Section 7.2Populations & 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 j-shaped 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).