IB DP Biology Option C-3 Impacts of Humans on Ecosystems

1. Option C.3 Impacts of Humans on Ecosystems
IB Biology
R. Price
v. 1 2015

2. Allott 625

3. #1: Introduced alien species can escape into local ecosystems and
become invasive
• Endemic organism = native. Part
of a food web.
• Alien = introduced. If survives,
may take over.
• Compete with native species. Can’t have
two organisms in same niche
• May not have a predator in new location
• Introduction may be accidental,
intentional, or a form of
biological control

4. Accidental Introduction: Zebra Mussels
Intentional Introduction: Japanese Knotweed
Pest Control Introduction: PR Cane Toad

5. #2: Competitive exclusion and the absence of predators can lead to
reduction in the numbers of endemic species when alien species
become invasive
Competitive Exclusion:
• Alien species can be
reproductively successful
• May dominate ecosystem
• Two species with overlapping
niches cannot continue
occupying same niches

7. Puerto Rican Cane Toad
- Introduced: Queensland, Australia (1935)
- Job: Eat Sugar Cane Beetles
- Evaluation : DISASTER
Sugar Cane Beetle

8. .
Scolia ruficornis (Scoliidae)
- Introduced: Thailand (1963)
- Job: Eat Coconut Rhinocerous Beetle
- Evaluation : SUCCESS
http://www.agnet.org/library.php?func=view&id=20110718163847
Coconut Rhinocerous Beetle
(accidental introduction: rubber
trees import)

9. Allott 627

10. Allott 627, 628

11. Allott 628

12. Allott 628

13. Allott 629

14. Allott 629

15. #3: Pollutants become concentrated in the tissues of organisms at
higher trophic levels by biomagnification
Bioaccumulation
• Some toxins not excreted easily
• Some toxins are fat-soluble
• These toxins build up in the body
Biomagnification
• Toxins become more concentrated
at each trophic level
• Each stage in food chain, consume
large quantities of prey
Bioaccumulation + Biomagnification

16. Allot 631

17. Allott 631

18. Allott 632

19. Allott 632

20. Allott 633

21. #4: Macroplastic and microplastic debris has accumulated in marine
environments
Macroplastic & microplastic debris is mostly
from liter blown into water systems
Consequences:
• Degraded plastic releases chemicals into
ocean (bioaccumulate & biomagnify)
• Plastic absorbs other chemicals &
concentrates those toxins
• Animals eat or become tangled
Enormous “islands” of garbage around the
globe called gyres.

22. Allott 634

23. Allott 635

24. Sources
Content
Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014
ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.
Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge:
Cambridge UP, 2014. Print.
Images
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