1. Human activities can negatively impact ecosystem function by introducing invasive alien species, polluting the environment, and accumulating plastic debris. 2. Case studies show how invasive cane toads in Australia and zebra mussels in North America outcompeted native species. Pollutants like DDT biomagnify up food chains and accumulate in top predators, thinning bird eggshells. 3. Large amounts of plastic debris, especially microplastics consumed by zooplankton, harm marine environments. A study found 40% of Laysan albatross chicks died from ingesting plastic trash mistook for food.

1. C.3 Impacts of humans on ecosystems
Essential idea: Human activities impact on ecosystem function.

2. Understandings, Applications and Skills
Statement Guidance
C.3 U.1 Introduced alien species can escape into local ecosystems and become
invasive.
C.3 U.2 Competitive exclusion and the absence of predators can lead to
reduction in the numbers of endemic species when alien species become
invasive.
C.3 U.3 Pollutants become concentrated in the tissues of organisms at higher
trophic levels by biomagnification.
C.3 U.4 Macroplastic and microplastic debris has accumulated in marine
environments.
C.3 A.1 Study of the introduction of cane toads in Australia and one other local
example of the introduction of an alien species.
C.3 A.2 Discussion of the trade-off between control of the malarial parasite and
DDT pollution.
C.3 A.3 Case study of the impact of marine plastic debris on Laysan albatrosses
and one other named species.
C.3 S.1 Analysis of data illustrating the causes and consequences of
biomagnification.
C.3 S.2 Evaluation of eradication programmes and biological control as measures
to reduce the impact of alien species.

3. What Are Native Species?
• Native species are those that normally live and thrive in a particular community.
They occupy specific habitats and have specific niches in their native environment.
They have natural predators that help to keep their populations in check.
What Are Non-Native Species?
Species that migrate into an ecosystem or are deliberately or accidentally
introduced into an ecosystem by humans.
C.3 U.1 Introduced alien species can escape into local ecosystems and
become invasive.

4. • Competitive Exclusion Principle – complete competitors cannot
coexist.
– One species must be displaced or go to extinction
• Fundamental niche – the set of resources a species can utilize in the
absence of competition and other biotic interactions.
• Realized niche – the observed resource use of a species in the presence
of competition.
– Realized niche may be found on the edge of the fundamental niche as a
result of competitive exclusion
• Does competitive exclusion occur in natural communities?
What are Invasive Species?
• A species introduced into an environment that is
able to outcompete and displace the native
species
C.3 U2 Competitive exclusion and the absence of predators can lead to reduction in
the numbers of endemic species when alien species become invasive.

5. Competition for a Niche in Nature
• Competition in nature is rare
• Competition has been very common throughout the evolutionary history of
communities and has resulted in adaptations that serve to minimize competitive
effects
– Species have evolved to reduce competition
• We currently see the results of competition
• Invasive species?
Species can live together
Species may be driven to
extinction, change habitats, or
evolve feeding differences.
Some resources are not being
used, and a benefit can be gained
by utilizing that resource.
C.3 U2 Competitive exclusion and the absence of predators can lead to reduction in
the numbers of endemic species when alien species become invasive.

6. C.3 U.2 Competitive exclusion and the absence of predators can lead to reduction in
the numbers of endemic species when alien species become invasive.
• The Cane Toad (Rhinella marinus) is an invasive species in Australia and other parts of
the world to control agricultural crop pests on sugar cane.
• Largest of the Bufonidae family at 4 lbs., with a length of up to 9 in. They reproduce in
large numbers, secrets toxic material from there skin and will eat just about anything.
• Some effects long term effect on Australian environment are:
 the depletion of native species that die eating cane toads
 poisoning of pets and humans
 depletion of native fauna preyed on by cane toads
 reduced prey populations for native insectivores.

7. C.3 A.1 Study of the introduction of cane toads in Australia and one other local
example of the introduction of an alien species.
Example of Alien Species invasion:
Zebra Mussels
• Small “D”-shaped clams
• Dark brown and white stripes
• Native to Caspian and Black seas.
• Arrived in the Great Lakes in 1980’s
in freshwater ballast of ships

8. C.3 A.1 Study of the introduction of cane toads in Australia and one other local
example of the introduction of an alien species.
• Damage ecology of lakes
and rivers
• Colonize in thick mats on
docks, boats, motors
and submerged rocks
• Killed native mussels
• Foul beaches with sharp
shells and pungent odor
• Compete with fish for
food
• Clog water supply pipes
and boa engines

9. Controlling Invasive Species
• Controlling invasive species once they have become established is
difficult.
• Control is also usually very expensive!
• There are four main ways that invasive species are controlled:
– Physical control
– Chemical control
– Biological control
– Prevention
C.3 S.2 Evaluation of eradication programs and biological control as measures to
reduce the impact of alien species.
The Impact of Invasive Species
Ecological:
• Reduce native biodiversity
• Direct predation on local species
• Spread of disease
• Upset balance of local ecosystem

10. Chemical Control of Invasive Species
• Chemical control involves
applying poison to eliminate
invasive species
• E.g. Eradication of rats on
Henderson Island
– Use rodenticide (rat poison)
• Insecticides & pesticides
to control insect pests
• Herbicides (weed-killer)
to control plants
Biological Control of Invasive Species
• Uses a living organism to control
invasive species
• This organism may eat the invasive
species or cause it to become
diseased
• Biological control agents must be
carefully assessed before release to
ensure the control species will not
become invasive itself
Physical Control of Invasive Species
Controlling plants:
• Mechanical – excavation, trimming,
etc.
• Removal of plants by hand
• Installation of growth barriers
Controlling animals:
• Culling
• Trapping and hunting
• Putting up barriers or fences
C.3 S.2 Evaluation of eradication programs and biological control as measures to
reduce the impact of alien species.

11. Biotechnology
• Blocking conception in rabbits –
called immunocontraception
• Single sex in offspring for carp – to
only produce male offspring
No functional gene -> no enzyme ->
no females!
As existing females in the population
die, each successive generation
will have fewer and fewer
females, until only males.
C.3 S.2 Evaluation of eradication programs and biological control as
measures to reduce the impact of alien species.

12. 1. Soil tainted with pesticides
washes into a river system where
it enters the bodies of
zooplankton
2. A hundred of these small
organisms are eaten by one small
fish
C.3 U.3 Pollutants become concentrated in the tissues of organisms at higher trophic
levels by biomagnification.
Biomagnification is a process in which
chemical substances become more
concentrated at each trophic level. DDT,
dioxins, pesticides, TBT and mercury are all
examples of highly toxic chemicals that are
biomagnified.

13. C.3 U.3 Pollutants become concentrated in the tissues of organisms at higher trophic
levels by biomagnification.
1. Soil tainted with pesticides
washes into a river system
where it enters the bodies
of zooplankton
2. A hundred of these small
organisms are eaten by one
small fish
3. A hundred of these small
fish are eaten by one large
fish
Biomagnification of DDT
Cause: DDT is a synthetic pesticide sprayed on crops and can be used against malaria
Mosquitoes . It is washed into waterways in low concentrations, where it is biomagnified
up the food chain. It is highly toxic at high concentrations

14. C.3 U.3 Pollutants become concentrated in the tissues of organisms at higher trophic
levels by biomagnification.
1. Soil tainted with pesticides
washes into a river system
where it enters the bodies of
zooplankton
2. A hundred of these small
organisms are eaten by one
small fish
3. A hundred of these small fish
are eaten by one large fish
4. A predatory bird eats 10
large fish
Consequences: Store in fats and accumulates quickly. Very high concentrations in large
Fish and seabirds. It is responsible for reduced reproductive function and shells thinning in
birds, which has impacted populations of large birds of prey (e.g. bald eagle or osprey) heavily.
In humans, it has been linked with cancers, fertility and development problems in humans.

15. C.3 S.1 Analysis of data illustrating the causes and consequences of biomagnification.
Analysis questions:
1. Describe the trend shown by the
data.
2. Deduce the strength of the
correlation
3. Evaluate the limitations of the
data in supporting the link
between DDT and the decrease in
Osprey.
http://fresc.usgs.gov/products/papers/2345_Henny.pdf
Biomagnification of DDT
effect on
Osprey (Pandion haliaetus):
http://fresc.usgs.gov/products/paper
s/2345_Henny.pdf

16. C.3 S.1 Analysis of data illustrating the causes and consequences of biomagnification.
Analysis questions:
4. Describe the trend
shown by the data in
relation to the use of
DDT
5. Estimate the
percentage change in
egg shell thickness
between 1972 and
2008
6. Suggest why the range
of egg shell thickness
increased after 1972.
http://fresc.usgs.gov/products/papers/2345_Henny.pdf

17. C.3 S.1 Analysis of data illustrating the causes and consequences of biomagnification.
Analysis questions:
7. Describe the correlation between DDE and egg shell thickness.
8. Evaluate the limitations of the data supporting the link between DDT and egg shell
thickness in Osprey.
9. Explain why egg shell thickness is correlated with sightings of Osprey
http://fresc.usgs.gov/products/papers/2345_Henny.pdf

18. C.3 A.2 Discussion of the trade-off between control of the malarial parasite and DDT pollution.
Sources of DDT
• DDT in soil can be absorbed by some growing plants and by the animals or people who eat those
plants
• DDT in water is absorbed by fish and shellfish in those waterways
• Atmospheric deposition
• Soil and sediment runoff
• Improper use and disposal
http://www.epa.gov/pbt/pubs/ddt.htm
What is DDT (dichlorodiphenyltrichloroethane)?
Prior to 1972 when its use was banned (in the US), DDT was a commonly used
pesticide.
What is it used for now?
Some parts of the world continue to use DDT in disease-control programs.
Why Are We Concerned About DDT?
Even though DDT has been banned since 1972, it can take more than 15 years to break down in our
environment.
What harmful effects can DDT have on us?
• Human carcinogen (e.g. liver cancer)
• Damages the liver
• Temporarily damages the nervous system
(damages developing brains)
• Reduces reproductive success (lower fertility and
genital birth defects)
• Damages reproductive system
How are we exposed to DDT?
• By eating contaminated fish and shellfish
• Infants may be exposed through breast milk
• By eating imported food directly exposed to
DDT
• By eating crops grown in contaminated soil

19. C.3 A.2 Discussion of the trade-off between control of the malarial parasite
and DDT pollution.
http://www.npr.org/templates/story/story.php?storyId=6083944
http://www.scientificamerican.com/article/ddt-use-to-combat-malaria/
http://www.telegraph.co.uk/news/science/science-news/10600234/Banned-pesticide-DDT-may-raise-risk-of-
Alzheimers-disease.html

20. C.3 A.2 Discussion of the trade-off between control of the malarial parasite
and DDT pollution.
Pros Cons
• Affordable and effective at killing
mosquitoes that carry malaria
• It is sprayed inside homes and
buildings and people exposed may
suffer serious health effects (inc.
reduced fertility, genital birth
defects, cancer and damage to
developing brains)
• Where the use of DDT was
discontinued for malaria vector
control malarial rates and deaths
increased.
• Alternative strategies were not as
successful.
• Persists in the environment for long
periods of time (more than 15 years)
• Health costs (of treating malaria)
greatly reduced

21. C.3 U.4 Macroplastic and microplastic debris has accumulated in marine
environments.
The “Little Blue Dot”
 Our Planet is made up of
70% water.
 There Is
326,000,000,000,000,000,
000 gallons (326 million
trillion gallons of water on
the Earth).
 96% of water on the Earth
is ocean water

22. C.3 U.4 Macroplastic and microplastic debris has accumulated in marine
environments.

23. Facts on Ocean Pollution
 Fourteen billion pounds of
garbage, mostly plastic, is
dumped into the ocean every
year
 Over 80% of the pollution in the
ocean is runoff from the Land
 Almost 90% of all floating
materials in the ocean are plastic
 Marine debris, especially plastic,
kills more than one million
seabirds and 100,000 mammals
and sea turtles every year
 Dead Zones which are areas of
oxygen deficient water were life
ceases to exist, have increased
drastically over the past decade.
C.3 U.4 Macroplastic and microplastic debris has accumulated in marine
environments.

24. C.3 U.4 Macroplastic and microplastic debris has accumulated in marine
environments.
• Large visible plastic
debris > 1mm (e.g.
bottles, nets, bags,
buoys) is defined as
Macroplastic

25. C.3 U.4 Macroplastic and microplastic debris has accumulated in marine
environments.
• Plastic debris < 1mm is defined as Microplastic
< 1mm. It is harder to see but it is estimated to
account for 65% of all ocean debris
Sources include:
 plastic bottles and bags
 detergent containers
 food wrapping
 synthetic clothes (fibers released after every
wash)
• Most plastics are not biodegradable and may
persist for centuries.

26. C.3 A.3 Case study of the impact of marine plastic debris on Laysan
albatrosses and one other named species.
• Bits of plastic debris litter the shore:
bottle caps, toys, cigarette lighters,
fishing line and other garbage.
• Plastic trash leaves a wake of death
and disease that directly affects
seabirds.
• In many areas of the globe, birds
inadvertently feed on plastic floating
on the water, mistaking it for food
• A report by scientists studying the
stomach content of Laysan Albatross
chicks on Midway Atoll in the Pacific
Ocean revealed disturbing results:
Forty percent of Laysan Albatross
chicks die before fledging.

27. C.3 A.3 Case study of the impact of marine plastic debris on Laysan albatrosses
and one other named species.
Zooplankton:
• Typically these tiny animals are found near the
surface in aquatic environments. Usually weak
swimmers and usually just drift along with the
currents .
• Zooplankton are at the bottom of a food chain for
an entire food web stretching from the smallest fish
to the largest whale. Many of the ocean's largest
animals feed on zooplankton. When they ingest
zooplankton they are ingesting plastic with them.
• Microbeads are nano-size plastic fragments which
are easily absorbed by sea life from plankton, which
are then eaten and remain in the food chain in
larger fish - and even humans.
• Some lab tests have shown that these fragments
can even enter cells and cause tissue damage.
Read more: http://www.dailymail.co.uk/sciencetech/article-3330671/The-hidden-
PLASTIC-lurking-food-Hundreds-tiny-micro-beads-sea-salt-swallow-1-000-
year.html#ixzz3trsizOkl

28. Bibliography / Acknowledgments