1. Sustainable Ecosystems
UNIT 1
Sustainable Ecosystems
Chapter 1: Nutrient Cycles and Energy Flow
Chapter 2: Populations and Sustainable Ecosystems
Chapter 3: Biodiversity

2. Populations and Sustainable Ecosystems
CHAPTER 2
In this chapter, you will:
explain that populations tend to increase until they reach a natural limit
explain how factors affect the carrying capacity of an ecosystem
describe how no two species have exactly the same function in an ecosystem
explain the value of ecological processes, known as ecosystem services
assess your own impact on the ecosystems that sustain you
Copyright © 2010 McGraw-Hill Ryerson Ltd.

3. Reducing Wildlife Mortality with Fences
(Page 47)
Wildlife deaths due to vehicle collisions are increasing. These deaths can have a major influence on the population and status of a species.
What measures could be taken to reduce animal mortality? Do you think they will work?
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4. 2.1 Populations and Resources
(Page 49)
A population is all the individuals of a species of organisms that occupy a particular geographic area at a certain time. All populations tend to increase when individuals reproduce at rates that are greater than what is needed to replace individuals that have died or left.
Exponential growth is accelerated growth that produces a J-shaped curve when the population is graphed against time. This type of growth only occurs in nature under certain conditions for a short period of time.
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5. Exponential Growth
(Page 50)
Species that have been previously eliminated in an area can be re-introduced. These re-introduced populations can experience exponential growth if the populations and their habitats are well managed.
Exponential growth cannot be sustained in nature because no ecosystem has an unlimited supply of the things that organisms need for survival.
Limiting factors are factors that limit the growth, distribution, or amount of a population in an ecosystem. Biotic factors such as food availability and abiotic factors such as temperature and pH are examples of limiting factors.
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6. Carrying Capacity
(Page 51)
Carrying capacity is the size of a population that can be supported indefinitely by the available resources and services of an ecosystem.
As shown above, populations can increase exponentially until they reach the carrying capacity of their environment. When a population is maintained at its carrying capacity, it is said to be in equilibrium.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

7. Carrying Capacity
Click the “Start” button to review the connection between carrying capacity, limiting factors, and equilibrium.
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8. Human Activities and Carrying Capacity
(Page 52)
When humans alter ecosystems to meet their needs, the carrying capacities of these ecosystems change. Sometimes the carrying capacity for certain “urban-friendly” species increases, but, for most wild species, the carrying capacity is decreased.
Urban sprawl is the growth of relatively low-density development on the edges of urban areas. The image on the left shows the “Golden Horseshoe,” where almost one-quarter of Canadians live. The areas marked in pink are the most densely populated.
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9. The Story of the Redside Dace
(Page 53)
The redside dace is a small fish that previously inhabited large regions around the west end of Lake Ontario. Increased urban sprawl resulted in fewer stream-side shade trees and increased drainage (run-off). These factors drastically reduced the carrying capacity of the area for the redside dace, and its population has decreased.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

10. Intensification
(Page 54)
Intensification is a policy that is designed to reduce urban sprawl. The policy requires that a large percentage of new development occur within the boundaries of a city. An example of this policy in practice would be the adding of additional floors to an existing building instead of constructing a new structure on another piece of land.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

11. Concepts to be reviewed:
Section Review
(Page 55)
Concepts to be reviewed:
What is exponential growth? How and when does it occur?
What must occur for the carrying capacity of an ecosystem to be reached?
How can the carrying capacity of an ecosystem be affected by human alterations? How can these effects be limited?
Copyright © 2010 McGraw-Hill Ryerson Ltd.

12. 2.2 Interactions Among Species
(Page 56)
In addition to resource needs and abiotic factors, the growth and size of a population can be greatly affected by interactions among the different species in an ecosystem. These interactions can have negative or positive effects.
The major types of interactions are predation, competition, and symbiosis.
Interactions, along with limiting factors, restrict populations to particular places, roles, and sizes within an ecosystem.
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13. Occupying Ecological Niches
(Page 57)
An ecological niche is the way that an organism occupies a position in an ecosystem, including all the necessary biotic and abiotic factors. Niches can also be described as being the “role” or “job” of the organism or the “service it provides to the ecosystem.”
There are millions of species on Earth, and, thus, millions of niches.
Species have adapted to the ecosystem and niche they occupy.
Carnivorous plants exist in ecosystems with nutrient-poor soils. These plants have adaptations for getting their nutrients from insects.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

14. Predation and Population Size
(Pages 58-9)
Predators are organisms that kill and consume other organisms. Prey are organisms that are eaten as food by a predator.
Bottom-Up Population Regulation describes what occurs if a shortage in a resource at the base of a food chain causes a decline in the animals in the higher trophic levels.
Top-Down Population Regulation results in a decrease in organisms at lower tropic levels because of an increase in animals at higher trophic levels.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

15. Reviewing Predation and Population Size
Click the “Start” button to review the connection between predation and population size.
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16. Do Wolves Affect Moose Numbers?
(Page 59)
The number of moose available influences the number of wolves, the top predator. But does the size of the wolf population affect the size of the moose population?
Copyright © 2010 McGraw-Hill Ryerson Ltd.

17. Competition
(Page 60)
Competition occurs when two or more organisms compete for the same resource, such as food or space, in the same place at the same time.
Competition can limit the size of a population and can also influence the ecological niche of an organism.
As populations increase in an ecosystem, so does competition for resources. The more energy an organism spends competing for resources, the less energy it has for growth and reproduction.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

18. Competition and Stickleback Fish
(Page 61)
When species such as these two types of sticklebacks are forced to compete for a resource, they will divide the resource up by occupying a narrower niche. If no competition exists in an ecosystem, a species will occupy a broader niche.
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19. Symbiosis (Mutualism)
(Page 62)
Symbiosis is the interaction between two different species that live together in a close association.
Mutualism is a symbiotic relationship in which both species benefit.
Colourful coral represents a mutualistic relationship between the coral and a photosynthetic algae. The algae supplies the coral with energy, and the coral provides the algae with protection, nutrients, and CO2.
If the mutualistic relationship fails, both of the species suffer or die. Without the algae, the coral bleaches (turns white) and dies.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

20. Symbiosis (Parasitism)
(Page 63)
Parasitism is a relationship in which one of the species benefits and the other is usually harmed. The parasite is the organism whose niche depends on a close association with a larger host organism.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

21. Concepts to be reviewed:
Section 2.2 Review
(Page 64)
Concepts to be reviewed:
What is an ecological niche?
How can species adapt for life in narrow niches?
What are the main types of relationships between species?
How can relationships affect a population?
Copyright © 2010 McGraw-Hill Ryerson Ltd.

22. 2.3 Human Niches and Population
(Page 65)
Lacking both the ability to move quickly and the big teeth or claws that other animals have to protect themselves, humans have had to rely on their well-developed brains in order to survive.
Humans have used their brain power to design and build complex tools, control external sources of energy, and expand their use of resources.
Humans have moved out of the very narrow niche occupied by their ancestors and are now able to live successfully in many different ecosystems.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

23. Humans and Carrying Capacity
(Page 66)
For humans to continue to occupy the broad niche they have become accustomed to, they must make sure that their use of resources is sustainable. Sustainable use is 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.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

24. Humans and Carrying Capacity
(Page 66)
Human exploitation of natural resources has increased Earth’s carrying capacity for humans. Recently, the human population has expanded rapidly. The current doubling time (the time required for a population to double in size) is only about 60 years.
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25. Ecological Footprints and Carrying Capacity
(Page 67)
An ecological footprint is a measure of the impact of an individual or a population on the environment in terms of energy consumption, land use, and waste production.
Patterns of activity by a population that lead to a decline in the function of an ecosystem are said to be unsustainable. Sustainability is achieved if Earth’s resources, including land and water, are used at levels that can continue forever.
Developed countries like Canada tend to have the largest ecological footprints.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

26. Concepts to be reviewed:
Section 2.3 Review
(Page 68)
Concepts to be reviewed:
How have humans managed to expand their ecological niche?
How have humans increased the carrying capacity of the ecosystems that support them?
Why has the human population been able to increase so rapidly in recent years?
What is an ecological footprint? How does it relate your personal use of resources?
Copyright © 2010 McGraw-Hill Ryerson Ltd.

27. 2.4 Ecosystem Services
(Page 69)
Ecosystem services are the benefits experienced by organisms, including humans, that are provided by sustainable ecosystems.
Ecosystem services allow ecosystems to function, which is a requirement of sustainability.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

28. Ecosystem Services
(Page 69)
Ecosystem services are the natural result of all the activities that occur in the biosphere. They include:
the provision of food and clean water
the cycling of nutrients
the conversion of atmospheric carbon into biomass
the pollination of crops and natural vegetation
the balance of processes such as growth and decomposition
the provision of beauty and spirituality
Copyright © 2010 McGraw-Hill Ryerson Ltd.

29. The Influence of Forests on Climate
(Page 70)
Trees extract huge amounts of water from the soil that then escapes through the stomata, adding water vapour to the atmosphere. The water vapour helps reduce the temperature and form rain clouds.
Desertification is the change of non-desert land into desert; desertification may result from climate change or unsustainable farming or water use.
Watersheds, areas of land over which the run-off drains into a body of water, benefit from the existence of forests. Forest loss leads to increased run-off, which causes loss of soil and the nutrients in it.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

30. Insects and Ecosystem Services
(Page 70)
The majority of plants rely on animals to move pollen from one flower to another. Studies have shown that plant productivity is increased among natural and human-grown plants when pollinating animals are involved in the process of cross-pollination.
The best-known pollinators are honeybees.
Cross-pollination by insects could be responsible for aiding in the production of one-third of our foods such as vegetables, fruit, seeds, and spice crops and livestock.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

31. Insects and Decomposition
(Pages 72-3)
Decomposition is the breakdown of organic wastes and dead organisms. This fifth important type of ecological relationship allows the nutrients and energy locked up in dead organisms to be recycled.
Insects, bacteria, and fungi are the three main groups that serve as decomposers in ecosystems.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

32. Why are Honeybees Disappearing?
(Pages 72-3)
In recent years there has been a mysterious disappearance of honeybees from North American beehives. Although they are not sure, many scientists and beekeepers believe that the reduction is due to a combination of factors, including parasites, pesticide use, and beekeeping practices.
Given the important role that bees play in our food production, this is a problem that must be solved.
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33. The Role of Migratory Birds
(Page 74)
Migratory birds often feed on many of the flying insects we consider to be pests. Unfortunately, the populations of many of the aerial insectivore birds that breed in Canada have declined since the 1980s.
Habitat destruction or poorly regulated insecticide use in the tropical areas these birds migrate to each winter might be responsible for the decline in their numbers.
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34. Coffee Plantations and Canadian Birds
(Page 75)
Many Canadian songbirds winter in tropical ecosystems where coffee beans are grown. The practice of producing coffee in sunlit plantations such as the monoculture shown in image A provides less suitable habitat for birds. The practice of producing shade-grown coffee as shown in image B provides sustainable ecosystems for the birds.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

35. International Co-operation for Ecological Connectivity
(Pages 76-7)
Connectivity is the collection of links and relationships between ecosystems that are separated geographically. Governments have recognized that even ecosystems that are separated by large distances can affect each other’s sustainability. Co-operation between governments is important in maintaining this sustainability.
Copyright © 2010 McGraw-Hill Ryerson Ltd.

36. Ecotourism , Beauty , and Spirituality
(Pages 76-7)
Ecotourism is a form of tourism that is sensitive to the health of an ecosystem and involves recreational activities provided by sustainable ecosystems.
Many aboriginal peoples practice spiritual traditions that are connected to nature.
Artists have been, and will continue to be, inspired by ecosystems.
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37. Concepts to be reviewed:
Section 2.4 Review
(Page 78)
Concepts to be reviewed:
What are ecosystem services? How are they provided by species occupying their niches?
How do forests influence climate? How do they play a role in the regulation of watersheds?
How is the health of migratory birds affected by the ecosystems they visit?
What is ecological connectivity? How does it depend on international co-operation?
How do ecosystems provide visual beauty and spiritual appreciation to humans?
Copyright © 2010 McGraw-Hill Ryerson Ltd.