Section 7.2 Populations

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Section 7.2Populations Sustainability

• Science 10

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Population

• All the individuals of a species that occupy a
  particular geographic area at a specific time.

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Exponential growth

• Accelerating growth that produces a j-shaped
  curve when the population is graphed against
  time.

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Limiting Factor

• A factor that limits the growth, distribution, or
  amount of a population in an ecosystem.

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Carrying Capacity

• The size of a population that can be supported
  indefinitely by the available resources and
  services of an ecosystem.

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Ecological Niche

• The way an organism occupies a position in an
  ecosystem, including all the necessary biotic and
  abiotic factors.

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Sustainable use

• Use that does not lead to long-term depletion of
  a resource, or affect the diversity of the
  ecosystem from which the resource is obtained.

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Unsustainable

• A pattern of activity that leads to a decline in
  the function of an ecosystem.

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Sustainability

• Use of the Earths resources, including land and
  water, at levels that can continue forever.

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1. When do population numbers have a tendency to
increase? Identify any factors that could
contribute to the population increase.

• Population numbers have a tendency to increase
  when individuals reproduce at rates that are
  greater than the rate at which individuals are
  dying or leaving the area (natality vs
  mortality).
• Factors that can contribute to population growth
  are an abundance of resources and lack of
  predators.

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2. Use the exponential growth of elephants in
South Africas Kruger Park to explain the pros
and cons of exponential growth.

• Kruger Park began protecting elephants that were
  being hunted for their ivory tusks. With
  protection in place the elephant population has
  been able to recover (pro) however they have
  caused damage to plant life and habitats due to
  their large size and mass (con).

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3.Explain why ecosystems cannot support
exponential growth. Use the yellow perch as an
example.

• Exponential growth is a population explosion that
  cannot be sustained by ecosystems due to limited
  resources.
• The female yellow perch have the ability to
  produce 23 000 eggs per year and if each egg
  survived the population of adult perch would
  reach 1 trillion in 5 years.
• The ecosystem would not be able to support such a
  population due to limited resources such as food,
  dissolved oxygen and light. These resources are
  limiting factors that will restrict the
  population numbers.

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4. Explain and identify some examples of density
independent factors that limit population growth.

• Density independent factors are one of two
  categories of limiting factors that influence
  population growth.
• These are factors that do not depend on the
  number of members in a population per unit area.
• Some examples are natural phenomena like weather
  events and pollution.

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5. Explain and identify some examples of density
dependent factors that limit population growth.

• Density dependent factors are one of two
  categories of limiting factors that influence
  population growth.
• These factors are dependent on the number of
  members in a population per unit area.
• Some examples are disease, parasites, predation
  and competition.

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6. Fully explain how carrying capacity affects
population numbers in an ecosystem.

• Carrying capacity is the size of a population
  that can be supported by the resources in an
  ecosystem.
• The carrying capacity helps keep population
  numbers of various species balanced. There is a
  delicate balance between population numbers and
  the amount of food and resources available. If
  population numbers exceed the carrying capacity
  then the population numbers will decrease until
  it is in balance with the available resources
  once again.

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7. Explain how PGI was used to estimate the
carrying capacity of white tail deer in Nova
Scotia.

• PGI, known as the Pellet Group Inventory, was
  developed to help manage the deer population in
  NS.
• Each spring the number of deer pellet piles was
  counted and the population number of deer was
  estimated based on the pellet piles.
• The data collected was used to calculate the
  density of the deer population and the carrying
  capacity.

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8. The ecological niche of an organism includes
biotic and abiotic factors along with
relationships with other species. Describe the
ecological niche of a brown bat.

• The ecological niche of a brown bat includes
  biotic factors such as all the insects they eat,
  their competitors (i.e., nighthawk) and their
  predators.
• It also includes abiotic factors such as the
  places they use for roosting and hibernating, the
  time of night they hunt for food, airspace for
  flying while hunting and temperature ranges they
  can tolerate.

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9. What are some examples of services that
different species may provide to their ecosystems?

• There are many different services that species
  can provide to ecosystems such as regulation of
  population sizes of other organisms, and the
  recycling of matter to assist in energy flow.

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10. How have bog plants adapted to occupy their
nutrient deprived niches?

• Bog plants such as the pitcher plant have adapted
  to their surroundings which contain plenty of
  sunlight and water but lacks nutrients such as
  nitrogen due to poor water flow.
• Through the consumption of insects they can
  obtain the nutrients they need.

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11. Explain why humans are able to occupy so many
different ecosystems.

• Unlike other species, humans have a very highly
  developed brain that has allowed them to expand
  their narrow niche occupied by their ancestors.
• This allowed for the creation of complex tools,
  control of external forms of energy and expansion
  of our use of resources. This all lead to the
  ability to live successfully in many different
  ecosystems such as deserts and the arctic regions

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12. Why is the sustainable use of ecosystems so
important?

• If humans do not begin the sustainable use of
  natural resources our niche may begin to shrink
  overtime and this includes the resources needed
  for our survival.

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13. Fully explain how humans have been able to
increase the carrying capacity of the biosphere
for their species.

• The human species has increased the carrying
  capacity of its niche through the use of tools,
  fire and weapons.
• They have also been able to exploit natural
  resources to provide public health, education,
  agriculture, medicine and technology.
• All of these improvements have increased the
  carrying capacity of the human species on our
  planet.

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14. Identify two ways to increase the carrying
capacity of an ecosystem.

• Two ways to increase the carrying capacity of an
  ecosystem are to alter it so more energy and
  resources can be consumed and to alter behaviour.

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15. What is an ecological footprint?

• An ecological footprint is the measure of the
  impact of a human individual or population on the
  environment.
• It includes energy consumption, land use and
  waste production what is needed to support an
  individuals standard of living.

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16. Current ecological footprints in developed
countries are unsustainable. Identify ways
individuals can reduce their footprint to become
more sustainable.

• Individuals can reduce their ecological footprint
  by consuming fewer resources or by using existing
  resources in a more sustainable way (energy
  efficiency and recycling).