Conservation Biology

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					Population Dynamics
 Principles of Population
• Population
  – A group of organisms, all of the
    same species, that live in a specific
    area at the same time.
• Population growth is defined as
  an increase in size of a population
  over time…
• However, populations grow
  at different rates.
        Linear Growth
• If a population grew at a set
  amount each year, say by 10
  organisms per year, then the
  population has LINEAR GROWTH
• However, populations normally do
  not have linear growth. Linear
  growth looks like this
  (Please draw in your notes)
•  Your parents give you two options for
1. 1,000 a month
2. A penny on the first day of the month
   that doubles to two pennies on the
   second day
   and so on until the last day
   of the month
• Which option do you choose?
                .01          .02         .04          .08          .16         .32

   .64        1.28         2.56         5.12       10.24          20.48     40.96

81.92         163.84      327.68       655.36 1310.72             2621.44    5242.88

10,485.76    209711.52     41943.04    83886.08   167772.16 335544.32       671088.64

                                                    Over 10
1342177.28                5368709.12                million!!
                                                   On 31 day
             2684354.56                             months
    Exponential Growth

• If you graph the allowance we just
  saw on the graph it will look like
  this: (Please draw in your notes)









             1   2   3   4   5   6   7   8   9   10   11   12   13   14   15   16   17   18   19
      Exponential Growth
• A population that is growing without any
  limits, would have exponential
• Meaning that as the population gets
  bigger, it also will grow faster
• But, populations cannot keep
  exponential growth for very long,
  because the environment would
  not be able to support it.
Exponential Growth
     Carrying Capacity
• The environment has a
• Carrying capacity is the number
  of organisms that an environment
  can support.
• Once a population reaches its
  capacity, its growth stops.

• What are some examples of things
  that can limit growth?
 What can limit growth?
• Limiting factors limit growth
• Different sizes of populations
  will also have different factors
  affecting them.
• When growth has been limited
  its graph will look like this:








              1   2   3   4   5   6   7   8   9   10   11   12   13   14   15   16   17   18   19
 Density Dependent Factors

• Density Dependant Factors are
  factors that have an increasing effect as
  the population increase, hence will
  affect larger populations.
    Examples: Disease, Competition,
        Parasites, Predators, Food
• These types of factors spread more
  quickly in larger populations.
Density Independent Factors

• Density Independent Factors
  effect any population, regardless
  of size. Population size does not
• Examples: Volcanic eruption,
  Temperature, Storms, Floods,
  drought, chemical pesticides
 Organism Interactions Limit
      Population Size
• Predation
  – Predator consuming prey on a large enough
    scale can have a drastic effect on the size of
    prey population and hence predator population
• Competition
  – Many individuals competing for scarce supplies
  – Density-dependent factor
• Crowding and Stress
  – Also density dependant. Stress symptoms
    include aggression, decrease in parental care,
    decreased fertility, and decreased resistance to

• Do any populations exhibit
  exponential growth?
Human Population
Human Population Growth
      World Population

• Census - Taken in the US once
  every 10 years
• Demography - Study of human
  population size
  – 6 Billion in 1999
  – 1.3 Million per year in 2002
Human Population Growth

• Human Population Growth is
  Different than other organisms
  because humans consciously
  change their environment
  – Eradication of diseases
  – Methods for producing more food
  – Technology
  Calculating Growth Rate
• Birthrate - Number of live births
  per 1000 population in a given
• Death rate - Number of deaths
  per 1000 population in a given
    Immigration vs Emmigration

• Immigration is the movement into
  a country.
• Emigration is the movement out of
  a country.
•   (Birth Rate + Immigration Rate) – (Death Rate + Emigration Rate)
    = Population Growth Rate (PGR)
       Age Structures

• Age Structures tell us how many
  people are in each age group…
• A younger aged population will
  grow more rapidly than an
  older population.
• Which age   A
  has more
  young       B
• Why might
  that be?
Biological Diversity and
   Biological Diversity

•Biodiversity - Variety of
 species in a specific area
 Importance of Biodiversity
• Interdependence of organisms
  – Life depends on life
• Stability
  – Many species and diversity allows for better chances of
• Important to people
  – Foods
  – Industrial products
  – Medicines such as painkillers, antibiotics, heart
    medication, anti-depressants, anti-cancer drugs
  – Depend on other organisms for oxygen, nutrients
  – Clothes, Furniture, Beauty…
• Can you think of any other reasons why
  biodiversity is important?
Loss of Biodiversity
• Extinction -
  Disappearance of a
  species when the last of
  its members die
   – Passenger Pigeon (1914)
• Endangered Species -
  Numbers become so low
  that extinction is possible
   – Humpback Whale
• Threatened Species -
  Populations decline rapidly
  and are likely to become
   – Grizzly Bear
 Threats to Biodiversity
1. Habitat Loss
  – The largest threat
  – 70’s – 80’s Amazonian rainforest
  – Coral reefs
Threats to Biodiversity
2. Habitat Fragmentation
  –   Separation of wilderness areas from other
      wilderness areas
      •   Increased extinction of local species
      •   New opportunities for invasions by introduced or
          exotic species
      •   Increased risk of fire
      •   Changes in local climate
  –   Smaller fragments mean less biodiversity
  –   Geographic isolation leads to genetic
  –   Some organisms need large areas – for
      hunting and reproduction
Biotic Effects of Fragmentation

• Animals that require large areas in
  which to graze can no longer do so –
  animals starve
• Likewise large predators can not obtain
  enough to eat in a small spot - animals
• Migration becomes difficult and species
  either starve or get wiped out after
  events such as fire
        Abiotic Effects of
• Climate can change in the areas
• Think about the temperature in a forest
  vs. open spaces…
• Edge Effect – The different conditions
  along the boundaries of an ecosystem.
  as areas become smaller the changes at
  the edges start to influence the
  conditions inside.
Threats to Biodiversity
3. Habitat degradation - Damage
   to a habitat by pollution
   • Types: Air, Water, and Land
           I. Air Pollution
• Importance: can have negative effects on
  organisms, such as breathing problems,
  genetic mutations, as well as irritating the
  eyes & nose.
• Causes: Volcanic eruptions, forest fires,
  Chlorofluorocarbons (CFCs),
• burning fossil fuels is the #1 cause
 Problems from Air Pollution
• Acid Precipitation - Caused by
  emissions from burning fossil fuels.
  These emissions combine with water
  vapor in the air to form rain, snow,
  sleet and fog with low pH values
  – Leeches nutrients from the soil, kills plants,
    lowers pH of water supplies, Responsible for
    killing many trees in US forests
  – Also strongly effects lake ecosystems killing
    plants, animals & other organisms
   Air Pollution Continued
• Ozone layer depletion - Ozone =
  O3, It absorbs some of ultraviolet
  waves striking atmosphere –
  natural sunscreen
    • CFCs break down ozone
       – CFCs used in refridgerators, air conditioners,
         some aerosols and used to make polystyrene
    • Spring – hole at largest
    • Hole allows more UV rays in which
      causes increased exposure to UV
      radiation, this can lead to mutations.
     II. Water Pollution
• Importance: degrades aquatic
  habitats in streams, rivers, lakes and
  oceans thereby strongly affecting and
  even killing aquatic life.
• Causes:
  1. Excess fertilizers, animal wastes
  from farms can be carried into the
  water. These nutrients cause algal
  blooms which can further harm
  aquatic life by removing needed
  oxygen from the water. Additionally,
  silt from eroded soils can clog gills of
  2.Detergents, heavy metals, chemicals
  3. Abandoned drift nets – kills ocean
Water Pollution
    III. Land Pollution
– The average American produces
  about 1.8 kg of solid waste daily
  • Most trash becomes part of landfills
  • Possible contamination of ground water
– Pesticides
  • DDT passed through food chains
   IV. Exotic / Introduced
• Exotic/Introduced Species -
  Species that are not native to a
  particular area
• People sometimes introduce a new
  species into an ecosystem
• Can cause problems for native
Figure 52.5, 2

   Introduced species

  When species that are not native are introduced to an area, a number of different problems can occur.

   Competition: In North            Disease: An introduced            Predation: The brown tree
   American marshes, purple         fungus has virtually              snake has extinguished
   loosestrife is crowding out      wiped out the American            dozens of bird species on
   native organisms.                chestnut.                         the island of Guam.
Introduced to control erosion on roadcuts.
         Sea Lamprey
Introduced to Great Lakes in 1800’s thru
        Saint Lawrence Seaway
Conservation of Biodiversity
        Conservation Biology
•  Conservation Biology - Study and
   implementation of methods to protect
1. Natural resources - Parts of the
   environment that are useful or necessary
   for living organisms
2. Legal protection of species
    –   US Endangered Species Act 1973
    –   Illegal to harm endangered or threatened
             Conservation Biology

3. Preserving habitats
  –   Natural Preserves
      •   Yellowstone National Park
      •   Big Cypress National Preserve
      •   Crater Lake National Park
4. Habitat Corridors
  –   Protected strips of land that allow the
      migration of organisms from one
      wilderness area to another
  –   Allows populations to be connected to
      each other
  –   Why is this important?
  Conservation Biology

5. Working with people
 – Rangers
 – Sustainable use - Enable people to
   use natural resources in way that
   will benefit them and maintain the
    Conservation Biology

Reintroduction and Species
 Preservation Programs - Release
 organisms into an area where the
 species once lived
• Captivity
  – Organism that is held by people
• Protecting Plant Species
  – Protect environment
  – Cool seeds and store for long periods
    of time in a seed bank

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