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TRANSCRIPT
OPTION C.3 – IMPACTS OF HUMANS ON ECOSYSTEMS
INTRO
IB BIO – C.3 2
https://i.ytimg.com/vi/nmhoOxrSCNY/maxresdefault.jpg
Many human activities affect
ecosystems in many ways.
Examples include:
• Introduction of invasive
species
• Biomagnification
• Plastic pollution
C.3 – A – Invasive Species
Understandings
U1: Introduced alien species can escape into local ecosystems and become invasive.
Key Terms
Endemic Species
AlienSpecies
IB BIO – C.3 4
https://en.wikipedia.org/wiki/European_rabbit#/media/File:Oryctolagus_cuniculus_Tasmania_2.jpg
Human activities can result in
species being introduced to new
areas that they did not previously
inhabit.
Species can be:
• Endemic - native to an area and
not introduced by humans
• Alien - NOT native to an area
and introduced by humans
The left photo shows the
European rabbit, which was
introduced to Australia by an
English farmer in 1859.
Understandings
U1: Introduced alien species can escape into local ecosystems and become invasive.
Key Terms
InvasiveSpecies
IB BIO – C.3 5
http://fullspectrumbiology.blogspot.com/2013/06/european-rabbits-australian-nightmare.html
Invasive species are alien species that are able to reproduce and
spread rapidly in a new area. For example, once in Australia the
European rabbit population grew exponentially, damaging crops.
Understandings
U1: Introduced alien species can escape into local ecosystems and become invasive.
Key Terms
InvasiveSpecies
IB BIO – C.3 6
https://i.ytimg.com/vi/oMPBukVALw0/maxresdefault.jpg
Species can become invasive if
normal limiting factors are not
present in the new environment.
Factors that contribute
include:
• Excess food/space availability
• Lack of predators
• Lack of disease
• Lack of competition
Left: The snakehead fish
originated in Asia and invaded
many areas in the US.
Understandings
U1: Introduced alien species can escape into local ecosystems and become invasive.
Key Terms
InvasiveSpecies
IB BIO – C.3 7
http://photos.invasiveswatch.org/salvinia%20molesta%201.jpg
Invasive species can have negative effects on their new ecosystem,
even resulting in the extinction of species. For example, S. molesta
covers the surface of lakes, killing native aquatic species below.
Understandings
U2: Competitive exclusion and the absence of predators can lead to reduction in the numbers of endemic species when alien species become invasive.
Key Terms
InvasiveSpecies
IB BIO – C.3 8
http://www.dfo-mpo.gc.ca/ae-ve/evaluations/16-17/img/6B139-graph2-eng.jpg
Alien species that are very reproductively successful and aggressive
can dominate the new ecosystem. Competitive exclusion and lack of
predators can lead to a reduction in the numbers of endemic species.
Understandings
U2: Competitive exclusion and the absence of predators can lead to reduction in the numbers of endemic species when alien species become invasive.
Key Terms
InvasiveSpecies
IB BIO – C.3 9If an invasive species occupies a niche inhabited by an endemic
species, competitive exclusion predicts that one species will prevail
while the other migrates or dies out.
This graph shows the population density of zebra mussels (invasive)
and unionid mussels (endemic) in the Hudson river.http://www.caryinstitute.org/sites/default/files/public/images/lesson-plan/unionid_zm_graph.png
Applications
A1: Study of the introduction of cane toads in Australia and one other example of the introduction of an alien species.
Key Terms
IB BIO – C.3 10
https://images.theconversation.com/files/142469/original/image-20161020-8852-waskh3.jpg
Case Study: Cane Toad
Cane toads were introduced in Australia as a method of controlling
the cane beetle population. It was native to Central & South America.
Applications
A1: Study of the introduction of cane toads in Australia and one other example of the introduction of an alien species.
Key Terms
IB BIO – C.3 11
https://imgur.com/GnS1fSm
Case Study: Cane Toad
However, cane toads have varied diet and are aggressive competitors
for food. As a result, the population exploded and spread.
Applications
A1: Study of the introduction of cane toads in Australia and one other example of the introduction of an alien species.
Key Terms
IB BIO – C.3 12
https://pbs.twimg.com/media/DUqp-rfVQAENhXu.jpg
Case Study: Cane Toad
However, cane toads have varied diet and are aggressive competitors
for food. As a result, the population exploded and spread.
The map to the left shows the
predicted range of cane toads
based on their access to water
points.
The toads were initially
introduced in the North West
region.
Applications
A1: Study of the introduction of cane toads in Australia and one other example of the introduction of an alien species.
Key Terms
IB BIO – C.3 13
https://pbs.twimg.com/media/DUqp-rfVQAENhXu.jpg
Case Study: Cane Toad
Their largest effect is on their predators. Cane toads have glands that
produce toxins and so are lethal to many species that consume them.
http://detk34b2vej48ehj51qbb541.wpengine.netdna-cdn.com/wp-content/uploads/2016/06/ZEBRA-MUSSELS-e1464906584985.jpg
Applications
A1: Study of the introduction of cane toads in Australia and one other example of the introduction of an alien species.
Key Terms
IB BIO – C.3 14Case Study: Zebra Mussel
Zebra mussels are native to the Caspian Sea. In the 1980’s they
were carried to the Great Lakes in the ballast water of ships.
https://nas.er.usgs.gov/UserImages/current_zm_quag_map.jpg
Applications
A1: Study of the introduction of cane toads in Australia and one other example of the introduction of an alien species.
Key Terms
IB BIO – C.3 15Case Study: Zebra Mussel
The mussels attach and form colonies on hard surfaces just below the
water line. They are also able to survive out of water and spread
from one body of water to another.
http://ww2.kqed.org/science/wp-content/uploads/sites/35/2014/07/Quagga_fouled_outdrive.jpg
Applications
A1: Study of the introduction of cane toads in Australia and one other example of the introduction of an alien species.
Key Terms
IB BIO – C.3 16Case Study: Zebra Mussel
Impacts of growing populations
include:
• They attach to boat motors and
hulls, which reduces efficiency.
• They clog irrigation intakes and
other pipes.
• Mussels eat tiny food particles
by filtering water. This reduces
food available for other aquatic
animals.
• They can attach to and smother
native mussels.
Skills
S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species.
Key Terms
IB BIO – C.3 17
https://commons.wikimedia.org/wiki/File:Candlebush_(Senna_alata)_invasive_species_from_Mexico_..._(23007468340).jpg
The impacts of invasive species
can be reduced in a variety of
ways that aim to prevent
populations from growing.
Two approaches include:
• Eradication programs
• Biological controls
Left: Candlebush is native to
Mexico and invasive in the wilds
of Florida.
Skills
S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species.
Key Terms
Eradiation Program
IB BIO – C.3 18
https://www.treefarmsystem.org/stuff/contentmgr/files/1/81fc27573a416ecdeb3d620b07a58878/files/picture1.jpg
Eradication programs involves
efforts that artificially reduce the
invasive species population.
Programs aim to reduce the
population size faster than the
members reproduce.
Methods can include:
• Trapping and culling of
animals
• Use of herbicides
• Harvesting plant species
Skills
S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species.
Key Terms
Eradiation Program
IB BIO – C.3 19
https://modernfarmer.com/2013/09/killing-goats-galapagos/
For example, in the Galapagos Islands feral goats were eradicated
by hunting. They had spread across the islands and were
overgrazing, which threatened native Galapagos species.
Skills
S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species.
Key Terms
Biological Control
IB BIO – C.3 20
http://www.bates.edu/biology/2015/03/12/invasive-zebra-mussels-and-alligatorweed/
Biological controls aim to control invasive species by introducing a
predator. For example, South American insects were released to
control alligator weed that had infested >80% of Florida waters.
REVIE
WIB BIO – C.3 21
1. Differentiate between endemic and alien species.
2. Define invasive species.
3. List three factors that could lead to a species
becoming invasive.
4. Outline possible effects of invasive species on an
ecosystem.
5. Discuss one real-world example of an invasive
species.
6. Outline the use of eradication programs and
biological controls in reducing impacts of alien
species.
VID
EO
SIB BIO – C.3 22
• TED-Ed: The Threat of Invasive Specieshttps://www.youtube.com/watch?v=spTWwqVP_2s
• Epic Wildlife: 11 World’s Worst Invasive Specieshttps://www.youtube.com/watch?v=yqLkSHlf5DE
• Nat Geo WILD: Venomous Cane Toadshttps://www.youtube.com/watch?v=rI8IiLqIEV0