Transcript 4. Section 7.2 answers

Section 7.2
Populations & Sustainability
Science 10
Population
• All the individuals of a
species that occupy a
particular geographic
area at a specific
time.
Exponential growth
• Accelerating growth
that produces a jshaped curve when
the population is
graphed against
time.
Limiting Factor
• A factor that limits the
growth, distribution, or
amount of a
population in an
ecosystem.
Carrying Capacity
• The size of a
population that can be
supported indefinitely
by the available
resources and
services of an
ecosystem.
Ecological Niche
• The way an
organism
occupies a
position in an
ecosystem,
including all the
necessary
biotic and
abiotic factors.
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.
Unsustainable
• A pattern of activity that leads to a decline
in the function of an ecosystem.
Sustainability
• Use of the Earth’s
resources,
including land and
water, at levels
that can continue
forever.
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.
2. Use the exponential growth of elephants in
South Africa’s 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).
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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 individual’s standard of living.
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).