoid recapture
   – or become trap-happy and attempt to get caught when they
     learn there is food involved and that they will be re-
Population Ranges Limiting Factors
• Abiotic conditions
  – Temperature
  – Humidity
  – Rainfall
  – Sunlight
• Biotic conditions
  – Predators
  – Competitors
  – parasites
      Density independent factors
Def. – any factor that does not depend on the
 number of organisms in a population in a given

• Abiotic
  – Weather – drought, flooding, extreme heat/cold,
    tornados, hurricanes
  – Water
  – Fire
  – Sunlight
      Density Dependent Factors
Def. – any factor that depends on the number of
 organisms in a population in a given area

• Biotic factors
  – Predation, disease, parasites, competition
• More members of a population = more predators
• Outbreaks of disease tend to occur when
  population size has increased
  – Disease is transmitted faster
  – True for humans as well as animals
• Parasites increase at higher densities
• When resources become limited animals
  – Within a population or between 2 different species
  – Lead to starvation – population can decrease
        Population Growth Rate
How do we figure out population growth rate?
• Must know birthrate and mortality
• Emigration – moving out of a pop.
• Immigration – moving into a pop.
  – Immigration rate = emigration rate

• Calculating growth rate
=(population at end – population at beginning)
           Population at beginning
Different Growth Rates
What is a density dependent factor?
What is a density independent factor?
Agenda for Wednesday June 1st
1. Finish notes
2. Human pop. Graphing
3. Biodiversity
        Exponential Growth Rate
• Starts slow – few organisms
• Faster because all organisms
  are reproducing

• Rarely happens
  – WHY?
  – Limiting factors – food, space
          Logistical Growth Rate
• Logistic growth occurs when a population’s
  growth slows or stops following exponential
  – Carrying capacity
               Carrying Capacity
• Maximum number of individuals that an
  environment can support for the long term
  – Limited by energy, water, oxygen, nutrients available

• Population grows until carrying capacity
  – Births outnumber deaths
  – Exceed carrying capacity then deaths outnumber
          Reproductive strategies
R-strategy (rate strategists)
• Produce as many offspring as possible in a short
  – Little energy in raising young

K-strategists (carrying capacity strategy)
• Few offspring that have a better chance of living
  – Expend a lot of energy raising young
Human Population Growth
    Trends in Human Population
• Was slow and stable

• Recent increase in growth
  – Technology – agriculture, medicine, shelters

• Developing countries add more than
  developed countries
                     More trends
• Zero population growth
  – birth rate + immigration rate = death rate +
    emigration rate

• Age structure
  – # of males and females in three age groups
     • Pre-reproductive (0-19), reproductive (20-44), and
     post –reproductive (45-80+)
      Human Carrying Capacity
• Humans have a carrying capacity

• Technology allows an increase in carrying

• Concerns about reaching/exceeding carrying
  – resources being used
Describe what is happening to the
 population in the graph below.
Agenda for Wednesday Jan 26th
1. Finish Notes
2. Human pop. graph

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