Transcript Ch.3 Ecology

3.1 How Changes Occur Naturally
in Ecosystems
• When an organism is born, it belongs to a species,
but it also is born with unique characteristics.
 Like humans with different coloured eyes and different heights.
 Sometimes, these unique characteristics give that individual an advantage
within their niche. ie, a salmon with a slightly larger tail may be able to swim a
little faster or a little farther in a river.
• Natural selection is the process where
individuals with advantages are better able
to reproduce and pass along their traits.
 Those with unfavourable characteristics have
less chance to reproduce and pass along their traits.
 A salmon with a smaller tail may never have a chance
to spawn because it can’t swim to the correct location.
See pages 108 - 109
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How Organisms Adapt to Change
• The Galapagos Islands, off the coast of Ecuador, are perhaps the
most famous example of natural selection.
 Many species on these islands are very similar to each other,
and also to species on the South American continent.
 There are thirteen species of finch on the islands.
 Each is descended from a finch species from the mainland.
 Each species has very unique characteristics that allows
them to thrive in their own niche, and not compete with
other finches for resources.
Galapagos
finches
• Adaptive radiation is the term for this type of
natural selection.
 Many different species appear from one original species.
See page 110
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Adaptive radiation
• Darwin’s finches on the left.
• Ancestors of an ancient dinosaur on the right.
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How Ecosystems Change Over Time:
Primary Succession
•
Ecological succession refers to the changes in the biotic
characteristics in an area over time.
 Over time, the life in an area changes
 There are two types of ecological succession:
primary succession and secondary succession.
1. Primary succession - begins with nothing but bare rock
 Where glaciers scrape away dirt, or a volcano erupts
 Wind carries spores of lichens and organisms that can survive and eventually,
combined with the weathering of rock, help form soil.
 The first organisms to survive and reproduce are pioneer species.
 Pioneer species alter the abiotic and biotic environment in some way.
 Soil improves, plants are able to grow, animals begin to appear.
 Primary succession occurs in this way in all parts of the world.
 This stage can last for hundreds of years,
See pages 111 - 113
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until a mature community eventually forms.
How Ecosystems Change Over Time:
Secondary Succession
•
Mature communities are very stable, and can appear
to be unchanging over long periods of time.
 These are also known as climax communities, but “mature” correctly implies
that there are still changes occurring, albeit more slowly.
2. Secondary succession - after a major disturbance in an area that
already has soil and once had living organisms.
 Forest fires are the most common reason for secondary succession.
 The soil remains for plant growth, and contains
seeds, micro-organisms, earthworms and insects.
 Secondary succession is much more rapid than
primary succession.
 There is already soil, seeds and insects, so it
only lasts decades.
See page 114
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How Natural Events Affect Ecosystems
• Many other disturbances can affect mature communities.
• Flooding
 Water is not contained within natural or artificial barriers.
 Generally occurs in locations where water levels can change rapidly.
 It can result in soil erosion, as well as the spread of pollutants and harmful
bacteria associated with wastes.
 Climate change and global warming may be increasing incidents of flooding.
 A tsunami occurs when huge waves, from large earthquakes or volcanic
eruptions, floods coastal areas.
• Drought
 Occurs when an area receives a lower than average amount of rainfall over a
very long period of time.
 Prolonged drought can have severe effects on organisms.
See pages 115 - 116
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How Natural Events Affect Ecosystems
(continued)
• Insect infestations
 Many insects play important roles in their ecosystems.
 Even insects that appear destructive, such as the
mountain pine beetle, actually play a role in the
renewal of the forest.
 The beetles even have a symbiotic relationship with a species of fungus that
inhibits the trees’ ability to use resin for protection.
 However, when normal conditions are changed, infestations can occur.
 Trees can be stressed from overcrowding, drought or animal grazing, and do not
resist the insects as effectively.
 A warmer climate, and lack of forest fires, allows the insects to spread much
more effectively than in the past.
 Not only are the trees affected, but so is the entire forest ecosystem, as well as any
human industries relying on the forest.
See page 117
Take the Section 3.1 Quiz
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3.2 How Humans Influence Ecosystems
• Wetlands are special ecosystems that contain completely waterlogged soil for long
periods of time.
 Not only do wetlands contain high biodiversity, but they also filter many impurities out
of the water that slowly flows through them.
 For this reason, they are sometimes called the “kidneys” of the Earth.
 Because they hold large amounts of water, they can help prevent flooding.
• Human encroachment has caused many
BC wetlands to disappear.
 In the past 100 years:
 Up to 70% of the wetlands in the lower
Fraser Valley have been lost.
 Up to 85% of the wetlands in the South
Okanagan have been lost.
Wetlands are vital ecological
features in British Columbia.
See pages 122 - 123
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Understanding Sustainability
• “Sustainability” is a word that is used often, and can be defined in
more than one way:
 “The ability for an ecosystem to sustain ecological processes”.
 These processes enable biodiversity and keep the ecosystem healthy.
 “People using an ecosystem to meet their needs today without reducing the
function or health of the ecosystem in the future”.
 Sustainable practices maintain, or even improve, healthy ecosystems.
 Economic opportunity, biodiversity and ecosystem health are all possible.
Returning young coho salmon
to rivers near Port Alice can
help maintain sustainability.
See page 125
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The Effects of Land and Resource Use
• “Land use” refers to how humans use land around us for urban
development, agriculture, industry, mining and forestry.
 All of the land around us, even in cities, was once a part of an ecosystem.
• “Resource use” refers to the ways we obtain and use naturally
occurring materials.
 Most products you use every day involve the use of some natural resources in
their production.
• If the land and resources are not used directly, they are often
processed and exported to other places for use.
The processing and export of resources like
lumber, coal and sulphur are very important
to BC’s current economy.
See page 126
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Habitat Loss
• The use of land and resources have seen humans encroach on
natural ecosystems very aggressively in the past 150 years.
 As a result of this expansion, habitats have been lost or fragmented.
 “Habitat loss” refers to to loss of habitats due to human activities.
 “Habitat fragmentation” is the splitting of large habitats into many smaller
ones, resulting in disrupted natural activities for plants and animals.
Habitat loss (left) and habitat fragmentation (right)
reveal the effects of human activities on ecosystems.
See page 126
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Habitat Loss (continued)
See page 127
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The Effects of Deforestation
• Deforestation is the clearing or logging of forests for human use.
 The resulting barren land is never reclaimed or replanted.
 The agricultural crops that are planted are often one species = monoculture
 This reduces biodiversity, and leaves the crop vulnerable to pests or disease.
 Polycultures, of many plant species, are more economically and biologically
diverse.
 Deforestation is still occurring in many tropical rainforests.
 Deforestation results in soil degradation.
 Soil degradation is when moving wind and water
erode topsoil and leave bare land behind.
 Topsoil, the upper layer of soil, is where most
of the nutrients, water and air are found
for plant growth.
See page 128
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The Effects of Agriculture
• If fields are left exposed during non-planting seasons,
water and wind erosion can occur.
• In areas like southwestern BC, the soil can become compacted.
 Soil particles are squeezed together and become compacted.
 This is due to farm animals or vehicles.
 There is no room for water or air to enter the soil.
 Water then runs off the soil instead of soaking in.
Farm animals, such as these
cows, can compact soils.
 Loss of water, increased erosion and the addition
of farm fertilizers and pesticides to the ecosystem.
 Aeration, which involves removing small plugs of soil,
loosens soils and can reduce run-off.
See page 129
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The Effects of Resource Exploitation
•
Resource exploitation = resource use



Humans depend on resource exploitation for jobs,
materials, food, shelter and energy.
Exploitation can lead to habitat loss, soil degradation
and contamination of water supplies.
 Contamination is the introduction of harmful
chemicals or micro-organisms into the environment.
 Many mining and resource exploitations require reclamation efforts.
• Reclamation attempts to reduce environmental impacts of exploitation, and
tries to restore the original (or at least functional) habitats.
Overexploitation is the extraction of resources until they are gone.
 This can result in extinction, such as with the passenger pigeon.
 Food webs can be greatly affected over long periods of time
 The overexploited species could be a keystone species.
See pages 130 - 132
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Resource Management and Traditional
Ecological Knowledge
• In Aboriginal cultures, traditional ecological knowledge is passed
down from generation to generation.
 This knowledge reveals what past condition were like, and also how the
ecosystem and humans interact.
 Knowledge is found in stories, songs, cultural beliefs, rituals, community laws
and traditional practices.
 Current ecological restoration and usage guidelines often involve this
traditional knowledge from Aboriginal representatives.
 Traditions such as the “Spring burn” allow
for ecological renewal.
 Fire suppression, enforced in BC for over
100 years, has led to recent issues like the
mountain pine beetle infestation and huge
wildfire losses.
See pages 133 - 134
Take the Section 3.2 Quiz
(c) McGraw Hill Ryerson 2007
Understanding Sustainability
• “Sustainability” is a word that is used often, and can be defined in
more than one way:
 “The ability for an ecosystem to sustain ecological processes”.
 These processes enable biodiversity and keep the ecosystem healthy.
 “People using an ecosystem to meet their needs today without reducing the
function or health of the ecosystem in the future”.
 Sustainable practices maintain, or even improve, healthy ecosystems.
 Economic opportunity, biodiversity and ecosystem health are all possible.
Who is this player?
See pages 8 - 9
Take the Section 8.1 Quiz
(c) McGraw Hill Ryerson 2007
Understanding Sustainability
• “Sustainability” is a word that is used often, and can be defined in
more than one way:
 “The ability for an ecosystem to sustain ecological processes”.
 These processes enable biodiversity and keep the ecosystem healthy.
 “People using an ecosystem to meet their needs today without reducing the
function or health of the ecosystem in the future”.
 Sustainable practices maintain, or even improve, healthy ecosystems.
 Economic opportunity, biodiversity and ecosystem health are all possible.
Who is this player?
See pages 8 - 9
Take the Section 8.1 Quiz
(c) McGraw Hill Ryerson 2007
3.3 How Introduced Species
Affect Ecosystems
• Native species are plants and animals that naturally inhabit an area.
 Because of the immigration to North America by many people from other
continents over the past 400 years, many new species have been introduced
accidentally (and on purpose) here.
 These new species of plants and animals are called introduced species
• Aka foreign species, non-native species, exotic species or alien species.
• Many of these species are harmless, or sometimes even beneficial.
 An invasive species, such as Purple Loosestrife, negatively impacts native
species, and often reduces biodiversity as a result.
The
European
leaf-feeding
beetle (left),
and the
Purple
Loosestrife.
See pages 138 - 139
(c) McGraw Hill Ryerson 2007
The Impact of Introduced Species
• Invasive species often take advantage of their new habitat.
 They may have no predators, are aggressive competitors, and reproduce fast.
 Competition: while the native species have an established balance, the
invasive species can throw off this balance.
 Predation: if the invasive species is a predator, it may
The sea lamprey
have a huge advantage, as the native species may have
no methods to survive.
 Disease and Parasitism: by weakening certain species,
a micro-organism invading an ecosystem can drastically
alter the entire ecosystem and the niches within it.
 Habitat Alteration: some invasive species can change
the physical structure of the ecosystem by digging,
burrowing, blocking sunlight or changing the
chemistry of the ecosystem.
See pages 140 - 141
(c) McGraw Hill Ryerson 2007
Invasive Species in British Columbia
See page 142
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Saving an Ecosystem Under Siege
• It often takes human intervention to save established ecosystems.
 The Garry Oak Ecosystem Recovery Team (GOERT) is trying to save several
areas of the Garry Oak ecosystem in BC.
 95% of the original ecosystem has been lost to urban development, and the
remaining 5% is threatened by invasive species.
 Garry Oak trees are a keystone species.
 Scotch broom, English ivy and other
plant species are its biggest threats.
• GOERT has representatives from many groups.
 The BC government, First Nations, conservationists,
scientists and businesses believe this work is critical.
 Garry Oak forests may be better suited to survive in
the future than Douglas fir forests.
See page 143
Take the Section 3.3 Quiz
(c) McGraw Hill Ryerson 2007