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

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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

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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

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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

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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

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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

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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