OPTION C.3 IMPACTS OF HUMANS ON ECOSYSTEMS

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1 OPTION C.3 IMPACTS OF HUMANS ON ECOSYSTEMS

2 INTRO IB BIO C.3 2 Many human activities affect ecosystems in many ways. Examples include: Introduction of invasive species Biomagnification Plastic pollution

3 C.3 A Invasive Species

4 IB BIO C.3 4 Understandings U1: Introduced alien species can escape into local ecosystems and become invasive. 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 Endemic Species Alien Species 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.

5 IB BIO C.3 5 Understandings U1: Introduced alien species can escape into local ecosystems and become invasive. 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. Invasive Species

6 IB BIO C.3 6 Species can become invasive if Understandings U1: Introduced alien species can escape into local ecosystems and become invasive. normal limiting factors are not present in the new environment. Factors that contribute include: Excess food/space availability Lack of predators Lack of disease Invasive Species Lack of competition Left: The snakehead fish originated in Asia and invaded many areas in the US.

7 IB BIO C.3 7 Understandings U1: Introduced alien species can escape into local ecosystems and become invasive. 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. Invasive Species

8 IB BIO C.3 8 Understandings U2: Competitive exclusion and the absence of predators can lead to reduction in the numbers of endemic species when alien species become invasive. Invasive Species 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.

9 IB BIO C.3 9 If an invasive species occupies a niche inhabited by an endemic Understandings U2: Competitive exclusion and the absence of predators can lead to reduction in the numbers of endemic species when alien species become invasive. species, competitive exclusion predicts that one species will prevail while the other migrates or dies out. Invasive Species This graph shows the population density of zebra mussels (invasive) and unionid mussels (endemic) in the Hudson river.

10 IB BIO C.3 10 Applications A1: Study of the cane toads in Australia and one other example of the an alien species. 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.

11 IB BIO C.3 11 Applications A1: Study of the cane toads in Australia and one other example of the an alien species. Case Study: Cane Toad However, cane toads have varied diet and are aggressive competitors for food. As a result, the population exploded and spread.

12 IB BIO C.3 12 Applications A1: Study of the cane toads in Australia and one other example of the an alien species. 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.

13 IB BIO C.3 13 Applications A1: Study of the cane toads in Australia and one other example of the an alien species. 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.

14 IB BIO C.3 14 Case Study: Zebra Mussel Applications A1: Study of the cane toads in Australia and one other example of the an alien species. 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.

15 IB BIO C.3 15 Case Study: Zebra Mussel Applications A1: Study of the cane toads in Australia and one other example of the an alien species. 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.

16 IB BIO C.3 16 Case Study: Zebra Mussel Applications A1: Study of the cane toads in Australia and one other example of the an alien species. 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.

17 IB BIO C.3 17 Skills S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species. 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.

18 IB BIO C.3 18 Skills S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species. 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 Eradiation Program Use of herbicides Harvesting plant species

19 IB BIO C.3 19 Skills S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species. 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. Eradiation Program

20 IB BIO C.3 20 Skills S2: Evaluation of the eradication programs and biological control as measures to reduce the impact of alien species. 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. Biological Control

21 REVIEW IB BIO C 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.

22 VIDEOS IB BIO C.3 TED-Ed: The Threat of Invasive Species 22 Epic Wildlife: 11 World s Worst Invasive Species Nat Geo WILD: Venomous Cane Toads