1. Watch this Video

2. Study this Summary

Human Impacts on Biodiversity

Humans are driving a sixth mass extinction through various activities that are reducing biodiversity and pushing species toward extinction.
In recent years, extinction rates have risen to 1000 times beyond the background rate of extinction.

The Extinction Vortex

Small, isolated populations are especially vulnerable due to genetic drift and inbreeding, which decrease genetic diversity, lower adaptability, and create a vicious cycle of declining population size.

Major Causes of Biodiversity Loss

1. Habitat Alteration and Destruction

Urban development, agriculture, and infrastructure projects replace natural habitats with cities, fields, and roads.
These modifications reduce available space for native species, leading to population declines and extinction.
Habitat destruction and degradation is the number 1 cause of biodiversity loss on Earth today.

2. Overexploitation

Unsustainable hunting, fishing, and harvesting have led to species extinctions and population crashes.
Examples of animals that have suffered from over exploitation or overhunting include
- Tasmanian wolf (extinct)
- Passenger pigeon (extinct)
- the American bison (nearly extinct)

3. Habitat Fragmentation

Large, continuous habitats are divided by roads and human developments, creating isolated populations.
Fragmentation increases edge habitat, which has different environmental conditions that may not support species adapted to the environment in the habitat’s interior. .
Small, disconnected populations are more vulnerable to genetic bottlenecks and loss of adaptability.

4. Introduction of Invasive Species

Invasive species are those that 1) are not native to an ecosystem, 2) spread rapidly and persistently once introduced into an ecosystem, and 3) cause ecosystem disruption.
Invasive species 1) have high reproductive rates, 2) can tolerate a wide range of environmental conditions, and 3) have a generalist ecological niche.
Once introduced into a new area, invasive species are freed from the controlling forces such as predators or competitors they faced in their native environment.
With these controls gone, invasive species often expand exponentially, out-competing native species, destroying an ecosystem’s resource base, and spreading diseases (through the parasites that they might carry).
A disease-causing fungus is responsible to an ongoing mass die-off of amphibians.

5. Deforestation

Cutting down forests, particularly tropical rainforests, destroys some of the most biodiverse ecosystems on the planet.
Deforestation leads to habitat loss, disruption of ecological processes, and increased carbon emissions.

6. Climate Change

Alteration of climate is changing the conditions in various ecosystems at a rate that exceeds the ability of species within those ecosystems to adapt.
It’s also changing the geographical range of species, often pushing them further north in the northern hemisphere, or further south in the southern hemisphere.
This is pushing many species, already stressed, to the point of extinction.

3. Master these Flashcards

[qdeck bold_text=”false” qrecord_id=”sciencemusicvideosMeister1961-Ecosystem Disruption Flashcards, APBioVideoPath”]

[h]Ecosystem Disruption

[i]

The worldwide amphibian decline has been linked to an invasive fungus and habitat degradation.

[q json=”true” yy=”4″ dataset_id=”AP_Bio_Flashcards_2022|1073c8eba6110″ question_number=”423″ unit=”8.Ecology” topic=”8.7.Disruptions_to_Ecosystems”] How bad is the current extinction crisis? List some of the major things that humans are doing that are causing the current extinction crisis.

[a] In recent years, extinction rates have risen to 1000 times beyond the background rate of extinction. These extinctions have been caused by human activities, including 1) habitat destruction and fragmentation, 2) introduction of invasive species, 3) introduction of disease-causing organisms, 4) overhunting and overharvesting wild species, 5) deforestation and 6) climate change.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10614dcd44510″ question_number=”424″ topic=”8.7.Disruptions_to_Ecosystems”] What’s the # 1 cause of the current extinction crisis? Name the cause, and elaborate.

[a] Habitat destruction/degradation is the # 1 cause of today’s extinction crisis. Every time a habitat is destroyed or significantly altered, the species living in it have to flee or perish. An example of habitat destruction would be converting a forest to grassland for ranching. An example of degradation would be cutting down a natural forest and replacing it with a less diverse second-growth forest designed for timber harvest. That reduces the ecological complexity of the forest, making it impossible for the species that formerly lived in it to survive.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1055f4134cd10″ question_number=”425″ topic=”8.7.Disruptions_to_Ecosystems”] What is habitat fragmentation? Explain how habitat fragmentation is contributing to the current extinction crisis.

[a] Fragmentation occurs when human activity breaks apart a species’ range into smaller areas. Because each of these fragments is too small to support a viable population, and because gene flow is usually not possible between fragments, subpopulations in each of these areas decline. In addition, fragments have large amounts of edge habitat, which can be quite different from the undisturbed habitat in the interior.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|1042e3f1f2110″ question_number=”426″ topic=”8.7.Disruptions_to_Ecosystems”] Explain how climate change is contributing to the sixth mass extinction.

[a] Alteration of climate is changing the conditions in various ecosystems at a rate that exceeds the ability of species within those ecosystems to adapt. It’s also changing the geographical range of species, often pushing them further north in the northern hemisphere, or further south in the southern hemisphere. This is pushing many species, already stressed, to the point of extinction.

[q json=”true” yy=”4″ unit=”8.Ecology” dataset_id=”AP_Bio_Flashcards_2022|10363af14a510″ question_number=”427″ topic=”8.7.Disruptions_to_Ecosystems”] What are invasive species? How can they affect ecosystem dynamics?

[a] Invasive species are those that 1) are not native to an ecosystem, 2) spread rapidly and persistently once introduced into an ecosystem, and 3) cause ecosystem disruption. Once introduced into a new area, invasive species are freed from the controlling forces such as predators or competitors they faced in their native environment. With these controls gone, invasive species often expand exponentially, out-competing native species, destroying an ecosystem’s resource base, and spreading diseases (through the parasites that they might carry).

[q json=”true” yy=”4″ unit=”8.Ecology” topic=”8.7.Disruptions_to_Ecosystems” dataset_id=”AP_Bio_Flashcards_2022|142ea40c7e0bf1″ question_number=”428″] Describe the traits that predispose a species to become an invasive species

[a] Invasive species 1) have high reproductive rates, 2) can tolerate a wide range of environmental conditions, and 3) have a generalist ecological niche.

[q json=”true” dataset_id=”AP_Bio_Flashcards_2022|2208c06647fda5″ question_number=”431″ unit=”8.Ecology” topic=”8.7.Disruptions_to_Ecosystems”] What are some key principles for nature reserve design that can help preserve biodiversity?

[a] 1) Make the reserves as large as possible so that the populations within them can be of viable size. 2) Create corridors between adjacent reserves to allow for gene flow between the populations within the reserves. 3) Choose to protect areas that have a wide variety of habitat types within them. 4) Reduce the amount of edge habitat by creating round-shaped reserves.

[x]

[restart]

[/qdeck]

4. Tackle this Quiz

[qwiz qrecord_id=”sciencemusicvideosMeister1961-Disruption of Ecosystems Quiz, APBioVideoPath”]

[h]Disruption of Ecosystems

[i]

[q]Loss of biodiversity caused by human activities is giving rise to the Earth’s sixth [hangman] [hangman].

[c]bWFzcw==[Qq]

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[q]Development of cities, farms, and recreation areas has all destroyed wildlife [hangman].

[c]aGFiaXRhdA==[Qq]

[q labels = “top”]If an animal or plant is ______________ or threatened, ____________ loss or ______________ is the most likely cause. Note that the problem isn’t development in and of itself. The problem is the _____________ to which development has modified the surface of the Earth: up to 50% of the Earth’s surface has been in someway ___________ by human activity.

[l]degradation

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]endangered

[fx] No. Please try again.

[f*] Correct!

[l]extent

[fx] No. Please try again.

[f*] Good!

[l]habitat

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]altered

[fx] No. Please try again.

[f*] Great!

[q]Habitat [hangman] occurs when humans divide wildlife habitat into discontinuous, unconnected pieces.

[c]ZnJhZ21lbnRhdGlvbg==[Qq]

[q]Particularly for [hangman] species like wolves and lions that are at the top of the [hangman] [hangman], the problem with fragmentation is that the remaining area can be insufficient for these animals to find enough prey to sustain themselves

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[c]Y2hhaW4=[Qq]

[q]Fragmentation also leads the populations trapped within the fragment to experience a population [hangman]. Without [hangman] flow from adjacent populations, each isolated population will experience [hangman] drift, leading to a loss of genetic [hangman].

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[c]Z2VuZQ==[Qq]

[c]Z2VuZXRpYw==[Qq]

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[q]Assume that the two images below represent proposed nature reserves. The problem with proposal 2 is that the four combined fragments will have much more [hangman] habitat than proposal 1. This habitat will be unsuitable for species that require an environment that’s only available in the interior. As a result, you can predict that overall [hangman] will be lower in proposal 2. In addition, the populations in each fragment in proposal 2 will be smaller, subjecting them to more genetic [hangman].

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[q labels = “top”]Small populations can also become trapped in a disastrous __________ feedback loop called an ____________ _________. In this situation, small size leads to a lack of _________ diversity, which reduces ________, which lowers the rate of ________________, which further reduces population size.

[l]extinction

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]fitness

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]genetic

[fx] No. Please try again.

[f*] Excellent!

[l]positive

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]reproduction

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[l]vortex

[fx] No, that’s not correct. Please try again.

[f*] Excellent!

[q labels = “top”]Complete this list showing the key traits of invasive species.

________ growth
Rapid ________________.
High ____________ ability
____________ of a wide range of environmental conditions.
For animals, an ability to live off of a _______ range of food types (____________, rather than a specialist)

[l]dispersal

[fx] No, that’s not correct. Please try again.

[f*] Correct!

[l]generalist

[fx] No, that’s not correct. Please try again.

[f*] Great!

[l]Rapid

[fx] No. Please try again.

[f*] Good!

[l]reproduction

[fx] No. Please try again.

[f*] Great!

[l]Tolerance

[fx] No, that’s not correct. Please try again.

[f*] Correct!

[l]wide

[fx] No. Please try again.

[f*] Correct!

[q]When an introduced species starts to grow exponentially in its new environment, it can become what’s called a(n) [hangman] species. Such species often have very high rates of [hangman].

[c]aW52YXNpdmU=[Qq]

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[q]By reducing the populations of their competitors and prey, invasive species can force native species to enter an extinction [hangman] that can be hard to escape from.

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[q json=”true” multiple_choice=”true” unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption” dataset_id=”2019 AP Bio Dataset|1fce1cb5e3948″ question_number=”472″] Bighead Carp are a fish species native to China. Because their diet includes algae, detritus, and small invertebrates, they were brought to the southern U.S. in the late 1960s and 1970s for use in improving water quality in aquaculture (fish farming) facilities. However, floods enabled them to escape their holding ponds and establish wild populations in the Mississippi and Missouri river systems.

In the wild, Bighead Carp mostly feed on plankton (floating organisms). They reproduce more rapidly and grow more quickly than most fish that are native to North American river systems.

As Bighead carp spread into new aquatic habitats, the most likely long-term effect is that

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[q json=”true” multiple_choice=”true” unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption” dataset_id=”2019 AP Bio Dataset|1fa71ceeb8948″ question_number=”473″] Invasive species typically

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[q json=”true” multiple_choice=”true” unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption” dataset_id=”2019 AP Bio Dataset|1f3e3196e6548″ question_number=”474″] When introduced into a new area, the most likely thing that an invasive species will do is

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[q json=”true” multiple_choice=”true” unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption” dataset_id=”2019 AP Bio Dataset|1ec0c1964ad48″ question_number=”475″] The combination of factors that constitutes the biggest threats to diversity are

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[q json=”true” xyz=”2″ multiple_choice=”true” dataset_id=”2019 AP Bio Dataset|214da1cd85785a” question_number=”467″ unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption”] All species of gorillas are categorized as Critically Endangered by the International Union for Conservation of Nature (IUCN). Conservationists estimate there are 100,000 gorillas left in the wild. The most severely endangered is the mountain gorilla with an estimated population of only 880 left in the wild. Which of the following genetic results is most likely to occur for this species?

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[f]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[Qq]

[q json=”true” xyz=”2″ multiple_choice=”true” dataset_id=”2019 AP Bio Dataset|2106efe07ba45a” question_number=”468″ unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption”] In the last 200 years, what has been the most significant cause of extinct or endangered species?

[c]IEludmFzaXZlIHNwZWNpZXM=[Qq]

[f]IE5vLiBJbnZhc2l2ZSBzcGVjaWVzIGFyZSBjYXVzaW5nIHNpZ25pZmljYW50IGltcGFjdHMgb24gb3RoZXIgc3BlY2llcywgbGVhZGluZyBtYW55IHRvIGJlY29tZSBlbmRhbmdlcmVkIG9yIGV4dGluY3QuIEJ1dCB0aGVyZSYjODIxNztzIGEgYmlnZ2VyIGNhdXNlIG9uIHRoaXMgbGlzdCwgYW5kIGl0IGhhcyB0byBkbyB3aXRoIGh1bWFuaXR5JiM4MjE3O3MgY29udmVydGluZyB1bmRldmVsb3BlZCBsYW5kcyBpbnRvIGNpdGllcyBhbmQgZmFybXMuIFdoYXQgZWZmZWN0IGRvZXMgdGhhdCBkZXZlbG9wbWVudCBoYXZlPw==[Qq]

[c]IEhhYml0YXQgZG VzdHJ1Y3Rpb24=[Qq]

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[c]IENvbW1lcmNpYWwgbGl2ZXN0b2NrIGZhcm1pbmc=[Qq]

[f]IE5vLiBDb21tZXJjaWFsIGxpdmVzdG9jayBmYXJtaW5nIGNhbiBjYXVzZSBhIHZhcmlldHkgb2YgZW52aXJvbm1lbnRhbCBwcm9ibGVtcywgaW5jbHVkaW5nIHRoZSBkZWdyYWRhdGlvbiBvZiByYW5nZWxhbmRzLCB3YXRlciBwb2xsdXRpb24sIGFuZCBlbWlzc2lvbiBvZiBncmVlbmhvdXNlIGdhc2VzLiBCdXQgaW4gdGVybXMgb2YgY2F1c2luZyBleHRpbmN0aW9uLCB0aGVyZSYjODIxNztzIGEgYmlnZ2VyIGNhdXNlIG9uIHRoaXMgbGlzdCwgYW5kIGl0IGhhcyB0byBkbyB3aXRoIGh1bWFuaXR5JiM4MjE3O3MgY29udmVydGluZyB1bmRldmVsb3BlZCBsYW5kcyBpbnRvIGNpdGllcyBhbmQgZmFybXMuIFdoYXQgZWZmZWN0IGRvZXMgdGhhdCBkZXZlbG9wbWVudCBoYXZlPw==[Qq]

[c]IElsbGVnYWwgYW5kIHVucmVndWxhdGVkIGh1bnRpbmc=[Qq]

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[c]IFJhcGlkIGh1bWFuIHBvcHVsYXRpb24gZ3Jvd3Ro[Qq]

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Cg==

[Qq]

[q json=”true” multiple_choice=”true” unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption” dataset_id=”2019 AP Bio Dataset|212b5bad7b948″ question_number=”469″] A citizens committee has been appointed to design a national biodiversity reserve. Given the attributes shown in the diagram below, which combination of attributes will best preserve biodiversity?

[c]IENvbm5lY3RlZCwgbXVsdGlwbGUgZWNvc3lzdGVtcywgbGluZWFyLCBsYXJnZSwgZGl2aWRlZCwgb25lIGFyZWE=[Qq]

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[c]IENvbm5lY3RlZCwgbXVsdGlwbGUgZWNvc3lzdGVtcywgY2lyY3 VsYXIsIGxhcmdlLCB1bmRpdmlkZWQsIHNldmVyYWwgYXJlYXM=[Qq]

[f]IEV4Y2VsbGVudCB3b3JrLiBZb3UmIzgyMTc7dmUgY2hvc2VuIHRoZSBhdHRyaWJ1dGVzIHRoYXQgbWF4aW1pemUgYmlvZGl2ZXJzaXR5Lg==

Cg==

[Qq]

[q json=”true” multiple_choice=”true” unit=”8.Ecology” topic=”8.6-8.7.Biodiversity_and_Ecosystem_Disruption” dataset_id=”2019 AP Bio Dataset|206573bac7948″ question_number=”470″] The diagram below shows various attributes of nature reserves.

What characteristics are optimal for maintaining the genetic diversity of the populations within it?

[c]IERpdmlkZWQgbmF0dXJlIHJlc2VydmVzIGFyZSBiZXN0IGJlY2F1c2UgdGhleSBzZXQgdGhlIHN0YWdlIGZvciBhbGxvcGF0cmljIHNwZWNpYXRpb24u[Qq]

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[x]

[/qwiz]

What’s next?

This topic ends Unit 8 of AP Bio (Ecology). It also ends this entire AP Bio course. Congratulations!

To prepare for the AP Bio exam, go to our AP Bio Review Menu
To review Unit 8, Ecology, go to the Unit 8 Review Page (with unit Objectives, Flashcards, MCQs and FRQs)
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